PDA

View Full Version : I need your opinions



jcarter
01-30-2008, 06:29 PM
I have a shaft out of a transmission that has a gear riding on it. The gear has a bronze bushing in it. The shaft is worn where the gear rides on it. The shaft diameter where the gear rides was 1.000". It is worn to .975". How would you repair this? The spline next to the journal is .964"OD. I am reluctant to weld it up and machine it down for fear of changing the temper of the spline or adjacent gear.I thought about making a press fit sleeve. Or I may be able to get a smaller ID bushing and make the shaft fit the bushing. According to my customer these parts are not available separately- the manufacturer wants to sell a complete transmission.In the attached photos the white X identifies the worn journal.
http://img.photobucket.com/albums/v679/j-carter/IM002497.jpg
http://img.photobucket.com/albums/v679/j-carter/IM002498.jpg
http://img.photobucket.com/albums/v679/j-carter/IM002499.jpg

rhmalsch
01-30-2008, 06:53 PM
Hard chrome plating?

boggers
01-30-2008, 07:08 PM
Chances are that the shaft hardening (if any) has been compromised so I'd be reluctant to go any smaller for a working surface. It may have been too soft to start with, hence the failure.

What are the chances that you can bore the gear and use a bushing with a thicker wall? If my calculations are correct, taking the shaft down to the spline diameter would allow only 0.018" wall on your new sleeve if you bring it back to the 1.000" diameter.

Say a 0.035" wall sleeve (roughly double the 0.018") and a new thicker wall bushing to accommodate it would give a long life fix. Or if the bronze bush has a thick enough wall, just bore it out to fit what ever shaft diameter you settle on.

I certainly wouldn't press the sleeve on. I think I'd allow 0.001" to 0.0015" tight fit, heat it up and shrink it on. Allow enough wall thickness to turn it back to whatever final shaft O.D. you decide upon.

Rusty Marlin
01-30-2008, 07:09 PM
I assume the bronze bushing is smoked too? Make a new bronze bushing to press fit in the gear at .970 ID and clean up the shaft at whatever the RC4 or RC5 running tolerance of .970 is.
For RC5
Shaft would be .970 -.0016/-.0024
Bushing would be .970 +.0012

Press the new bushing in before boring it.

steverice
01-30-2008, 07:36 PM
Its been pretty hot, so the heat treat is probly gone.

If not then I might grind both surfaces and find a suitable needle bearing.

I would also check the material and heat treatment to be sure that i wont be damaged by the bearing. I might go as far as to press a race into the gear for the bearing to ride on the OD.

I would think that if I had a gear box shop (traction products in costa mesa) build them from scratch would be around a grand.

Bushings suck.

Evan
01-30-2008, 08:51 PM
I doubt it was hot enough to lose much hardness. That takes 800 to 900 degrees. That looks like burnt oil stains to me. Clean it up to a smaller diameter and make a bushing to fit. You will find out real quick how hard it is when you try to turn it.

oldtiffie
01-30-2008, 09:39 PM
A "shaft sleeve" may be a viable option.

They work very well.

http://www.durasleeve.com/shaftsleeves.html

http://www.durasleeve.com/oursleeve.html

http://www.google.com.au/search?hl=en&q=shaft+sleeve&btnG=Google+Search&meta=

I hope it helps.

darryl
01-30-2008, 10:42 PM
Just another idea for what it's worth- you aren't going to want to reduce the diameter of the shaft very much at all, but if you have to reduce it to less than the diameter of the splines, then you could make a bushing in two halves. You'd probably have to start with two bushings, then cut each one for a slightly larger than half piece. Trim as required to make the pair a fully round bushing again. Press them into the gear. Turn a piece of scrap to the same diameter as the re-worked shaft, then use that to aid in boring the bushing to a fit. Press the bushing halves out of the gear, assemble them over the shaft, then press the gear on again. You may need some temporary shims between the bushing pieces and the gear on the shaft while pressing the other gear on.

It doesn't appear that there's much room to bore the gear out for a thicker bushing, so hopefully you can get a thin enough one in there without mashing it, in the event that your repaired shaft still has a larger diameter there than the splines.

One thing I would not do it try to run rollers on the repaired shaft. Needle rollers are nice and all, but won't last long unless that section of shaft is sized very closely, hardened, ground, and polished. If the needle roller bearing is complete with inner and outer races, that's another story, but again I don't think there's room there for that.

Carld
01-30-2008, 11:12 PM
The shaft is probably scarry expensive. I would turn the worn area down about .030" on a side, heat the shaft up and weld it and turn it to size. Then send it out to have it rehardened.

You would have to test it for hardness before working on it. I would try to weld it with something that can be hardened. It would take some checking to find out what to weld it with.

If you weld it while it is turning the stress should be even and it may not warp. It can be straightened.

We used to do stuff like that all the time.

lane
01-30-2008, 11:24 PM
Take to your local machine shop. Get shaft metal sprayed the turn are grind back down to size . Good as new them. Every day occurrence.

bob_s
01-31-2008, 12:07 AM
No brainer solution, send it to John Stevenson.

tony ennis
01-31-2008, 12:38 AM
Get shaft metal sprayed...

Will someone expand on this a little please?

oldtiffie
01-31-2008, 01:17 AM
Get shaft metal sprayed...


Will someone expand on this a little please?

Tony.

Try these.

As Lane says, it works really, really well.

You can choose the process/metal and consequently the way you finish it off.

http://www.gordonengland.co.uk/cws.htm

http://www.metalpowders.com.au/spraypowders/plsmhvof.htm

http://www.plasdip.com.au/metal.htm

http://www.google.com.au/search?hl=en&q=metal+spraying&btnG=Google+Search&meta=

jcarter
01-31-2008, 11:30 PM
Thanks for the input everyone.I have bushings ordered with the correct OD and smaller ID. I am going to use my toolpost grinder to clean up the journal then bore the bushing to fit the shaft.I'll be sure to post photos when I do the job.

Oldbrock
02-01-2008, 12:48 AM
I have a shaft out of a transmission that has a gear riding on it. The gear has a bronze bushing in it. The shaft is worn where the gear rides on it. The shaft diameter where the gear rides was 1.000". It is worn to .975". How would you repair this? The spline next to the journal is .964"OD. I am reluctant to weld it up and machine it down for fear of changing the temper of the spline or adjacent gear.I thought about making a press fit sleeve. Or I may be able to get a smaller ID bushing and make the shaft fit the bushing. According to my customer these parts are not available separately- the manufacturer wants to sell a complete transmission.In the attached photos the white X identifies the worn journal.
http://img.photobucket.com/albums/v679/j-carter/IM002497.jpg
http://img.photobucket.com/albums/v679/j-carter/IM002498.jpg
http://img.photobucket.com/albums/v679/j-carter/IM002499.jpg
The only option I can see is to turn if soft enough or grind down the fit and spray weld it then grind to size. regular welding wouldn't be an option if it is a hardened shaft, which it probably is. hope this helps Peter