Jack is right. Things are moving well with the axles thanks to Jacks own
considerable efforts. Let me update you on what Jack has done:
He met with two metallurgist friends of his on Tuesday. Both of these
friends have impeccable qualifications. Their input to the project included
a recommended material spec. (4140) and suggested hardening specifications
(C50). They were not very enthusiastic about the reduction in diameter of
the main length of the shaft but did agree that the shaft proper, as it
approached the splines should be slightly less than the root spline
diameter.
The later TR-4A axles eliminate the turned shoulder altogether. There is a
shrunk-on collar that is pressed on the shaft while very hot. The shrinkage
and interference hold it in place. I ran a pair of these axle in the race
car last year for a few weekends. They did not fail, but I sheared one of
the keys and trashed the axle and hub. This was before I learned about the
lapping procedure.
This approach to the project would reduce cost by substantially reducing
the amount of machine work required. It would save in material because a
much smaller diameter rod could be used since the integral shoulder, as on
the early axles, would be eliminated. And, if accomplished properly, should
help relieve stress concentration within the shaft at that point.
The downside, well...It may be a little more difficult to arrive at the
correct combination of heat and interference. This will obviously will
require more research. It is clear that Triumph made the change later in
the TR-4 run. Was the change made solely as a cost saving measure or did it
improve the axle reliability? Or maybe both?
On another not, I took an axle by my friendly (really!) local machine shop.
They suggested that we concentrate on shops that have a CNC lathe. And
suggested that the splines be rolled by someone equipped to do so.
Chris K. has sent a list of axle manufacturers and I'll be contacting them
as soon as we finalize the design.
Please provide Jack and myself with any input you would like to make to
this project at this point. If you perhaps know of a retired TR service
manager, if you could call him and try to get a feel for axle failure and
if there is a correlation with shaft type, that would be a help.
More as it becomes available........
Chip
|