Tuesday, December 5, 2006

VW - Hoover on Trikes

> I've seen trikes that run without a fan or engine tin at all, and >that's one option I'm considering.


Don't. Unless you live in Norway.

The cooling equation calls for a given rate of air flow down through the fins. Keep that in mind all the time because no matter what it looks like, the VW is not an airplane engine; it wasn't designed to use ram-air cooling. It uses an engine-driven impeller to pump air into plenum chambers where it is directed to the corners of the engine (ie, the hottest parts) and then forced down through the fins which are drafted according, having an outlet area slightly larger than the inlet to accommodate the expansion of the air as it absorbs heat.

What you got to get a handle on is that to make the flow go, there has to be difference in pressure. It's not a lot and is normally measured in inches of water instead of inches of mercury and mercury is heavier than lead for crysakes... about 14x heavier than water. All of which means you're not talking about a lot of pressure and that means it is easy to fool yourself that things are getting lotsa air when they ain't.

How much? Airplane engine, designed to use ram air, with forged heads and machined fins on the barrels and lots of other neat little tricks, you need a minimum of about 6" of water pressure-differential equivalent to keep the engine's temps within spec.

VW, with its cast heads and fins needs more. A lot more. Such as 9" of water.

What's that in miles per hour for ram air? 120, 140, something like that. Doesn't really matter because whatever it is, sure as babies shit green you ain't going to see it on three wheels with a VW under your butt.

Standard Day is pretty cool. Run up to visit the Presidents, you won't see many Standard Days coming or going. Sturgis isn't Narvik and that kewl Norsky bike we all admired in the magazine, with its chromed barrels and chromed valve covers and no shrouding and all that other neet stuff has probably got a trailer & a Volvo to pull it tucked into the trees just out of the photo.

It really gets down to if you want to talk three-wheeling or ride them. If you want to ride, you need a reliable engine. You can hang all the chrome on it you want but you can't fool with Mother Nature and she's the gal that wrote the book on thermodynamics. So dress it up. Blind those fools! But under the shouding, inside the engine, you gotta obey the rules because it ain't nice to F**k with Mother Nature.

If you go with one of those Taiwanese blower housings... ( "Early Porsche Style!" All bullshit, of course. The round Porsche housing weighed about as much as Buick; that piece of Taiwanese crap will fall apart if you yell too loud.) ...you'll have to tinker with it to get it accept the thermostatically controlled air vanes, then you'll have to make a connecting rod to fit. The key point on the air vanes (yes, you need the thermostat and all the junk that goes with it) is that they have to align with the middle fin on the heads when fully open. The air vanes have their own frame. Look at a regular blower housing to get some idea where the holes have to go then put the thing in position and start tinkering. (Yes, you need the engine assembled and the alternator mounted).

Paint the crankcase with a light coat of flat black Rustoleum. Ditto for the valve covers and your push-rod tubes. Yeah, I know -- everybody else sez.... Just look them right in the eye and say, 'God told me to do it,' then shut up and keep looking at them. You can repeat it up to three times if you have to. After that it's obvious you're dealing with a heathen so just go ahead and deck the sucker. (Hanky and a roll of quarters; dimes if you got small hands. Wind the hanky tight. Bust a knuckle, you can't shift for shit.)

Balance everything to a gnat's ass or finer. Lighten up your flywheel. You won't be pulling any stumps so go ahead and pick a wiggle stick that'll let that puppy rev. You don't need a lot of cubes for a trike. Machine-in 88's are smart; even stock works good. Run an oil filter but not a filter/pump adapter unless you got one that actually fits; do it right. Round up the parts to convert your crankcase to use a dog-house cooler. You can run one of those itty-bitty Porsche-type blower housings if you want, just make sure you get one that will accept the thicker fan and that has all the bits & pieces for the dog-house. And you gotta run all the tin-ware. Use cool-tin under the jugs but you got to modify the lower shield to accept the cool-tin plus you gotta modify the lower shield to mate with your J-tubes.

What you're creating here is the lower plenum chamber of the cooling system. It has to be sealed off from any ram air produced by your forward motion but open to the rear, where you want a lip to create a good suction zone. You got to do all this and get it to fit perfect -- no gaps or leaks at all -- then you got to spend about a thousand hours making it smoother than snot on a door knob before you take it to the plater and see if he'll accept it. You know the guys I mean; the ones who still know how to do real chrome, starting out with a layer of copper then a layer of nickel then a layer of chrome thick enough to shrug off salt water, cigar butts and the occasional state bird of Texas.

Now, you see that dog-house oil cooler? See that cute little exhaust duct, where it's supposed to poke through the forward breast tin that you ain't got? For homework this weekend I want you to whip up a duct that arches down and under the lower shrouding. Doesn't have to extend aft very far, just so's its below the shrouding and pointing south when you're going north. Bell the mouth a bit to provide some suction. Put a couple of nut-serts on the lower shrouding to support it. You'll probably have to safety-wire the bolts.

If you promise to never go over 5000 rpm, not smoke, don't use any swear words and be home by midnight you can use a stock crankshaft. Otherwise you want one with counterweights on the flanges and you want it and the flywheel and the pressure plate and the fan pulley all assembled and torqued and balanced as a unit.

Don't look at me like that, it's not my idea it's Mother You-Know-Who with her idiot son Isaac Whats-his-name and all those Laws of Motion bullshit, with his phlugoid motion this and axis of rotation that.

Yeah, I know. None of your buds do it that way. But when you put the hammer down most of your bud's engines start doing the River Dance. Yourz'll be doing the lambada.

I guess you know you can't fly a trike. You've been on one, haven't you? You know you can't use your elbows as curb feelers anymore dontcha? All you can do is sit there and steer. Like a geezer on his Courtesy Cart at Wal-mart, right down to the cute little flag on the antenna. Trikes ain't bikes and you gotta learn to live with that. (Find an old 8-track, put it in there somewhere. Couple of Lawrence Welk tapes where guys can seeum. Mention how much you and 'the little woman' enjoy your 'motorcycle.' Shuts them right up, except for the snickers. But when you blow past them doing ninety going up a grade they won't know whether to shit or go blind :-)

So whatllya get for all that horsepower-wise? Not as much as all the bullshiters claim but more than you'll need to kill yourself. You'll probably end up with squirrely dual-carb arrangement that'll wear out the engine from running rich and sucking in dirt through those tea-cozy air filters before you ever get the thing running right. But anything other than a dualies, you'll have trouble with carb and manifold icing because of the exhaust system you'll probably use. Nothing wrong with dual carbs -- VW used them on the Type III & IV, as did Corvair and lotsa others. But most of the after-market dual carb kits are crap. Unless you spend some serious bucks for the Good Stuff, the cross-bar will fall apart the first time you rev the engine, the filters are a joke and those push-on fuel hose fittings are as scary as an ex-girlfriend waving a MAC-10.


Despite all that, get it running, it's a lot of fun, assuming you remembered to do give it a brake job :-)

Now, what all the above was in lieu of is the fact there's a world of difference between something that runs and something that runs sweet. Starts at the first touch of the button. Nice idle. Twist it and she winds right up, no stumbling or hesitation or jerking around. And it not only runs sweet, it runs cool. After your dog, death and taxes, a properly built engine is the one thing in your life you can count on. I'm not just talking reliability or durability, I'm talking old fashioned loyalty. You can't buy it and you can't bolt it on, you have to build it in.

-Bob Hoover

PS -- the gear shift linkage doesn't have to be such a pain in the ass. To support the gear shift lever, try and get ahold of the shifter out of a bus. It's got a supporting sleeve on the front that pokes through a bushing in the shifter frame. You're going to be higher up and at an angle to one side or the other, as comapred to the shift-rod installation in a bug or bus. Don't try to over-engineer the thing, just go ahead and weld a stub onto an old coupler so the stub sticks up above the torsion bar housing where you can get at it. Use aircraft style ball-end fittings. You want at least one threaded section so you can take out the slack as wear accumulates. The shifter-rod don't have to be straight, it'll still work even with some bend to it.

Good luck with your trike and write if you find work :-)

1 comment:

jon strom said...

Subject: cool tins vs. deflector plates

Hi Bob,

I have been reading and re-reading your blog entries as I prep my engine for assembly. I have learned a wealth of knowledge from your experience and logical explanations. One thing you seem to have not discussed is the difference between Type one air deflectors that mount under the cylinders and the Type 3 "cool tins" that are all the rage at the kiddie parts stores. You mention cool tins briefly in your entry about trikes, but I have found a can of worms on websites such as Samba, etc. when researching the difference between these two methods of cooling the cylinders effectively. My Type 1 upright engine is bound for a fiberglass kit car, that does not have a method of sealing the bottom half of the engine compartment from the top half as in a stock VW. I am ducting fresh air to the fan intake from a remote location, but I still am unsure of which method is better at cooling the (bottom side of the) cylinders.

The argument seems to be VW designed the cool tins to be used with the "pancake" engine cooling setup, and are ineffective when using an upright fan housing, and then there are those who swear by them. I am just trying to discover which is actually better at keeping my cylinders cool. Using the "cool tin" style would make it a lot easier to create a vacuum/venturi effect to help exhaust the hot air out the rear of the vehicle and prevent it from recirculating back to the fan intake. But I don't want to use them if they are ineffective at keeping my cylinders cool.

Any insight of yours would be appreciated.


Jon Strom CBTE
KDSM Fox 17

April 15, 2009 2:47:00 PM PDT