First time installing a modern fourth main. I don't care for a modern bearing as I feel the Babbitt fourth main is fine as long as the transmission is in alignment. Why a modern bearing, my friend wanted it.
Use a new brake drum, line bored bearings and trued the bolt flange.
Drive plate had new bushing, line bored and trued the flange.
Bolted together had less than .002" run out
Chucked brake drum into four jaw and centered under .001"
Supported drive plate shaft with steady rest with no runout.
Turned to size and ended up with .005" - .006" run out on cut surface. Dial indicators were left in place during turn and were very still.
Not happy with results, were did I go wrong
If it were me, I am so incredibly novice on the lathe, I would have used the tail stock and bull nose instead of centering in the steady rest. Could there be just enough force from the cutting tool and play in the steady rest combined with a hard spot in the tail stock shaft so it forced it out of alignment? or that .001 out at the chuck was magnified at the other end at turning speed.
No problem if these thoughts are wrong because I need to learn how to do such work too.
I did try a cone in the tail stock and couldn't begin to center. I did start the centering with a shaft through the the part on centers and that was close but thought using the steady rest after centering would have worked. I am lost.
Most that have came with a modern bearing to my shop are cut of center, another reason I don't like modern bearings.
If I understand your procedure, you assembled the drum and the driving plate and had less than 2 thou run out on the tailshaft. Then you placed the steady rest on the tail shaft and cut. It could be you pushed the tailshaft over some when you used the steady rest. You can't rely on zero run out after installing the steady rest to tell you the piece is aligned. It will always show that. But if you kept your dial indicator on the tailshaft throughout the procedure and it didn't move after installing the steady rest, then I don't know.
The other way I would consider is making a dedicated face plate to mount the drive plate too. I would guess after the drive plate and shaft were centered you would need to check the tail shaft end where it was drilled and broached for the u-joint, clean up so the tooling at that end would be centered to your lathe, then use the bull nose.
Actually I wouldn't be disappointed with 5 to 6 thou run out. We toss numbers around as if they were nothing. 5 to 6 thou is really very little wobble.
I have a main shaft that is shorten so the bearing in the drive plate is not in contact. Short main shaft is mounted on the mill deck and three bolts install loose. You can than bump the drive plate a bit to center. Knowing that I was going to cut the bearing surface down I stop at ,002". That maybe part of the off center issue.
Nothing like shooting your own foot. LOL
After the drum and drive plate was bolted up it was than moved to the lathe. Center both ends and than the steady rest was use but all the time watch the dial indicators to see if I push the unit off, been there, done that.
Too many modern bearing are install in our Ts. was hoping someone here has done this and will share.
Good idea Mark
Use a new brake drum, line bored bearings and trued the bolt flange.
Drive plate had new bushing, line bored and trued the flange. "End Quote"
Mike, truing flanges is of no help.
The break drum has to be align reamed, with a jig, as a Wilson or others. I have never found a lathe of any use for this as, no way to center the break drum on both ends.
Same way with the drive plate bushing. They have to be jig align reamed, if you don't want over .001 thousandths, or less run out.
Your 4 Jaw chuck and alignment is right, if the bushings inside are right.
Many a tail shafts do have hard spots that will push a steady rest out of alignment.
So, after you get the 4 Jaw centered, and the little place by the pin hole surface that is all that is left to indicate that is untouched by wear.
When centered that way, cut a 60 degree chamfer in side the tail stock, outer edge, and then use a ball bearing center in the tail stock to hold the unit, it will not give. Just make sure it is still true, when done cutting the chamfer.
Your photos are the best!!!
Thanks Herm for the rest of the story, looks like I was partly on track.
I'll try cutting a 60 degree and use a center next time.
I wish I had a Wilson drum set up but I have only seen one in many years and it wasn't for sale. So you do the very best you can with what you have to work with.
Great pictures by the way.
I forgot that the New Brake Drum I used, was a J & M Machine drum.
When I got done with the tail shaft, and before I took the unit out, I also checked their ban surface on the drum for movement.
It was all zeroed, the Dial Indicator needle did not move at all.
But I have found that all their drums and parts are like that.
Your dial indicator nearest the chuck may have shown the drum shaft running true, but possibly so only where your indicator was running. Had you moved the indicator closer to the drum, would it have also showed little to no runout?
I hope you will "fix" the ball bearing unit before you use it. They are usually made wrong. This has led them to gaining a poor reputation. It needs to be a tight fit on the transmission shaft and have the ability to move in the housing. If it is a slip fit on the transmission shaft it will eventually wear the shaft and the inside of the bearing. If it does not have the ability to float lengthwise on the outer race and it is locked on the inner race it will not last at all. Done correctly it will outlast the engine easily
Les, I'm in the middle of this same job. Could you explain further your fix? PK
Les, I would sure like to see pictures of the ones that failed, what brand, and what happened.
Never had any failures in the ones we have made, when I get time, and that is in the hundreds.
You want a close fit of a bearing on a shaft, about .000-30 tenths. If you press the bearing on the shaft, and leave the bearing loose in the housing, it will wear the ball cap housing out.
The tail shaft has to be cut clean, true, and polished.
I know of 3 ball caps that fail.
1. Is a needle bearing set up. They fail because the tail shaft is to soft to take a hardened needle bearing.
2. Is a ball cap made and machined out of Aluminum. Aluminum is to soft to support the drive shaft tube ball as the ball gouges it bad, and I have seen 3 new ones and all the bearings were about 1/4 inch off in there settings as when the bearings were pressed in, Aluminum burrs rode up in front of the bearings, and were caught between bearing, and cap. So when you put it on a K.O.Lee expanding Mandrel, the gasket flange is the 1/4 inch off.
3. The last one is made of a bronze casting. The bearing is larger, and has a Aluminum sleeve in the bearing that is instructed to be glued on to the shaft, so it will not move. Lots of luck with that one. If you do it that way, if the bearing don't move on the shaft, it will move it in the housing, or pull the bearing apart.
The transmission does, and has to move back and forth from heat expansion, and what ever end play is in the rear main cap.
The draw back also with number 2., and 3. cap is you have to cut the ball back on the drive shaft tube, because of the size of the bearing they used, and many guys don't like that idea.
Moved the dial indicator all over the shafts, this one happened to be round with no wear. As shown in the picture was where I left the, during the turn process.
Les. Got your email. I have a honest .0005" slip fit of the bearing to the drive plate shaft.
Not my first choice, but I hope it works. I go for about a size on size for the inner race and a good .001 of clearance on the outside. I have also added a O ring groove into the bearing holder on some. With this combination I get no oil leaks at the back of the engine
I have never seen one of yours up here. I have succeeded in fixing all the ones up here over the last 30 years, so no failures here to photograph
Using Herm's suggestion on cutting a 60 degree chamfer on the drive plate and using a cone on the tail stock made all the difference. While I didn't get to his run out number of .0005” I had less than .001”. The difference could be that I line bore the bearings in the drum and drive plate. Thanks Herm for the information.
Glad it worked, Mike.