Friday, April 27, 2007

Drilling for Eight

Almost as soon as I posted '4-into-8' (which should immediately precede this article) I began receiving messages saying the drill-jig I've been using since the early 1970's didn't work. (!!) I even got a couple saying it didn't exist... and if it did exist, it wouldn't work. :-)

(That's it over there on the left. And just for insurance there is an uglier-but-identical home-made copy of it in my toolbox.)

What works (and exists) according to the instant experts, is a different type of drill-jig having six holes instead of eight. According to the folks who wrote, 'everyone' uses the six-hole type, pictured on the right.

I don't.

As I said, I've used the 8-hole type -- successfully -- for more than 30 years and think this whole discussion is a bit lame, partly because of the assumption on which it is based but more so on the fact that, having used both types, I've found the 8-hole version to be not only more accurate, since it is indexed using four dowels, but far easier to set-up and use.

Over on the right you can see the drill-jig installed in the spigot of a cut-down flywheel.

The four new holes are drilled using a 5/16" bit, a spindle speed of about 900 rpm and a liberal dose of cutting oil. (I use SulTex.)

After drilling, the holes are sized depending on their use. If they are in the crankshaft they are reamed to 8mm; if in the flywheel they are opened up to Letter Size 'O'. The edges are carefully chamfered, the part is cleaned and you're all done.

So what's all this nonsense about the thing not working? (Or not existing :-)

As a matter of fact, it is possible to screw things up. If you put the drill-jig on the clutch-side of the flywheel, for example, the off-set hole will now be off-set in the OPPOSITE direction. Hammer as long & hard as you like, a flywheel drilled in that fashion simply won't fit.

I think that's what's behind the messages. Somebody did it wrong, blamed it on the drill-jig, and told all his buds that the thing didn't work. And if you've been on the internet for more than five minutes you're probably aware that 99% of the 'information' you'll find there is hearsay; people parroting something they've read or heard, as opposed to direct, personal experience.

When the 8-hole drill-jig is used correctly, you'll end up with a tight, precise fit. And I've got pretty good evidence it will last a long time if given a bit of care.


Thursday, April 26, 2007

Stoning Your Rods

Last Sunday after church I was chatting with an Eager Young Airman building a Volksplane. Started around Christmas, he’s just finished covering the wings and was about to start on his engine.

“The parts are due to arrive tomorrow,” the Eager Young Airman said. “I’ll put the engine together after I get home from work.”

I must of done something because he squints at me and sez: “What?”

How do you explain chartreuse to a blind man? In the end I merely shrugged, “I generally take a bit more time.”

“Yeah,” he smiles. “I’ve read some of your stuff.” He doesn’t laugh aloud but you could hear it. “I’ve put together a lot of engines,” he brags. “I won’t have any trouble.”

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(And with that kind of a lead-in you can guess what comes next :-)

Around noon-time Thursday he called me from work, a bit less perky than before. Was there a chance I could come by his house that evening? He’s having a bit of trouble with his engine.

No. In fact, hell no! He lives some distance away and the local freeways slow to about 15mph between five and seven. “What’s the problem?” I ast him.

Pregnant pause then: “Nothing seems to fit!” His voice is filled with frustration, exasperation and - - to his credit - - a hint of embarrassment.

“Like what?”

“Well... the rods lock-up.”

“You got the right bearings?”

“STD’s,” he sez. (In Engine-Tok that means ‘Standard,’ rather than a dose of clap.)

“On the carton or on the bearing shell?” He doesn’t answer, which means the carton was marked STD. He’s got no idea in the blue-eyed world what was inside of the box. “Didja mike the crank? ID the rods?”

His answer is: “It’s all brand new stuff!” (Which means 'no.')

I can’t help but laugh at that. “Yeah, but from where?”

Turns out, he doesn’t own a 3" mike; doesn’t even know the spec for the crank’s journals. I tell him to bring it by the following day, let me take a look at it.

Friday evening he shows up with an engine’s worth of parts rattling around in his back seat. I’ve cleared some bench space and as we’re hauling the parts into the shop he mentions that it’s twenty-seven miles from his house to mine, which is about five dollars-worth of fuel each way. He sounds sort of surprised.

“No kidding?” (Okay, mebbe with just a hint of irony :-)

His crankshaft is one of those Chinese jobbies, an 82mm stroker for which he’d paid less than $200. Why so cheap? Partly because it's not very good. The #2 rod journal miked more than a thou over spec and the #1 Main was 2.1638" - - four tenth under the lo-spec of 2.1642". Run-out is seven-tenths, right on the outer limit. He starts yelling about returning the parts, suing the retailer for his lost time and other Yuppie bullshit.

“Don’t bother,” I tell him. “Shop by price and this is what you’re going to get. This is the norm nowadays." Trying to sue the people who sell this junk is throwing good money after bad.

“But it doesn’t fit,” he wails.

“Of course not,” I said. He makes a WTF gesture. “Making things fit is your job,” I tell him.

“I’ve never had any trouble before,” he says. Which means he’s probably only worked on stock engines.

I’m checking his rods. They aren’t new, they are stock rebuilt units that happen to be too short for use with an 82mm crankshaft. Enormously popular, of course. But as rods go these happen to be a pretty good set, with a weight span of only 4 grams. He follows me back & forth as I lighten the two fat rods to match the two skinny ones, each of which weighs within a tenth of a gram of the other. Of the two heavy rods, one is a tad less than two grams out, the other just over four. Four grams is a lot of grinding, followed by smoothing things up with the belt polisher.

He has never seen the jig for doing big-end/little-end balancing, asks: “What’s that for?” Which tells me I’m wasting my time.

I split the rods, pull them apart. None have been stoned; all show the usual burr created by honing. (Note: Stoning away the sharp feather-edge left by the hone produces a distinctive line of light. Steel-backed bearing shells usually require the same treatment, at least on the back-side of the shell.)

I show him the burr, let him feel it. On one rod the burr has a wrinkled appearance, apparently folded under when he installed the shells. It's more than enough to cause the rod to lock-up. He can’t believe it. “Where’d that come from?” I toss his new bearing shells into some lacquer thinner while I stone his rods, wiping away the burr. Then I clean his bearing shells and do the same with them.

“I never had any trouble before,” he says again in a voice small enough to ignore, which I do.

Chucked into the vise and torqued to spec, the mikes show the usual spread across the rod’s big-end ID’s and I paint a big ‘2' on the fattest of them. Over on the clean side of the shop is two shelves of bearings, odds and ends acquired over forty years of building VW engines. Which happens to include a set of ‘Silverline’ conjinetes para motor that I know to be a few tenths under spec. I clean the rod and install the shells, put the assembly in a plastic bag. “Take your crank to HDS in Escondido and have them polish a couple of tenths off the #2 rod journal.” Since shit happens, I use fingernail polish to mark the correct journal. “When you get it back, after you pull those damn plugs and clean the thing, install this particular rod on #2.”

Some of the oil passages on his Chinese stroker are drillings sealed with 4mm socket-head set-screws. They need to be pulled and the oil passages cleaned then re-installed with Loc-tite and straked. Which he hadn't done. But even as I explained the what & why I had a hunch he wouldn’t bother. After all, he’s built a lot of engines. And never had any trouble.

He’s been here nearly two hours. His particular collection of parts will probably need another twenty hours of work before they’re ready for assembly but I've a hunch it's never going to happen. It’s late, I’m tired and he still thinks its all bullshit. So I wish him good luck and wave him on his way. Maybe he'll read this and get the hint. But after spending two hours with him, I doubt it. Really good engines are more than an assemblage of parts.

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Is this sort of thing common? Nowadays the answer is a loud ‘Yes!’ The surface-finish of the guy’s crankshaft was pretty bad (it should look like a mirror), a fact he’ll learn for himself when he sees the difference between the journal polished by HDS (an automotive machine shop) and the other journals. Other than being the wrong rods for the engine, they were okay but the cam was a joke, intended to move the power-band well above the point of optimum efficiency for a propeller. But trying to explain such things is usually futile. This particular builder has some prior experience but it’s of the ‘Compleate Idiot’ variety, where you’re told it’s okay to scrape machined surfaces with a pocket-knife and pound on bearings with a sledge hammer. (I’m serious here, folks.) He's convinced that my attention to detail is unnecessary. After all, he's assembled a few engines and they ran just fine... in a car.

I wouldn’t want to fly behind the guy’s engine but that applies to most of the converted VW’s I’ve seen. So long as the ‘experts’ are telling people it’s okay to paint their engine with barbecue paint and that it will rust out before it wears out, we’ll continue to see newbies risking their lives behind improperly assembled engines.


Saturday, April 21, 2007

4 -- into -- 8

As originally designed the Volkswagen’s flywheel was located using four 7mm dowel pins. The pins were quite short, extending barely a quarter of an inch into the crankshaft and even less into the flywheel. When the Porsche 356 was introduced in 1948 it used many Volkswagen components including the engine, although with numerous modifications. One of those mods was to replace the flywheels four 7mm dowel pins with eight pins. When American hot-rodders began massaging the VW engine one of the first things they did was to re-dowel the flywheel following the Porsche pattern but using 11/32" (8.73mm) dowels three-quarters of an inch in length, seating the dowels deeper into the crankshaft and full depth through the flywheel. Volkswagen eventually followed the American’s lead - - as they did with many other hot-rod innovations such as case-savers and the external oil cooler - - but using only four 8mm dowels.

Four 8mm dowels proved sturdy enough even for fully laden Transporters but eight dowels have become standard for all high-rpm engines. One reason for this is that in the Porsche pattern one of the extra dowel pins is offset by 1.25mm, allowing the flywheel to be indexed to the crankshaft in a specific orientation. Since the crankshaft and flywheel are balanced as a unit for high rpm engines, the Porsche pattern ensures the as-balanced orientation will not be disturbed.

Nowadays most VW engines converted for flight draw upon the VW racing community for parts and while 8 dowel pins are not needed in a flying Volkswagen, after-market crankshafts usually comes with the extra dowels already installed. This leaves the homebuilder with two options. They may remove the extra four dowel pins, being sure to pull the set that includes the off-set pin, or they may re-drill the component that must mate to the 8-doweled crank.

Here's a Great Planes flywheel-end flange about to be drilled to fit on an 8-dowel crankshaft. Steve will sell it to you already drilled for eight. Or sell you a drill-jig (but not like mine) so you can do the job yourself.

Pulling a flywheel dowel is a no-brainer if you’re tooled up for it, which most homebuilders aren’t. The basic tool is a slide-hammer with a set of metric collets - - probably $150 at todays prices (2007). The tricky bit here is that collet sets aren’t created equal. In some, the collar is too large to allow the 8mm collet to get a bite on a VW’s dowel pin. Then too, even with the proper collet some dowels refuse to budge, usually because a bit of swarf was trapped in the bore when the dowel was driven home. And finally, there are homebuilders who simply can’t afford an 8mm collet, let alone a whole set.

A reasonable substitute for an 8mm collet is a cheap pair of vise-grips. Not real American-made Vise-Grips with their hardened jaws but a pair of cheap Chinese copies with jaws that flatten out the first time you use them. Find yourself a set like that and you can make a dandy dowel puller by simply drilling the jaws with a letter-size ‘O’ drill (which is pretty close to 8mm). (Dressing the jaws flat with a file will increase their grip on the dowel.) Add a whiff of valve grinding compound to the jaws and they will grab ahold of the hardened steel dowel even more tightly than a collet.

Heating the crankshaft to about 200 F. is always a help in pulling dowel pins.

Finally, when you get one that is seriously stuck, install a round-nosed punch in a chatter gun or riveting hammer, press it firmly against the bottom of the threaded bore on the pulley-end of the crankshaft and give it a brappp whilst pulling gently on the collet. The dowel will ‘walk’ out of its bore like a magic trick.

The other option - - re-drilling a part to match the 8-dowel crank - - is equally easy. You simply buy a suitable drill-jig from an after-market VW retailer. I took a snap-shot of the one I use, along with an assortment of dowels. It’s more than thirty years old and still works okay. But shop around. In writing this article I checked with half a dozen sources and found the price of a drill jig varied from less than $20 to more than $70.

The hole is always drilled undersize, of course, using a 5/16" drill bit. For a press-fit, once drilled, you use an 8mm reamer to bring it to size. The reamer you use for your valve guides will work but you’ll get a better finish on your guides if you reserve a carefully honed reamer for that task alone. For dowels, a cheap foreign-made reamer will work just fine. But again, shop around. Lotsa guys will charge you fifty bucks for an eight-dollar reamer. If you want a free fit you’d drill it out with a letter-size ‘O’ drill bit and not bother with the reamer. In either case, always chamfer the edges of the finished hole.


Friday, April 20, 2007

Rainy Friday

Gravity is silent. The stately tick-tock of the pendulum clock is the only sound in the shop, the lathes and mills lurking beneath their shrouds as I try to reason with Mr. Ohaus. Unlike the clock, which is made of wood, Mr. Ohaus is a man of metal but both are powered by gravity. A spate of rain sweeps over us, loud on the metal roof out behind the shop and for a moment I hope it will somehow change Mr. Ohaus’ mind but he is stubbornly insistent: the connecting rod weighs 605.9 grams.

Deep sigh.

I take the rod out back where the narrow belt of the polishing sander whisks away another film of metal, first on one side, then the other. Then follows a careful cleaning and back to the scale: 605.7, less a tad. I repeat the ritual as more rain blows in, a regular shower this time. I give the belt-sander two-potatoes less than before, clean the rod, weigh the thing: 605.5, plus a tad.

Big Smile. Because 605.5 grams is what I’ve been chasing for the last half hour, hiking back & forth between the sander - - a ‘dirty’ tool not allowed to associate with lathes and the like - - and the Ohaus triple-beam balance, trapped in its varnished cedar box over in the corner with other Precision Stuff.

A stock VW con-rod is about 5.4" c-t-c. Forged from mild steel, its weight may range from 505 to 550 grams. They are sold in sets graduated by weight with a 10 gram variation across the set of four. But for a good engine you want them to all weigh the same, or close to it. The rods I’m working on today aren’t stock. They are 5.6" c-t-c, intended for use on a crankshaft having a throw of 84mm (stock is 69).

This is the fourth set of rods I’ve ordered for this engine. The first three sets had been tampered with, probably by the clerks who shipped them, so that the weight difference across the set of four was as much as 16 grams. Since you can only remove about seven grams from an H-beam rod, it renders them unusable in a properly built engine. Which gets you a massive shrug from the people selling such junk.

This particular set of rods was ordered on 15 March from a retailer less than a hundred miles away (G.Serrano in Torrance). After several phone calls the rods finally arrived on 20 April. Fortunately, the set proved usable but even then, the carton had been opened and one of the rods removed from its protective wrapping. Had the set NOT been usable it would probably have taken another month to obtain replacements or a refund, which will help you understand why it has taken five months and three different retailers to obtain a suitable set of rods for this engine. In one case I was forced to pay a ‘re-stocking fee’ even though the parts were not to spec. Air-cooled Volkswagens are a vanishing breed and most of the remaining retailers simply shrug; take it or leave it, we’re only here for the money.

(So what to do? Buy your parts from Steve Bennett at Great Plains Aircraft Company. He builds his engines differently from the way I build mine but he’s an honest person and you will benefit from obtaining everything from a single source.)

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In the mid-1950's the Ford Motor Company published (in the SAE Journal) the results of a decade-long test comparing the wear of engines fitted with a full-flow oil filtration system to other maintenance strategies, including frequent oil changes, by-pass filtering and so on. Full-flow oil filtration was the hands-down winner, reducing some types of wear by as much as 60%. Which is why all modern engines are equipped with full-flow oil filtration.

All of the VW engines I’ve built since the late 1960's have been fitted with a full-flow oil filtration system. This is accomplished by blocking the normal output of the oil pump and installing a new pump cover having a threaded fitting. The full output of the pump is plumbed to a filter canister then returned to the engine via a threaded fitting installed in the main oil gallery.

The VW oil pump can produce up to 300psi and a basic rule of engineering is that the first thing ‘seen’ by the output of such a pump should be a pressure relief valve, so as to protect the system from excessive pressure. The full-flow installation in the typical VW engine violates this rule since the filter canister is the first thing seen by the pressurized oil. Since the typical oil filter bursts at about 100 psi, starting a VW on a cold morning can be one hell of a mess.

(Yeah, they make high-pressure canisters... which typically cost $10 and up, when you can find them.)

In comparison to the connecting rods, finding a suitable oil pump cover is a slam-dunk. I called Dee Berg, widow of Gene, chatted for a few minutes and had a pair of suitable pump covers in my hands about eighteen hours later. (Gene Berg Enterprises is even farther from my shop than the outfit selling the con-rods :-)

Gene made his pump covers out of high-density cast iron that wears even better than the stock VW pump cover. He also offered a cover fitted with a ball-type pressure relief valve (GB-239x) that pops-off at about 90 psi that has become the standard for all serious engine builders. It costs significantly more than the bubble-pak’d cast aluminum crap but it’s money well spent. Not only will you recover the cost by about the fifth oil change, the cover will last in excess of 100,000 miles if treated with WSX (ie, tungsten disulfide dry lubricant). By comparison, even when hard anodized an aluminum cover will wear beyond spec in about 10,000 miles and show a steady decline in pressure thereafter.

Ed.Note: A reader suggested I define '...significantly more..' When I ordered the GB-239 pump cover in April of 2007 the price was about $50.

On the back-side of the GB-239 cover you can see the large hole for the normal outlet and the small hole for the over-pressured oil to feedback to the inlet-side of the pump.

Before using the GB-239 I take it apart, clean it good and break all the edges with a file. The socket-head screw securing the pressure spring goes into the jig and gets drilled for safety wire. The sharp edges of the outlet port are polished smooth then the Blanchard-ground surface is burnished on a surface plate using #600 W&D flooded with WD-40. After a careful cleaning the valve is re-assembled and the flatted surface treated with WSX (ie, a Tech-Line product).

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The rain has turned into a steady drizzle, a welcome background for the tick-tocking clock. The day has gone gray as I lock Mr. Ohaus into his shiny wooden box, wipe down my tools and put things away. I stopped building engines for sale years ago, devoting more time to horology, itty-bitty steam engines and black-powder, which makes it kinda hard to explain why there’s so damn many engines in the shop. Probably because it’s good fun - - plus, you get to go flying now & then.

The coffee is hot in the house and there’s a screen-full of mail to be dealt with plus a pride of indignant cats pointing out that water is falling out of the sky and wanting to know what I plan to do about it. Guess I’d better get busy...


Sunday, April 15, 2007

VW - What's an Old Bus Worth?

One method of determining the value of something is how much someone is willing to pay for it.

Everytime someone sees a $25,000 bug or $45,000 bus they say "That's crazy!"
Then things get crazier :-) Because another method is 'Replacement Cost;' the amount you would have to pay to get the same reliability, load-carrying capacity, fuel economy and so forth. The crazy part here is the fact that no modern-day vehicle can even come close to matching the attributes of my 1965 Volkswagen bus.

People laugh at my old bus. Big, ugly roof rack. Dented nose. Scaberus
paint. They laughed at it in Alaska. Mexico, too. Back east, its tatty looks and California tags earned comments at almost every fuel-stop. It even draws smiles out here in the western US.

Old VW bus makes a hell of a good joke, even when it's in better-than-new mechanical condition, always starts, pulls folks out of the ditch or collects them from a snow bank and keeps chugging right along. Great story to tell the folks when you get home. I've even read about me on the internet (!) Crazy guy in an old bus, pops up out of no where, gives the idiot a gallon of gas then chugs off into the night. It makes me sound like the motorized version of the Flying Dutchman :-)

The main reason I haven't painted my bus is because I actually drive it. It's my daily driver -- a working machine instead of some Yuppie's toy. Make it pretty, the odds are it would get stolen, which is a pain in the ass even when you get it back. (Do you know about TinyTrac? GPS? Ham radio? Swipe my bus and you will :-)

A point all the Yuppies miss by a mile is that, dollar-wise, using an old car for transportation is right up there with Unified Field Theory when it comes to smarts, assuming you know how to keep it running. My wife and I just finished putting together the package for the tax man. Last year 2002) I didn't drive my '65 bus as much as usual, barely ten thousand miles. Total cost, as in TOTAL cost... tags, insurance, gas, oil, filters and two used tires, came to $1,107 for 10,053 miles. (I'll let you do the math :-)

What's my old bus worth? Based on how much it saves me compared to driving anything else, a conservative amount would be in the mid-six figures (ie, life-time 'worth). Of course, no one will believe that. Not now. When they're older, mebbe. Folks usually begin to understand it when they hit the big Five-Oh and look back on their life and wonder where all the money went :-)

If this leaves you wondering what the hell I'm talking about perhaps you should look into the Forever Car philosophy and get acquainted with the real cost of personal transportation, most of which goes for interest and taxes. An old vehicle, one you can maintain yourself, cuts you out of that loop.

Yeah, I know. You couldn't possibly do that. You don't have the time or the tools or the space or the... whatever. And besides, it ain't kewl. It would make you stand out from the crowd; people would laugh at your old bus, even when the joke's on them.

Up to you. It's your money.

-Bob Hoover
-(originally posted in 2003)

Wednesday, April 11, 2007

Drying out a Gauge

Sean writes:

I've noticed something quite annoying: Sometimes, on humid or rainy days or nights, when I turn the headlights on and, consequently, the internal gauge lighting, the gauges fog up from the INSIDE, and eventually the warmth of the internal light defogs them, but it takes a good long time. Why do they do this? Humid day at the factory when they sealed the gauges or what??? It's really really annoying. I don't recall the oil temp gauge I had in the '78 doing this.



The fog inside your instruments may not be water vapor. If could be volatile vapor from plastics or paint used in the gauge. If so, it may dissipate in time. But the odds are, it's water vapor. You are going to have to get the water out of your gauge or it will go bad.

You can 'de-mist' a foggy gauge by making a desiccant 'getter', such as cubes of gypsum board, baked in a warm oven for two or three hours then sealed into a balloon or Mason jar, having a brass nipple soldered thru its lid.

To demist the gauge you must make a hole through its case and couple the dry atmosphere from your 'getter' to the moist atmosphere inside the gauge using a bit of tubing. You can promote an exchange of atmosphere between them by using a bit of heat.

I realize there is some hazard associated with making a hole in your gauge but the risk is often less than the damage that will be caused by the moisture. If the body of your gauge is plastic you should be able to melt a tiny hole in the case. If the case is metal, the best method is to punch a hole in the case using a needle you've made for that purpose.

But before you begin making holes in your instruments you need to figure out how you're going to connect the desiccant bottle and how to seal the hole when you're done. The usual method is make a nipple onto the instrument case by attaching a short length of brass tubing to the body of the instrument with one of the commonly available filled-epoxy resins such as J-B Weld or similar. Such nipples would normally be placed on the rear of the instrument.

To melt the hole in the case you pass the heated wire down through the brass nipple you've created. A paper-clip, straightened and secured to the tip of a soldering iron is handy for melting small holes in plastic. The nipple also serves to guide the needle when punching a hole into a metal case.

The instrument is then plumbed to your desiccant 'getter' using vinyl tubing. Obviously all components are selected for their fit. Hobby shops that cater to model airplane builders carry a variety of fine-gauge brass tubing as well as vinyl tubing of matching diameter. A straight piece of hard 'music wire' about 3/32" diameter by three inches long, sharpened on a stone to a fine needle-point, makes a suitable punch for metal-cased instruments. In the latter case the brass tubing for your nipple should have an ID to accommodate your 'needle'.

Once the moisture has been absorbed by the desiccant 'getter', the hole in the instrument case is sealed with wax or an RTV compound.

But the odds are you needn't go through all that trouble. It is rare to find a sealed automotive gauge (which is how the moisture got in there to begin with). Nearly all inexpensive gauges are vented to the atmosphere for the simple reason they would implode at high altitude of they were not. (Expensive gauges are sealed but fitted with a metal or rubber diaphragm that flexes with changes in atmospheric pressure.) When there is already a hole in the instrument case it may be possible to replace its moist atmosphere with a dryer atmosphere by simply blowing 'canned' air into the thing.

On more complex instrument panels the gauges are often plumbed to a desiccant chamber fitted with a bladder to accommodate changes in atmospheric pressure.

Copyright © 1997 Robert S. Hoover