Riding Lawn Mower Gear Box?

Question:

I have a vertical engine and a vertical transaxle.  Can't I just use the transaxle on my go kart?  It should be easier this way right?


Answer: Great question.  Many people are asking the same question.  "I have this old lawn tractor and it has this transaxle, can I use it?

Vertical Engine Problem

The problem with a vertical engine is routing the power from the engine to the horizontal wheels on the go kart.

Typically the standard method for transferring the power involves a gear box.  

For example on a lawn tractor the gearbox is designed with a pulley on the top of the gear box (probably very similar to what you are asking about.)

 Additionally, because the main purpose of a riding lawnmower is to cut grass, the vertical engine layout works very well for driving a mower deck too.

The temptation comes in to play to use the gear box in the gokart and keep the unit simple that way.  Unfortunately, it is not really simpler, but more complex, not to mention unrealiable.

Transaxle Problems and Pitfalls

Additionally, I would strongly steer you away from using a riding lawnmower gearbox for the following reasons:

- Width of the rear axel system is too narrow.  

The width of a gokart drive wheel layout should be relatively speaking wide: 36”+ for good stablility and anti-roll characteristics. 

Riding lawnmowers are under that width, being naturally unstable and very prone to tippage.  

Also the gear box will pose a difficulty in powering the rear wheels.  Mounting the gearbox is another issue that requires special bracketry that would need to be fabricated and mounted to the framework.

-Gear boxes are not designed for high speed as in 20+ mph.  This is a serious consideration, especially with gear boxes that do not require lubrication and do not have roller bearings.  The gear box may end up siezing up.

-Gear Box Engagement requires belt tensioning devices.  Typically, the gearbox is activated by tensioning the belt.  To answer your question about internal clutches, most gear boxes are not that sophisticated, they just require the belt to be tensioned to engage the gear box.

Belt Tensioning systems also require careful thought (complexity) in their design so that the activation of the clutch can be deactivated when the rider is starting, or idling the go kart.   

-Switching gears on the fly is not possible without good engine/gearbox knowledge.  The gearbox on a riding lawnmower does not have synchronizers with it, so the gearbox must be completely idle or still for the gears to be switched.  

Actually, in order to get gears to mesh properly, both the mating gears must be in the same position.  This can be accomplished by running the gears at the same speed, but this does take some understanding of how a gear box operates.  

Unskilled drivers will have extreme difficulty getting the gearbox to work.   More than likely, the gear box will be destroyed in a relatively short period of time, if shifting is considered on the fly.

The Go Kart Guru Has The Answer Though

There are, however, more compact, easy to maintenance and very cost effective methods
covered in the Go Kart Building 202 Vertical Engine Course. 
The nice thing about these designs is that they fit right into the Go Kart Phi Alpha 10 Frame which is available on this web page too.

The Go Kart Building 202 series is a comprehensive Vertical Engine Drive course that goes through the different drive layouts, the  issues with calculating the correct component sizes and shows you how to get the components right for your go kart 
design.

The 202 course shows you what parts to order, what size, where to fit it, how to lay it out, what to issues to be aware of.  It basically is a How To Manual for Vertical Go Kart Engine systems.

I would strongly suggest, that if you are new at this whole thing, that you also take the Go Kart Building 201 driveline course The reason why I suggest you take this is to help design the drive line so that is not smoking clutches, or stalling your motor.  This is important, especially when you are dealing with a Vertical Engine.

And finally, because you are using a lawn mower, the Go Kart Building 102 course, takes a riding lawnmower and shows you what parts to use and to only spend 200 bucks on the go kart.

Just so you understand, all the courses will become part of ONE BIG book called the Go Kart Guru's Comprehensive Guide On How To Build A Go Kartand will be available later this year. 


 
 

Great Birthday Present:  The Father and Son Wood Go Kart Project

Wood Go Kart Project


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