Images/Ideas for Street Bike Engine Powered VW Bug

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Fred
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Images/Ideas for Street Bike Engine Powered VW Bug

Post by Fred »

Things about sport bike engines that may not be obvious:
  • Gearbox is integral in block like an old mini
  • Output from gearbox is single splined shaft that usually carries a sprocket
  • No reverse gear at all
  • If driving from this using a chain to a diff, you must have the sprocket on the rear of the engine or you'll get 6 reverse gears and no forward (yes, this is obvious)
  • Sprocket is offset toward centre of engine rather than out at extreme, so you can't run it forward from here as is
There is an R1 Bug on youtube, but it's mid-mounted with a chain drive down toward the rear axle. http://www.thesamba.com/vw/forum/viewtopic.php?t=494071

There is another R1 Bug chassis, but he hangs the engine off the back and to one side (yuck) and drives it through the VW box AS WELL as the bike box (yuck).

Pics of 4 cylinder bike engine setups:

Image

Image

Image

Image

Image

So, my idea:
  1. Extend the output shaft of the box far enough to clear the rest of the engine and properly support this with a bearing
  2. put the sprocket on the end of this extended shaft
  3. run a chain forward from here to a quad style diff like this one from #20: http://stuff.fredcooke.com/vw.bike.engi ... arrier.jpg
  4. maybe hit another sprocket, move drive back more central before going forward to diff (two chains)
By doing this the engine will be a fairly good fit under a beetle bonnet/boot leaning forward like they do stock in the bike and requiring no panel mods, just a new diff setup.

As pointed out by Sean a while back, reverse can be achieved using 1st, non-running engine and the starter motor wired backward through relays. Good enough.

Fred.
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by 90turbovan »

A couple other things about sport bike engines that may not be obvious:

-The drivetrain is designed for a 400lb bike with a 200lb rider and one driven tire.
-The clutch is designed for the aforementioned weight.
-They generally use timing chains with sprung/oil pressure charged tensioners.
-Bike carburetors are not designed for lateral acceleration.
-Bike electrical systems are very small.

The first two are easy and can be taken care of with careful driving.

That third one makes me cringe with your plan for reverse. When you spin the engine backwards, it will unload the tensioner. I could see this leading to the chain skipping teeth. Gears will solve this, not sure what high displacement bikes used them.

As for the fourth, well, that should be obvious based on the forum name.

I've seen driveshaft mounted alternators to take care of the last one. Please don't do that. Careful power budgeting may make it a non-issue anyway.

Chains are not your friend. I highly suggest coming up with some reasonable driveline loads and trying to design a chain system to handle them. It is really surprising how bad they are at transmitting the kind of loads and speeds required in an automotive drivetrain. That diff carrier looks like it has more "design" in it than engineering. The lack of sealed bearings scares me a little bit and the lack of straight load paths on the mounts scares me even more. I'd also question the durability of quad parts in a car. They're generally designed for much less traction than you'll have available on tarmac.

With the above said, the redneck engineer in me says that it'll probably work anyway. Not trying to rain on your parade, just don't expect 20,000 miles out of it.

The problem of placing bike engines in things with four wheels is extremely well studied at the college level. For your education (maybe) and entertainment (definitely): http://fsae.com/groupee?s=763607348&cdra=Y
Keep in mind that these cars weigh about as much as the bikes.
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Fred
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by Fred »

Great post! Thanks for your insight :-)

1) True, but the gear sets are designed to hold the torque the engine makes, too. Not worried.
2) I could tolerate regular clutch disk change-outs from slip wear from getting moving. As long as I got 10k km out of each set, I'd be happy.
3) Interesting and for sure worth exploring before preceding, however some bikes come with this stock, apparently. Who knows what type of cam drive they have, though.
4) ;-) I'd be going for something EFI stock like a late model CBR1000R(R) or GSXR1000/1300 or R1, too.
5) Yeah, well aware, but thanks for mentioning it, a glaring omission. You get about 25A out of them, IF you can get the regulator to hold together (use better built reg). Provided there was no stereo system, it'd be fine most of the time.

"The first two are easy and can be taken care of with careful driving." I need to drive you in something some time. This is NOT going to happen :-)

Chains may not be my friend, but they can and do hold the forces that the engine and trans can make in the bike stock. The lack of mass has almost no effect on the forces involved, it just means you accelerate faster for the same force ;-) For sure, though, before pouring any money at any of this, it'd get designed through. The centre of gravity of a bike does have an effect on how much load you get on all of it, though (wheely if excess).

I had the same "where are the triangles" thoughts when I saw that diff carrier. But those diffs, have you seen inside one of them? When I saw it all I could think was "piss weak" but when they cracked it open all I could think was "shit, those teeth are way bigger than I thought, and those clutch packs will never wear out". Having said that, they're pricey...

Keep in mind that the full wet weight of a VW beetle from the early 50s is not much over 700kg stock. Replace some of the bolt on bits with composite equivalents and you're only 2 or 3 times the bike weight.

Weights of those cars is usually in the 140kg to 350kg range with 350 being obese and 200 being pretty standard, so yeah, similar to the bikes :-)

A friend of mine (slacker.cam on here) was in the Auckland FSAE team years ago. I helped them put their car together for a show late one night and used the workshop for 3 parts on my truck (flywheel mods/lightening, flange creation from old pulley, re taper fuel rail for different injectors).

PS, den00bed you.
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by Fred »

For a better idea of the packaging required, in case you have better ideas than my poorly formed ones:

A low res shot of the empty engine bay, stock bell is flush with firewall:

Image

A big shot of the cross section of the whole car, a later one, but close enough:

http://stuff.fredcooke.com/vw.bike.engi ... beetle.jpg

And a crop of it:

Image

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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by Fred »

Fred wrote:So, my idea:
  1. Extend the output shaft of the box far enough to clear the rest of the engine and properly support this with a bearing
  2. put the sprocket on the end of this extended shaft
  3. run a chain forward from here to a quad style diff like this one from #20: http://stuff.fredcooke.com/vw.bike.engi ... arrier.jpg
  4. maybe hit another sprocket, move drive back more central before going forward to diff (two chains)
The bold red bit won't work reliably. Doing some reading around and realised short chains are unreliable due to high duty cycle.

So I wonder if there's space to put the big sprocket hard on one side of the diff?

Also, early bugs are swing axle, so I'd need to support that somehow too. This might be the biggest challenge.

Why the extreme-resistance to modifying the body or pan? I'd like this to be modular, drop it in half an hour and drop a stock engine back in for inspection. I'd also like to maintain the feel of the old car. But I want it to go like hell. Don't care how well it stops to be honest, that would imply cornering worth a damn, which without lots of work, it just won't.

I have some links to drop in here later.

Fred.
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by Fred »

The layout of a VW back end from above:

Image

And why my plan won't work without offsetting the engine a lot (yuck) or at all (sad).

Image

Back to the dreaming board, urr, I mean drawing board.

Fred.
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by BenFenner »

These folks have a solution to turn a bike engine into a normal car engine for use with a normal car transmission. They plan on selling it as a kit I believe.

http://www.motoiq.com/Projects/Mazda/Miatabusa.aspx

This might solve most of your problems if the engine will fit lengthwise.
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by BenFenner »

And Hartley apparently makes a crankcase which solves the common issues as well.

http://www.h1v8.com/H2.html

Money grows on trees, right?

Edit: Nevermind, the Hartley solution has no engine speed reduction built in, so the transmission sees all 11,000 RPM, which is not going to play nice with most transmissions and would result in the need for oddball diff ratios.
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by tooly »

this guy build his own engine based on two yamaha FZR 1000 engines and put it into an super7

http://www.motorbau.de/

its only in german but the pics are interesting too
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Re: Images/Ideas for Street Bike Engine Powered VW Bug

Post by masterkorp »

Why not just place the engine sideways, and match the shatfs, if it sticks out, it sticks out :p
Cover it with an 911 turbo style hood or something.

And or move the whole rear axle forwards a bit.
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