Originally Posted by ttsquirrel
hello again all,
I am about page 35 now out of 194. now i have even more questions!!!
im trying to figure out all the FDR numbers and am confused. everyone seems to be running different FDR's and i understand that it is because of different motors. i still cant get my head around it. FDR's are being run between 4.0 and 8.0. I am assuming the higher the FDR, the lower the turn on the motor. is that correct?
w wanted to use the stock gearing and 21T motor but read that i couldn't get the right size pinion on motor because there is not enough room to get the fdr to a 4.1 which is what i should be running right? so i would have to get the 76T spur and put on a 35 pinion. with a 21T motor is a 4.1 FDR good? what happens when the FDR goes higher with this setup? slower acceleration?
than after the 21T motor, i plan on putting a 17.5T motor to advance to the next class. what is the proper FDR for that motor?
soo confusing.. does anyone have a site where this is explained and what the FDR numbers will do as far and top speed and acceleration?
For a 21.5T motor a FDR around 3.5 is better to start with and then either lower or raise it from there.
Yes you are correct - a higher FDR is for lower wind motors and lower FDR's are for motors with more winds on them.
With a 21.5T motor a higher FDR will give the car better acceleration but will have lower top end speed, where as a lower FDR will have less acceleration but you will gain more top end speed.
Now here's the tricky part, with motors they have an ideal gearing ratio (or butter zone as it's sometimes called) and while it's around the same for all types of a particular wind there will be some differences between brands and models of a particular wind.
To lower the risk of over gearing your motor and burning it up by using a FDR too low for the motor start high and slowly work your way down with FDR settings. For example with a 21.5T motor start with 3.8 and work your way down to 3.2 - 3.1, and when doing this monitor the temperature on your motor every 1-2 minutes when you drive the car.
To do this on the Zero S you may need the optional "Vertical Motor Mount
", which will allow you to use smaller spur gears that higher turn motors need to get the lower FDR's. With this motor mount you must flip your belts over ie short belt to the left side of the car and long belt on the right side.
With one of my 21.5T motors I use a FDR of 3.4 and use a 61 tooth & 34 tooth pinion to get that ratio.
Hope this helps.