more thoughts about needle bearings

[Dragsinger]

Consider this thought,

In ref to bushed lifters vs needle bearing lifters, driveshafts have needle bearings in the u-joints.

[GerryP]

I'll keep that in mind next time I lash my driveshaft.

[Dragsinger]

My comment is intended to provoke thought. In ref to needle bearings being overloaded on roller lifters and some builders installing bushing style lifters. Thus, Think of the load a u-joint needle endures.

Simply food for thought

[this post is a continuation of an earlier post about lifters [bushed vs needle]

[racear2865]

Hell people dont grease the joints, except, when installed. So why do u think they will with a bushing, which has to have lube
reed

[Dragsinger]

I suspect my "food for thought" is being misunderstood.

The point I am attempting to make, simply consider the stress a u-joint needle bearing endures. Then, it is reasonable to consider that roller lifter needle bearing can endure high stress.

Do we see solid bushing in modern u-joints?

[GerryP]

Actually, there are solid bushed U-joints. They're very popular in off road/rock crawlers. I have no experience with them myself, but they seem to be more durable than needle bearing joints.

[dwilliams]

Lifters see cyclic impact loads and run a much higher RPM than U-joints.

[Geoff2]

The U joint [ along with front wheel brgs ] is another example of how LITTLE lubrication needle/roller brgs require to survive....Why is why I think the marketing of 'pressure' fed needle roller lifters...is BS....just marketing hype.

[digger]

what is the issue with "low" idle rpm then if its not an oiling issue? the nose force decreases with increasing rpm (quadratically?) until the point of float so the lower the rpm the higher the force over the nose. but if you look at a revkit and the large benefits in life people have seen would seem to only benefit at higher rpm where the pounding is highest rpm^2.

[MadBill]

The theory (and AFAIK, it is just a theory) is that at idle and low RPM the roller slows its rotation when it comes off the closing ramp and then skids as it's spun back up to speed on the opening ramp, thus reducing long term street durability. The rev kit spring keeps the roller in full contact (as with a hydraulic roller) and so avoids the decel/accel cycles.
A few thoughts/observations:
o Does the roller really have time to overcome the shear forces in the oil films and slow drastically or stop in say the 30-40 ms it's on the base circle at 1,000 RPM?
o If it does, wouldn't the failure mode be skid wear on the opening flank of the lobe and/or the roller OD, not needle failures?
o If skidding is the issue, why isn't a bushed roller as bad or worse, due to its reported higher rolling resistance?
o Bronze alloy particles are far less effective engine killers than hard steel needles.
o One scenario explaining the value of both bushed rollers and rev kits would be that slack lash monitoring allows large clearances to develop and the resulting heavy impact loads cause needle damage and brinelling of the roller ID.
o Another would be that in the effort to reduce the roller loads, too soft springs are chosen, which cause premature valve float and heavy impact loads as above.

[statsystems]

The theory (and AFAIK, it is nothing more than that) is that at idle and low RPM the roller slows its rotation when it comes off the closing ramp and then skids as it's spun up to speed on the opening ramp, thus reducing long term street durability. The rev kit spring keeps the roller in full contact (as does a hydraulic roller) and so avoids the decel/accel cycles.
A few thoughts/observations:
o Does it really have time to slow drastically or stop in say the 30-40 ms it's on the base circle at 1,000 RPM?
o If it does, wouldn't the failure mode be skid wear on the opening flank of the lobe and/or the roller OD, not needle failures?
o If skidding is the issue, why isn't a bushed roller as bad or worse, due to its reported higher rolling resistance?
o Bronze alloy particles are far less destructive than hard steel needles.

IIRC, it was either Chase Knight (if you still are hanging around you can verify) or Dan Jesel told me that at lower rpm there is less oil (talking about non pressure fed lifters) so they run short on lube.

Someone else told me that things like cranking the starter with the ignition off to build oil pressure does more damage to the lifter than just starting it does.

[Enigma]

My comment is intended to provoke thought. In ref to needle bearings being overloaded on roller lifters and some builders installing bushing style lifters. Thus, Think of the load a u-joint needle endures.

Simply food for thought

[this post is a continuation of an earlier post about lifters [bushed vs needle]

In the u-joint, there is very little play between cap, needle, and joint leg. Add in .030 play between them and see what happens. Hammers the joint leg to death in short order. Put a horribly worn u-joint in a good track car, and launch it a few times. That's what happens at the interface of the lobe/roller/needle/axle.

[modok]

Needle bearings don't like shock.
A ball bearing can never be out of alignment with it's groove, since....... it's a ball, but a needle can become so if it is allowed.

[peejay]

Consider this thought,

In ref to bushed lifters vs needle bearing lifters, driveshafts have needle bearings in the u-joints.

And bushed U-joints are stronger than needle bearing U-joints...

[cjperformance]

The theory (and AFAIK, it is just a theory) is that at idle and low RPM the roller slows its rotation when it comes off the closing ramp and then skids as it's spun back up to speed on the opening ramp, thus reducing long term street durability. The rev kit spring keeps the roller in full contact (as with a hydraulic roller) and so avoids the decel/accel cycles.
A few thoughts/observations:
o Does the roller really have time to overcome the shear forces in the oil films and slow drastically or stop in say the 30-40 ms it's on the base circle at 1,000 RPM?
o If it does, wouldn't the failure mode be skid wear on the opening flank of the lobe and/or the roller OD, not needle failures?
o If skidding is the issue, why isn't a bushed roller as bad or worse, due to its reported higher rolling resistance?
o Bronze alloy particles are far less effective engine killers than hard steel needles.
o One scenario explaining the value of both bushed rollers and rev kits would be that slack lash monitoring allows large clearances to develop and the resulting heavy impact loads cause needle damage and brinelling of the roller ID.
o Another would be that in the effort to reduce the roller loads, too soft springs are chosen, which cause premature valve float and heavy impact loads as above.

On this one Bill, talking needles, personally I say it has little to do with skidding of the roller on the lobe and more to do the needles bunching up as the roller decellerates onto the closing ramp , then as the opening ramp reloads the needles there is some movement/vibration of the needles as everything loads up again, I (only my guestimation here) will say that this is why a higher idle speed or more consistent higher rpm running helps, possibly keeping the needles more stable by not allowing the roller to slow as much after the closing ramp.
If you pull a needle solid roller lifter apart that has not failed you can clearly see where the needles witness marks are more pronounced at either edge of the shaft and inside the wheel,, whereas (yes lower typical spring pressures) do the same with a hydro needle roller and the markings are more even across the shaft and wheel giving me the impression that the needles do not get the chance to move about so much when kept on the lobe.
The acel and decel rates and rpm difference from base circle to nose are huge and I think anything that stabilises the roller after closing and before opening helps a lot.
For the skidding side , I dont believe the wheel ever stops over the base circle and with adequate lube I really dont believe that the small skid onto the opening ramp is of real detriment when everything else is well , but once a needle OR bush fails or is beginning to fail and the skid becomes more pronounced and breaks thru the lube film things get nasty. I think a lot of people then see these obvious skid marks and believe that the skidding caused the failure. These are only my opinions and observations, im always happy to hear other ideas/opinions or be 'proven wrong in the name of learning'.