When will a motor move you?

General Discussion
41

closed gearbox?

  1. trial and error with different gears/motors

  2. designed and nice looking gearbox

42

I would demonstrate that thereā€™s actually a problem before trying that. 750kv on only 3S may be good with normal 2.5:1 - 3:1 gearing and 97mm wheels

43

The problem here is that he wants 50mm wheelsā€¦

1 Like
44

Why would it be any different from a 50mm wheel? If anything higher gearing would help the torque

45

Wheel size directly affects the gear ratio.

46

I think itā€™s doable. Its a cool challenge from an engineering standpoint.

I would do a 2 stage planetary gearbox. 13:1 from 750kv+

47

Explain. I donā€™t see it. The only thing it affects in my head is the size of the gear you can mount

48

The circumference of the wheel is directly affected by wheel diameter, and the wheel circumference is the amount of ground covered per one revolution.

49

2 stage = double as expensive :joy: Its definetely possible, but i dont see it efficient or proctical in any kind of way.

50

i am not talking here about efficency. i am talking here about of doability. since you never testet it, why would you know it doesnt work?

51

I swear Iā€™ve seen them on rc airplanes before. I have a reisenauer one but it cost ā‚¬300 lol. Iā€™m sure there must be a cheap one on hk or aliexpress or something!

Reisenauer doesnā€™t make the 13:1 anymore either

52

Right, but it doesnā€™t increase the torque. The purpose of gearing down would be to increase torque and usable throttle range.

53

I donā€™t think you need that. Driving a 750kv motor from 3S is a similar ratio to driving a 225kv motor on 10S. Just gear it down about 3:1 and use a big wheel, like 97mm. It should be pretty close to good. Adjust from there if you need to. If you need more torque, decrease the wheel to 83mm. For more speed, increase it to 107mm.

54

@Acidfie bruhā€¦

1 Like
55

the question is how good

56

Yes but the motors we are talking about cannot put out as much torque as a larger one.

Eg: 6374 sk3 200kv on 10S geared 3:1 can put out 1.2Nm The 3639 motor you linked at 3S, geared 3:1 can put out 0.14Nm

Changing your wheel diameter does not change the amount of torque the motor puts out. It affects your speed at a set RPM but not the torque.

E: I guess a larger wheel hs more inertia and therefore requires more torque to get rolling than a smaller one, but I imagine this is not that significant

57

I donā€™t see anyone giving importance to shaft diameter. The one you posted is 5mm and previous one is 4mm. Is it not important?

58

U could get a scorpion motor kit and get a small motor w a low kv made and that would be nice. Or rewind something. Otherwise itā€™ll be a loud big gear n risking bottoming the motor out also and bottoming the gear out. Or too few teeth and early deterioration or slipping. Maybe thereā€™s a nice gearbox out there though that would suit

59

Not really. As long as the pinion doesnā€™t slip on the shaft it should be good. The only times Iā€™ve seen that happen is with 3mm shafts.

1 Like
60

The amount of torque the motor puts out doesnā€™t matter. The only thing that matters is the amount reaching the ground. Changing wheel size drastically affects the gearing ratio.

Also OP stated hills donā€™t matter. Iā€™m well aware that this will be weak. I intentionally suggested it that way based upon what the OP has asked for.