RC Tractor Gearbox

[RC Tractor Guy]

I just taught I would share some experiences about choosing a motor and gearbox to drive your homemade RC tractors. I'm working with 1:32 scale diecast siku model tractors, for my first attempt at a drive I used a small servo with plastic gears modified for continuos rotation. I used lego gears to drive the tractor axle, a worm gear on the servo and a small gear on the axle. This worked great for a while however eventually the strain of pushing a heavy diecast model around and issue of having nothing to slip if the tractor hit a wall or other obstacle meant that the plastic gears in the servo eventually failed. Lesson number one, plastic gears simply wont put up to the stress unless there is something to slip before the gears break.

With that in mind I then decided to use a pulley system with rubber o rings, this meant that when the tractor hit a wall the o ring would slip on the pulley wheel without breaking anything. The problem with mine anyway is that the pully probably slips a little too easily which means that the tractor can't pull up hills or pull heavy loads which isn't great.

I'm currently working on my second homemade RC tractor, this one is a fendt 936. This time I have decided to use a SIKU motor and gearbox, I chose the gearbox from the SIKU control 32 fendt 930. This gearbox has metal gears and a solid connection between the axle and the wheels. I am hoping that this motor might be capable of spinning the wheels before it damages itself but I haven't gotten to a testing stage yet. This method was about five times more expensive and require a lot of filing to the model body to fit it in but it has a very solid mounting in the frame now, much better than the previous tractor so I am very optimistic. If anyone wants to find out more let me know and I can update if there is an update

[Michael]

You should try using some tamiya motors, they make small ones for RC tanks at scales like 1:35. If you look on ebay for Tamiya 70189 you'll find a small motor with gearbox, it only has plastic gears but you can adjust the gearing ratio to give you the most realistic speed. They are a lot cheaper than the SIKU ones but I'm sure if they would pull as hard, maybe you can test them since you already have the SIKU one and tell us.

[Tom Greenan]

I've used a bigger Tamiya twin motor gearbox, the 70097 for a small robot and it worked good. Has plastic gears too but its still good. Might be useful if you wanted to make a kind of skid steer on your tractor although you're probably looking at 1:16 scale tractor realistically.

the Tamiya 70103 is a small one, haven't used it so dont know about pulling power. Just suggesting another small motor gearbox for the 1:32 guys.

[RC Tractor Guy]

Thanks for the motor suggestions guys, I was actually thinking of using a Tamiya 70189 for my Universal Hobbies 7810 because it needs to be a very small motor. When I get that made I'll be able to do a video comparing the pulling power but I'm very confident it wont pull like the SIKU motor but it will be a good test non the less.

[Martin]

If i wanted to use the N20 motors..... what motor RPM would i need for the rear wheels?? and if i wanted to use this same type motor for a front loader what RPM would i need for that?

[tomek]

Look at blog, 21 march

[RC Tractor Guy]

Hi Martin, as tomek said I did a video about this in march trying to figure out the best motor rpm. The siku motor was around 72rpm at 3 volts I think, you can check the video here.

I also made a calculator here for scale speed but tomek has pointed out before that sticking to this might make the tractors too fast to easily control and to get speed you need to sacrifice torque so it may be better to go for a slower more powerful motor.