SeatTime's DC motor Sim

This is how I drill my motor shafts, as I do not have a lathe.

Parts used - screw shaft, suitable nyloc nut and smaller nut/washer that is a tight fit inside nyloc nut.


Place small nut/washer inside nyloc nut.



Screw nyloc nut onto shaft so small nut is centered (Not too tight). Place in a vise and use the hole in the small nut as a guild to drill pilot hole.


Remove nut and drill out to the required size.

In place with Hall Effect pot.

thats a good idea for sure, I really must try that , especially with my shaky hands

how is the pot being held in the axle bolt ? just pressure fit or did you glue it in ?

Unfortunately I did not have allot of room to do much else but epoxy it in, as it was not originally designed to have the pot fitted directly to the shaft. Works well and I don't expect any problems. In regard to the Hall effect pots, I have not noticed much difference in response between my good quality wirewound pots, although over time I expect the wirewounds would wear out. There was although an improvement in going from gear driven to direct driven for the off driven slack in the system.

Beware the epoxy will eventually snap , I pin through the bolt with a 2.5mm R Clip. But as long as you are aware of this and check regularly there wont be a problem.

2mm drill bit right through bolt and pot, a bit of wire twisted through to hold it all

You could tap in a hole on the side with threads to ensure it doestn move

NM I see what you did now, same idea.

I will say that out of welding, motors, wiring and all that goes into the build I found mounting the POT to be the biggest pain and problem to solve.

Sim is finally out of the garage and in its home. Way more comfy and I can close the door and turn out the lights for full immersion.


Also acquired some 300mm stroke actuators (possible future project) for the right price. I am going to connect a spare 200W DC motor up to one (no gearbox) and see how they perform . Tested with just a battery drill connected directly to the leadscrew and they easily lifted me on my chair off the ground. May not be as fast as my current setup though - time will tell.

beawdy mate! Looks good, and keep us informed on actuator conversion.

Re actuator: The screw seemed to be of decent quality (metal) but the drive portion is made of nylon and ended up binding and finally destroying itself in load testing. As a separate question - has anyone fitted different ratio gear boxes to the Motion Dynamics 200W mass produced 12V worm drive motors? I would like to try different ratios, but the replacement gearboxes they sell do not seem to fit (from looking at the drawings/photos) the mass produced motors.

50:1 boxes have the same mountings , most of the MC2 and MC4 boxes have the same mounts, most have 3-4 bolt holes in the boxes face and the motor either have 2 or 4 bolt mounts.
@bsft has changed a pair out recently for a mates sim 25:1 changed to 50:1.

Hi Rob, Do you or @bsft know if you can put the hollow shaft from the 200W mass produced motor/gearbox in the 50:1 gearbox, instead of the solid shaft they appear to have?

Good to hear, so the 4 bolt gearboxes can mate with the two hole motors. Designing/testing for my possible 6DOF begins - The small electric motors also run at a similar speed to what I am planning to run the real sim at.

Ah no solid shaft not removable, Bsft made a simple connector for it for his mate, he will probably chime in and share a photo or two.

@SeatTime nice idea for model. And yes testing with a simular speed motors will help.

There is a hollow shaft gearbox available, but its expensive . @Roadster2 , do you have hollow shaft gearboxes for 50:1?

pots mounted with custom levers on solid shafts on 60:1 boxes

New steel gearbox turned up 60:1, fitted OK to my spare motor although I had to slightly 'adjust' two of the holes in the gearbox so it mated properly with the motor. Powered it up, works fine. Seems to be no noticeable backlash or drive back, although I have not load tested it yet . Once I make up a test rig for it will begin load testing. As shown in bsft image, drilling the back of the solid drive shaft looks the best way to fit a feedback pot.

First lot of carbon fibre bits have turned up - might be able to start building soon .