Electric motors/gearing?

[LosiXXX-S]

Is there some kind of table or equation out there to figure out what the lowest and highest gearing for each turn motor?

[teamlosiisback]

LOL trial and error is best way, start out at low gear, and work way up

[rocknbil]

Welcome aboard LosiXXX, that really is a loaded question.

The weight and transmission gearing of each RC is going to be different. The best thing to do is start with the recommendations of the manufacturer for a 27T stock motor and go from there. As you go less turns on a mod, you're going to get higher RPM but less torque, so you need to gear down.

Some manufacturers have a table for mods (like the TC3.) If you have that it's always good to follow, but the rule of thumb is to run one battery through your setup and check the motor for overheating. If it's too hot to touch for thre seconds or so at the end of a run, you are very likely geared too high. The other test is watching how long it takes to wind up - from a dead stop it should get up to full speed in under 20 feet or so when properly geared.

[highroller]

I suggest purchasing an assortment of pinions say 3-5 in each direction of the suggest gear ratio suggested by the motor and vehicle manufacturer.

Experience with motors also play a part in knowing or having the idea motor may not be geared right. While temperature range can be an indicator for me it's not 100% accurate due to the fact different motors vary in temperature with some being uncomfortable to touch when geared properly. I stop running vehicle is acceleration seems to be a bit slow, takes a long distance to run before it reaches speed or seems to hesitate, begins to slow after only running for half of the battery pack. Based on experience with the motor and temperture range - I'll also look at the color of the wire on the armature - if it changed from a shiny copper to a dark tarnish to a blackish blue then I have an idea the gear ratio was not right. I'll look further by pulling brushes and looking at the color, color changes with also indicate if motor wasn't geared properly slight changes from copper to tarnished - normal wear, Black or bluish depending how far is goes up brush - slightly improperly gear to sever improper gearing , Silver color extreme point and brushes need to be changed some instances springs will also require changing and motor may not work properly afterwards.

[Electricjunkie]

rocknbil: wow I never heard that, reach full speed in under 20feet, are you going to climb hills? lol!! that's way too much torque and it will overheat anyways,

LosiXXX-S: It's hard to know the proper ratio to each motor however; if you tell us more about the motor you're running and where you run it, on a track I suppose we may be able to give you hints based on our experience with the xxx-s and diferent #of turn motors btw if you are going to gear your xxx-s to top end under 20 feet make sure the track has a 40 to 50 foot stretch... where I race the track has a 190 feet back stretch, way too long but at least it's a permanent track.

[rocknbil]

rocknbil: wow I never heard that, reach full speed in under 20feet, are you going to climb hills? lol!! that's way too much torque and it will overheat anyways.

Explain your logic. Where do you see "torque" anywhere in that explanation? If you can't pull the full RPM of the motor in 20 feet or so, unless you're running an oval you are overgeared and are going to overheat the motor. So tell me how a well geared motor that accellerates to full RPM in 20 feet will overheat. This will be interesting.

Keep in mind the poster's name is LosiXXXs and is most likely an offroad racer.

[Electricjunkie]

It's very simple, max rpm in under 20 feet, it is like red linening a motor,(over rev) very similar to go on a 1:1 scale car trying to go 75mph on first gear, on both cases motor will overheat.

[Electricjunkie]

I guess it would only make sense to me racing off road , sorry I didn't know it was off road, did not read your last sentence.

[rocknbil]

OK let me clarify: Maximum running RPM for that motor in that vehicle. When you put a motor against a 3-4 lb RC, there is no way it is ever going to reach the motor's no-load RPM because it's always going to be pushing a load.

[LosiXXX-S]

Thanks everyone for the tips..Right now everything is stock. I plan on getting into mod motors in the future. Anyone have a brushless setup? How do you like it?

[highroller]

Of all the types of gearing charts, speed formula calculator, rollout charts most have not been 100% accurate. You almost have to compensate in a 10-15 percent variant in what you get for the results.

rocknbil is right in his explanation you could have a motor that reaches it's power band in only 20ft, while another would take 30ft so the two would have to be geared differently so each could reach their individual power band.
Even the same identical motors may make power at different ranges, and would need a different pinion size to allow it to get up to it power band and stay cool.