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    Motorcycle engines and car transmissions....why ain't it done?
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    This has bounced around the back of my brain a lot in the last several years. A lot of people are building buggies with powerful sportbike engines and, in order to get reverse, they're having to spend gobs of cash on an FNR box or find awkward workarounds to pull it off.

    So why not use a car transmission? A manual transmission out of a civic can be had from a junk yard for $100, will hold up to 250hp, has common parts you can go to Autozone and get, and is a really compact setup. You can get a generic open differential or a limited slip without much fuss. Reliable, proven reverse.

    Add to that the motorcycle transmission, which seems redundant, but allows you a HUGE variable in gear ratios. Pretty much every bike is geared 1:1 in 3rd or 4th...keep the bike engine there for typical riding. Climbing? Drop it down a gear or three. Want to see if you can break some speed records? Pick it up a gear or three. This can even be controllable from the cab. On the fly.

    Tying them together could be as simple or as complex as you want it to be. You can use the splined hub from a friction plate welded to a keyed shaft...and hardened...that will carry your input sprocket...<$100. Or weld a sprocket carrier to said splined hub and cut the bell housing off...do it yourself for free if you're cheap. Or have the input shaft machined to hold the sprocket properly...$$$.

    This seems fairly easy, cheap, and like it would have a lot more pros than cons. But I'm really not that innovative so I imagine if it was all super awesome it'd have been done already.

    So what am I missing?
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    Intense Moderator Rat4020's Avatar
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    There's member here that have been runnin a Honda trans behind a Turbo Busa for quite a few years now with no problems his user name is Arowhead from OR and he winters down around Buttercup . I stoped in and saw his buggy a few years back there very nice setup . The trans gives you four gears in R gear LOL
    The question is not if its gona roll. Its when ..

    That be some kind of church cruzzer or commuter bike thingy ?
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    Quote Originally Posted by Rat4020 View Post
    The trans gives you four gears in R gear LOL
    Well, who hasn't ever wanted to get out of a situation as quickly as they got in it.

    I'll have to look it up...see how he tied it all together. I knew I couldn't be the first person to consider this.
    Last edited by Rat4020; 01-26-2016 at 12:20 PM.
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    I know that Sand car from here in Oregon.
    Probably one of the best examples of a long travel, very light weight (~800#'s) and low cost Busa powered Sand car due to the builders creativity.
    For example, the front brakes are from a mountain bike and the rotors are bolted to the hub of the aluminum spindle wheels.
    Using the Honda transmission required a fair amount of fabrication, but works great.
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    Intense Moderator Rat4020's Avatar
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    Quote Originally Posted by makenzie71 View Post
    Well, who hasn't ever wanted to get out of a situation as quickly as they got in it.

    I'll have to look it up...see how he tied it all together. I knew I couldn't be the first person to consider this.

    Correction 6 gears in rev
    The question is not if its gona roll. Its when ..

    That be some kind of church cruzzer or commuter bike thingy ?
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    Senior Member SamR's Avatar
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    I've seen a couple of discussions about honda transaxles around. General consensus is they won't hold up to 1000cc+ motors for very long. Far as I've found Arrowhead and Whitedragon are the two that have had working setups, Arrowhead swears by it and Whitedragon blew a few up before scrapping the idea. I'm currently wedging one behind a 929 so I'll find out for myself sometime this summer.
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    What parts aren't holding up?
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    Gearboxes are rated for torque, which is in simplified terms is HP divided by speed.

    ie, the higher your speed for a given HP, the less torque you are putting into the gearbox. Conversely, the lower the speed, the higher the torque loads.

    If you use the motorcycle gearbox for shifting, the combination of the reduction of the low gears and the (relatively) high power will create low speed and therefore high torque into the car gearbox and will more than likely blow up.

    Like you say, you could select a motorbike gear that is about 1:1 and use the car gearbox to shift, but then I think you lose one of the major benefits of a motorcycle transmission - Sequential shift and dogged gears.
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    I'll be doing something similar. I'm mating a zx14 turbo to a Toyota starlet gt turbo gearbox. Plan is to sit the starlet box in 4th (0.969:1) and use the bike gearbox to shift. I get reverse, a choice of 5 final drive ratios and a diff that's already mounted with bearings and seals.

    The only downside I can find is the extra 50kg. I wanted to chain drive the rear on a floating diff but due to the size constraints the chain would be tiny. After extensive research it seems the only people without chain issues on high hp setups, are people without chains

    I also agree with Iggsy. The bike sequential box was half the reason I chose a bike motor.
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    Re: Motorcycle engines and car transmissions....why ain't it done?
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    Millenium Member nutz4sand's Avatar
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    I have a Honda Tranny I intend to try to use myself.

    I am 123.6678594876894786% convinced that the tranny failures of honda front drive trannys behind bike engines are FAILURE TO SUPPORT INPUT SHAFT PROPERLY.

    You CANNNNNNNNNNOT just put a sprocket on the tranny input shaft after cutting off the bellhousing.

    The side pull will destroy the tranny yesterday. You look at the tranny IN the car it came out of.

    The engines crankshaft supports the tranny input shaft and it NEVER EVER EVER sees a sideload! ONLY rotational torque!

    You have to remember the shaft needs to be supported on both ends and in the car the crankshaft IS one of those ends!

    AND IT ONLY INPUTS rotational torque!. NEVER A SIDE LOAD. A side load that could pull the shaft sideways makes the gears have improper tooth contact and they fail and the trannys inner bearing gets tweaked and it fails and its game over if either let go.

    Arrowhead removed his belhousing but then did a heck of a job of supporting his trannies input.
    Instead of removing the bellhousing I intend to use it to make a adapter plate that supports the input shaft.

    That said I have been also looking for an automatic tranny that could do the same. One issue is it WILL weigh more. But it would be nice to shift it to reverse OR select the next higher or lower range like that. Plus Autos tend to have some electronics you will have to deal with. And more parasitic drag.

    Not sure if a Honda Automatic would take a lot of horsepower?

    I have also looked at a Chevy Powerglide setup. These have zero electronics and can take more power than a bike motor can make. EDIT: These can also be run without a torque converter so its just a two speed forward with reverse gearbox. Weighs less than a regular powerglide and more efficient.)

    Making a smaller car built like a Sandrocket (if you know what those are. They use Chevy small or big block engines up front with turbo 350 automatics and feed the power to a IRS rear diff. Way better than the rear engine with a mendeola (spendeola) which needs a $$$ rebuild far to often.

    Was wondering about the amount of drag you would get by placing a Hayabusa sideways like they use them in a dwarf car and feeding the power into the front of the powerglide and then to an IRS rear diff.
    Last edited by nutz4sand; 01-26-2016 at 06:50 PM.
    Now that NOBAMA has PROVEN he is the absolute WORST president in the history of history Jimmy Carter can thank him for stealing the dunce crown.

    Lets hope the next guy repeals NObama care along with the rest of the stupid crap this blight on our windshield has done.
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