While testing a J type OD we noticed it seemed to get hotter than the A type we
had tested earlier so we set up a comparison test as follows: We ran both units
in a test stand at ~2600 RPM output (~54 mph) in high gear with OD engaged.
Near the end of the run we elevated the gearbox front for two minutes at a 12
degree angle, then did the same to the back and then let run level for a few
minutes. This was to mix the oil from the front and back in an attempt to
equalize the temperature of the oil. We then measured the temperature of the oil
in the gearbox.
The oil temperate in both units was 138 degrees F. The fact that the
temperature in both gearboxes rose to the same final temperature is a
coincidence. The ambient temperature was a few degrees warmer (~80 vs. 75) when
the A Type was tested because we had the widow open to disperse the fumes from
curing powder coating. There were probably a half dozen other parameters that
affected the results so all that we can say is that the temperature rise is
similar, a little over 1 degree F per mph. There are all kinds of other effects
when the gearbox is in operation carrying a load. For example, the surrounding
temperature is much higher because of engine & exhaust heat, there is much
better ventilation when one is going down the road at 60 mph, the bearing load
is higher when transferring power through the gearbox/OD, etc. However, FT's
earlier observation that his A type was hot enough to fry an egg is probably a
typical temperature --- 100 degrees ambient in VA, and going 100 MPH -- that
makes it about 212 degrees F, could boil water on it.
We also found the J type solenoid seemed hotter than the A type so we computed
the power for each:
A type solenoid consumed 12 watts
J type solenoid consumed 21 watts
This explained why the J type solenoid was much hotter.
Nelson Riedel
Granville, OH
76 TR6 - J OD (repairing damage from fender bender)
68 TR250 - A OD (next project - new paint)
70 TR6 - A OD (all the parts in a pile ready to assemble)
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