# Lawn Tractor Racing



## THUNDER (Mar 17, 2010)

Hi everyone I have come across this site in hopes of getting pointed in the right direction for a project I think would be fantastic for the sport I am in which is lawn tractor racing. I do not have any experience with electric motors or any of the switches or that like. what I want to do is make a electric racing lawn tractor I am sure it is possible, but at what cost will it be for al the components I will need to make this tractor go 65 -70 miles a hour. I already have the tractor which is race ready. It has a live axle system in it a excellent steering system and hydrolic rear brakes. So there it is could someone fill in the blanks please.


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## Woodsmith (Jun 5, 2008)

Hi, and welcome.

That is a good and not to complex project to get started with.

I am currently building an electric compact tractor in the link in my sig.
You might also want to have a look for jimdear2 as he builds little tractors for pulling competitions.

Do you have any photos of your current race machine you are going to convert?


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## THUNDER (Mar 17, 2010)

Hi thanks alot for the quick reply at this time I do not have a pic of the tractor I am going to convert . As soon as I get the pic I will post it here. so how will I go about attaining 60-70 miles a hour ? How many motors and what size . The way i get my tractors to do that speed is a pulley from the engine which goes to a 90 degree gear box on the bottom of the gearbox it changes over to chain drive to the rear live axle. The gear ratio from motor to gear box is one to one the gearing from the output of the gear box to the live axle is 6.5 to 1. 
Any help here would be great .


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## Woodsmith (Jun 5, 2008)

I did type a long reply and then lost connection.

Generally a 9" diameter motor will push a car up to 60+mph.

You difficulty will be that you will be on grass and lawn tractors are hardly aerodynamic.
There are EV calculators to determine approximate power required for a vehicle but I am not sure how effective it will be for a tractor.

One issue will be air resistance. You will need to know the cross sectional frontal area of you and the tractor and also the Cd. I doubt you will find this in the tractor manual.
I have a little spread sheet I made up with some data for aero drag and rolling resistance that might help with the approximations or you can send me some data and will run it through and see what sort of ball park you are in.

When you have a photo and maybe some video, yours or YouTube, of lawn tractor racing post a new thread up in the conversions forum and it will get more attention.

Where are you based?


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## THUNDER (Mar 17, 2010)

Hi and thanks I will as things progress. I live in kingston ontario canada.


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## Woodsmith (Jun 5, 2008)

Hi,
Have you got any further with your race tractor idea?

Here is the rough and ready table output I use for my calculations.
I used tyres on sand for the rolling resistance and a crossectional area of 1 and Cd of 1 as at 10mph air resistance is minimal.

Using LiFePo4 cells:








Notice that at low speed there is little effect of air resistance. At 60 yours will be considerabbly greater.

Using lead acid cells:








The extra wight of the batteries makes a fair difference to the rolling resistance.

Gear ratio table:








The table is generic and can cope with a 5 speed transmission, transfer box and final drive. However, in my case, the final drive is actually the chain drive from the motor to the transaxle and the transfer box ratios are the overall transaxle ratios there being no other transmission components.


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## THUNDER (Mar 17, 2010)

Hi and thanks for the table and the time it must have took you to compile it. I have been looking a two different tractorsI may use not sure which one to use yet. Will post pics when I decide which one.


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