Re: CV Joints
Posted: Fri Apr 25, 2014 9:33 pm
Ah but Greg, you neglected the whole scientific mouse fart comparison
Lee Spuhler wrote:The Ideal gas law is derived from Bolye's law and Charles' law is PV=nRT where n is the number of moles of gas and T is in degrees Kelvin or K. 0 degrees C is 273 degrees K, so air tempature is about 300 degrees K. R has something to do with molar mass and avogrado's number and is a constant in this case anyway, My memory tells me it is around 8 but I wouldn't bet on that. (after all I was wrong once today already, I got out of bed and my feet hit the floor, to which I heard my wife mumble "damn it")
First off the number of moles of the gas in the boot is very small and as stated R is a constant. Assuming the operating tempature rises 50 degrees then there is about a 20% change in tempature. I think it is safe to say that the small mole number of the air in the boot is going to dominate the calculation. So a 20% change times very very small leads me to estimate that the pressue volume change in the boot is about the equvaliant of a mouse fart!
srf99 wrote:Well... I pull everything apart every winter, which means taking the CVs off the half shafts. I then clean out the old grease, repack thoroughly with new, and then put everything back together. I haven't yet found a way to reuse the clamps, and even if I did, I'm not sure I'd want to. .
Lotus5 wrote:To repack with grease, you are just pulling back the boot adding grease and replacing. Not removing the axle. Correct? What do you do about the metal boot clamps. Replace them each time?
GregCirillo wrote:I'm no engineer, but have my doubts about the "excess pressure" issue. Really, how hot can it get? Starting pressure is 0 lbs at ambient temperature. Even if it heats up to 175 degrees, what sort of PSI will that create? And why can't a very flexible boot handle that increase in pressure?
srf99 wrote:I don't know as I've ever see my CV boots bulging after a session. Then again, I don't use the grease that comes with the CV kits, as it turns completely liquid when it gets hot, and I'm not sure how well that lubes and protects the CV. When I repack my CVs at the end of every season, the grease looks nearly new...