MOD 1 pinion question
 

I am sorry for asking and have tried to use the speed estimator with no luck...my question is what size/tooth count of pinion do I need?
truck has....

45T/11T diffs

48T Center diff

Motors will be duel running feigao 7XL

Power im planning to use is 4S for each motor and if I can get away with it then 5S?!?!?!

I spent awhile typing in info for the speed calculator but no matter what I did I kept getting17-20MPH, I am thinking gearing for 60MPH is a good starting point for now.

Thanks for the help, this money in PayPal is dieing to be spent :)

What numbers did you use in the calculator?
Your diff ratio is 45/11 = 4.0909090909'
It's hard to tell exactly what pinion you'll need to get those sorts of speed, because things like tire ballooning, voltage drop, and motor loading can vary a lot, but on 4s I'd say 20-22t pinion, and 18 or 19 on 5s.

&xl on 4s will be plenty, 5s will be too much motor rpm.

What vehicle, tires size(overall diameter in inches) do you have. That will make it much easier to advise on a pinion.

The problem you are having is the high diff ratio of 4.09:1 and the largish spur of 48T. To get a lower rollout ratio with those values for the speed you're looking for, you're gonna need a large pinion. And since you are looking for a real 60mph speed, you should probably be shooting for a calculated speed between 65 and 70 mph, because wind resistance will drag you down a bit.

FYI, when you enter tire size, use the entire tire diameter, not just the rim.

What vehicle is this in?

sorry guys left out some key info, its the emaxx im building. Actual weight is still undertermind.
Thanks pat- I am guessing I entered the wrong diff ratio in the calculator:whistle:
thanks link- 4s it is. :)
Brian- would it be a better idea to run the kyosho plastic 46T? I was thinking the twins would tear it up?? Tire size I just entered 5.5 with a ballooning of .5, tires are badlands and I know they balloon more then .5 but I figured I be conservative?

Thanks again guys ill mess with the calculator more when I get off work.

An stock emaxx diff is 37/13, or 2.846:1 ratio.

Are you using a tranny, or a center diff, or what? The emaxx tranny listed in the drop-down is for the original version, not the newer one.

And yes, a 46T spur would make pinion selection easier when trying to get high speeds.

its this one.
http://www.rc-monster.com/forum/showthread.php?t=9153

thanks for all the help guys :) some days I am hopeless LOL

I should have asked sooner, why is 5S to much for the 7XL? is it because of material quality/bearings or will it just cause to much heat in the motor?

need advice
 

hi guys, i plan to order some stuffs from mike
Neu 1515 1y/F or Neu 1515 1.5d/F
Electric Motor Mount-XRay
XRay Truggy Chassis Brace
Neu Rear Endbell Cover
Battery Tray Kit
High Amp. Gold Plug. 5.5mm, 150 Amp(Male and Female, 3/ea)
BTW, i got a XRay XT8 Truggy(ALL STOCK, I MEAN EVERYTHING!!!)
i'll Only use NiMH BATTERY(12 CELL 4200-4600mAh)"NO LIPO FOR ME!!!"
just wondering what Mod 1 Gear(???t) should i get??? "mike recommanded me to use 14t with the Neu 1515 1y/F, THANKS IN ADVANCE! SamSam from Hong Kong.

I would go with what Mike recommended.

What is the differential ratio? And what is the spur tooth count? Once you know these, you can use this page to get the right pinion for the speed you're looking for.

hi BrianG, pls check PM and see if you could help me to solve the problem! Thanks

PM answered (sorry about that)...

Anyway, here is the answer I sent you:

14T will get you around 34mph on that motor/battery/gearing combo. NiMHs tend to drop voltage a bit more than lipos at higher currents so you'll probably get 30-32mph. If you want more speed out of NiMHs without quite as much current (thus, better runtime), I'd go with 16 cells, the 1515 2d, and a 12T pinion.

hi BrianG, sorry about one thing! i forgot to tell you that i got the Mamba Max ESC and it only handle up to 12 cell NiMH.....:surprised: so, should i still go for the set up that Mike recommanded???(Mamba Max/12cellNiMH/14t/Neu15151yF) or should i get the Quark Monster Pro 125B Brushless Sensorless Speed Controller, if that's the case, any suggestion on how many cell and gear should i use???really A THOUSAND THANKS FOR ALL YOUR TIME AND HELP!!!
Best Regards, sam from Hong Kong