Use a straight edge to see if the bend had taken place in windings part of the armature. I think that it would be rare but its a quick check. Hold the straight edge on the winding parallel to the axis of the shaft and repeat every 45 degrees. I assume that bends are typically between the large bearing and the windings because the shaft may be necked down in that area for the windings themselves. The steps listed are based on that assumption.
Arbor press

Having some V-blocks makes the straightening and checking process, easier and safer but some plain blocking would do in a pinch. Note that checking runout will be difficult with plain flat blocks since the armature will move in relation to the indicator.
Use the blocks to support the armature at the bearing locations. The bend occurred while the armature was supported at the bearing locations so the straightening will be done under the same conditions. I would leave the bearings on at this point to protect the shafts from getting nicked or flat spotted.
Shim the small diameter end block so the armature is parallel to the press table
Position a dial indicator under and near the end of the output shaft. Note the runout and set the indicator zero to split the difference. For example; a .010” runout should read +.005 to -.005
Rotate the armature so that the high spot is down. (Pressing the shaft center will raise the end)
Place a large block, one long enough to cover the laminates of the windings, and position armature so the ram is near the output end of the windings. The ram needs to be over the windings. While pressing here is not ideal, the motor may not have other areas that are accessible.
Activate the ram and press until the indicator reads zero.
Release the ram. Most likely the bend will spring back some. Use the difference between indicator readings to determine how much spring back there is and use that to get an idea of how much over shoot you need to get to zero.
After each pressing, rotate the shaft to see if the high spot moved to a different position. This could happen because of an over press.
Once things start looking good, also use the indicator to also check output shaft runout near the bearing end. Check winding runout as well.
Repeat pressing and checking as necessary. I would think that if you get the output to be within .002" runout would be awesome
Remove and discard the bearings. The balls may have been damaged during the pressing. Its always a good idea to replace bearings when the motor is apart anyway. Its a cheap maintenance item.

Use the lathe for final inspection if you have one. Deburr (especially the threaded output end) and clean the centers in the ends of the armature shaft.
Mount between centers in the lathe. Verify runout at the output shaft and bearing locations (bearings removed).

Regards,

Dean A. Stuckmann

5432 County Road U

Newton, WI 53063

On Nov 14, 2021, at 6:29 PM, Chris Zach <cz@alembic.crystel.com> wrote:

Interesting. Well, these are three new blades that were stacked together for a decade plus. It's possible the blade is way out of balance, but I think it's the shaft. How did you straighten it, and did you have to remove the bearing?

C

On 11/14/2021 4:39 PM, Dean Stuckmann wrote:
I had an experience with a bent motor shaft many years ago with one of the skinny motors. I straightened it out, verifying the process by checking it in a lathe.
Things seemed ok for a while but some of the wobble came back. I don't recall hitting anything else with so I’m assuming that the shaft had some metal memory of the bend. Just my thought.
Personally I would replace the motor or armature as soon as you can as the vibration is tough on bearings and could cause the magnet to break free.
With that in mind I purchased a very good blade balancer. https://www.magna-matic-direct.com/products/mag-1000-balancing-instrument.html <https://www.magna-matic-direct.com/products/mag-1000-balancing-instrument.html>
I couldn’t believe how much quieter the deck got after I used it. Not cheap but well worth it in my opinion.
Good luck!
Take care,
Dean
On Nov 14, 2021, at 12:36 PM, Chris Zach via Elec-trak <elec-trak@cosmos.phy.tufts.edu> wrote:

Took the E20 out yesterday to start on the leaves. The process is deck, tractor, vacuum, trailer with very big bag. The right deck motor has a slight axle wobble but it wasn't the end of the world. So off we went.

Then I noticed it was vibrating a *lot* more so I decided to swap out the armature. Not a biggie, just used a spare I had, took the top off the motor, dropped the armature through the bottom leaving the casing and magnets on, then put it all together. Fired it up, noticed it was still vibrating a bit, then saw another problem.

The bracker that goes around the mower motor to hold it on the deck had broken off in one spot. *Great*. The second spot had a crack in it right by a mounting bolt, but the first one was broken off in two places.

Normally I would pull the motor but these are getting rare. So out came the wire brush to clean up the edges and the collar on the motor, and out came the Elec-Trak welder, also known as the "glue gun".

The welder is pretty good, but you're doing DC stick welding so it is a bit tricky. Went to get my helmet and found that my good helmet (the auto-dimming one) was missing, leaving me with the stupid standard helmet. Which is a pain because you can't see *ANYTHING* until you strike the weld, usually in the wrong location.

So out came the 300 watt portable Halogen light which gives me a very very dim view of the work when I shine it right on the spot to be welded. Stuck some arcs, got used to it, and happily tack welded the flange part back on.

That should hold for leaf season, but once I'm done with that I'm going to put the deck up for repairs and properly re-weld it. Glad to have the welder, it comes in *very* handy for problem projects like this.

Question: Can a motor repair shop straighten a bent motor shaft? Should I pull the bearing or will they do that?

C

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