ST Head disassembly

[Doug]

I had 2 ton C&M hoist on a Jib for that job....
Also a small fork lift and all manner of slings and stands.

The trick is to think threw a job and get as much space as needed, tools, stands ect at the ready.
Your also far less liekly to make a mistake that results in blackend fingernails and language that unsuitable for mix company....

Doug

[dkwflight]

Hi I have to agree the right tools always make the job go easier.
But then sometimes you have to make do.
Dennis

[Tom]

I have not done this yet, however I would think it would be easiest to stand the generator on the brush end cover and lift the rotor out. The bearings in my ST5 are a bit noisy so I've been thinking about how to do this.

[dkwflight]

Hi The St5 is a lot lighter, in its parts. I did mine on its mounts, normal position. You should be able to take the brush end bell of easily. The three small bolts hold the brush holder in position. Remove them first. then the big bolts holding the end bell on. With those bolts off the end bell can be started off. you might need a knife or small chisel to begin the separation. Then you should be able to wiggle the end bell off the bearing. The bearing may stay on the shaft or come with the end bell. Some solvent or penetrating oil in the bearing hole and on the shaft may help disolve the grease and make removal easier.

The drive side on mine did not have any retainer. Getting a big enough puller over the shaft and hooked on the bearing was my problem. Be careful of the blower. Mine is cast iron, very thin.

When removeing the rotor, lift from both ends of the shaft and slide out the drive side. lift and slide gently. If you just pull it out you may damage the windings.

Good luck

[Doug]

A bearing that stays in the end bell and not on the shaft is a warning sign something is a miss.

The end bells should slide on/off bearings with moderarte effort with little wigle. Of course of there is dirt and rust it may require some penetrating oil.

A bearing should never come off a shaft with out the use of a puller and should always require about 200 F worth of difference in heat to slide on the shaft. If you can slip it on cold all the way with your hands and back offf again its too loose something is wrong! The fit of the outer race to the end bell should be possible cold but require effort ( effort means wigle, some light oil as much force as your able to with a bare hand, this is not a job for a hammer of any kind ). If you preheat and end bell to make the job easier again no more than a 200 F spread in temperature and it should slide on with minimum effort. If its too hard to slide on with heat again something is wrong stop and find out why.

The wigle test:

When the machine is reassembled grab hold of the output shaft. Try and move the rotor back and forth. If your head has a spring washer you should be able to compress it in the housing with a lot of effort and it should come back. It should be obvious the out races of the bearing and end bells are excerting enough presure to make this difficult but not impossible. With the machine sitting on its feet pull the out put shaft up and down there should might an almost undetectable movement caussed by the .003 C3 clearence of the bearings, but this is very hard to feel and you may not.

If you are sure you feel some up and down and the end bells slid on realy easy or the inner race to shaft was a little loose of a combination of both trouble is in the mail. Run the head with the from now on watch listen and from time to time repeat the wigle test untill something changes and it gets worse, you need to have shaft and housing rebuilt. Any changes like increased noise or a slightly warmer than normal bearing, tinny hissing sounds
indicate things are begining to fail.

When ever you strip an generator or motor for service, its good practice to clean its windings with an electrical solvent and repaint it with Glyptal 2001 ( A ). Never use compressed air over 30 PSI to remove dust .

Doug

[dkwflight]

Hi Doug

Good points and true, Assuming the original machineing was correct.

My drive side bearing needed a touch of heat on the inner race to break it loose, then the cheap puller brought it right off. The brush end slid right off with a puller.

$23 at harbor freight got a set of three pullers that did the job easily.

Very little clean up and lube allowed the bearings to be tapped on with a brass punch and hammer.

I brazed the broken piece back on tonite. Some paint and I am ready to reassemble tommorow.
Dennis

[Doug]

I had some special chisels I ground and kept dressed for those times when a bearing properly warned refused to slide onto a shaft but you have to be very careful when hitting the inner race not to miss and some bearings like Nachi were famous for chipping if you hit them too hard.

Doug

I had pullers but 50% of the time I used one of my special chisels.
I could fill a 50 gallon drum with scrap bearings in about 5 weeks.

[dkwflight]

Hi
Well I broke four wires in the inner windings of the stator. I think that gives me 16 combinations to try for the repair.
Any ideas on how to identify the correct combinations?

As a plus I hurt my back pulling the rotor. It is a heavy SOB. Which is why or how I broke the wire going in.
Dennis

[ronmar]

Wires on the windings, or feed wires that connect the stator windings up to the dog house?

[dkwflight]

Well I broke four wires in the inner windings of the stator

[phaedrus]

I will know how you slide that puppy in and out soon enough - but on full sized generators - stuff like maybe 40 megawatts, one greases garlok gasketing material and pulls the rotor through with come-alongs, then slings both ends to center the rotor in the space, then removes the garlok. garlok is really hard-stiff stuff, almost like formica. Anyway I'm going to use something like it and see how that goes...