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John Stevenson
04-15-2009, 06:53 PM
Following on from robo's thread about the bent screw on his mill I'd like to ask the forums views on this bent shaft.

http://www.stevenson-engineers.co.uk/files/P1000673.MOV

Do you think a well placed whack with a rawhide hammer will cure this ?
The shaft is 2- 1/2" in diameter BTW.

.

kmccubbin
04-15-2009, 07:21 PM
Naww. Wait for the circus to come to town and present it to the strong man.

camdigger
04-15-2009, 07:21 PM
Unlikely you'd be able to remedy using the cross slide either:D

20-50T hydraulic press, I'm thinking.

randyjaco
04-15-2009, 07:24 PM
You must have a BIG rawhide hammer. :D

lane
04-15-2009, 07:39 PM
It all depends. If you can hit it in the right spot with the correct amount of force and no more. It should come straight. but the odds are slim to none. But look at it this way it`s screwed up now so you cant make it any worse. Only better.When You Are In A Hole Stop Digging.

John Stevenson
04-15-2009, 07:53 PM
Lane,
I like your odds. ;) problem is this has to be knob on as there is a massive pulley fitted to this and even a couple of thou run out will make this puppy wobble all over and it runs at 3,000 rpm

The start of the bend is inside the winding and there is no way to support this on vee blocks under a press.
Touch the winding and I'm dead.

Forgot to add, it's wanted for 11:00am tomorrow :mad:

motorworks
04-15-2009, 08:06 PM
11:00 am !
Well you will have to be up by 10:00 ;)

Looks like a job for STUBMAN

Good luck and post pics

eddie

lane
04-15-2009, 08:25 PM
Well i was going to say you are out of luck. But I know better than that . Cover the armature and start welding.Good luck.

Bill Pace
04-15-2009, 08:30 PM
say you are out of luck. But I know better than that .
Hah!, aint that the truth -- Sir John will no doubt pull the rabbit out of the hat....

You will share the outcome wont you??

dp
04-15-2009, 08:58 PM
Looks to be about the same effort as straightening out a set of bengt phorks (google) on a murdercycle. If that doesn't work I'd install it in an already noisey hunk of machinery where a little more noise won't be noticed.

aboard_epsilon
04-15-2009, 09:04 PM
john knows the solution already

he will turn it down till true ..

then deposit weld on it ...and turn again to original diameter.

all the best.markj

Jeffw5555
04-15-2009, 09:10 PM
You must have a really big f'ing rawhide hammer if you think that will cure this....:D

Here's two ways I can think of curing this.

Press: Take a short section of very stout I-beam, lay one end on the lower frame of your 50 ton Hydraulic press, perpendicular to the axis of the press. Create a makeshift vee-block fixture; one end supports the bent shaft end of the armature down to the I-beam, at a level close to the end of the press shaft, so the press presses down on the long end of the bent shaft at or near the end of the shaft. The other end of the vee-block fixture will try to move towards the ceiling, so affix a length of stout chain around the end down to the I-beam, taking up the slack with a load-binder.

Indicate your bent end to start so you know how far you are out to begin, and mark the high spot. Align press shaft on mark, indicate underneath, apply pressure to bear down on shaft. Do a test; if you have a pressure gauge on the press, press beyond your initial indication reading noting the press pressure, de-fixture and re-measure runout. You are trying to find out how much pressure causes fixture deflection vs bending the shaft back. You should try to creep up on the bend. Should only take a few tries to get it straight.

Weld method. Weld a bead along the negative indication of the shaft bend. Weld will pull the shaft in that direction. May take a few beads. Turn shaft afterward to clean off weld beads on the one side.... Protect the windings from heat with wet rags close to the windings.

Let us know how you make out.....

Carld
04-15-2009, 10:07 PM
When they are bent as you describe we pressed them out and made a new shaft. The rotors with laminations have to be pressed out and back in from the same end and some times it's hard to see which end has the bent lamination showing the direction of pressing.

wierdscience
04-15-2009, 10:24 PM
Yup,what Carl said,last one I did was 125hp,bent in a helix.

Tinkerer
04-15-2009, 10:59 PM
Following on from robo's thread about the bent screw on his mill I'd like to ask the forums views on this bent shaft.

http://www.stevenson-engineers.co.uk/files/P1000673.MOV

Do you think a well placed whack with a rawhide hammer will cure this ?
The shaft is 2- 1/2" in diameter BTW.

.
I would of like to seen this as you do some amazing magic with shafting. But for some reason I can not get this thing to play on any app. Could you post this on youtube or at least put a photo so we that can not see what's what at least have a idea. ;)

Thanks

Carld
04-15-2009, 11:24 PM
The video is in QuickTime and there's a free download for it.

John Stevenson
04-16-2009, 04:42 AM
Carl,
I'll get some better pics of it before it goes out.
problem with DC rotors is that you can't press the shaft out without wrecking the windings as the comm and laminations are separate and when you start pressing you crush the windings forcing a rewind and they hate to rewind these puppies if not needed as a lot of them don't use wire but flat strip bent to a special shape then fed in the slots.

Some of these strips are that special they have to me made by specialist manufacturers which puts a lot of delay on the job.

This one is actually an AC motor with a hollow shaft at the other end that carries the infeed wires and it's very small, long and thin, not something to get on a press.

The core of this holding the laminations is skeletal and any pressing will crush it.

Mark got the answer, it will have to be a turn down, weld and re-turn to standard. I welded it last night so the weld would be dry this morning.

Pics later.

Jpfalt
04-16-2009, 11:59 AM
In looking at this I wonder if you couldn't grab the output end in the chuck as close to the windings and you feel comfortable and push on the other end. When the back end runs true, turn around and finish the remainder of the shaft extension.

John Stevenson
04-16-2009, 12:35 PM
In looking at this I wonder if you couldn't grab the output end in the chuck as close to the windings and you feel comfortable and push on the other end. When the back end runs true, turn around and finish the remainder of the shaft extension.

Two things make this a no go.
One is I'll need a lathe this a 2- 1/2" bore to get close to the windings.
Second is I'd need to be Mad Mountain Dean to bend a 2- 1/2" shaft by hand :rolleyes:

camdigger
04-16-2009, 01:11 PM
Even pushing it with the cross slide would take more force than I'd be comfortable with...

Timleech
04-16-2009, 01:27 PM
Two things make this a no go.
One is I'll need a lathe this a 2- 1/2" bore to get close to the windings.
Second is I'd need to be Mad Mountain Dean to bend a 2- 1/2" shaft by hand :rolleyes:

Use that big transformer you showed us the other day to warm it up ;)

Tim

Carld
04-16-2009, 01:32 PM
Yes, with that kind of construction it would be hard to press out and replace it. Turning down and welding and machining to size is the only way and that has it's issues as well.

pcarpenter
04-16-2009, 03:12 PM
Ya know, Sir John, as you post these motor rescue projects over the years, I keep thinking I would love to see video of said motor running before you got it, preferrably showing the mode of failure. I would hate, for example, to have been around when something bent that shaft. You think there is wobble in the pulley if you only get it to a few thousandths runout? Wonder what it looked like when it went (at the point of failure)!:eek: I will bet there were a lot of "clean undershorts" moments associated with some of the stuff you have had in or showed us here!

Paul

John Stevenson
04-16-2009, 04:23 PM
Paul,
Most times I only get the shrapnel, or what's left of it and rarely see the extent of the damage, however in this case I did get some idea, but more later.

No shot of skimming the bend out that was just plain turning at a low speed for obvious reasons.
Drag out the lathe, probably close to 300 pounds, and weld up.

http://www.stevenson-engineers.co.uk/files/bentshaft2.jpg

This is the result of my crappy welding, found a decent bit to support on with a steady whist the centre was single pointed to make good and true, the tool is just visable.

http://www.stevenson-engineers.co.uk/files/bentshaft3.jpg

Start to clean up, first pass on the left, second pass in progress just standard cheap 16mm triangular tips, this one is a used one with the top flashed up freehand on a diamond wheel as it will get ruined cutting this crap, no point wasting money.
I often regrind each edge of the tip a couple of times on jobs like this.

Rough down, leave to cool and finish to pulley diameter and bearing diameter.
Usually fit new tip at this point but as this tip had done all the roughing with only the one regrind i ground it again and took a test cut and it was cutting Ok so cheap job this one, all done on a scrap tip.

http://www.stevenson-engineers.co.uk/files/bentshaft4.jpg

Moved to the mill for the 5/8" keyway, note vise jacked up on packings to line up with shaft. Armature is sitting on the bed and the shaft is being held parallel to the bed by the vise.
This shot shows better the skeletal construction, rough out with a smaller cutter and one pass with a decent 5/8" cutter to finish.

http://www.stevenson-engineers.co.uk/files/bentshaft5.jpg

Finished armature, note the hollow thinner end that would stop it being pressed straight, also not the new El Stevo patent armature barrow.

Behind is the end shield off the same motor that split when the bearing let go.
Another 4" and this would have been in two pieces, welded up, with nickle rods and bored and sleeved for the new bearing.

It's been a lot of work but electrically it was OK and this type of motor is virtually unobtainable nowadays so well worth the 3 pounds 18 shillings and sixpence cost of repair.

.

aboard_epsilon
04-16-2009, 04:30 PM
how do you stop all the heat from the welding heating up the windings and melting the shellac..........

do you have to do the welding over many hours

all the best.markj

SDL
04-16-2009, 04:30 PM
Is that a Abwood vice? surely all micron std work has to be in a Kurt:D

Steve Larner (Tongue in cheek).

DICKEYBIRD
04-16-2009, 04:49 PM
Awesome job Sir J. I'm very glad you take the time to document & post this stuff. I luv it!:)

Could you give a quick run-down of the welding process? I think you said you use a MIG? If so is it bare wire or flux core....how many amps, type of wire & gas yada, yada. Do you slobber on a bunch; let it cool a bit, clean off the accumulated oxidation and go at it again or just keep throwing it down until it's big enough?

I'll probably never own anything more than my 220v AC/DC stick welder but you never know.

John Stevenson
04-16-2009, 04:51 PM
Probably an Abwood, I don't own a Kurt vise for the simple reason the scrap man has never found one yet :D

Something this size doesn't get that hot that quick, do a bit,leave it a bit then carry on.
You can get shafts nearly glowing before it get to the windings and even then they stand quite a bit of heat.
.

kmccubbin
04-16-2009, 05:00 PM
I've heard many people refer to a "wheel barrel". Now I know what they're talking about!

Kerry

Tinkerer
04-16-2009, 08:52 PM
Once again John... You Da Man! :cool:

Carld
04-16-2009, 09:15 PM
:eek: surely you charged more than 3 pounds 18 shillings? Very nice job John but worth many more pounds for that job.

Robo
04-16-2009, 10:06 PM
Fine job sir. It is amazing some of the things that happen with the larger motors machinery etc. I have seen the remnants of a 5" or so line shaft running off of a 250 hp motor let go. What a mess, glad I just seen the remnants. Man I hate being around those things when they are running give me the creeps:) Now can you fix a mill table for me?:)

tony ennis
04-16-2009, 10:28 PM
Well, it cost 3 pounds to fix it, but Crafty John charged them 5 pounds. That's 2 pounds pure profit!