# Calculating a TJETS Gear Ratio



## vaBcHRog (Feb 19, 2003)

I need someone to confirm my calculations on a TJETS gear ratio.

First is the formula correct

Divide the final cluster gear by the motor pinion 24/14 = 1.714
Then multiply it times the cluster pinion crown gear ratio
15/9 = 1.66 ie 1.714 X 1.666 = 2.845

If this is the correct wat to calculate a TJETS gear ratio then

9T = 2.845
12T = 2.142
14T = 1.836

for a 15T Crown and

9T = 3.616
12T = 2.708
14T = 2.313

for a 19T crown

Also for slim-lines or Mini TJETS they have a 9T motor pinion

Divide the final cluster gear by the motor pinion 24/9 = 2.666
Then multiply it times the cluster pinion crown gear ratio
15/9 = 1.66 ie 2.66 X 1.666 = 4.441

9T = 4.441
12T = 3.33
14T = 2.853

No wonder the slim-lines are slower on most tracks but do well against standard TJETS on short tracks. I am going to have to build a 14T slim-line to see how it compares to a standard TJET on the DYNO. Should be interesting.

Roger Corrie


----------



## Hornet (Dec 1, 2005)

This site makes it a bit easier Roger
http://virtualgarage.net/Automobilia/Miniatures/SlotCars/Tips/ModelMath.jhtml


----------

