Picking the right motor for the right application

[mickeymoose]

Hi everyone, I like to jump in with some questions while this subbject is being discussed if it's OK? I have built an LST2 using a Feigao 8XL, Quark 125B Monster Pro esc with a Quark external BEC, E-Maxx Tranny, custom top and botttom aluminium chassis plate. the rest of the truck is stock LST2. I've just been running 2 GP3300 stick packs so far for testing and tweaking the setup. I'm using the stock 66T E-Maxx spur gear with a 16T and 18T pinions so far. I have also locked the Tranny in 2nd gear. Even with this setup there is plenty of torque, the truck will pull wheelies from a dead stop and flip if you don't get out of the throttle. The motor temps are low to mid 130's and the esc is barely over 100. top speed as a guesstimate is probably around 30mph ( it's a hair faster than my buddy's E-Zilla ). Do you guy's have any suggestions on better overall gearing. Oh yeah the truck weighs about 10.5lbs without the batteries, and I'm running proline 40 series dirt hawgs. Thanks for any help.

[BrianG]

IMO, the size of the motor depends on the weight of the truck. If the motor is too big/powerfull, it's a waste of money. Kinda like putting a 1,000HP motor in a mid-size car; it's nice and all, but not very practical unless you can actually use it. Likewise, putting a 50HP motor in a mid-size car is not practical either because it is underpowered.

Plus, using a motor too big doesn't load it enough. Using a motor that's too small loads it too much. Some of this can be compensated with via gearing to a point.

The wind of the motor depends on the voltage used. Obviously, for a very large motor, you want to use higher voltage to produce the current needed for the HP.

From what experience I've had (and that's not really all that much). Using a high wind (low KV) motor geared really high is not ideal. Nor is using an unreasonably low wind (high KV) geared really low. In either case, some or all parts gets too hot and efficiency falls. It seems moderation works best.