possible cause and fix for damage to the bearing surface of variator drive cone?

[TorontoBuilder]

In rebuilding my chipmaster lathe I took apart the variator to assess the overall condition. It had been making a slight noise but that turned out to be bolts on the timing gear contacting the housing.

But I did find something curious.

One ball was pitted and the other two were in much better shape. The outer ball retention ring had no sign of any abnormal wear, nor did one of the drive cones. But the second drive cone has this pitting on it. My first thought is that the cone casting may have had some porosities to it that were not exposed during the machining of the cone face, but were exposed over time and that the bits of metal that broke off would be what damaged the one ball.

Any other thoughts? Here are pics of the two cones sitting one on top of the other... as I rotated them 360 degrees to view the entire wear surface. My fear is that the pits are deeper than the allowance I have to regrind that surface.

 

[TorontoBuilder]

Close up of one of the pitted areas

Im not sure what the balls are made of but they're about 3" in diameter. Heavy and appear like they were plated, or the oil or something else in the housing caused them to be discoloured with what appears to be copper. Maybe they were copper plated then nickel plated over top? Just thinking how they may be repaired...

 

[Tom Kitta]

Which year is your lathe? Old models had 3 balls, new had 6.
Mine is OK to about 1000 rpm, at 1500 rpm its unhappy and feels like it may explode. At 2000 rpm it feels like it already exploded. If I turn the wheel too fast past 1000 rpm it suddenly will loose all power and then if I do not turn the sucker off it will regain power after say 30 seconds with loud bang. When I say it feels like its about to explode is not just the gear like noise but also increased shaking.

 

[TorontoBuilder]

mine was made in 1967, both the lathe and variator serial numbers confirmed it.

Have you thought to rebuild your variator? I'm waiting for a reply to my parts price inquiry to see to what extent I will fix mine or ditch it for a countershaft and VFD

 

[Susquatch]

I agree that it looks like casting porosity. Very common for two parts made on the same line to have different porosity. You got one bad one and one good one. I doubt you could grind it out even if you did have enough meat - you would just hit more voids. I also doubt it can be repaired properly. But if you don't need it to be like new, you might be able to fill the voids with Devcon Steel. Just be prepared for a shorter life expectancy. The balls are probably not repairable at all - at least not in any typical shop.

Can you get replacements?

 

[Darren]

5-7.5hp motor and a VFD are probably cheaper than getting new balls and whatever other bits are no good. Also 65 year old technology vs more modern equipment.

My DoAll bandsaw had a reeves drive, similar concept, and it was in good shape but is was a lot easier to remove it since i was using a VFD anyway. The VFD covers the speed range nicely.

 

[Tom Kitta]

Min is 1965 or 66, so I guess I have three ball setup same as you.

Most people when they need to do something about the speed control go the VFD way.

Through it would be interesting what the price list says - I do not feel like it will be cheap - but you never know.

For now I simply ride on what I have - certainly going with 7.5hp or 10hp motor and VFD would be a solution to speed control - but it is indeed a project to have everything setup.

 

[jcdammeyer]

To me it looks like porosity. Trash it and replace with either 3 phase motor + VFD or AC Servo. Whichever is cheaper.

 

[TorontoBuilder]

I agree that it looks like casting porosity. Very common for two parts made on the same line to have different porosity. You got one bad one and one good one. I doubt you could grind it out even if you did have enough meat - you would just hit more voids. I also doubt it can be repaired properly. But if you don't need it to be like new, you might be able to fill the voids with Devcon Steel. Just be prepared for a shorter life expectancy. The balls are probably not repairable at all - at least not in any typical shop.

Can you get replacements?

5-7.5hp motor and a VFD are probably cheaper than getting new balls and whatever other bits are no good. Also 65 year old technology vs more modern equipment.

My DoAll bandsaw had a reeves drive, similar concept, and it was in good shape but is was a lot easier to remove it since i was using a VFD anyway. The VFD covers the speed range nicely.

Yeah Darren, I had an old wood lathe with a reeves drive. Much easier to remove than a variator.

Susquatch... I trust your opinions, and I did want to keep the lathe all original. It wont be my primary lathe either so I can get away with less than perfect repair. I think I'll try devcon steel epoxy. I wont grind it but likely use a buffing wheel to smooth any irregularities when it dries... I can usually apply expoxy fairly smoothly.

The balls, I'm hoping it is pitting more than raised edges, but I can try to burnish any raised edges on a machinists stone... or my wife's finest foam emery board board for her nails. What have i got to lose?

I have a VFD and a motor, but I discovered my motor is 3400 rpm which wont work well... so time to watch more auctions or kijiji for bigger badder if the fix fails

 

[Susquatch]

I think I'll try devcon steel epoxy. I wont grind it but likely use a buffing wheel to smooth any irregularities when it dries... I can usually apply expoxy fairly smoothly.

Buffing the epoxy might not work too well depending on how you do it. I have found that working epoxy too much (think heating it) breaks the epoxy chemical bonds and softens it. I'd think a mild abrasive or your wife's emery file would be better than buffing.

But ya, have a go at it. It's gotta be better than leaving it! Apply the epoxy from the bottom of the pitt up like filling a tooth at the dentist so you don't get air bubbles in there. Also, use the high temp epoxy.

 

[Engmaxx]

Marine grade JB weld is tough stuff; you can pick it up at Crappy Tire. Maybe worth a try as I believe it is tougher than the epoxy but I'm no expert...

 

[TorontoBuilder]

Marine grade JB weld is tough stuff; you can pick it up at Crappy Tire. Maybe worth a try as I believe it is tougher than the epoxy but I'm no expert...

Thanks for the input Michael. I'll have to weigh this decision up carefully against my budget. I just may want to do this job cheaper now so I can save money to put into brand new lathe in a few months

 

[jcdammeyer]

If you were to try and repair it it might we worthwhile using the same material used to build up worn ways on lathes. Rough up the entire surface. Sandblast perhaps. Then coat the entire pulley and machine back down to a smooth surface.

The only issue I see is that lathe ways don't really have a point contact but the load is spread over a fair distance. Bearings rolling around on a surface are point contact, however briefly.

 

[TorontoBuilder]

If you were to try and repair it it might we worthwhile using the same material used to build up worn ways on lathes. Rough up the entire surface. Sandblast perhaps. Then coat the entire pulley and machine back down to a smooth surface.

The only issue I see is that lathe ways don't really have a point contact but the load is spread over a fair distance. Bearings rolling around on a surface are point contact, however briefly.

I dont know if that teflon material is tough enough.

Now the manufacturer of the variator says that properly lubricated that there is no contact between the ball and the cones and that the oil behaves in a non-newtonian manner so that the viscosity changes when under force to either more liquid or more solid. I think that this ability is what is supposed provide the cushion between the surfaces and become the means of energy transfer without actual contact. BUT they're speaking about ideal scenarios rather than reality...

IF only I had two variators to experiment with

 

[Tom Kitta]

I dont know if that teflon material is tough enough.

Now the manufacturer of the variator says that properly lubricated that there is no contact between the ball and the cones and that the oil behaves in a non-newtonian manner so that the viscosity changes when under force to either more liquid or more solid. I think that this ability is what is supposed provide the cushion between the surfaces and become the means of energy transfer without actual contact. BUT they're speaking about ideal scenarios rather than reality...

IF only I had two variators to experiment with

That is correct - power is transferred through liquid - same as in a car with auto transmission.

This is why correct oil viscosity is very important (ISO 18).

 

[TorontoBuilder]

I dont know if that teflon material is tough enough.

Now the manufacturer of the variator says that properly lubricated that there is no contact between the ball and the cones and that the oil behaves in a non-newtonian manner so that the viscosity changes when under force to either more liquid or more solid. I think that this ability is what is supposed provide the cushion between the surfaces and become the means of energy transfer without actual contact. BUT they're speaking about ideal scenarios rather than reality...

IF only I had two variators to experiment with

ahem @Tom Kitta ??

 

[TorontoBuilder]

That is correct - power is transferred through liquid - same as in a car with auto transmission.

This is why correct oil viscosity is very important (ISO 18).

I wonder then if teflon would be counter productive and allow too much slip compared to steel surface of the cone.

 

[140mower]

Even if the races can be "repaired" there's still the balls to contend with...... I think any repair here, short of replacement will be a temporary fix. As much as I like to keep things original, the truth is, everything can be improved upon, and I think this is one of those things. A good 3phase motor and vfd should be a good upgrade to what appears to be a weak link.
I feel your pain of missing a key tool..... Two shapers and nothing to shape with, the clutch went on the one I have been using and the time has come to redesign the drive on it, it was so noisy and the transmission leaked faster than one could fill it it seemed.
Going with a vfd and eliminating the clutch and trans.

 

[Tom Kitta]

I wonder then if teflon would be counter productive and allow too much slip compared to steel surface of the cone.

Yes, they may change the relationship that allows the whole thing to function.

This whole Swiss variator is an amazing work for when it was developed. A lot of physics went into it.

 

[TorontoBuilder]

Even if the races can be "repaired" there's still the balls to contend with...... I think any repair here, short of replacement will be a temporary fix. As much as I like to keep things original, the truth is, everything can be improved upon, and I think this is one of those things. A good 3phase motor and vfd should be a good upgrade to what appears to be a weak link.
I feel your pain of missing a key tool..... Two shapers and nothing to shape with, the clutch went on the one I have been using and the time has come to redesign the drive on it, it was so noisy and the transmission leaked faster than one could fill it it seemed.
Going with a vfd and eliminating the clutch and trans.

I do very much love a VFD.

I don't very much want to have to fabricate a countershaft with my welding skills. I guess a bolt together affair will work