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12-10-2005, 10:42 PM #1
So I optimistically bid on a Kuhlmann SU-2 cutter grinder on ebay. Not many pictures, but considering the price was relatively low I thought what the heck. I won the auction, and it finally arrived.
Upon close examination, it became obvious that the entire grider had spent some time underwater. The silt inside the electrical box under the motor clinched it. The spindle bearings are toast, as are the motor bearings. From the appearance of the oxidation inside the motor housing I suspect it may have been salt water. The rest of the machine is in fairly nice shape. Everything cleaned up to usable condition. The motor runs, however the bearings make the noise of bearings past their prime. Now the question is, do I just replace the motor bearings or is this a catastophe waiting to happen. There is a small amount of rust on the stator magnets, although apparently the windings are still intact. It will be impossible to thoroughly clean the rust from the stator and the oxidation from the inside of the housing without further damage. I haven't priced a new motor yet, but expect it to cost big bucks. If anyone has any experience using electric motors after a bath, I sure would appreciate hearing some opinions.
12-10-2005, 11:09 PM #2
- Mike -
12-10-2005, 11:20 PM #3
Unless the motor has an unusual frame size or other physical characteristic, generally replacement makes more economic sense than a rewind/rebuild, at least up to 10 HP or so.
12-10-2005, 11:20 PM #4
Don't think so. First of all it was shipped from
Arkansas. Then there were a number of spider webs inside the main casting, leading me to believe that the dunking was more than two months ago.
12-10-2005, 11:28 PM #5
Bearings are inexpensive & easy to replace (or have pressed off and on). It'll cost under $20 to see if that does it.
Usually, you can remove a few nuts/bolts and take both end bells off. Wipe inside the stator housing, clean the rotor, clean the centrifugal switch (if it's a capacitor start motor), etc.
Not much in there to go wrong, other than bearings and maybe the starter switch.
12-10-2005, 11:42 PM #6
Before you panic on the motor, clean the stator up good with clean water, a soft brush, and Woolite. Flush liberally with warm water. Dry it out good with a bake in a 150 degree oven for a few days. Then megger the leads.
If the motor dries to 100 megohms or better have the motor guy put the growler on it (or if he's up to date, the analyser). If all is OK you saved yourself the price of rebuild or replace and you saved making the decision too.
Replace the motor bearings if they are stock conrad bearings. If the motor direct drives the spindle, you'll need to do a careful job of replaceing them. Check the spindle bearings first. A little blood rust may not hurt a precision bearing so long as the spindle wasn't run under power post dunk.
Conduct a careful survey first. After you have hard facts to go on, then worry about rewinding stators, replacing bearings, etc.
[ 12-11-2005, 02:44 AM: Message edited by: Forrest Addy ]
12-11-2005, 01:03 AM #7
I'd agree with Forrest..... and I'd suggest doing the final rinseoff with grocery store distilled water (the stuff for irons), especially if you have hard water etc. Mineral deposits can cause leakage later.
For drying, I'd suggest using a step-down transformer and a variac, if you can get hold of one.
Put the low voltage on the appropriate winding, and feed HV input with variac. Adjust to get full load current in the winding. Let it go until nice and warm, at least 5 hours or so, then switch to next winding, and leave on about the same time. Same for third winding.
If it's single phase, don't bother with the start winding, you can cause problems messing with it.
That bakes it out from inside, and works better than oven drying. The motor folks used to recommend that.
DEfinitely don't spend money on something that may not be salvageable.
The "ugly-ass" 1HP motor on my "new" DP (another thread) had bad bearings, and stuck rotor, etc. Looked bad, wouldn't turn reliably, noisy as heck.
Disassembly showed lots of metal chips, and some greenish rock inside. Rock chips looked like copper ore, and were definitely not corrosion, hard pieces a little smaller than the size of fishtank gravel.
Cleaned that all out, and then made motor run, checked leakage, etc.
Only then did I decide it was worth replacing the bearings, which cost about $25 per each, and finishing the cleanup to get it to usable condition.
I spent that much time only because it was a nice 1HP 1140RPM that fit the machine.
12-11-2005, 02:14 AM #8
u might consider taking the stator to your local rewinder, let him test it, clean it and dry it, after which he can redip it in varnish and dry it.
everyone here has given solid advise, just wanted to add the redip to the equation.
12-11-2005, 08:13 AM #9
yes to above
try bearings there cheep
if that don't do it
new is generally cheaper
12-11-2005, 10:38 AM #10
Thanks to all of you for the advice. The motor is a 115V single phase. A start capacitor housed in a two piece aluminum housing is mounted to the base. I'm sure it got wet, but it still works. The motor drives the spindle through a belt. There is a slight draggy spot when the spindle is rotated. It's a cartridge type spindle, so it should be fairly easy to relace the bearings and get everything lined up. The rest of the machine looks to be approx. 11 years old. There is a manufacturing date of 1994 on the power cord and 1993 on one of the castings. It looks like its had little use and was limited to grinding high speed tooling(no trace of carbide dust). Should be a nice machine once its rebuilt and repainted.
12-11-2005, 11:04 AM #11
Don't stop with the motor. All of the electricals would benefit from a good dunk in distilled water followed by thorough drying. That salt is a problem waiting to happen.