Hi Paul, Do you have any more info on Tracy's box, like the shaft and
internals, I can't figure out where the thrust goes etc. The box is
very chunky, I would say overkill somewhat. Also I can't see any oil
supply, in or out. You wouldn't have to saw off the flange, I would
do my box and then remove it from the pattern before casting others.
From the side view it looks like the prop shaft is one piece, is this
right ? Also, is the box intended to be bolted up to a plate or a
bell housing. Chris.


Tracy used a cut down GM pick up truck rear axle and ball  bearing.
The bearing was retained by a pressed on collar with  several tons of
force. Tracy fed the box with oil from the engine. So too the Ross
but the Ross had all needle bearing so it required less oil.

Very heavy at 9 pounds, I would not do it that way.

I would use a hollow shaft like the  Ross with a separate prop
flange. No forging required. The flange would be retained by special
set screws called  "Extended Point" . A relatively new idea and much
stronger  than pins that go all the way trough the walls of the shaft
(which is what Ross used for years) or splines and much less cost.
Easy to machine with a rotary table.

About a 2 inch OD steel tube with a .190 wall is about right. Just
like the Ross box. That is about the largest needle bearing you can
buy.

Use about eight or ten of these .25 inch screws and they are almost
as strong as a one piece shaft and flange. Here are some pictures.

Do you use a dwg program Chris? If not I suggest getting a Rhino. It
will save you money in the long run.

Paul Lamar

Speaking of the Ross PSRU, if one just decided to cast his own housing [perhaps out of an
aluminum alloy], what would be the best alloy to use…decent properties and not too
expensive or hard to do?
Gene Kahn


356 is the usual casting alloy and the foundry heat treats to T6 hardness.
Paul Lamar

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