[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: (ET) Bearing job, magnet reglue, I hate hubs



Well, went out this afternoon and pulled the supports from the magnets. It seems to be holding well, so I put the motor together for a test.

No shorts to ground (good), the bottom plate does not have a tab on it to align it with the motor housing (odd) and I got the motor all together for testing.

It runs. Smoothly and pretty quietly. Pulls about 2a at 4 volts and just turns slowly, on a six volt battery it runs nicely, 12v runs faster, 24v runs quite quickly. Quiet in both directions and no wobble on the shaft.

Good news!

Bad news is that the endplay is excessive (1/8 of an inch) so it looks like the circlip is missing and the bearing went too far down. I'm guessing I have to put a new bearing on it if I move the old one with the puller, correct?

Now to find a circlip. Anyone know the diameter of these shafts off the top of their head? Or I could just take one from my dead mower motor...

Chris

On 8/4/2019 2:33 PM, Chris Zach wrote:
Ok, so I went out and spent $50 bucks at harbor freight for a bearing puller. Nice enough set, use the big puller for these bearings and not the small one.

First I practiced on an old motor shaft. Rear bearing is simple to remove, tapping on the new one with a socket just a bit smaller than the inside race got it on with no problems.

I could not remove the blade hub from the bottom: Putting bolts in the hole all the way simply results in the bolts collapsing with the puller. Heat didn't help, so I gave up for now. Maybe I need a tungsten rod or something like that but the forces here are simply insane.

Next up was the real motor shaft. Back bearing came off pretty easily but the front one was another matter. First the bearing exploded: It broke apart and the outer race cracked. So much for that. Getting the inner ring off took heat, pressure, and whacking away at the puller with a hammer but finally it started to move and came off. I cleaned up the shaft, used the old inner race as my spacer with some 3/4 washers and a 21mm socket to tap on the new bearing (once again only pressure was on the inner race) and I think I drove it on a tiny bit too far. Will see what that does to the motor alignment.

Next job was to fix the magnet. Before I started gluing I noticed that it was impossible to really hold the magnet in place because it pushed away from the other magnet in line with it, and it always wanted to smack into the magnet on the other side. So after a moment of though I got some 1/2 playwood, and started making jigs.

First I cut a strip a bit wider than the normal separation amount of the magnets. Then I used the grinder to make a perfect snug fit so the wood would just go down the side. Then I did the other side, now I have a set of guides for the new magnet.

But even that is not enough as the magnet pushes away from its neighbor. So I made a second spacer that went across the inside diameter of the motor magnets. Just barely fits. Now I'm ready: I cured up some JB weld, covered a good bit of the magnet face and the inside metal face, put in my two side jigs, put in the magnet (I marked it, also it's easy to see the side that butted the other magnet as it's pretty clean), then drove in the center spacer, made sure everything was as aligned as I could, and am leaving it for a couple of hours to cure.

Hopefully this works. If so I'll assemble it and give it a try on a small 12 supply. Should spin right up.

Next I am going to need some sort of end seal, as I didn't see one on this motor, and something's got to keep junk from getting in there. I am using sealed bearings this time as opposed to the stock open ones with metal shields, we'll see what happens.

Any other ideas on getting these hubs off, or should I just cut them lengthwise with my cutting wheel?

_______________________________________________
Elec-trak mailing list
Elec-trak cosmos phy tufts edu
https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak