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[Roadster2]

Having just bought some of these myself I thought it worth passing the information on to other members here.

A UK supplier, Motion Control Products, is having a clearout of some of their stock and have put these on eBay. The motors, are 12V, 180W, 5000rpm http://www.ebay.co.uk/itm/380393781762?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_500wt_1413. Although sold separately they also have 25:1 MCP4 gearboxes http://www.ebay.co.uk/itm/110751091855?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649#ht_500wt_1413.
When purchased together the gearbox will be fitted to the motor.

The motors are £29.99 and the gearboxes £19.99 so excellent pricing.

I have checked with the supplier and they are happy to ship outside the UK. They have also been extremely helpful prior to making the purchase.

I have no association with the company. I'm simply happy with the units I have purchased and would like to give other members the opportunity to buy their motor/gearbox units at a discount price.

[TowMater]

The price is good.
However isn't the speed a bit to much if i want to replace my wiper motors with these ones . 200rpm unloaded. My wipers is more like 60rpm?

[Roadster2]

The Dayton DC motors that some members use are 180rpm output from the gearbox so not too different. I'm not in a position to try these yet, far from it, so perhaps others might be able to give a better response. There are methods of reducing the speed but I'm hoping that these wont be needed as it will only complicate the build.

[bsft]

I use these motors with great success.
The 180 rpm concerned me at first, but I used the PID of the controller to slow the motors reaction down, as well as some well written profiles, so I can get slow , slushy motion as well as fierce bumps, all out of the same race.
They do tend to drain some power I found, so expect up to and over 30 amps per motor if you are really pushing them.

[Roadster2]

Hi David. Thanks for your input here.

If my calculations are correct then at 200rpm it's going to take 0.15 seconds for half a revolution of the shaft. If the actuating lever was 60mm hole to hole then 180 degree rotation could move the tie rod 120mm in 0.15 seconds, therefore around 800mm/sec. This is assuming no losses and in action the actuator lever will probably be set to travel through less than 180 degrees.

50:1 gearboxes are available which would reduce the output speed by half but if my physics memory is correct this would also reduce the torque available.

If I can source a couple of beefy power supplies and a couple of Pololu controllers I'll hook everything together for testing. I think I may then be asking you about using the PID !!

[value1]

If you compare two motors of the same spec but one with different nominal RPM you will see that the motor with the lower nominal RPM has
• higher nominal (continously applicable) torque (dotted line MN at 3.7 vs 3.0 Ncm)
• higher starting (maximum) torque (point, where the three lines cross the x-axis at 15.7 vs 12.7 Ncm)
• is more efficient at lower speed (see dashed vs solid red line).

However with 180W power you have enough buffer to compensate for the lower efficiency
And the position is controlled by your driver (jrk, amc, whatever) and not by the motor. So the driver will just issue less or shorter impulses to mover your sim.

[bsft]

OK, that looks more complicated than I can understand.
I put a lever 45mm ctc on each motor. I have run them 300mm at the back under the seat from the pivot point, 350mm forward under frame of pivot point, 350mm forward and 200mm out to the side connecting to the steering wheel mount and finally at the foot level on my current sim at 700mm forward of pivot point.
I found them from the beginning to be fast, but it was just a matter of using the PID of the JRK to slow and settle them to a point I could sort them out. The PID is to slow them , but not too much and to stop errors in the JRK utility. I am not sure of rpm as they are under load, I guess its maybe 120-140 rpm currently. I wrote profiles so lateral and longitudinal was soft and bumps were harsh.
Needless to say, they are good motors , and have impressed a few people with their working. Yes they require power. I run a 13.8v 32 amp power supply in parallel with a car battery. I have no problems what so ever with this combination.
And by the way, the JRK will run 30 amps continuous as long as it has a decent size heatsink and good fan cooling.
Feel free to ask questions, but as far as PID goes, I am only familiar with the JRK, so if it is any other control board, I cannot help.
And I am NOT associated with Pololu whatsoever.

[Roadster2]

Hi value1. Thanks for your detailed input but don't forget that it wouldn't be a case of comparing two motors with different nominal speeds. In both cases the motor itself would be identical, it's the gearbox that would be different. Running the output of the motor through a 25:1 ratio gearbox is going to reduce the speed but increase the torque. The question is when using a 50:1 ratio gearbox on the same motor the speed will be reduced even further (to 100rpm) but will the torque available then be lower or higher than when using the 25:1 ratio gearbox ? I suspect my initial assumption above, that it would be lower may be wrong and that in fact it might be greater - slower speed, greater torque.

I'll check with the supplier and come back on this when I have a chance.

[bsft]

usually a larger ratio will give more torque, but at the cost of speed. Think of a bicycle with gears, you pedal and the chain goes to a set of gears, so if the gear is larger on the wheel (not the pedals), it is slower, but you get more torque.

[TowMater]

bsft is right. Lower gear ratio = more torque (in most cases)

I would say, moving 120mm in 1 sec would be good. 120mm in 0,15sek is really fast, maybe to fast if we do not want to max the current all the time. It is all about hardware, (drivers motor etc)