MM5700 Gearing - RC-Monster Forums

Nick · **MM5700 Gearing -** 09.10.2006, 02:40 PM

Mambamax 5700 in a T4, with a 81t spur.

1) I will be using 7 cells at first, what pinion would people suggest for a "mid" balance.

2) 3s lipo, mid balance again.

When I say mid balance, sort of not high geared and not low. :)

What would you say the low-high range is for pinions on both battery setups to?

Thanks,
Nick.

MetalMan · 09.10.2006, 03:39 PM

I used BrianG's speed calculator to estimate a good pinion gear setup.

1) 15t pinion should yield almost 40mph on 7cells.

3) 12t pinion will yield about 40mph with 3s Lipo.

Nick · 09.10.2006, 05:41 PM

Great, thanks alot. :)

Can I ask, how do you figure out the gearing? What pinion to use? I've never understood it.

SpEEdyBL · 09.10.2006, 06:24 PM

You can actually use any gearing for the mamba max motors (unless they over heat). It just depends on how fast you want it to go. If you want it to go 40 mph, you just find what size pinion will get it there, given the motor rpm. So 5700 x 11.1=63270 rpm. 81/12 x 2.6 = 17.55 FDR
Multiplying the RPM at the wheel by the tire circumference in feet and dividing by 88 gets you to speed in MPH.

Assuming a tire circumference of 1 foot, 63270/17.55 x 1/88 = 41 mph.

Calculating speeds above 40 mph gets a little hairy because you have to consider the voltage drop constant of the battery, the rpm drop constant of the motor, the number of amps that the motor pulls and tire balooning. Tire balooning is the most difficult to calculate.

MetalMan · 09.10.2006, 06:33 PM

I think the best thing to do is to just get a pack of pinion gears by Robinson Racing and just playing around with them until you find the gear that gives you the best performance/heat ratio.

BrianG · 09.10.2006, 10:20 PM

I don't know how heavy a T4 is, or the rest of the ratios (diff, tranny), but my Jato was clocked at 47mph on 2s2p moli cells with 54/22 spur/pinion, with a 4600 motor. That is pretty close to what my calculator comes out to. Of course, it depends a lot on how stable the voltage is under load. A higher capacity battery will drop less under load and will consequentially go faster, especially with a high kv motor like the 5700.

Nick · 09.11.2006, 04:39 AM

Thanks guys.

Quote:

Originally Posted by MetalMan

I think the best thing to do is to just get a pack of pinion gears by Robinson Racing and just playing around with them until you find the gear that gives you the best performance/heat ratio.

Yeh I've just bought about 5 pinions, ranging from 12-22