Servo motors

[frogeye]

Greetings all,

Great site, found by a redirect form the yahoo group - learnt a lot already

I'm considering the purchase of a TRIAC that has been retrofitted with gecko 320's and 'servo motors'. I've found out that these servos are infact 24v DC mobility scooter motors (2 x 100W x and y, 200W z)

Does anyone have knowledge of a retrofit like this, or could you offer some helpful insight?? What is the difference between a DC motor intended for traction use, and a servo motor??

Thanks all,
Paul

[Triac whizz]

real servo motors are designed with a skew rotor. which makes them more suitable for exact position control but it doesn't preclude other dc motors from being used. It's a case of suck it and see, in this case it would seem to work, using geckos, the geckos will fault if the encoder reports back more than 128 steps lagging so you will know its not keeping up.

Not having tried servo designed motors I don't know how well they hold a stationary position, they may tend to hunt about, that is oscillate about the postion they should be in. If that was the case, depending on the resolution of the encoders & gearing (if not reduced much) this would show up in the machining of straight lines.

[comet]

Hi,
I think that machine was mine I have sold it now,not to paul though.
The little 24 volt scooter motors work very well,there 6 amps and will take loads of abuse,plus you can buy them off ebay for about £10 brand new.
As far as "cogging" goes there not to bad, yes proper servos have skewed rotors and two sets of brushes,buts thats only nessary for real low speed work ie 1 turn every few seconds or so. For our purposes they are fine. Another usefull advantage is that they will run at 36 volt with the gecko's giving you about 4250 rpm. If you gear to travel about 2mm per rev you wont go wrong. Encoders can be cheap agilent or maxon,s Ive used 100 & 500 count encoders with success.
Having said all that,there are a glut of 48 volt 120watt servo,s on ebay fitted with 512 count HP/agilent encoders that would be a very good choice fot the x&y