Lawn Tractor Kart Build

[Fawteen]

I was given a 12 horse Crapsman lawn mower, which I've decided to convert into a go kart for my Grandson. It's going to be a REALLY simple build, no suspension, using as many of the lawn tractor parts as I can. Speed is not a goal initially due to Jarod's inexperience and the inherent weaknesses of a lawn tractor transaxle.

Here's what I've got so far:

Pic#1 - Overall view of frame
Pic#2 - Attachment at transaxle end
Pic#3 - Original (screwed up) attachment at steering axle
Pic#4 - Steering axle with modified frame to allow tire clearance.
Pic#5 - Mocked-up steering arrangement

Waiting on new pulleys for the TA and engine shaft, decided to speed up the first reduction by 25% Once the pulleys are in, I can start setting up the engine mount and idler clutch arrangement.

 

[weirdarmadillo]

What transaxle are you using?

 

[Rotore]

nice

 

[Fawteen]

What transaxle are you using?

It's a Spicer 137637.

Got the steering shimmed up and installed, looks like it'll work just dandy. I was a little worried about the ratio being quick enough, but it's less than a full turn lock-to-lock so that should be okay

 

[Rotore]

nice transaxle

 

[Kaptain Krunch]

It's a Spicer 137637.

Got the steering shimmed up and installed, looks like it'll work just dandy. I was a little worried about the ratio being quick enough, but it's less than a full turn lock-to-lock so that should be okay

Not the strongest transaxle, but it'll do if your not expecting more than 10-15mph.

I like the project though, have you considered a centrifugal clutch between engine and transmission for ease of use?

 

[Fawteen]

I like the project though, have you considered a centrifugal clutch between engine and transmission for ease of use?

I'm still debating that one. I'll make the final decision after I mock up the engine mounting position.

Plan A is to use a loose-belt/spring loaded idler system using parts off the lawn tractor. If that looks like too much work, I'll probably look into a centrifugal.

 

[Rotore]

I'm still debating that one. I'll make the final decision after I mock up the engine mounting position.

Plan A is to use a loose-belt/spring loaded idler system using parts off the lawn tractor. If that looks like too much work, I'll probably look into a centrifugal.

its not that much work actually. it's a fairly easy setup

 

[brendonv]

go with a belt and tensioner setup, wayyyy easier and cheaper.

 

[Fawteen]

A little more progress today. My new pulleys came in from Surplus Center, so I can start figuring out the engine mount. After mounting both pulleys and doing a little measuring, I was able to determine how high above the frame the base of the engine needed to be to get the pulleys to line up. That turned out to be 7".

I've offset the engine to the right side of the frame and have the shaft centers (T/A to Crank) 9" apart. Offsetting the engine allows me to move it a bit closer to the T/A and also leaves me some room on the left side to put the battery and mount the starter solenoid and clutch linkage. I'll probably offset the seat just a tad to the left to keep weight distribution pretty much on the centerline.

Things are just tacked in place right now, I MAY need to crowd the engine back another inch to have room for the seat. Plan A is to shorten the steering shaft which will move the wheel forward and down, giving more room for the driver.

Also cut and rotated the muffler and brazed it back together.

Tomorrow I'll start dubbing around with the idler/clutch setup.

 

[Fawteen]

My handy-dandy V-belt length calculator says the belt should be 35.5" for based on pulley size and shaft centers. I figure a 37 or 38 would be about right for the loose-belt system. Anybody have opinions/experience with sizing belts for this sort of application?

 

[skid20]

My handy-dandy V-belt length calculator says the belt should be 35.5" for based on pulley size and shaft centers. I figure a 37 or 38 would be about right for the loose-belt system. Anybody have opinions/experience with sizing belts for this sort of application?

I made a kart years ago with one it kinda just depends on the throw of the tensioner arm and the position it sits while disengaged. You can always adjust the tensioner to fit the belt length.

 

[modelengineer]

Tensioner is very simple to set up.

 

[weekend-fun]

I was given a 12 horse Crapsman lawn mower, .

I have never herd of CRAPSman lawn mowers

 

[Fawteen]

I have never herd of CRAPSman lawn mowers

Heh, heh, heh...

That's my way of saying I ain't all that impressed by Craftsman stuff. Their hand tools used to be okay, but even they have gone down the crapper, quality-wise. And their power tools never were worth a **** IMHO. Black & Decker's cheapest homeowner grade stuff, re-badged and marked up.

 

[IHcubguy]

not hard to tell were i got my steering wheel from!! works nice, the date is wrong on the pic, it was taken only a month ago!

 

[TOO FAST]

Oh I hate to say this but I have to. I don't think that small pulley on the engine is gonna
work. It just doesn't have enough area to grab the belt and will slip when you put the
torque to it. Sorry but I think you'll need a jackshaft.

 

[modelengineer]

You talking about my pic?

Sorry mate, but it does work. No slip at all when you let the clutch out. It's only a 3.5hp 2-stroke.

DW, I didn't think it would work either, but it's the only way I could get 8:1 reduction without a jackshaft (and it still had crap acceleration!)

 

[Kaptain Krunch]

have you considered the small pulley being the cause of bad acceleration (slippage)? I was thinking the same thing as Too Fast but didn't want to say anything.

 

[Fawteen]

Alrighty then. Over the last day or two I've cut down the steering shaft and finalized the steering, replaced all the bushings and bearings in the front axle and wheels, and gotten the clutch and linkage figured out and installed.

Pic 1 is the cart as it sits at the moment with the seat just laying on the frame to check clearances.

Pic 2 is the idler clutch mounting bracket and clutch cable rigging.

Pic 3 is the front of the clutch cable. I'll be going with a rod from there to the clutch pedal. Clutch and brake pedals are my next step.