Heinzmann armature insulation failure

[passpato]

My old 36v Heinzmann has blown two controllers in six months. The controller supplier says its an unusual fault and something they don't see often. At first I thought it was aluminum corrosion dust causing arcing on the armature but I have stripped the motor down and found the insulation damaged on the winding plate. See photo
http://www.flickr.com/photos/75570124@N02/6974559080/ copy and paste to browser
Is this my problem ? Does anyone know if I can repair this ? A new motor is so expensive.
I have a spare motor with a better winding plate but it too is making noises from behind the winding plate.I can't get the gear off the back of the shaft without breaking the housing. Has anyone done this?
See photo
http://www.flickr.com/photos/75570124@N02/7120644001/ copy and paste

Also does anyone know how to keep the shim and spring washer in its housing near the brushes when reassembling the motor? The magnets pull it out before the motor closes.
Any help appreciated
Marcus in England

 

[amberwolf]

There is probably a lockring or pin on that gear, securing it to the shaft. If you can get a good closeup of that, I could tell better, but am only guessing ATM.

Regarding the insulation, unless coils are shorting against each other, then there is probably no way for those coils to short on anything else. There should be a large enough airgap between them and the magnet(s) to clear easily. Unless there are scratches on the magnets corresponding to the coil radius, they aren't shorting on the magnets.

I have a similarly-made coreless axial flux motor, out of a radiator fan, and some of it's coils are not fully embedded in the plastic, yet there was never a problem with either it or it's twin that I ran in parallel off the same little controller.

 

[passpato]

Thanks Amberwolf. Here is a close up of the gear. No pin or clip,just a press fit that carries all the drive.
http://www.flickr.com/photos/75570124@N02/7120804417/
There is a bearing behind the gear which heat would destroy and as soon as i start pressing the shaft the aluminium case warps. I can't get a puller behind the gear either.
Great news that you dont think the wires are the cause of my problem. There was a lot of corosion dust and damp inside the motor do you think this was my problem? I have now cleaned and painted the inside of the hub with self etch primer and will seal the motor with silicone.
4qd (controller supplier) say that dirty motors,sticking brushes etc cause a charge build up and sudden back flow of electricity to the controller causing a mosfet blow.My motor goes for 3 months then it blew under no load on flat ground. 4qd are baffled by the damage (identical twice) but not normal damage they have seen before.
Do you think epoxy resin would be a good idea on the exposed wires?

 

[dogman dan]

MMMM, toasty.

To my knowledge that gear doesn't come off.

Too bad, there are some nice things about the heinzmanns, like the round axle and integrated torque arm. But maybe it's just time for you to start over, with a brushless planetary gearmotor such as a Mac from Emissions Free. Slower to overheat than a brushed motor of any kind for sure.

 

[amberwolf]

There is a bearing behind the gear which heat would destroy and as soon as i start pressing the shaft the aluminium case warps. I can't get a puller behind the gear either.

Is there zero space between the gear and the center bearing collar? If there is enough space, you might be able to get thin steel wedges between the bearing face and the gear, inserting them equally-spaced all around it, then tapping in others between them, until it begins to force the gear away from the bearing. Eventually there would be enough space to get the puller in there.

Sticking the whole thing in the freezer may make the shaft contract enough to let the gear come off, too, since it must be an interference fit if there is no retainer or pin or anything for the gear. Might need more than a normal freezer temperature, more like dry ice or something.

Great news that you dont think the wires are the cause of my problem. There was a lot of corosion dust and damp inside the motor do you think this was my problem? I have now cleaned and painted the inside of the hub with self etch primer and will seal the motor with silicone.

If there is buildup of stuff in the thin gaps between rotor and housing, or magnets, then yes, it could cause drag/etc. If it builds up on the commutator or brushes, then brush carbon could also build up on it and when damp it might conduct better--at high currents and high voltages it can cause an arc flash, too, if it gets hot enough, but this is unlikely within a small low voltage motor like that one.

4qd (controller supplier) say that dirty motors,sticking brushes etc cause a charge build up and sudden back flow of electricity to the controller causing a mosfet blow.My motor goes for 3 months then it blew under no load on flat ground. 4qd are baffled by the damage (identical twice) but not normal damage they have seen before.

Well, if 4QD is baffled, that's saying something, cuz they (at least the proprietor/originator) definitely know brushed motors and controllers and how they fail. :? I learned an awful lot from him.

It is definitely possible for brush/comm buildup of stuff to cause problems, especially in unsealed motors. One of the powerchair motors I used had grease leakage from the gearbox into the motor, and it ran REALLY hot because the grease caused EVERYTHING that got into the motor to stick to everything and build up till it caused friction, and the grease got on the comm and burned, etc. Never killed my 2QD or the Curtis becuase of it, but definitely was bad for the motor.

Do you think epoxy resin would be a good idea on the exposed wires?

[/quote]
I don't think I'd put anything at all on the rotor--it could unbalance it, and that coudl eventually cause other problems from the vibration. I left fan motors alone for that reason.

Unless the actual wire is exposed, with enamel rubbed off, there's not much to worry about. The only thing the epoxy they are in is for is to hold them all in shape, to create the rotor itself, not to prevent conduction.

 

[passpato]

The problem with freezing is that the gear would contract as well as the shaft and there would be no gain.It would be usefull for assembly.
Im thinking If I fill the holes with epoxy it should improve the balance.There was plastic there before.I don't think you can see it well in the picture but there are pieces of plastic missing out of that rotor and the aim is to stabilise the damage and improve insulation.I don't know the motors rmp but it must be low and the rotor is not heavey so I dont think balance is an issue.
I have now found a burnt spade connector on the motor side of the controller that I suspect is the cause of all my woes.
I agree about 4qd. They are very knolledgable and they have been very helpfull and understanding.Im glad I bought from them.

 

[amberwolf]

If the spade connector is burned, then likely it was not making a good connection, and arced. Could be corrosion or simple mechanical failure of connection.

 

[passpato]

I used yellow crimp connectors with a ratchet crimper thinking that its the crimp/ wire connection thats unreliable but I think it got loose on the connection causing an arc. Im using the copper spades 4qd supply now. Wish I could solder them on but couldnt get the cover off then. They should change this connection for a clamp down type connection on the controller.
btw .. Just exploring your address Sol , Local bubble, Orion arm, Sol being our Sun from the Latin for Sun as in Peruvian currency and local bubble our universe in the Orion arm but what points to Earth? Wouldn't want you to loose any post ! I think you nead to add "terra Nova"