Calculated motor specs/recommendations

[xcntrk]

Hey all, I’m new to the electric side of the house. I have a (noisy) nitro supermaxx that I’m in the process of converting over to BL. I’ve been hashing out various motor setups for days using the RC calc and think I found a nice setup for my rig. How do these values below look? It’s essentially a pair of 2s (s-14.8) with a Neu 1515/1.5D. Plan to use a Quark 125 w/external BEC.

Differential Ratio: 3.3076923076923075
Transmission Ratio: 1.7222222222222223
Other Ratio: 1
Spur Tooth Count: 51
Pinion Tooth Count: 20
Total Voltage: 14.8
Motor KV: 2700
Tire Diameter (inches): 5.75
Tire Ballooning (inches): .1
Motor Current Draw: 120
Motor coil Ω: 0.004
Spur/Pinion Ratio: 2.55 : 1
Total Ratio: 14.52628 : 1
Tire Circumference (inches): 18.69 inches (474.79 mm)
Total Motor Speed: 38664 RPM
Vehicle Speed: 47.11 mph (75.68 km/h)
Effective Speed Rate: 3.18 mph/V (5.11 kmh/V)
Estimated Adjusted Speed: 44 mph (71 km/h) - 6% loss
Effective KV Value: 2612.43
Motor Torque: 0.31 ft-lbs
Final Torque: 4.55 ft-lbs
Final Power: 1776 watts (2.4 HP)

All comments appreciate..

[BrianG]

Sounds good to me, if geared a tad too high. Unless this is specifically for high speed runs, a truck running at 47mph is a bit hard to control. I would gear for 40mph max, but that's just me. And since you're running a Neu motor, you could actually move up to 6s on that same motor for a little extra speed. Of course, the Quark may not run 6s, but I'm just thinking of future upgrades.

Depending on your upgrade timeline, you may want to wait until the MMM comes out. It will include a motor based off the Neu design and be a 6s capable controller out of the box for ~$300.

[xcntrk]

^^Thanks for the input. (nice work with the calc BTW, very useful tool!)

With the setup above in mind, is 38664 RPM too hot for a Neu motor? Also, stepping down the spur/pinion ratio (say to 18p) would result in more manageable top speed but also produce over 5ft-lbs torque. How does that translate to back-flipping, wheel standing, torque? In the ball-park or still manageable?

~Thanks

[BrianG]

Thanks!

The Neus run fine well over 40krpm. Gotta love those high-end motors!

Yes, an increase in max torque will give you more back-flipping power, but you can manage that with the trigger. Seriously though, if it's too much, you can reduce the start power setting in the ESC. I would much rather dial out the power if I needed to than to not have it available...