DPittman
Ultra Member
Yup I guess that would work also.
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Dc motor brush sparking
- Thread starter DPittman
- Start date
DPittman
Ultra Member
Wow that's a nice selection. I'd probably buy any that you want to sell. I'm not really sure what ones are mostly likely needed but I'd like to have a selection available. I only have a 1/4 diameter ones so a couple of the 3/8" might be nice and then maybe some of the .015" thickness ones??
I once looked into buying some cutters from Martindale but I believe I had to have an account and minimum order and so I just moved on as it was not real pressing for me.
I'm trying to convince myself that I should buy your whole setup but then I have to make a run to Calgary
DPittman
Ultra Member
Well $60 is cheaper than I can drive to and from Calgary but then I wouldn't get the fun of a drive. Usually a Calgary trip for me is seeing some sort of doctor and usually not so fun.
There is a little info in the thread below, although similar to what has been suggested here. I used to turn the comms down in some AC motors, clean the grooves out with a hacksaw blade as suggested in this thread (below) and then with new brushes, expected some sparking till they formed to the comm. But it was a more consistent spark. I think yours is more erratic. Are the brushes for that motor ie OEM? Is there different grades of brushes? I thought there was/is but I am not sure. It was in the hospital so we had to replace with OEM parts only. Are there AC and DC brushes? Different hardness? I do agree that the comm looks rough and could be causing the brushes to jump..?
I just got a 90 vdc motor back from a motor repair shop. It is used in a squash ball machine (like a tennis ball machine but smaller balls....
) It is a little motor. When I took it apart years ago, the majority of the windings were broken where they bent around the contact at the armature. It was weird. I suspect the design of the machine caused it. When the ball drops, it falls between two wheels, which fire the ball into action. This results in a jarring action and it is direct drive with two motors driving two wheels. I was hoping for a rewind but it would be super costly so the shop did a repair for me. The motor is no longer available. We will see if it lasts.
My 2 cents.
forum.allaboutcircuits.com
I just got a 90 vdc motor back from a motor repair shop. It is used in a squash ball machine (like a tennis ball machine but smaller balls....
) It is a little motor. When I took it apart years ago, the majority of the windings were broken where they bent around the contact at the armature. It was weird. I suspect the design of the machine caused it. When the ball drops, it falls between two wheels, which fire the ball into action. This results in a jarring action and it is direct drive with two motors driving two wheels. I was hoping for a rewind but it would be super costly so the shop did a repair for me. The motor is no longer available. We will see if it lasts.My 2 cents.
Motor carbon brush sparking. Why it happens and how can I fix it?
Hi, I have a 300W electric saw (small), and the motor carbon brushes start sparking "like crazy" whenever I turn it on. First, I'd like to know what can cause a spark (short circuit, simple friction between brush and metal???). The brushes are really easy to take out, so I did and they look...
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DPittman
Ultra Member
No I put in some generic brushes I bought off Amazon. I have no idea if the previous set were original but I would bet they were. They were not worn down to nothing but were pitted so I figured $10 for brushes would be an easy and cheap fix.
I have read that there are different qualities of brushes and I suspect I hot the bottom of the barrel for quality in my replacements but I am guessing that original would have also been similar.
As I turn up the potentiometer when running the sparking gets crazy and then blows a fuse. I must have a short somewhere I guess.
In the linked thread discussion you provided I learned that mica is no longer used in modern motors, and apparently does not need undercutting as it wears down itself. Good info.
Looking at your pictures it seems that the mica is not cut low enough closest to the windings. The front part looks good. I've used a hack saw blade in the past to cut the mica on starter motors. The signs of good brush contact is a thin black film on the circumference of the com.
DPittman
Ultra Member
Yes my motor is very similar dimensions to that, however the body construction is different.
I cut the mica grooves on the commutator deeper to see if that would help. No difference.
I believe the spring pressure on the brushes is sufficient but will look into that again.
I tried running it in a bunch hoping the sparking would reduce but it doesn't seem to help. I can only run the motor at about 1/3- 1/2 speed before sparking gets like fireworks. The motor seems to get overly hot in the running I did.
I agree.
Based on a close up view of that commutator, something bad is going on there. It looks like someone filed it. Not likely so the next possibility that jumps into my mind is excessive current (the sparking you see. You said you tested the winding earlier. Try testing them using the brushes as your contacts to the winding with the motor being rotated slowly by hand and an ohmeter across the brushes. You can expect it to jump around, but it should have a regular "rhythm" to it.
This might be a stretch but i would take a piece of fine emery cloth 400ish?, cut it to fit around the commutator and then tape it in place, rough side out. Then put the brushes back in, and turn the comm a few times,or many, to see if the brushes can be shaped to a nice fit on the comm. You will also be able to see what wear patterns you are getting on the brushes and perhaps glean info on the seating. . The sand paper can be held together with a piece of tape "upside down" on the inside of it. The trick will be to get it tight enough to stay in place on the comm. Perhaps the same effect can be gained outside of the motor housing with some fancy rigging but if the brushes are making an irregular contact with the comm, maybe it can be improved......
I would think, no air gap, no spark to observe sooooo....
Also, at higher speeds, more current and more bounce on the brushes, if that is what is occurring. I would stretch the springs a bit to increase the force a bit too.
Another 2 cents by Shawn
I would think, no air gap, no spark to observe sooooo....
Also, at higher speeds, more current and more bounce on the brushes, if that is what is occurring. I would stretch the springs a bit to increase the force a bit too.
Another 2 cents by Shawn
DPittman
Ultra Member
Ok put the armature back in the lathe to examine straightness....looks okay.
The bearings feel smooth but the one still in the back housing is hard to tell for sure. But wait! Do I sense a wee bit of side play in the other bearing??? Gosh it's hard to tell just by hand and such a smallish bearing and all.....so I chuck the armature back in the lathe this time on outside of the questionable bearing and by gosh now at the end of the armature I can definitely see some play!
I don't have any of those bearings on hand but I'm sure they will be cheap and I think that is likely much of my problem.
DPittman
Ultra Member
Ok I did find some bearings on hand and put them in. Still no difference. Definitely some shorting somewhere I'd say, the motor gets too hot for the bit of running I did and even the controller board seems to get warmer with this motor than with a good motor. Well the motor is a right off I guess but I did learn a few things. Thanks for all the help folks.Ok put the armature back in the lathe to examine straightness....looks okay.
The bearings feel smooth but the one still in the back housing is hard to tell for sure. But wait! Do I sense a wee bit of side play in the other bearing??? Gosh it's hard to tell just by hand and such a smallish bearing and all.....so I chuck the armature back in the lathe this time on outside of the questionable bearing and by gosh now at the end of the armature I can definitely see some play!
I don't have any of those bearings on hand but I'm sure they will be cheap and I think that is likely much of my problem.
I must of missed something in my testing with the multimeter.
Well...that looks exciting.....
