wet clutches/brakes vs. dry clutches/brakes

[SmotalChaos]

ok guys, I was never able to figure this out. Whats the advantages/disadvantages to wet clutches and brakes?? Or "oil bath" clutches or brakes? Why do heavy equipment have them? More weight capacity? Longer life? Cooler running I would imagine, but then why not use them on class 8 trucks? Must be a reasonable explanation that for the life of me I can't come to...

 

[440Magnum]

Originally Posted By: SmotalChaos
ok guys, I was never able to figure this out. Whats the advantages/disadvantages to wet clutches and brakes?? Or "oil bath" clutches or brakes? Why do heavy equipment have them? More weight capacity? Longer life? Cooler running I would imagine, but then why not use them on class 8 trucks? Must be a reasonable explanation that for the life of me I can't come to...


Its hard to generalize because there's so much overlap in capability, but in general wet multi-disc clutches have longer life, better cooling, can run while "slipping" for extended periods if needed, etc.

Why not use them as primary clutches on class-8 rigs? Because class 8 rig clutches only get used from a dead stop. All other shifts are clutchless in most cases. Search Youtube for "shifting twin-stick" and watch the clutch feet not get involved at all ;-)

Also dry clutches probably (in general) have a little bit better ultimate holding power- IOW can transmit a bit more torque without any slipping, which is what's needed for a main driveline clutch in a class-8.

 

[ac_tc]

heavy equipment can use geared brakes so the brake will rotate faster and not need to take the wheels full torque. This puts the
brake inside the gearbox and in there there is oil-duh.
Cooling is also much easier since oil will transport heat away from the linings. As for holding capabilities-thats a design criteria....look at a powerglide mounted to 2000hp blown meth engine, it doesent slip if built correctly.

 

[onion]

I agree with all of the above advantages of wet brakes/clutches. Generally speaking, they're more expensive and more difficult to service than dry brakes/clutches. And maybe that's why we don't see them on trucks?

Although, clutch replacement is a pretty common and expensive job on heavy trucks. I think a wet clutch could be a real improvement over the standard dry clutches nowadays... but this would require a MAJOR redesign of the transmission, bellhousing, etc.