Lawn mower transaxle

[buddyochoa]

I am planning on building a good sized off road go kart. I'd like to use a larger engine(18-21hp). When it comes to these engines, vertical seems way cheaper then horizontal. To convert the vertical shaft to a horizontal shaft that can be used to power rear wheels, the easiest solution seems to be to use a lawn tractor transaxle.

Because the transaxle is geared for power and not speed, would it be possible to use it more like a jackshaft? In the sense of putting sprockets at the ends of the axles, and hooking them to the rear end? This way I could modify the gear ratio there, rather then make the transaxle spin faster then its designed to.

 

[r97]

I have suggested doing so before, but to my knowledge no one one this site has. I think it is an idea worth trying, it extends the life of the gearbox, and it allows you to use a stronger axle. The downfalls are the increased size/weight/cost, and you need to either weld up the differential, or put sprockets on both sides of the trans-axle.

That said, what you are doing is using the trans-axle only as transmission. You would be better off finding a lawn mower with a separate transmission, or removing all the unnecessary parts from the trans-axle.

 

[buddyochoa]

How common are lawn mowers with separate transmissions? Also, here is a diagram of how I was thinking of making it work.

 

[Doc Sprocket]

It can be done, but I agree with the previous comments. Your best choice would be a transmission. Failing that, your next best bet would be to lock the transaxle and run off one side.

Shop carefully for your transaxle or transmission. Some mower units are better suited to the rigors of karting than others. Slight mods can be made to these units to help them hold up to the task. I'm still learning about these- The Peerless 700 is a very popular transmission for this sort of thing, as is the Peerless 800 transaxle.

 

[buddyochoa]

I'd assume using the setup I have the Peerless transmissions could handle it without modification as i'm not asking it to turn faster then it normally would.

 

[OzFab]

Adding to previous comments: a standard axle has a diff centre so, with this setup, you will most likely get unever power transfer unless you "lock" the internal gears (I've never seen this done successfully).

Great concept though...

 

[Doc Sprocket]

Further observation- if the differential were to remain open, you will have to mount brakes to both axles. Do not use the factory transaxle brake, it it not up to the task. Avoid mounting the brakes to the transaxle output shafts, too- as a chain failure would result in a brake failure.

 

[buddyochoa]

For brakes I'd like to go with a rear disc break setup. I haven't located one yet, but I'm sure they aren't hard to find.

 

[Mr.Wizzard]

You mentioned it being an off road kart, you could put a sprocket on each end of the transmission and use a live axle with two sprockets that line up with the transmission sprockets. it will add a little weight but it will also run the power through the whole transmission with less load on each side=longer life for the transmission. Then just use one disk brake in the middle of the live axle.

 

[Doc Sprocket]

You mentioned it being an off road kart, you could put a sprocket on each end of the transmission and use a live axle with two sprockets that line up with the transmission sprockets. it will add a little weight but it will also run the power through the whole transmission with less load on each side=longer life for the transmission. Then just use one disk brake in the middle of the live axle.

The idea is sound, but the issue is that the OP wanted independent rear suspension.

 

[buddyochoa]

IRS isn't a requirement, though if I am already using two sets of chain and sprockets it seems like IRS would be the way to go.

 

[tractor guy]

I thought about doing something to that effect. The idea was to run a chain from one axle to a live axle, then weld the other axle on the transaxle to its housing. Stoping one side from spinning makes the other spin faster. There are some flaws with this idea like longjevity if the spinning axle but i still think its possable.

 

[Doc Sprocket]

I thought about doing something to that effect. The idea was to run a chain from one axle to a live axle, then weld the other axle on the transaxle to its housing. Stoping one side from spinning makes the other spin faster. There are some flaws with this idea like longjevity if the spinning axle but i still think its possable.

Two thoughts-

One- how do you propose to weld a steel axleshaft to an aluminum housing?

Two- (and you touched on this) You're running all your power thru those weenie little spider gears, and if you haven't "race-prepped" it, they'll sling the grease off and be done in short order.

 

[tractor guy]

Like i said, there are flaws in this idea. Lol thats why i never attempted it. I decided against two axles when useing a smaller pully would work better with less work and whieght. Plus i prefure to have an open diff for better steering function, transaxle life, tire life, and not leaving tracks through the yard.
I have three transaxles i think would work best for a kart application. All are all MTD. MTD commonly uses a variabe speed pully system rather then multible forward speeds in the axle. Two of mine are simply forward, neutral, and reverse, and one (the biggin) has high and low range, neutral and reverse.