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Autometric gasket material/thickness

rke[pler

Diamond
Joined
Feb 19, 2002
Location
Peralta, NM USA
A couple months ago I pulled the gearbox on my Autometric to fix an issue with neutral and one gear, and on reassembling found that the gearbox input is really tough to get into place - tough enough that the original part was broken when I'd pulled it apart and I needed to make a replacement. The input is supported by a pair of bearings and located by dowel pins, the gearbox is located by taper pins. I'm pretty sure the difficulty was caused by the last owner deleting the gasket on the gearbox putting it further inside the base than needed.

Measuring the distance from the input shaft to base wall (not the best but about all I've got) shows about .028" off-center to the rear, suggesting something like a .016 gasket.

So: suggestions on what might have been used back in 1950? I'm thinking a 1/64th paper gasket. Thoughts?
 
If you choose not to use paper. Could you modify the parts, housing, or anything to give you clearance ?

Not on a machine tool, but a Cat 3500 engine comes to mind. Reverse problem I think. Flywheel housing originally did not use a gasket, update called for a gasket :D. Problems with oil leaking between block and flywheel housing anyway. Part of the update called for machining the surface to keep gears from contacting housing once gasket was added.

Some followed the update as written. Others ground out where gears might contact. I think some bolt heads may have contacted as well, they removed flat washers from the bolts to gain that clearance.
 
I could possibly put some 1/64" shims under all the bolts holding the gearbox to the base, but that would leave the 1/64" gap everywhere else on the flange that I'd have to seal. I think at this point it's about the same effort to take everything off, again, and pull the gearbox so I can make a decent one piece gasket. Paper, since it never gets hot or sees any pressure and also because I have a decent size roll of the paper.

I just wish I'd thought of this before I put it all back together.
 
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Welp, took everything off, pulled the gearbox and added 1/64" gaskets to most everything that takes a gasket (even though it's really the gearbox that needs it for location). Restabbed the gearbox (getting better at this, only took 1/2 an hour) and checked the fit of the input shaft - worked great, just the right amount of tight and went 75% of the way on with no real work until the drive pins engaged the pulley (I never got that quite right when I remade the pulley input shaft). So the gearbox, at least, needs the gasket. I'll see if there any other things happier with the gearbox location now.

Last concern - the pulley and the gearbox input shafts were run about an couple hours by me and unknown time by the PO. Thoughts on the bearings on each being run almost .030 out for some time? I didn't feel anything loose but that can't have been good for the bearings or the input shaft...
 
Last concern - the pulley and the gearbox input shafts were run about an couple hours by me and unknown time by the PO. Thoughts on the bearings on each being run almost .030 out for some time? I didn't feel anything loose but that can't have been good for the bearings or the input shaft...

Yea, .030" is excessive, but too tight is way worse than too loose if we're talking tapered roller bearings. Too tight will smoke them quick. Too loose meh, how many wheel bearings in automotive or even heavy trucks have you seen with some play, just tighten them and roll on. And those carry a lot of weight.

All sorts of applications, after in use a while will usually loosen up a bit without any kind of damage to the bearing.

If it placed a gear a little lower, might have unfavorable wear pattern if run significant amount of time. But I would guess your total run time and that of PO maybe less than 24 hours. I can think of many other applications that run harsh and 24 hours a day. I wouldn't sweat it.

If its nice and quiet, no vibration, any symptoms. . .surely good to go. Being aligned will do wonders too.
 
It's really .015 off, I was measuring .030 difference between the shaft and the sides of the bore. Still a lot for a pair of 6009 (in the pulley assembly) and the pair in the input assembly whose specs I can't find.

Jig bore is back together, refilled the 6 gallons of oil and ran it a little bit and it sounds OK but then it sounded OK before. No oil leaks, yet.
 








 
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