Monday, November 20, 2006

VW - Align Boring

What is the correct procedure for checking alignment of shaft bores in a crankcase?

There’s more than one way to do this and the method I use isn’t very precise.

After checking that each of the re-machined bores is a true circle, I dismantle the crankcase and measure the depth of each half-bore using a plunger-mike that reads to tenths (i.e., .0001"). Because of the amount of ‘crush’ inherent in the design, you can have the bores asymmetric by up to three thou or so and still have a usable crankcase, assuming they are all the same. You’ll see this kind of asymmetry even in new cases. But what you can’t live with is to have the depth of one of the bores radically different from the others.

The problems I’m looking for usually show up on used crankcases that have been improperly align-bored but it’s worth your time to check even a new case.

On re-manufactured cases, you want to focus your attention of the #2 main-bearing web and bore. If the web has been severely pounded its re-machined bore will usually be asymmetric, so much so the case often isn’t usable.

In an ideal world all of the bores would be perfectly identical and symmetrical. That is seldom true. Tolerance is about seven tenths (i.e., .0007") for bore diameter so they should all fall within a thou of each other. I measure each bore at three or four points and record the measurements. The crankcase is torqued to spec with all of the fasteners in the plain of the crankshaft installed. Extremes of temperature should be avoided and if the case has just been machined it would be wise to put off any measurements until it has cooled off.

The half-depth is compared to the average of those measurements. After you’ve measured and recorded all eight half-depths a couple of times, any asymmetry should be obvious. If the asymmetry is consistent, it may be ignored so long as it’s under three-thou or so. Anything more, in either case-half, will lead to problems with the mesh of the distributor driver-gear. And of course, any single bore which is not in the same plain as the others is grounds for rejecting the case.

You should already have checked the run-out of your crank. Tolerance for run-out is about the same (i.e., .0007") but you have to take into account the diameter and allowed out-of-roundness of the journals on the vee-blocks at the time you check for run-out on the journal between the vee-blocks. See the Bentley manual for the spec, which I can’t recall . . . but it’s about a thousandth of an inch (.0010")

These problems are seldom a worry if you start with a good crank and case. As I said in an earlier message, Gene Berg’s cranks are the best I’ve seen, and any align-bore done by Larry Pauter’s shop (Pauter Machine Company) was always dead-on. But many one-time rebuilders have to work with what they have, using whatever machining services are locally available. It’s important to note here that I am not doing anything unique or unusual, nor am I looking for some exotic, one-in-a-million fit. All I’m doing is trying to ensure the components going into the engines I build meet Volkswagen’s published specifications. Assembling the parts is an entirely different subject. But as sure as God made little green apples, if you start with parts that are out of spec, there’s no way you’ll ever come up with a reliable engine.

-Bob Hoover

VW - Lower Tin-ware

The function of the splash shields (i.e., lower tin-ware which forms the exhaust plenum for the cooling system) is exactly the opposite of cooling, although there’s a footnote to that as well.

Here’s the situation: You are running at speed. You encounter rain, or a puddle, or you ford a creek (common stuff in Baja; no bridges!). Want to imagine what happens to your cast iron cylinders when they get an eyeful of water?

Situation 2. You’re running at speed, the air under the vehicle is at higher than ambient pressure. Beneath the cylinders the cooling air encounters higher exit pressure at cylinders 1 & 3, reducing cooling air flow. The result is that the portion of the cylinder at the 1 o’clock to about the 3 o’clock position (for #1 cyl; 9 to 11 for #3, in each case relative to an observer looking into the cylinder from the valves) is running hotter than the portion of the cylinder from about 4 to 6 (i.e., 8 to 6), since that lower portion is being super-cooled by the blast of air provided by the vehicle’s forward motion.

Situation 3 is as described in my sermon on push-rod tubes; they are part of your cooling system. But they are also part of your temperature control system, in that they help the oil heat faster thus achieving a stable operating temperature more quickly.

When the engine temperature is stable the engine performs more efficiently and with less wear. The splash shields form a plenum chamber for the cooling air exhaust, allowing the cylinders to enjoy a uniform airflow regardless of vehicle speed. Plus their name sort of gives it away; liquid water can cause sudden contraction of the cast iron jugs, resulting in oil leaks around the lower spigot and compression leaks at the heads. Bad things happen to a hot air-cooled engine when it gets doused with water. The splash shields form a baffle, and so long as the blower is blowing, very little water spray ever contacts the cylinders... and no liquid water at all... unless you’re really trying to win.

We learned all this the hard way, stripping our baja’s to the bone. Less weight, more acceleration. We eventually saw that Volkswagen engineers had already been there, done that. In the end, we re-designed our skid pans to perform the baffling/shielding function and thus ended a host of problems that had plagued us since our attempts to ‘improve’ on the original design.

If you really want to improve your engine, look at the Porsche, Corvair or the late 2000cc Type IV’s. Then work backwards, retrofitting to your bug or bus features found on those engines such as better lower shrouding (i.e., Kool Tin), shaft seals (i.e., Sand Seals), hydraulic lifters, full-flow oil filtration, electronic ignition, an external oil cooler (Dog-house Cooler) and so on. It’s really pretty easy to be a VW guru when Volkswagen, General Motors and Porsche has already paid the engineering bill.

-Bob Hoover

VW - Oil Cooler & Tin Mods

I was never able to duplicate Gene’s claimed results regarding engine temperatures and external oil coolers. Indeed, Gene never clearly defined what he was measuring. I believe I’ve already mentioned this situation in an article on external oil coolers.

My original interest was in learning how the Volkswagen engine was cooled so I could insure adequate cooling when the engine was installed in an airplane . . . converted VW engines in airplanes being notorious for swallowing the rear-most exhaust valves.

I dismantled the blower-housing from a 40-hp engine (this was in the late sixties) and replaced it with a sheet of plexiglas. Running on the test stand, I could introduce smoke-streams and figure out what VW was trying to do. Later, I rigged the big squirrel-cage blower I used on my flow-bench to suck air down thru an engine with the blower housing removed, using Temp-L-sticks, thermistors and the like to gain some understanding of the temperature change in the heads based on air-flow and engine speed.

I discovered the major emphasis in the original design was in providing the corners of the engine with air, with a very intricate series of air vanes and dams devoted to this purpose. Because of the obstruction of the oil cooler, the left head didn’t flow very well and because of the offset of the cylinders, #3 got the least air of all.

Removing the upright oil cooler brought an immediate improvement in air-flow although you had to do something about the ‘hole’. I first tried various forms of air dam before realizing I was going at the problem backwards.

Adequate flow can only come when there is adequate pressure and Volkswagens’ method of sustaining adequate pressure using a pair of deflector plates and the tin-ware skirts across the ends of #2 & #4 cylinder didn’t work very well. To maintain sufficient air pressure to ensure adequate flow to the ‘corners,’ you must improve the cowling of the underside of the cylinders, a step Volkswagen got around to a few years later.

For aircraft use, a tight upper plenum combined with tight lower cylinder cowling did the trick. This was not a popular fix because many lightplane designs do not include pressure cowlings.

There is also considerable improvement you can make in the heads, getting rid of any casting flash and insuring maximum air-flow down thru the fins around the exhaust stacks.

Getting back to external oil coolers, the dog-house cooler . . . and that of the Type IV . . . is an external-type, in that air used to cool the oil is exhausted to the atmosphere and not used for engine cooling.

In one of my articles I described the auxiliary oil cooler I designed for my ‘65 bus. I didn’t give a lot of detail about the design process but it involved making a manometer from plastic tubing, plywood and colored water to measure the air pressure inside the engine compartment. Addition of air scoops caused a significant increase in engine compartment air-pressure. While many still argue the merits of air-scoops on early buses one need only examine the cooling-air inlets of later model buses to see they too incorporate a scoop-type design.

Once I understood the problem I was able to come up with the design of an auxiliary oil cooler that worked, and very well too, as demonstrated on a run to Kansas City when I had to tow a Westy over South Pass (outside of Needles, California) in temperatures of over 100 degrees.

A couple of closing points.

I don’t want to get into a pissing contest with a dead man but I was never able to substantiate many of Gene Berg’s claims. Indeed, in many cases I couldn’t even get him to explain what he was measuring, where he was measuring it and how it was measured. I said as much years before his untimely death. Nothing has happened to change that.

The information I developed on auxiliary oil cooling applies mostly to my ‘65 bus. The general principles may apply to later-model buses but the wiser course would be to run some tests before cutting metal.

I don’t see any benefit in your idea of removing the oil cooler in your Type IV. However, should you need an auxiliary oil cooler there are convenient means of installing such without removing the stock oil cooler.

All of the Type IV’s I’ve seen that were experiencing problems with overheating, the fault was due to poor maintenance, usually the result of missing air-seals or tin-ware.

-Bob Hoover

VW - Normal Oil Temp

What is a normal oil temperature reading for a 74 bus 1800 engine? or any bus for that matter...i’m getting an oil temp gauge and once i install it i would be curious as to what normal is compared to “too hot”.

This is one of the most common questions I hear. The correct answer is rather fuzzy.

The fact is, there’s no one ideal temperature. By their nature, air-cooled engines have a wider envelope of ‘normal’ operating temperature than does their water-cooled cousins. What you’re given to work with in the case of air-cooled engines is a range of safe operation. On simple instruments the range of normal operation is usually marked in green, caution in yellow and waythehelltoohot in red.

I’ve never seen a published figure for the normal oil temperature range for any air-cooled Volkswagen but their Industrial Engine Division showed the green arc as being from 170 to about 220, with a yellow arc above that, apparently up to about 250, and red over the last segment of the dial-face.

You could get the industrial engines with a set of gauges for oil temp, oil pressure and amps. Pressure was picked-off at the gallery where the oil-pressure signal-lamp switch goes in vehicles. Oil temp was picked-off at the inlet to the oil pump, a suitable adaptor replacing the threaded plug found there. (Ed. Note: Only found on early crankcases.) Installing the OT sensor in a different location will give you a different reading, one that is typically lower than you'll see at the inlet to the pump, which probably accounts for the wide variation in Oil Temp figures cited by various VW owners. Then you've got the accuracy & precision of the gauge itself. ( ALWAYS calibrate your gauges. )

Another reason for the fuzziness has to do with that stuff we use as our cooling fluid . . . air.

The operating instructions for the industrial engines listed a range of air temperatures at which you could run with a maximum load on the engine. I think the upper limit was about 85 degrees Fahrenheit. Above that you were cautioned to reduce the load if the oil temperature rose out of the green . . . pretty much common sense, if you’re running a grain-drill or an irrigation pump.

It’s not too surprising to find the Owner’s Manual for Volkswagen vehicles saying about the same thing, albeit with reference to the oil-pressure warning lamp . . . if it’s a hot day and you’re driving fast or carrying a heavy load and the lamp begins to flicker, the manual tells you to slow down... to reduce the load on the engine.

The funny part here is that while a farmer is bright enough to figure this out, most driver’s somehow miss the point. I get a lot of messages from people asking why their bus overheats when they drive seventy miles an hour on a 90-degree day, as if there’s some dark mystery involved. Sadly, telling them they’re driving too fast often gets a rather snippy response. :-)

The truth is, air-cooled engines are more suitable for cold climates. Water-cooled engines do best in the desert. This is one of those grizzly facts that continually bumps heads with Conventional Wisdom... at least, until they bother to sit down and figure it out on paper. Pointing out that Berlin is as far north as Winnepeg sometimes helps but the myth of Kubelwagens in the Sahara usually overpowers any intelligent answer. There were some Bucket-Cars used in north Africa but according to German mechanics who were there, they had a habit of swallowing #3 exhaust valve, a failure-mode woefully familiar to anyone pounding across west Texas in an early beetle. (A lot of Texas is farther south than Cairo. Most of the north African campaign was fought near the shore of the Mediterranean, in Tripolitania and in the Libyan Desert, hundreds of miles north of the Sahara.)

This isn’t to say an air-cooled engine is unsuitable for a hot climate, it’s simply not as suitable as a water-cooled engine under those conditions. You can keep right on using your air-cooled engine in Brawley or Qunianga Kebir (which is in the Sahara Desert), but you’ve got to keep your foot out of it . . . you simply don’t have enough latent cooling capacity to handle maximum output at high ambient air temps.

So what’s the ‘normal’ oil temperature? I don’t know. I know what’s ‘normal’ for my engine and vehicle and instruments and load and climate. But I don’t know what’s ‘normal’ for yours.

If you’ll examine the archives you’ll see that the question of temperatures is a pretty popular theme. You’ll also see a lot of different numbers, the ‘normal’ temps registered by different people in different locations doing different types of driving with their vehicles. About the best you can do is make a note of the range of temperatures they’ve cited and see if your combination gives a number within that range. It ain’t too scientific but you could do a lot worse.

-Bob Hoover

VW - Kool Tin

Since my list query about sources for decent Kool tin (that is, not the Taiwanese tin foil grade, casual fit tin...) I’ve learned that Berg sells sturdy stuff and that the 1600cc non-North American vanagon engines also had such tin stock. I’ve read in one of your list posts that the Kool tin when used on a 1600 with properly modified upright tin can produce better cooling. Can you outline the tinware modifications necessary to make this work?

You mentioned leaving off the stock deflector plates and welding the Kool tin to stock tinware after modifications to get a tight fit. I could probably “wing” something based on this, but I’m hoping to benefit from your experience here and get some more detail so I don’t inadvertantly cutoff critical airflow with a less than astute mod ;).

Volkswagen leaves off the deflector plates when they install ‘kool tin’ lower shrouding. The deflector plates are not compatible with the tighter ‘kool-tin’ lower shrouding.

With the engine upside-down on the assembly-fixture and the push-rod tubes off, heads loose, trial fit the kool-tin, observing how it was meant to be fastened and exactly where it was meant to fit between the cylinder fins.

Stock VW kool-tin fits reasonably well but is rather loose, especially in the middle. Experience has shown the original method of installation was inadequate. The kool-tin always came loose, ended up down on top of the push-rod tubes.

The first and most obvious fix is to drill a couple of small holes through the central wedge . . . the part that goes between the cylinders . . . and thread some thin-gauge safety wire through the holes. With the engine right-side up you’ll see that it’s possible to cut & shape two short pieces of welding rod or heavy-gauge stainless steel safety wire to fit down into the cylinder fins and bridge the gap between the cylinders. This is what I use to secure the thin-gauge safety wire I’ve installed in the kool-tin, drawing the stuff up until it is tight to fins. I shape the tin-ware with rubber or plastic mallets where necessary, with my hands in other areas, grinding or cutting away anything that prevents a smooth, symmetrical fit

To insure the sides can not come free I use two procedures. At the rear of the engine I modify the air-dams that fasten to the cylinder tin (and trap the breast tin between them) to form a smooth fit with the kool-tin, typically by snipping the metal into a series of fingers, heating them and molding each finger to the shape of the kool tin, all this while the tin-ware is securely fastened in position. Each little finger is tack-welded using a aircraft torch with a small tip. When the thing is well secured I take it off, weld it up, sand-blast it and otherwise prepare it for painting.

At the front of the engine, in order for the kool-tin to fit, you must modify the basic bottom-tin-ware pieces, a full-length piece on the driver’s side of the engine, a shorter piece on the side of the engine mounting the thermostat bracket. The modification is simply doing whatever is needed to make the tin-ware fit with the kool-tin in place. Typically, this means reducing the convoluted curves and indentations of the original piece, which formed a very critical part of the engine’s shrouding, into a simply curved panel that will accommodate the kool-tin. The convolutions, bulges and so forth are no longer required since their function is being performed by the Kool-tin.

To insure a good mechanical fit, I then fabricate a flange of sheet-metal of a suitable thickness to fit between the upper and lower pieces of tin-ware (i.e., the cylinder head tin-ware and the lower tin-ware) of sufficient depth and shape (I put a little lip on it) to allow it be welded to the kool-tin. The lower-tin-ware is removed while this fitting and welding is going on, of course. It’s usually necessary to fasten the kool-tin into the proper position with wire or by some other means in order to accomplish the weld . . .once you remove the lower tin-ware, the kool-tin is no longer held in position and will move around on you. I generally tack the flange at a couple of points then reassemble the lower tin-ware to be sure I’ve gotten it right. You’re after a really snug fit here, something that will force air to flow through the fins rather than around them.

Once I have a nice fit fore & act I clean the welds and paint the parts. This work should be done well ahead of any actual engine assembly.

The work doesn’t have to be pretty . . . no one is ever going to see it . . . but do the best you can, taking a bit of time to forge and grind your welds. You’ll have to use gas-welding, the tin-ware is a bit thin for MIG. And the thin stuff is prone to cracking so it pays to make a good job of it. Some of my first efforts were merely tacked together. They held up remarkably well but were not nearly so tight as fully-welded units.

On average, I spend about forty hours making up the tin-ware for a big-bore stroker. On the wider engines you must even modify the thermostat bracket... and make a new thermostat rod.

Except for final fitting, all of this work should be done on a mock-up since the welding, grinding and so forth might cause damage to a real engine. (A mock-up is any suitable crankcase . . . even one with a hole in it . . . fitted with suitable jugs & spacers to give the proper width.)

Welding the flange & air-dam to the kool-tin improves its stiffness but you’ll find the center is still ‘soft’. Although I continue to use the safety-wire fasteners, I also weld a couple of pieces of heavy wire across the bottom, exterior of the kool-tin. Normally, doing this would prevent the stock kool-tin from being removed but after the kool-tin has been modified there is no need to retain the stock securing notches other than as locators. With the notches ground into smooth ‘U’s the kool-tin drops into place on the head-studs without the bending required of the stock kool-tin. The welded wire stiffeners are about 1/8" in diameter and the width of the flat portion of the kool-tin. They add a remarkable amount of stiffness to the kool-tin, allowing it to be fastened more securely, eliminating any vibration that may develop.

I think it would be very difficult to not get better cooling using tighter lower shrouding, unless you installed it in such a manner that it could come loose. Some of the most valuable time you can spend would be to study the lower shrouding on the Corvair, VW Type IV, and most aircraft engines enclosed in pressure-cowlings. When you compare these more efficient cowling methods to the early VW engine it will make the short-comings of the deflector plates painfully evident.

Proper shrouding improves the efficiency of your cooling system. Not only will it cause your engine to run cooler, tighter shrouding allows the thermostat to keep the engine at a more even temperature, which greatly improves the engines service life.

-Bob Hoover

VW - Hoover Bit II

....on the 4 or 5 doghouse engines i’ve pulled apart in my short time, i can not once remember a bracket... at least, i cant ever remember having to remove any sort of bolt from there...


The bracket, which fastens to the two upper bolts securing the oil cooler to the adaptor, is missing on about half the engines I see. Ditto for the stamped steel air-dams under the cylinder heads. And on most of the engines I see, the usual complaint is overheating.

You don’t have to remove the fastener to remove the blower housing, just loosen it. The fastener is usually a Filster head machine screw, as for the other tin-ware. (I like to use bolts instead of screws.) It should have the large diameter washer plus a warpy washer. It fits in the notch just beside where the air-vane return spring is fastened.

Normally, the screw and washer are loosely installed in the bracket, mating with the blower-housing when the assembly is lowered over the oil cooler. Without the bracket & fastener, at high rpms the tin flap over the blower housing bulges out and most of the air escapes around the oil cooler instead of blowing through it. There’s a little foam gasket on the oil cooler that’s supposed to seal this leakage path but it’s easily defeated when the flap is not secured. (Hint: Use a full-width foam seal. And the proper fastener.)

Form follows function. The bracket is evidence of the critical attention to detail paid by Volkswagen to ensure maximum air-flow thru the cooler’s core. Failure to include the bracket in their article or to stress the need for the wider fan, is just another of those ‘little details’ the magazines don’t bother with. Unfortunately, attention to detail is the major difference between a good engine and a piece of crap.

-Bob Hoover

VW - Doghouse Retrofit

Time and time again, people visit my garage wanting a ‘Dog House’ oil cooler on their pre 1970 Bug. I am wondering if a late model oil cooler would work on an early case with the small oil holes on top of case where the cooler bolts on? If so, which oil cooler seals do I use?


Yes, a late-model dog-house style oil cooler can be retro-fitted to the early-model engines.

Somewhere in the archives, or perhaps in one of my articles, I’ve given all the details for adding a dog-house cooler to an early engine.

Mechanically, there isn’t much too it, although you need to drop the engine to do the swap. The oil cooler adapter bolts to the case, the late-model oil cooler bolts to the adapter and away you go. But like most things, success is in the details. You will need a dog-house-type blower housing, the 10mm wider fan, new forward breast tin (for the exhaust ducting) and the exhaust ducting itself. Local junk yards were charging $65 for all the necessary tin-ware plus $35 for a used oil cooler (the price is higher now). If you do not know the provenance of an oil cooler it is unwise to use it. If it is off a blown engine the oil cooler will have trapped a lot of metal particles that will cause early failure of a good engine. Best bet is to use a new or rebuilt unit.

For a leak-free installation you need two sets of grommets, one for the adapter, one for the cooler. That means you need to specify a post-71 gasket set, or you may be able to salvage grommets from the remnants of old gasket sets used to install upright coolers. Don’t even think of using old grommets. You need the ‘crush’ of the new grommets to provide tension on the fasteners. And don’t use any sealant on the grommets . . . it will get squeezed out and ends up in either the cooler or your bearings.

The adapter . . . available from Bug-pack or a junky . . . dictates the type of grommets (seals) you’ll need. In the overhaul gasket set there are two types of grommets, one for early engines with the small hole, one for later models.

The adapter dictates the OD the grommet, the crankcase the ID. Dig through the gasket set until you find the set that match your needs . . . you’ll be looking for the THIN-WIDE grommets (those for a Type III engine are THICK/ WIDE... whatever you do, don’t get them mixed up). Be careful not to over-torque when you install the adapter to an early case. You will have to replace the stud with a bolt of suitable length. With the proper grommet installed, the adaptor will come down flush on the crankcase. This is where you need to be careful. IF you don’t have the right grommets you’re liable to strip out the threaded bore for the bolt (i.e., where the stud was) or even break off one of the ears. If the adapter is not flush the oil cooler will be too high by that amount, causing a mis-fit of the blower housing, which can lead to air-leaks, excessive vibration and so forth. The different grommets are illustarated in Tom Wilson’s book ‘How to Rebuild Your Air-cooled Volkswagen Engine’.

Having a COMPLETE set of dog-house tin-ware is vital to the success of the conversion. The piece of tin-ware most difficult to find is the little gasket bracket which bolts to the back of the oil cooler and provides the nut-plate for securing the new blower-housing. Don’t leave this piece out. It forms a vital air-dam as well as serving to secure the ‘flappy’ part of the dog-house. Without it, you’ll have a massive leak of cooling air and vibrations from the unsecured blower housing will eventually cause the oil cooler to loosen and leak.

I always install new foam rubber gaskets on the oil cooler. They get torn rather easily by removal of the blower housing and they have a critical role . . . if the high pressure cooling air can find some way around the oil cooler, it will. The foam, in conjunction with the blower housing and ‘dog-house’, forms an air seal on the sides and top of the oil cooler. The little ‘mystery’ bracket (that most people leave out), with a small piece of foam attached, forms the air seal for the bottom of the oil cooler. Without it the oil cooler is only about 50% effective . . . the air blows thru the gap and at higher rpm, lifts the tin-ware away from the cooler core making the gap even worse. If you can’t find this little piece of tin-ware you will have to fabricate something to serve as the air-seal for the lower edge of the oil cooler. There are a number of ways to accomplish this but don’t put your faith in glued-on weather-stripping or the like . . . it will come loose in time and may block the oil cooler.

After-market tin-ware is especially bad when it comes to forming a proper seal around the oil cooler. I’ve a hunch the Taiwanese or Siamese or whatever have never seen a properly assembled dog-house style blower housing with all of the bits & pieces properly installed. For whatever reason, after-market dog-house style tin-ware often leaves gaps of an inch or more around the base of the oil cooler, defeating the whole purpose of the thing.

Sealing the exhaust ducting is equally important, not only where it attaches to the dog-house and the back of the blower housing, but where it passes thru the breast tin. I use RTV and literally glue the ducting in place. Since you’ll be replacing the breast tin, this is a good opportunity to install a bulkhead fitting for the fuel line. You’ll find this covered in at least two of my articles on the ‘sermon’ page.

Finally, drill out the upper bolt mounting hole on the driver’s side of the engine and install the threaded barrel found on the ‘71 and later engines. Once the dog-house oil cooler is installed you can’t get a wrench onto the nut.

The dog-house oil cooler, which is in fact an external oil cooler, represents a vast improvement over the old-style up-right oil cooler. The wider fan, new blower housing and external exhaust serves to make the oil cooler circuit separate from the normal engine cooling.

-Bob Hoover

VW - The 'Hoover Bit'

The Missing Piece

I’m guilty of taking VW-specific magazines to task for the many errors and omissions in their articles. I’m not against VW-specific magazines . . . there is no ‘hidden agenda’ in my criticism. Indeed, I’ve urged people to buy the magazines for their ads and illustrations. But I’ve also told folks not to put much faith in their technical content since it was often incomplete, inaccurate or skewed to favor a device or service offered by one of the magazine’s advertisers.

Over the years that I’ve been uploading articles to the internet my position with regard to the magazines and the poor job they do has earned me a lot of flack. Most of it comes from kids who simply don’t know any better, some from older VW owners who should. I thank them for their opinion and that’s usually the last I hear from them. But occasionally one of these misguided missiles will wave their lawyer at me. It’s all horseshit of course, but it gets tiresome. The truth is, the technical content of the VW-specific magazines is very low. Everyone associated with the magazines has a vested interest, either in their job with the magazine or some outside activity that is fostered by their relationship with the magazine. I don’t. My opinion may not be correct but it’s always my honest opinion, not dictated by fear, greed or financial interest. And while I may not always be correct, my opinion is based on first-hand experience . . . I’m the guy with the greasy fingernails . . . I spend more time at the workbench than the typewriter.

During the course of a recent thread having to do with the retro-fit of a late-model dog-house oil-cooler to an early engine, I mentioned a critically important piece of tin-ware, a small bracket that bolts to the cooler core, supporting the gasket(s) that serve as an air-dam for the cooler, and as a bolting bracket for the fan housing. The absence of this air-dam creates a substantial air leak, allowing air to by-pass the oil cooler. The bracket also serves to secure the blower housing to the oil cooler. Without the bracket and the critical fastener, the tin-ware around the oil cooler is blown out of position by the force of the cooling air, allowing as much air to go around the oil cooler as flows through it. The bottom line is that failure to install the bracket results in a profound reduction in the effectiveness of the oil cooler.

A Florida subscriber to the Type2 list read my comments about the benefits of the dog-house cooler and followed the recent thread, as well as asking a number of questions regarding air vanes and thermostats in private messages. He is new to Volkswagens, as were we all at one time and not especially confident of his skills as a mechanic, as were we all at one time.

He decided to tackle the job when an illustrated article on the modification appeared in the April, 1997 issue of ‘Dune Buggies and Hot VWs’ magazine (page 54). But the article made no mention of the critical bracket and, never having seen one, he could not deduce its location from the illustrations, a copy of which he sent to me by surface mail.

He couldn’t see it because it isn’t there. The bracket is neither mentioned in the text nor shown in the illustrations. Whoever did the work left the bracket out and Bruce Simurda, the Editor and Associate Publisher of ‘DB&HVW’s’, who wrote the article, obviously doesn’t know enough about VW engines to realize the part was missing.

Without that critical little bracket you’ll just be pissing away your money on the mod. Get the bracket. Do it right. Pour through the shop manuals until you see how it is installed . . . it only fits one way.

The article is the typical infomercial, touting SoCal Imports as one source of the components needed to do the mod. It would be interesting to hear their comments regarding the missing bracket.

-Bob Hoover

VW - Cooling System

Although the Fresh Air blower housing does not use engine cooling air for cabin heat, as is shown by the geometry of the blower housing and the position of the internal air vanes, leaving the Fresh Air heater outlets open will cause a pressure drop that will reduce the engine’s capacity to cool itself. The Fresh Air outlets must be blocked or connected to functional heat exchangers (that is, heater boxes that aren’t rusted-out).

Hoping to improve the cooling of up-right engines, I ran some experiments with the Fresh Air outlets blocked off, different oil cooler configurations and so forth. Blocking the heater ducts provided no additional engine cooling, whereas leaving them open caused a sharp rise in CHT and oil temps.

Removing the screen from the upright oil cooler, a fairly common practice at one time, reduced the CHT measured at #3 cylinder but produced a rise in oil temp. Apparently the screen acts as a turbulence generator, allowing the air to pick up a bit more heat as it passes through the fin-less cooler.

Removing the up-right oil cooler from the blower housing and mounting an external cooler over the cooling air inlet produced dramatically lower cylinder head temps for #3 & #4 cylinders as well as lower oil temps. A small air dam must be installed in the blower housing at the bottom, near the location of the missing cooler to insure adequate air-flow to the #3 & #4 cylinder head.

Mr. Gene Berg’s claim that removing the upright cooler caused a rise in temperature may have been due to his failure to include the air dam. I was not able to reproduce his results with the air dam in place. Even without it, oil temp was lower than before although CHT on #3 rose slightly.

Assuming the timing and carb to be correctly set and the lower cylinder air deflectors are in place, if an early engine has a chronic cooling problem it’s wise to inspect the oil pump for wear. A worn oil pump reduces both pressure and rate of flow and the effectiveness of your oil cooler depends on flow rate. Replacing the up-right style cooler with the later model dog-house cooler is the best solution of all. (The dog-house style cooler appears to be about 4x as efficient as the up-right cooler.)

The other most common cause of overheating is failure of the engine compartment seal. When in motion the air under the vehicle is at a higher pressure than the air over the rear window and deck lid, allowing the engine to re-circulate the heated air from under the vehicle.

If the vehicle is habitually parked near trees the cooling problem my be due to leaves blocking the fins on the cylinder heads.

-Bob Hoover

VW - Adjusting the Thermostat

With all this talk about thermostats, how does one adjust the thing properly?

Adjusting your thermostat is pretty simple. But first you have to get at it. To do that, you’ll have to remove the rear section of the lower tin-ware on the passenger-side of the engine.

Once you have access to the thermostat and its bracket, remove the bolt securing the thermostat bellows to the bracket. The engine should be cool and the thermostat bellows fully closed when you do this.

With the bellows free in the bracket, loosen the nut holding the bracket to the stud that projects from the side of the crankcase. You want to be able to slide the bracket up & down but the nut must be firm enough to hold the bracket in position when you let go. Now check your flaps to make sure they are fully open. The procedure here varies according to the year you have. The basic idea is that when the rod attached to the bellows is pushed up the flaps will be pushed open, so one way to check is to simply push the rod up as far as it will go. It should stay there, thanks to the spring attached to the connecting rod linking the two pairs of flaps.

Fully up . . . fully open . . . is the hot position.

Notice how the bracket completely surrounds the bellows? What you want to do is cause the upper part of the bracket to just touch the upper part of the bellows. In practice, the bracket serves to prevent the bellows from expanding too far, which can cause the bellows to crack.

When you have the bracket properly positioned, tighten down the nut on the stud in the side of the crankcase.

Now comes a bit of fumbling. Reach up, grasp the bellows and pull it down, rotating it as needed to cause the flat-sided boss on the bottom of the bellows to mate with the hole in the bottom of the bracket. The flat-sided boss prevents the bellows from rotating, which would cause it to unscrew itself from the actuating rod.

If the bellows can’t be pulled down far enough to mate with the bracket, you can back-off a few turns from the rod. But be sure you have at least six full threads of engagement (more is better).

Once the bracket is secured in the proper location, slid a warpy washer, then a suitable flat washer, onto a short M8x1.25 bolt, and thread it into the hole on the bottom of the bellows. The flat washer must be large enough to span the boss on the base of the bellows and contact the bracket, otherwise the thing will simply spring back up. Make sure the flat side of the boss on the bottom of the thermostat is properly mated with the hole in the bracket, then tighten the M8 bolt to about 8 ft-lb.

That’s all there is to it. The first time you do it, take as long as it takes. Once you’ve done it a few times, it takes only a couple of minutes to set the adjustment.

When pulling the engine for maintenance that involves removal of the blower housing, it’s usually most convenient to remove the thermostat from its bracket and to unscrew it from its rod as part of dropping the engine, when the vehicle is hoisted up and there is room to get at the underside. For the same reason, it makes good sense to hold-off re-installing the thermostat and lower tin-ware until you replace the engine in the vehicle.

The short bolt and large-diameter flat washer used to secure the thermostat to its bracket are unique. It’s a good idea to keep them with the bellows.

-Bob Hoover

VW - Install a Thermostat

Do it.

The thing will run without it, the better the climate, the better it will run. And if you’re running a full-flow oil filter the main bearings will last about as long.

But that’s it; that’s the limit of the ‘benefits’ you’ll receive from re-designing the Volkswagen engine, because that’s what you’ve done; you’ve told generations of superbly qualified engineers to stick it in their ear, that you know a better way to do it. Unfortunately, without the thermostat your jugs will wear like a bitch, as will your valve guides; you’ll burn more gas, suck a lot of oil and have a hell of a time passing your smog check. Of course, all the experts in the VW-specific rags say no thermostat is a wizard idea, along with blue coils and yellow wires itty-bitty fan pulleys and all the other bitchin’ tricks that made them rich and famous as builders of fine automobiles.

What’s that you say? They haven’t built any cars?

Oh. Well, then make them famous as builders of winning racers. Whats that?

Gee... you mean all they do is talk about it? Ummmmm.....

Put the thermostat back in. To a real mechanic, anyone who builds an engine without a proper cooling system -- and that includes a thermostat and air-vanes -- is like a guy going around with his fly unzipped.

Here’s how to do it.

You need a blower housing with a working set of air-vanes.

The connecting-rod across the front of the blower housing connecting the air-vanes together. Plus the spring that holds the air-vanes open.

The right-side set of air-vanes must have a thermostat link-rod.

Under the engine you need the thermostat bracket and the thermostat.

To install, make sure the thermostat link-rod slides down through the head and projects between the push-rod tubes under the engine. Secure the blower housing and generator (I’ll assume you took the opportunity to replace the modified intake manifold).

Under the engine, reach up and thread the thermostat onto the link-rod. Run it all the way up. Now put the thermostat bracket onto the thermostat. Make sure the base of the thermostat fits the opening in the bracket, which is flat-sided to prevent the thermostat from unscrewing itself as it expands and contracts. Now pull down on the whole assembly and fit the bracket over the stud on the side of the sump. Install a flat washer, a warpy washer and a nut. Pull down on the assembly until the air-vanes are fully closed.

Don’t over-do it. Tighten down the nut securing the bracket.

I’ll assume you tested the thermostat before you did all of this, and that your engine has all its tin-ware. The lower tin provides a plenum that insures the thermostat is bathed in heated air from the cylinders and heads.

The bottom line is that your engine warms up faster, idles better, runs sweeter and lasts longer.

On the other hand, you may wish to leave it off, unzip your fly and make your personal style statement to the VW world.

-Bob Hoover

VW - Electronic Ignition for Early Volkswagens

The Kettering ignition system of points, condenser and coil was never more than a compromise. (The Model T, with one coil per cylinder was more dependable but also more complex and costly.) The component most likely to fail in the Kettering system was the points, since they had to carry up to ten amps of current, a difficult task for any switch turned on and off fifty times per second. Until they found something better, Detroit designed their way around the problem with dual points and even dual ignition systems. The cure wasn’t found until the advent of the transistor in 1948, and didn’t gain commercial popularity for another twenty years.

The cure for the Kettering system is to use the points not as a current-carrying switch but merely as a signaling device to tell the ignition system when to fire the spark. The actual switching is done with a specialized form of transistor.

And instead of feeding the coil a diet of 12 volt current, it is fed 400 volts, allowing it to build up the maximum charge in the shortest time. The 400 volt energy is developed using a tiny switching transformer inside the ignition module, the energy stored in a large capacitor which is discharged into the coil at the appropriate time. This capacitance-discharge gave such systems their name, often abbreviated to CD.

‘Point-switched’ CD ignition systems require periodic maintenance as the rubbing block wore down, typically about every 10,000 miles. The points required replacement at about 50,000 miles, due to rubbing block wear. The points themselves are still in perfect condition at that time. Designed to switch a 120 watt load fifty times per second, they hardly notice the microampere load needed to signal the CD module.

The biggest advantage in CD ignition is improved efficiency. Spark voltage remains constant at all speeds, and constantly high. With a dependable 40,000 volt spark at all engine speeds the spark plugs may be gapped much wider, providing better flame-front ignition. The wider plug gap fouls less readily, giving even worn engines a boost in efficiency. With electronic ignition regular sparking plugs last about 25,000 miles, the new platinum jobbies up to 120,000. Over all, CD ignition insures better combustion, resulting in better fuel efficiency and lower emissions. The engine even runs cooler, thanks to less after-burning in the exhaust manifolds.

A point-switched CD ignition module is the wisest ignition modification you can make to an early VW since it supplants rather than replaces any of the stock ignition components. Indeed, should the electronic module fail you may return to the stock Kettering ignition by simply reversing a plug on the ignition module. Such redundancy is lacking on all modern electronic ignition systems, a potentially fatal flaw since they give no warning of incipient failure.

The most practical CD ignition module for Volkswagens was available from J. C. Whitney until March of 1995 (although it was never advertised specifically for VW’s). Cost was about $50 and installation took thirty minutes for a clumsy mechanic with few tools and no electrical background. J. C. Whitney’s current ‘VW-specific’ CD offerings cost about $100 and requires replacement of the distributor. This newer system, and all others presently offered by J.C.Whitney, use optical triggering. Properly installed, such systems need no adjustment for the life of the distributor, about 70,000 miles in most cases. But as with all optical or magnetically triggered systems, you cannot revert to Kettering ignition without reinstalling a set of points or replacing the entire distributor.

As to the dependability of such aftermarket CD modules, I have installed more than 100 (possibly twice that) with but a single failure, and that one was bad out of the box (and promptly replaced by the manufacturer).

I’ve used CD ignition modules since 1961, building the first few. (I am a ham radio operator.) I have more than 20 years experience with one unit, a Heathkit on my 1973 Datsun the week it was purchased (new). The Datsun has since accumulated 230,000 (on two engines).

-Bob Hoover

VW - CDI Debated

In a message dated 96-02-27 12:30:40 EST, Michael A. Radtke provided an accurate, well-reasoned summary of capacitance discharge ignition modules and inductive discharge ignition modules (other than capacitance charged), in relation to my several articles lauding the advantages of an after-market CDI module over the stock VW ignition system. His well-written dissertation concluded with the following:

THE QUESTION: Is CDI alive and well in current automotive design? What was done about the high voltage issue? >

Mike, Until you raised the question, I had not realized my lack of verbal precision. In my ‘sermons’ I’m guilty of mixing the terms ‘electronic’ and ‘CDI’ when I start waving my arms to convince people to update their Kettering ignition systems.

All of the electronic ignition systems I’ve worked on in recent years (Ford, GM and Toyota) are relatively simple inductive discharge systems that differ from the classic Kettering system only in the manner of switching the coil current. Out of curiosity, I’ve broken open several defunct ignition modules . . . ‘ignitors’ in Toyotaese . . . and found only components consistent with signal amplification and DC switching, no indication of HV inverters or storage capacitors. In so far as I know . . . which is not as far as many think. CDI modules are not used by any of the major auto makers. I assumed it was due to the lower cost of IDI systems but the background you provide in your message casts a new light on that conclusion.

Even so, I feel the factors explored in my articles on electronic ignition, and on which I based my recommendation for the installation of the CDI module mentioned in my article, remain valid. And perhaps I should add that I’ve no association of any kind with that company other than as a satisfied customer.

As to the high voltage issue, it may be a non-problem. Parked down in the field below my house is a ‘67 VW sitting with the engine exposed to the elements, as it has been since it was created more than 15 years ago. The original vehicle suffered extensive rear-end collision damage. The damaged sheet metal was cut away and a sturdy crash-cage of chrome-moly tubing fabricated to protect the engine. This is a typical ‘Baja’ conversion. The engine is fitted with a CDI module and non-metallic silicon/fiberglas spark plug leads. The leads, distributor and module are exposed to the weather. The vehicle has never failed to start, and runs reliably in all weather and temperatures ranging from zero degrees (two occasions) to more than 120 (many times). Such reliability was not always the case, but has been true for at least the last eight years, from when I installed the silicone ignition wires.

As to plug gap and the effect of high voltage, with the CDI modules I use, I gap the plugs to about .045". I arrived at this figure by widening the gap until ignition became unreliable at high rpm, then narrowed the gap by .010". I’ve noticed some variation here between engines of different compression ratio or chamber design but in general a plug gap of between .040 and .050 appears to work quite well with this particular assemblage.

I have not posted your entire message to the list because I believe a private message is exactly that, but I will make this reply a general posting because of my failure to speak clearly on what I consider a very important factor in Volkswagen maintenance. I’m also making this a general post in recognition of your successful effort to clarify the matter.

I believe your insight and experience are assets that make this list of value and would like to hear any other comments you may have on the ‘sermon’ files. I hope you will share them with the list at large.

-Bob Hoover

VW - CDI and $$

CD Ignition and $$$

While there is an initial cost for everything, some things are well worth the expense, as in the case of adding a Capacitance Discharge ignition module to an early Volkswagen engine.

Stock ignition does a fine job at low speed but as engine RPM rises, spark voltage falls. This is in response to fundamental electrical laws. In the stock system, as the points age and the rubbing block wears, resistance rises while system ‘on-time’ falls, further reducing the available spark energy. At 3,000 RPM the available spark energy may be only a quarter of the idle speed value. The result is incomplete combustion and an overall drop in engine efficiency.

CD ignition is justified because it provides 100% of the possible spark energy at ALL engine speeds.

The most notable improvement is increased fuel economy. Some users claim up to 25% increase in miles-per-gallon. In my ‘67 bug I get 35-37 mpg on long trips (>400 miles) at highway speed. Before installing the CD, I got 28-30. On that basis alone the CD is well justified. But then there are the added advantages of reduced maintenance and prolonged spark plug life.

Having used electronic ignition systems on a variety of vehicles . . . including a home built airplane . . . for more than twenty years, finding such systems on modern cars and motorcycle is really no surprise; CDI is superior to what has gone before.

-Bob Hoover

VW - CDI Modules

My articles about capacitive discharge ignition modules, archived by Mr. Richard Kurtz on his web site (the address of which I’ve lost again due to another system crash) generates a fairly constant stream of messages. The questions most commonly asked have to do with the following:

I do not work for Universal Corporation nor do I have any arrangement with them. I recommend their product because it has worked reliably for me in more than a hundred installations.

My recommendation is not based on any formal, quantified product-testing program. I’ve used a number of other electronic ignition systems but MSD is the only brand-name I can recall. The CDI module from Universal proved more reliable than the three MSD modules I tried. I have not used a Pertronics (sp?) system. (Revision Note: I has been about eight years since I wrote this article. Since then I’ve bought, tested and used the points-replacement modules offered by Pertronics and Compu-Fire. Both worked, and equally well.)

I do not know the absolute maximum rpm at which the Universal CDI module will operate with a 4-cylinder, 4-cycle engine but I’ve personally run them for relatively short periods of time, typically less than thirty minutes, above 7,000 rpm with no problem. (For sustained high-speed operation I think it would be wise to direct a blast of ram air at the CDI module’s cooling fins.)

I use commonly available silicon-insulated ignition harness (carbon-core) in conjunction with a stock (black, blue or what-have-you) Bosch ignition coil and Bosch platinum-electrode spark plugs. Using these wires, I’ve not seen any evidence of insulation failure on vehicles fitted with CDI modules. My baja-bug, in which the ignition harness is exposed to the weather, has used the same wires . . . El Cheepo stuff from J.C.Whitney . . . for the last ten years. Indeed, with silicon/graphite ignition harness the only cause for replacement has been failure of the air seals or distributor-tower boots.

The longest service I’ve gotten from a set of stock spark plugs was about 26,000 miles. I had a platinum plug fail after 56,000 miles and changed-out the whole set but I know of a V6 that has accumulated more than 80,000 on a set of platinum plugs and is still going strong.

I use commonly available ignition points, whatever is hanging on the rack at the local FLAPS. I observe the usual precautions when installing the points and lubricate the rubbing block with high-temperature silicon grease about twice a year. The rubbing block lasts . . . however long it lasts, usually about 25,000 miles but I’ve had some last more than 40,000. The points must be adjusted as the rubbing block wears, usually once a year, depending on the miles driven. Aside from some minor flattening, when triggering a CDI module the contact points show no signs of wear.

When it comes time to change the points, I just plug in the spare distributor, replacing the points at my convenience. I do not see the use of a points-triggered ignition module as a liability. The VW distributor normally requires service at about the same interval as the rubbing block wears. It is no problem to include point replacement with adjusting the distributor’s thrust shims. Indeed, the use of points-triggering provides an excellent back-up since it allows me to return to the standard Kettering ignition should the CDI unit fail.

I know of a case where a vehicle got a 25% boost in its mileage after a CDI module was installed... (20 mpg vs. 16) but I suspect there were other factors involved. Typically, I see a 5% to 10% improvement in highway mileage (i.e., constant high speed) after installation of a CDI module, based on a test-run of approximately 102 miles (that is, from my shop to Indian Truck Trail & return). These appear to be valid figures, borne out by longer runs on equally good roads but under less controlled conditions (San Diego to Kansas City & return). I was disappointed by my mileage on the Inuvik Run . . . about 22.5 mpg for about 8,500 miles . . . but the vehicle was carrying a fairly heavy load and the route included about 2,000 miles of bad roads.

CDI modules are a practical way to retrofit modern-day technology to a 1930's-era engine. The engine remains in tune much longer than those fitted with the stock Kettering-based ignition, which works best at low engine speeds. The spark voltage delivered by the CDI module is fairly constant across the operating range of the Volkswagen engine, providing a cleaner burn and better economy at higher rpms.

The strongest endorsement for this type of ignition modification comes not from me but from the automotive industry, which abandoned the Kettering ignition as soon as electronic systems of equal reliability became available.

Several messages asked how it was possible for a CDI module costing less than a hundred dollars to perform as well as a unit costing more than $600. In my opinion, the real question should be ‘How good a system do I need?’ Most of the messages which raise that question are comparing the Universal CDI module to units which claim they can power an eight-cylinder engine at twelve thousand rpm. In theory, when such a unit is used on a four-cylinder engine, it should provide a good spark all the way up to twenty-four thousand rpm. If you commonly run that fast with your Volkswagen, then by all means, buy something other than the Universal CDI module.

No bug or bus uses an engine turning 24,000 rpm. Nor 12,000, for that matter. For the owner of the typical air-cooled VW, the Universal CDI module is more than good enough.

-Bob Hoover

The Odd Thing About CAD...

I use DeltaCAD, a simple, inexpensive 2D replacement for the traditional T-square and triangles, to make patterns for parts, from a 56" rib to itty-bitty things for home-made clocks, tiny steam engines and similar stuff. And I talk about it, too. If you hope to share information at a distance you need good drawings and a simple CAD program is miles ahead of old-fashioned drafting and snail-mail.

That produces a lot of mail, almost all of it from guys telling me why they don't use CAD, or at least, not DeltaCAD. Such as the message I received last night in which the feller explained that the reason he didn't like DeltaCAD -- and only had it so he could print out my drawings of VW conversion parts -- was because he was accustomed to working in fractional inches.

"In the time it takes me to convert 27/64ths to decimal and get it typed in," he wrote, "I could have drawn it a dozen times with a drafting scale."

I had to think about that for a while. A private answer would have been more polite but if one person thinks DeltaCAD can't handle fractional inputs then others might, too. And the truth is, it handles them just fine. Want a line 27/32nds in length? Then select the LINE function, indicate the point of oirgin with your pointer and type in 27/32.

One and nine-sixteenths? Then type in 1 (space) 9/16. Two feet, three and three-sixteenths would be entered as 2'3 3/16.

I can appreciate the feelings some guys have when they're faced with converting a 1920's drawing into a digital format. Back then, everything was in fractions of an inch and American Wire Gauge, neither of which is in common usage today. But DeltaCAD, with which I have no relationship other than as a satisfied customer, really is handier than your T-square, triangles and drafting scale. The odd thing is that so few guys my age think so and I really can't understand why. The complete manual is only 218 pages long and most of that is white-space. In fact, compared to other CAD software DeltaCAD is so simple most guys start turning out usable drawings without ever reading the manual.


Rib Testing

The rib is supported upside down by a jig simulating the wing spars. The load, consisting of a single mass suitably divided by balance beams, is applied to the upper edge of the rib (as positioned in the jig), distributed by pallets of wood as needed to prevent stress concentration.

The test load is divided according to the manner in which lift is distributed across the chord of the wing. For the purpose of testing airfoils having a thickness ratio of 18% or less intended for airspeeds of 150mph or less, the following load distribution has been standardized.

As measured from the nose of the airfoil:

Zone 1 = 0 to 19.1% of the chord Zone 2 = 19.1% to 46.2% of the chord Zone 3 = 46.2% to 90% of the chord

Note that no load is placed on the extreme trailing edge of the rib.

The test weight is distributed according to the following schedule:

Zone 1 = Half the weight Zone 2 = One-quarter of the weight Zone 3 = One-quarter of the weight

Testing Procedure

The mass representing the test weight is to be positioned on a tray or pallet below the test jig, suspended from the mid-point of a balance bar, one end of which applies its load to Zone 1, the other end being divided by a second balance bar so as to apply its load equally to Zones 2 & 3.

When the testing jig has been assembled and balanced, weights are applied to the tray or pallet according to a schedule provided by the designer. The objective is to increase the weight in a graduated manner beginning with large amounts then tapering off with small amounts until the rib fails, at which time the last amount added to the pallet is subtracted from the total.

Practical Aspects.

Ensure you have enough weights on hand. A properly designed rib weighing only a few ounces is usually capable of supporting several hundred pounds.

Lead in the form of pigs, bars or bags of shot has proven to be the most practical form of weights.

Each weight must be individually weighed and marked. The weight of the balance bars, pallet and the stays connecting them must be included in the total weight.

Proof of Concept & Quality Control.

For a new design at least ten samples should be tested in order to define the minimum acceptable standard for strength.

For a proven design, three ribs, randomly selected from each production batch should be tested. Should any of the samples fail to meet the minimum acceptable strength, the entire batch must be condemned.

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The information above has been extracted from static and dynamic testing procedures found in the Civil Air Regulations, Part 04 (circa 1936) and the structural test section of the ‘Handbook of Instruction for Airplane Designers,' Air Corps, U.S.Army (circa 1937)


Post Script: When this article was first posted to the Usenet several people pointed out that today's methods of rib testing are far more comprehensive than those used in the late 1930's.


Screwing On The Cheap

(The original title of this illustrated article was ‘Screwing For Free' until a lady editor pointed out that nothing's really free nowadays.)

In 1991 my wife gifted me with a Makita battery-powered drill. Battery is that long 9.6v jobbie. Very handy tool, especially with the charger that plugs into the cigaret lighter. The tool isn't very useful as a drill for sheet metal work - - heavy and much too slow. But it has paid for itself many times over as a powered screwdriver, nut driver and even drilling an occasional hole, some of them atop radio towers and other awkward places.

Unfortunately, I live near Sandy Eggo, where electrical energy is considered a luxury, along with gasoline (we pay the highest prices for both in the Lower 48). To make matters worse the Quality of Service provided by San Diego Gas & Electric is of Third World standards, with frequent outages and 117VAC @ 60Hz a largely mythical goal - - something to strive for but rarely achieved.

On the other hand, we got lotsa sunshine.

I'm a ham radio operator and have always maintained my own emergency power system. In the 1980's I began plating the roof of my garage with photovoltaic panels, using them to keep a collection of used car batteries charged. Usta be, the batteries just sat there, waiting for the Big One - - the Richter 8+ earthquake that occurs periodically along this portion of the San Andreas Fault - - which is now overdue by a few years and we've been told to prepare for. But since the Oil Patch gang pulled off the big energy scam I've been using my ‘emergency' power system to run tools in the shop and some lights in the house.

And for screwing, too.

I realize most of you aren't hams and wouldn't know an erg from an amp if they walked up and pee'd on your leg but you really don't need to understand ‘lektrisity to use it and that's what this message is about.

May I assume you've heard of Harbor Freight? (If you haven't, lemme know where you live - - I wanna go there :-)

Harbor Freight sells a pretty good variety of PV panels - ‘solar' panels, et al - some of which you can simply plug in to your tools in order to charge them. One of the arrays they sell - - their Item Number 44768 - - is a small (1.5 W.) solar panel designed to clip to the sun visor and plug into the cigaret lighter of your car. While the output is small, it is sufficient to offset the current drain of the electrical vampires found in modern-day vehicles. Given a couple of days, it will also charge your Makita or any other battery-operated tools that's happy with 12vdc. The price? Ten bucks, if on sale. (Hint: Wait until it's on sale.)

Need I mention it will also work in airplanes?

Yeah, I know - - you're one of those rich bastards with a hangar. This message is for all the poor bastards, like me :-) But even if the bird is under cover that doesn't mean the solar panel has to be. Here in the States simply screw it to the south wall (outside, please), angled about the same as your latitude and run some light-gauge flex to the cockpit. (Or to an accessory plug under the cowl.) The nearer you are to the Line, the better it will work. (Sandy Eggo is about 33N; works pretty good.) Standing on your head in Oz? Then point it North. Hernando Chan? Just throw it out on the roof somewhere; the sun is almost straight overhead mostah the time.

Since the thing is designed to plug into a cigaret lighter socket, a handy accessory is a cheater consisting of a cigaret lighter socket connected to a pair of battery-sized alligator clamps. This is a standard 12v accessory among hams, most of whom roll their own bit it isn't that difficult to find already assembled. (All Electronics and American Science & Surplus have each carried them in the past. Which is no guarantee they've got them in stock. Radio Shack may carry them but I don't shop there; their prices are too silly.)

Folks who don't prepare for disaster tend to roll their eyes at those who do. But when Shit Happens, as it always does, it takes surprising little to ensure you will not become a burden on your community; that you will still have heat, light and communications. In the meantime, you can do a lot of screwing on the cheap.


The Best Airplane

England. World War II. An 8th Air Force bomber crew gets a chance for local leave. After visiting several museums -- including going to see the original, one-and-only Wright 'Flyer' (*) their leave ends with a swing past Stonehenge on their way back to the base.

The pilot, a young lieutenant with an aeronautical degree from Purdue says "It's amazing how they managed to do all this without higher mathematics."

The copilot, another young lieutenant with an ME from Georgia Tech gazed up at one of the surviving lintels dimly seen in the fog. "To me the amazing thing is how they knew which stones to use, without any strength-of-materials data."

The flight engineer, a grizzled sergeant a bit the worse for wine whose first radial was also a rotary took another nip from his flask and gave one of the huge stones a friendly pat. "What amazes me is that the sonofabitch ever flew at all," and wanders off muttering, "Best damn airplane ever built."

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In response to several messages from newbies asking "What's the best airplane for me to build?" I've mentioned a number of homebuilt aircraft including John Taylor's 'Titch', Kenny Rand's KR-series, Pete Bower's 'Fly Baby' and Calvin Y. Parker's 'Teenie-Two'. The 'Titch' is a plywood-covered design, similar to the Miles and other examples of that genre including the Hughes 'Hercules' (generally known as the Spruce Goose). The Fly Baby, with it's wire-braced fabric-covered wings is thought of as a fabric-covered aircraft even though the fuselage sides are plywood. The KR's use a plywood fuselage and composite wing-covering although the spars are wood. The Teenie is of course an all-metal design, assembled with drug-store grade pop-rivets and one of the few designs that flys quite well behind a stock VW engine.

There's really no such thing as ‘best' when it comes to homebuilts. I mentioned these particular planes because I'm familiar with them, having flown all but the 'Titch' and have contributed, great or small, to the construction of each type. I believe they offer a good cross-section of what is available and consider them relatively easy to build. Indeed, asking which plane is best is a bit like asking if you should marry a girl who is pretty or one who can cook. (If you can't find a pretty girl who's a good cook, there's no correct answer... it depends on your appetites :-)

Offering an opinion on the Internet always draws a bit of flak. One fellow took the trouble to explain why 'nobody' builds aluminum airplanes anymore... and spent the remainder of a rather tiresome message expounding on the virtues of his particular choice for the ‘best' airplane, a KR, which he referred to as an '...all-composite design.'

Does everyone understand the definition of 'composite'? Plywood is a composite material, as is reenforced concrete. If you mean a structure using some form of re-enforced plastic resin, you'd have to go back about 3000 years -- the re-curve bows used by Mongol horsemen were composite structures. And if you meant with regard to airplanes, molded composites have been in use since before the First World War (using plywood) and the first ‘plastic' airplane flew in the 1930's.

The KR's are a nice example of a moldless composite structure. As with the fabric covered balsa fairing from which they evolved, moldless composites allows an inexperienced builder to easily produce aerodynamically clean surfaces by carving or sanding a core material to match a template. The load is carried by the skin that is bonded to the core and while the skin is usually a composite of resin and fiber, it may also be metal.

The key point here, in my opinion, is not the use of composites but the use of a inexpensive, easily shaped core rather than a massively expensive mold.

Okay, so you all know about composites. That means you understand the limitations of one-off, hand lay-ups when it comes to specifications. Which is that their weight and strength can be all over the ball park. To ensure uniformity you need a good deal of experience or a good deal of tooling, such as vacuum bagging or even pre-molded skins... or you must accept a certain increase in weight, trading that weight -- in the form of extra resin or whatever -- for your lack of experience. And like it or not, most first-time homebuilders are not very experienced.

A majority of those who respond to the ‘best airplane' question insist wood is the only way to go, citing the ready availability of suitable wood - - in the United States - - and the fact every American boy has built a bird house or gun rack. As a matter of fact I never built a bird house until I had grandchildren but the point is valid if ‘best' means access to materials, since you can build a pretty good airplane from any reasonably well-stocked lumber-yard. Cheap, too, compared to most other alternatives. Of course, you need to know your onions when it comes to the characteristics of wood.

With aluminum, here in the States the newbie is effectively subsidized by our aerospace industry. Aluminum is also smart in engineering terms because the newbie starts off with more known, valid information - - there is a spec for the aluminum and for most of the fasteners you will use. Of course, if you elect to use pop-rivets from the hardware store it would be wise to set up a simple testing rig and get some idea as to the quality of each batch. (Just pop-rivet a couple strips of .020 together and use them to lift a hunk of 3/4" ply used as a pallet for your weights. That will give you shear and tear-out strength. For the bearing load, make up your test-strip in double-shear and hoist using the center test-strip.)

In most cases, if you copy a proven design there is a reasonable likelihood it's strength and weight will be within reason. But as soon as you depart from those norms, unless you are using certified materials -- materials having known specifications for strength -- you'll find yourself back in the days of the Wright brothers, facing all the problems and all the unknowns they had to face. The Wright's addressed those problems in a logical fashion, testing before risking. It's a lesson well worth learning.

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Among the more difficult problems encountered by the Wright brothers was the fact Aircraft Spruce & Specialty Company wouldn't answer the phone. Since they were building an airplane they naturally wanted to use aircraft certified parts but in 1903 such things were hard to find. Nor did the Dayton library hold any tomes on airfoils. And when they went shopping for an engine, the local Volkswagen dealer wouldn't talk to them.

It was all very frustrating.

So they built their own wind tunnel and developed their own airfoil data. And they set up a simplistic materials- testing lab to find out how strong was strong-enough, testing wood and wire and fabric. And of course, they had to build their own engine.

Each step along the way they proved what they had discovered with experiments, progressing toward their goal of a powered, man-carrying aircraft in a years-long progression of logical steps, even to the selection of the closest thing they could find to Muroc Dry Lake for their flight-test facility... the sandy dunes along the Carolina shore and a particular spot among them near a village called Kitty Hawk.

After the Wright brothers had flown, things got much better for the aviation industry which had been in a bit of slump until then. For one thing, you no longer had to build your own material's testing laboratory to find out which size of music wire to use, nor figure out how to make a ferrule of the pesky stuff or which grade of canvas made the best wings. The bicycle brothers from Dayton had figured it out for you and offered the information to all who asked.

Having flown one airplane it wasn't too hard to build another. But oh, those Wright's were the very devil to work for! They insisted every part be made just so. It didn't matter if you'd been carving ash wagon spokes for thirty years, the Wright boys insisted wing-struts were different and would fire you on the spot if they found you adding just a bit more beef or trying to make those curvey things they called 'ribs' a little prettier.

Remarkably, when the new batch of copied parts was assembled into an airplane, the copy flew almost exactly like the original. Which of course was the whole idea. And the idea behind standards and certification of those standards was to insure that same thing would happen, over and over again.

As the Russians discovered with the B-29 and innumerable 'designers' with the Teenie-Two, when you steal a design and copy it, the copy will fly pretty much like the original... if you are both a good thief and a good copy-cat.

Aircraft standards are a monument to copy-cat-ism. Buy a pound of AN470B3-5's (those are rivets, by the way) from a manufacturer on the west coast and sonofagun if they don't work exactly the same as a batch of AN470B3-5's purchased from a manufacturer on the east coast! The same holds true for certified aluminum and steel and all sorts of stuff. Even plywood. The 'certs' are reasonable assurance the stuff will meet certain minimum specifications as to strength, weight and dimensional tolerance. Very handy stuff to know when you're building flying machines.

Then there are guys like me, who occasionally make a box spar outta pine shelving and doorskins. (Or landing gear struts out of exhaust pipe.) Then, like the Wright brothers, I break it. By the time it breaks, I know how strong a spar I can make out of that particular batch of pine shelving using plywood from that particular pallet- load. Ditto for foam and fiberglas. Make it, break it and go on from there. Because the last time I checked, there were no certs for spars made from pine shelving. No aviation certification for fiberglas fabric from the local boat shop. No guaranteed strength figures for pop-rivets bought in bulk from J.C.Whitney. When you elect to use such materials in an airplane, like the Wright brothers, you must become your own material's-testing-laboratory.

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Psst! Hey, kid. Wanna build an airplane?

Because you can, you know... others have, meaning you can too. You can build it from composites or plywood or fabric or aluminum... each has certain advantages. And those materials may come from the hardware store, fabric shop and local lumber yard... and may prove perfectly suitable for your flying machine... if you are wise enough to test them.

Plywood, aluminum, fabric, composites... What do you want? A pretty face or a good cook? An expensive party-girl or a steady, stable home-body? Do you wanna build it quick... and lose interest just as quickly? Or are you planning on something you can use to commute to work, year in, year out. Need to get in & out of that strip of beach down in Baja? Or do you plan to use that abandoned SAC base outside of town?

Wanna know the best plane there is? It's the one you decide to build.

The Democratic Process does not apply. The fact all your buds are driving RV's or glasbackwards plastic planes doesn't mean you should too. The plane you select will be the one that most closely matches your particular mix of money, space, tools and experience.

The truth is, yammering about the best this or the best that is mostly a waste of time. You must decide; you are the Mechanic in Charge. But once you've picked a design, stick with the plans! If you do something every day to further the project you'll be flying in a matter of months. Seriously. The secret is in the habit of doing something on the airplane every single day and in NOT deviating from the plans.

No one does, of course. Everyone is smarter than the original designer. Or fatter. Or taller. Or richer or poorer. So be it. If you depart from the plans, the Wright brothers have laid a clear trail for you to follow in how to ensure your new design -- for that is what it is, once you start tinkering with someone else's plane -- will be strong enough. And light enough. And smart enough to fly.

-R.S.Hoover -EAA 58400

(*) So how did the epitome of American mechanical genius come to be dangling in a British museum? Look it up. It's a lesson in how power, wealth and politics may be used as a weapon against the common man, then as now.

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The Best Airplane is a recurring theme among wannabe homebuilders. This (edited) article was first posted in July of 1999. Same question. Same answer :-) Steel tube & rag wings were not mentioned here because they were addressed in an earlier article (‘Flying On The Cheap')

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