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View Full Version : The sweet purr of success (motor shaft repair on a Doerr motor)



abn
06-12-2004, 06:21 AM
Just wanted to post a thanks for the last couple motor shaft repair threads. In my case it was a motor shaft modification. I tried pressing on a stub and spot welding. But I'm such a poor welder I ended up putting a lot of heat in and warping the shaft. I cut away that mod and reasoned that it was the heat that was the enemy so I cold pressed on a stub with epoxy to eliminate the heat. I also ended up needing to bore the motor housing for a larger bearing (to accomodate the shaft modification). Still had runout problems.

The main hassle I found was that, with my existing equipment and experience level, working around the shaft with the rotor laminations, integral fan vanes, and balancing protrusions-coupled with the differing diameters on the stock shaft- it was very hard to find a machined surface to indicate off of and a surface to press on for shaft straightening that wouldn't cause damage. Workholding and just work in general were complicated, if I could get to a surface there was too much overhang. If part of the work wasn't in the way part of the machine was etc. etc. etc.

Finally after John Stevenson's reply in someone elses motor shaft repair post regarding pressing out the motor shaft. I investigated that. Pow, two spot welds cut with a carbide burr...a couple more minutes on the press and the stock shaft was out. I "blueprinted" the critical dimensions off the stock shaft. Chucked up some stock with a little extra length for workholding. Left the OD a little larger than stock and cut some retention splines in it with a 60 degree threading tool turned sideways using the lathe as a shaper (also learned here). Did it all in one set up, everything concentric, and a straight shaft. Cakewalk to measure and indicate everything. Unfortunately my shop time is measured in minutes rather than hours so I had to leave it. I finally got a chance to cut the keyway, trim the shaft to length, and press it in to the motor yesterday,cleaned everything and reassembled the motor, plugged it in...and it purrs like a kitten. I let it run in the backround for about 20 minutes no weird vibration, no stalling, comfortably warm to the touch. A success!! I'm ashamed to say I think it's taken me a good portion of a year among the distractions to get this thing fixed. But I learned a lot along the way. I think I've spent so much time learning to restore things and preserve the existing (which has its place) that I forget to think like a machinist and realize sometimes it's easier to just scrap stuff and make a replacement. Plus I really didn't know that the motor shafts were simple press in affairs, seems pretty obvious now.

http://img4.photobucket.com/albums/0803/abngineering/motorshaft.jpg

spkrman15
06-12-2004, 07:28 AM
Hey ABN,

Good job. Do you have a picture of the motor finished? Why did you have to modify the motor? Ah the curiousity of the HSM. Once again...good job

Rob http://bbs.homeshopmachinist.net//smile.gif

Paul Gauthier
06-12-2004, 09:57 AM
Good job. It is a nice feeling knowing you can fix you own stuff.

------------------
Paul G.

ibewgypsie
06-12-2004, 11:06 AM
In other words what I read,

You have learned a lot by sharing here on HSM's post?
I have too.
Hopefully I have gave back a little.

David

wierdscience
06-12-2004, 10:11 PM
A job well done indeed!

abn
06-13-2004, 11:29 AM
Thanks, here's a link to the completed motor:

http://img4.photobucket.com/albums/0803/abngineering/doerrmotor.jpg

I was having a hard time finding a 115V 1Phase 1HP 1725RPM motor (My electrical service is 20amp 115V 1phase via extension cord from house to shop). So when I found this one I got it. Plus it's shiney AND elctro-mechanical so I figured if I ever really pissed off IBEW, i could just show it to him and he'd be mesmerized long enough for me to get my wallet, keys, pack a light lunch, and run. It originally had some sort of gear drive thingy on it (I tried to find it to include in the picture but couldn't) and I assumed I could remove this and access the shaft. When I took off the thingy I found that there was no real shaft but a slotted key to drive the thingy. Originally, I was going to turn a NEMA C adapter and sleeve a standard motor to 3/4", but what really attracted me to this motor was the large diameter non standard mounting face that eliminates the need for an adapter for my mill.


<font face="Verdana, Arial" size="2">Originally posted by spkrman15:
Hey ABN,

Good job. Do you have a picture of the motor finished? Why did you have to modify the motor? Ah the curiousity of the HSM. Once again...good job

Rob http://bbs.homeshopmachinist.net//smile.gif</font>

John Stevenson
06-13-2004, 11:44 AM
<font face="Verdana, Arial" size="2">Originally posted by abn:
Thanks, here's a link to the completed motor:

http://img4.photobucket.com/albums/0803/abngineering/doerrmotor.jpg
</font>


IBEW,
DON'T LOOK AT THE PICTURE WITHOUT SHADES ON.

I know you are a dedicated drinker but painting you mill in Guiness colours so it don't shine is going too far http://bbs.homeshopmachinist.net//biggrin.gif

John S.

spkrman15
06-14-2004, 11:44 AM
Wow that is shinny? I had to turn down the contrast on the screen!!!

Rob http://bbs.homeshopmachinist.net//smile.gif