Replacement Servo Motor

[subpilot]

Been away for awhile but going to drag out the RN. Has anybody found a replacement DC motor for burnt up or shorted HSR-8498HB servo motors?
I'm well past the warranty and need to repair a shorted servo.

[engineer]

HEY subpilot, try going through the hitec catalog for a servo that has the same size motor,and through board lugs. I bet that will take less time than trying to get one .Though you could try E-mailing tony ohm @hitecrcd, he's pretty cool. does &ha40 = the acc. constant in your code? I recieved the bluetooth and am trying to get it playing. Also, the hsr-8498hb motor is glued in so CAUTION as you press it out. I don't know but it seems as if I always have either a servo on order or in for service, can't wait for the HSR-5498, or some on board current monitor so that I don't fry the H-bridges.

[subpilot]

Seems like that would be a crap shoot and/or too expensive to gut another servo type. I can get the motors out by pulling them with some hemostats. Don't think you can press them out because the shaft isn't exposed.
There are no markings on the motor to help figure out a replacement. I emailed Service at Hitec but will try Tony.
Seems like this problem is well documented and I would have to assume Hitec has a new motor supplier by now. Can't be very cost effective to replace servos constantly.
I had considered adding a SMT fuse to the servos to protect the FETs but don't think I'll bother if I can get reliable motors. The FETs are easy enough to replace and I have a good stock of them now anyhow.

You lost me on the code question.

[engineer]

delete

[engineer]

wow the coreless motors are pretty robust considering thier size, I've only smoked the H-bridges, and Hitec warranties them easy. I've had no joy trying to remove a motor in these servos, I had to rewire the gripper servo to exit the other side of the case. I tried to just slide the wire under and the servo only ran one way. Hitec r&r'd it in two weeks and the thigh servo I smoked three weeks ago is back they r&r'd that one too. Most servo motors are wired to the board not lugged down like these and it's easy to change them. If we were lucky a similar motor could be inside a low price servo, I'm glad their not LEGO servos, I smoked a few of those and they didn't r&r those. the code question was about the two axis accelerometer I've not been able to get the proper trigger values to get RN-! to respond to it.

[Humanoido]

All this talk of smoking servos has me jittery. What must I do to smoke a servo, so I know how "not to smoke one?!" I'm only aware of the problems that can result if a servo wants to move but it's being restricted.

Humanoido

[subpilot]

The one that went up in smoke on me was unloaded and not stalled. The motor winding is shorted. It's now ~0.3 Ohms instead of the ~4.0 Ohms it's supposed to be. That fried the driver FET.
I think there are many people who have experienced blown servos. I dissected mine and found the varnish on the windings appeared to be melted a bit. Don't know if that was a result of the winding shorting or if the motor over heated and caused the wire varnish to melt.
I'm wondering if it may be a problem with too little dead band and the motor is oscillating. That could possibly be causing it to overheat and melt the winding.
engineer, I haven't touched my RN for almost a year and don't recall exactly what I did with the accelerometer code. I've abandoned Robo Basic and I'm migrating to a Servo Pod controller board but if I get a chance I'll dig up the old code and post it. Seem to recall that it was pretty straight forward tho.

[engineer]

thanks subpilot, Humanoido the servo I had that smoked was #20 and did it while I was trying to program RN-! while sitting. I won't do that again heysub does the controller your using run multi thread or is the language that much better than robobasic? thnx

[Humanoido]

engineer, I'm not sure what took place. Did you have RN on and in a sitting position using the IR remote? When you say programming, were you downloading a program using the robobasic application software and cable? I have deliberately put my RN into a sitting position with the servos off and controller on, to save power, when writing/editing/downloading templates.

Humanoido

[DirtyRoboto]

This is what happened to Son of Robonova

[Humanoido]

woa! ...ummm, since he had only one DOF, he may have overheated when doing too many repetitive musical butt boogies... (I told you he couldn't keep up with Dad's drum dance!) but really, that looks terrible to cook like that - looks like a direct short... so we are dealing with some defective servos and/or servos that can't take extended use...and it sounds like the design can be improved...you probably know more than the original designers. Maybe hitec needs to guarantee something like 100,000 movements per servo, and lower the price of these less reliable ones to less than $7. Now I'm afraid to let RN do any dance routines! He'll have to sit home in the rocking chair.
Humanoido

[Bullit]

Subpilot, I'm still at a loss as how to get the motor out of this servo with out breaking the case. Can you fill me it a bit. I thought perhaps heating it up in the oven? On yours you say the the windings were toast but is the commutator in good shape? I had assumed on mine that it the commutator that had failed. I have had several failed HSR-8498HB's and most failed when the RN-1 suppossedly had the servos powered down.

[subpilot]

The commutator looks fine. A bit of wear but not shorted. The problem is definitely in the windings. I think Hitec is pretty good about repairing /replacing blown servos and I suspect they are aware of having a defective motor. But that said, if they were designed correctly you should not be able to blow the things up no matter what you do.
I didn't have to do anything but grasp the nub on the back of the motor with some hemostats and put a piece of metal across the plastic housing so I had good leverage and it came right out. I think it probably depends on how much adhesive they used when it was glued in.
I think the best thing to do is to just get Hitec to fix it. I would love to put a higher performance motor in there but it's hard to get small quantities and you would need to have the correct sprocket pressed on the shaft.

[engineer]

hi subpilot, if that motor came out that easy then you must have cooked the glue too. And yes the RN was sitting down with the motoroff while I modified the code to see if I could get the two axis accel parameters right so that the tilt routine would work. Pressing the puinion on and off shouldn't be as hard as getting the motor out, though I haven't repaired that many coreless motored servos. Now I shut down rn when I'm changing code. this forum has people that use an LCD for troubleshooting . To me the sonar code thier using is as greek to me,i'm limping into awareness in robobasick.