This is a post Rick sent Alan Goldwaite [sp] in 2003,
about a year before Ms Peel over rev'd apart his device. hobot >
With regards to the long term wear of my chain tensioners and related
components:
While it is true that I have many thousands (about 22,000) of miles on my own
tensioner, it is indeed only a sample of one, and we all know that the
scientific method would never accept conclusions made from a sample of one.
To be perfectly honest with you, I do not know how long my automatic cam chain
tensioners will last, but things are looking mighty encouraging. I can tell you
that of the 300+ units sold since it’s introduction in 1989, not ONE person has
ever requested a replacement shoe, nor have I ever heard of any problems with
the cam chain or the camshaft bushings.
Here is what I have learned, and what I suspect is happening inside those
timing cases:
During reassembly, most installers will notice a tightness in the chain, which gets even
tighter as you line up the idler gear/sprocket shaft with the cover bushing.
People should not be concerned by this. The side plates of the chain will wear two guide
grooves into the wear shoe as the chain finds it's running alignment. As the
chain rollers settle down on the top of the wear shoe, two very cool things
happen: 1) The tension in the chain relaxes, and settles in to the correct
running condition. 2) The rollers go into a hydrodynamic condition with the oil
film between the round rollers moving across the relatively straight wear
shoe. All wear appears to stop at this point. My own wear shoes, (and I have
tried this on 3 separate occasions), show a small patch in between the chain
side plates and in the middle of the wear shoe, about ½” long. This I have
determined takes place in only a few hundred miles of running. Subsequent peeks
into the timing chest at 1000, 6500, and then later 15000 miles showed that the
wear patch had not changed in size.
This evidence, combined with the fact that in 14 years, no one has ever ordered
a replacement wear shoe, leads me to believe that the hydrodynamic condition is
indeed being established here, just as it between the camshaft and big-end cam
bushing, or your crank journals and connecting rods.
I will not make the claim that my cam chain tensioner will last forever, but it
appears to be well on its way to lasting at least as long as any of the
other “wear susceptible” components in the engine
Regards,
Rick Avidano, Owner RMA Engineering