Because the manufacturers of the oil pump gears sets, (I believe they are
marketed in the US as "county" brand) found the inner gears comming loose
from the shaft was a problem, they began to install a pin though the rotor
and the shaft about 6 or 8 years ago. We had on of those pins work loose and
come out during engine operation and it consequently jammed the pump, which
immediately sheared the slotted upper end of the drive shaft. The pump
stopped turning completely at this point. The engine kept on running until
it ran the bearings.
Previously, using original Triumph supplied pump rotors, two times I
experienced the slot ears shearing off when there was no reason for them to
fail except normal stresses of operation. This always stops the pump from
turning. These shaft failures, I believe were cause by the shafts beiing to
hard and consequently somewhat brittle. They were, and the new repro parts
are also, machined with sharp corners to the drive slot in the top of the
shaft. These sharp corners are stress risers that will help induce the
begining of cracks. We remachine the slots so that there is a full radius in
the bottom, then glass peen the inside of the slot to remove the machine
tooling marks.
As for the pin that is designed to keep the rotor from turning on the
shaft, We found that the pin on the origiinal gear is VERY hard to drive
out, while the pins in the new gears are very easy to drive out. So we now
remove all of the pins, tap the hole through the rotor and the shaft, and
then loctite in a 3/16 allen set screw as a new "pin". Being loctited in
with maximum strength retaining compound and screwed into place, it is NOT
going to come out.
With gears modified in this manner, we have experienced no failures,
even in race engines turning over 7,000 rpm and pumping over 90 psi oil
pressure.
Regards,
Greg Solow
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