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Generators & Electric Motors General Discussion

Pole Shoe Removal Problem


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  #1  
Old 06-29-2016, 04:06:54 PM
George Andreasen George Andreasen is offline
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Question Pole Shoe Removal Problem

I have an antique 32 volt, 1/8 hp Robbins and Meyers motor that suffered shipping damage before it arrived at my house. The delivery people managed to drop the wooden crate and snap off the cast iron feet on both sides. As I see it, while irritating it can be repaired. My plan was to strip everything out of the housing and either braze or arc weld the feet back on to the casting, then machine them off flat on the bottom, followed by reassembly and restoration.

I pulled the end bells off and looked at how the two pole shoes were fastened to the housing, expecting to see a couple of screws........nope. In fact, there's no sign of any kind of attachment even after wire brushing and carefully filing the outside of the case. I now suspect that they might be riveted in place after a fashion, but I'm not sure as I can see no sign of anything. They sure didn't wind those field coils in place! Has anyone run into this before and if so, how did you remove the shoes/field coils? Until I get them out I can't move ahead with repairs.

Thanks for any help or suggestions!
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  #2  
Old 06-29-2016, 06:35:54 PM
Jim Rankin Jim Rankin is offline
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Default Re: Pole Shoe Removal Problem

Don't suppose they are cast with the housing?

Some of that old electrial stuff was pretty low tech and hand labor was used pretty liberally.

If you cannot find any rivets from the outside, perhaps there are screws or drive rivets that were driven from the inside of the pole pieces into blind holes in the housing.
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Old 06-29-2016, 10:03:07 PM
len k len k is online now
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Default Re: Pole Shoe Removal Problem

I was given a more modern 3 hp motor with cast iron feet that snapped off, used it for air compressor. There was just enough of the feet left for me to drill a new hole, used a much larger dia drill to sort of counter sink a pocket area for bolt head. Also had to grind down an eye bolt end into varying height to match slope of remaining "counter sunk area". Other than that just drill and tap a new mounting hole somewhere on the casting.

Think the snapped foot was on other side but this pic gives the idea.
http://www.smokstak.com/forum/attach...3&d=1349840985


One word of caution though, USE SAFTETY GLASSES !!!!!!!!!!

Was working very late into the night, thought that was why my eye were irritated for a week, come the weekend I found a steel splinter in it and had to go to eye doctor to remove it. Luckily it was not over the pupil or I would have had permanently distorted vision. I did not hear or feel the splinter come off the low speed drill's bit and into my eye. Guess it came off because of low speed and cast iron is brittle.

Last edited by len k; 06-29-2016 at 10:26:47 PM.
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Old 06-30-2016, 05:56:21 PM
George Andreasen George Andreasen is offline
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Default Re: Pole Shoe Removal Problem

Thanks for the replies! I've tuned it over in my mind and finally decided to have the local welding shop arc weld the pieces back on. I'll prep them by veeing out the break and having them restrict the welding duration to keep the heat down, with lots of "rest periods" in between. The field coils will be protected by a welding blanket.

Cross your fingers............
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Old 06-30-2016, 07:19:50 PM
len k len k is online now
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Default Re: Pole Shoe Removal Problem

Key to sucess in wellding cast iron is:
1) preheating the material,
2) do the weld
3) and then , post heating to slow the cooling

This is at odds with the need to keep winding insulation cool.


Also heard using a nickel welding rod inproves success odds.
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Old 06-30-2016, 09:07:25 PM
George Andreasen George Andreasen is offline
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Default Re: Pole Shoe Removal Problem

You're absolutely right and I should have made that clear......

Using a nickel rod ("nirod") allows the weld to be done quickly, thus keeping any excessive heat from building up and distorting the cast iron....if it's done properly. I can use that feature to keep the field coils from getting too hot. Most importantly, I'll have a local professional do it.

Besides, both welds won't really be all that big...maybe 3/4".
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Old 07-01-2016, 12:15:24 AM
Birken Vogt Birken Vogt is offline
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Default Re: Pole Shoe Removal Problem

What about making a new feet out of steel that fits the casting and then just drilling some bolts through the foot and tapping them into the casting?
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Old 07-01-2016, 01:13:27 AM
Vanman Vanman is offline
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Default Re: Pole Shoe Removal Problem

BTW, I'm curious if this was caused by a poor packing job? Or by the shipper?

I call those broken feet "UPS Feet" since UPS evidently has a policy of deliberately destroying packages unless they're from a major retailer, such as Amazon and the like.

I have a generator with broken feet, but I don't think it was caused by a shipper. Looks like the whole thing fell off a truck. A wonder the engine's feet weren't broken. These feet merely bolt on to the generator frame, and as such I have decided to just make new ones out of steel.
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Old 07-01-2016, 01:51:08 AM
Ken Karrow Ken Karrow is offline
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Default Re: Pole Shoe Removal Problem

Another thought if you are going arc with nickel rod, prepare all you pieces and then take a heavy zip lock bag partly filled with water and wrap it around the windings and put it in the freezer. When frozen repeat with other winding. When that is frozen remove from freezer, then weld. Use the ice as a heat sink in reverse.
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Old 07-01-2016, 08:36:19 AM
George Andreasen George Andreasen is offline
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Default Re: Pole Shoe Removal Problem

No, this was definitely shipping damage. The man that sold/packed the motor for me actually built a very substantial wooden crate inside a doubled cardboard box. Frankly, you couldn't ask for a better job. When I opened the box the wooden crate showed evidence of being dropped forcefully on one corner, distorting the entire thing and breaking off the feet. The motor itself had been bolted down, so it must have fallen at least six feet.

I considered making new feet, but there's at least 2/3rds of each foot left on the main housing.....would be a pretty involved grinding job.

Ice! Now that's one heck of a good idea.......in fact I'll take it a step further. Our local creamery sells dry ice during the summer and a chunk of that should keep those windings cool. Thanks for the idea!

Edit: Now that I had time to think about it, any ice (not dry ice) should be around the windings ONLY. The cast iron should be at, or near, ambient temperature or the thermal shock WILL break things.

Last edited by George Andreasen; 07-01-2016 at 12:11:48 PM.
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