Molyslip

listerdiesel · Feb 9, 2016

wammers said:
It makes them skid.

If you look at any needle or other roller bearing, the speed of the inner shaft is always different to that of the outer member, so there is a speed difference at the point of contact of the roller to the inner shaft and the outer member. The roller has to skid anyway.

Look up "Roller Bearing Skid" on Google.

Example: A 1" shaft running in 1/4" roller bearings inside an outer race of 1-1/2" diameter.

Outer track length is 4.713"
Shaft track length is 3.142"
Roller track length is 0.78"

Divide the roller track into the outer and inner, they are obviously different, so there has to be slip/skidding going on.

Check my figures, it's early for such technical stuff

Peter

wammers · Feb 9, 2016

listerdiesel said:
If you look at any needle or other roller bearing, the speed of the inner shaft is always different to that of the outer member, so there is a speed difference at the point of contact of the roller to the inner shaft and the outer member. The roller has to skid anyway.

Look up "Roller Bearing Skid" on Google.

Example: A 1" shaft running in 1/4" roller bearings inside an outer race of 1-1/2" diameter.

Outer track length is 4.713"
Shaft track length is 3.142"
Roller track length is 0.78"

Divide the roller track into the outer and inner, they are obviously different, so there has to be slip/skidding going on.

Check my figures, it's early for such technical stuff

Peter

BMC long ago prohibited the use of Molyslip in their gearboxes that contained needle rollers. Usually on the layshafts. If it was found the warranty was void. That was as good a reason as any not to use it. If people want to put it in that is for them to decide. There is no skid in a properly loaded needle roller bearing.

boguing · Feb 9, 2016

Pete, your figures are right, but you've forgotten a bit - in your example it means that a ball revolves four times as it travels right round the inner race, and consequently the outer race (inside which the ball would turn six times in a complete revolution) has only turned two thirds of a revolution. If this wasn't true, epicyclic gearboxes wouldn't work, because they don't slip.

listerdiesel · Feb 9, 2016

boguing said:
Pete, your figures are right, but you've forgotten a bit - in your example it means that a ball revolves four times as it travels right round the inner race, and consequently the outer race (inside which the ball would turn six times in a complete revolution) has only turned two thirds of a revolution. If this wasn't true, epicyclic gearboxes wouldn't work, because they don't slip.

In an epicyclic gear train, the gear sets are calculated to run at specific speeds and are locked together, not quite a fair comparison?

Peter

boguing · Feb 9, 2016

The gear ratio of an epicyclic is certainly chosen to suit the application, but the design bit is choosing the radii for the inner, planet and outer to get whole numbers of teeth. What I'm trying to say is that a roller or ball bearing is, in effect, an epicyclic gearbox. Slip happens for many reasons, but not because of circular geometry.

listerdiesel · Feb 9, 2016

Slip happens because the rolling diameters are mismatched.

Peter

boguing · Feb 9, 2016

Sorry Peter, but that isn't right. For each whole turn of the inner race, the balls don't make a complete revolution of the outer - it's a gearbox without teeth. The only slip in a perfect working bearing race is between the ball and the cage, or - importantly to the point Wammers was making - between adjacent balls when un-caged because they're sliding against each other at twice the their speed of travel.

Stanmac · Feb 9, 2016

Well that's got the juices working !! Thanks for all the input. End decision is that I will not be using Molyslip in the gearboxes. I changed the oil in the transfer box today and pleased to say the box is quieter. With all the abnormal problem of getting the drain plug free and knowing this vehicle's history over a number of years I have come to the conclusion that the oil hasn't been changed in years.

Stanmac · Feb 10, 2016

Hi and thanks to all who were interested in my question about Molyslip. After all the discussion I decided not to put it in the gearbox however I was going to put it into my overdrive and asked the manufacturer directly.
Here is their reply. " Unfortunately it is not recommended for automatics, overdrives, limited slip differentials or any other item that requires a degree of friction to work" Now make what you like from that.

Molyslip

listerdiesel

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wammers

No longer with us, RIP

boguing

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listerdiesel

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boguing

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listerdiesel

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boguing

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Stanmac

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Stanmac

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