This is a low cost PSRU because sprint
car parts are mass produced and therefor low cost.
They are mostly aluminum and magnesium for light weight.
The rear axle in a sprint car is called a live rear
axle because there is no axle housing. The entire axle
is one long piece of three inch diameter thick wall
aluminum tubing. Sprint cars take a heck of a beating
as they run on potholed 1/2 mile oval hard clay race tracks.
The stress on this three inch diameter half inch wall tube used
as a prop shaft is very low so it should last forever. It is machined
from a four inch diameter one inch wall aluminum tube.
The Ford six planet carrier is merely bolted on the back end
and a stock off the shelf low cost 42 splined sprint car rear
hub is used for the prop flange. The shaft with a 2 inch hole
and a 1/2 inch wall thickness weighs only 8.7 pounds.
Don Dunbar's steel output shaft and flange weighed 7.26 pounds.
Tracy's prop shaft with bearing and flange weighed 9.25 pounds.
http://www.sanderengineering.com/cat24.htm
The housing can be tig welded from telescopic aluminum
tubing and 1/2 inch plate and designed to bolt inside a
stock Mazda bell housing.
http://www.argylein.com/cgi-bin/search_dies.pl?words=TUBE
The prop shaft bearings themselves can be Torlon roller bearings
widely used in racing sail boat winches and blocks.
Torlon roller bearings will run directly on hard anodized
aluminum. No heavy bearing races required. Torlon is
25% of the weight of steel roller bearings.
The thrust bearings are conventional needle bearings.
http://www.drakeplastics.com/torlon_4435.php
My guess this could be made for under $1000.
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I am thinking of using a plain journal bearing for the
hard anodized aluminum prop shaft running in Tuflite bearings
fed with engine oil pressure. Has any body on here heard
of that being done?
I want to do this so the PSRU is compatible with a hydraulic
constant speed props. It will also save money and weight on the prop
shaft bearings.
www.aerospace.rexnord.com/CatalogPDF/tuflite.pdf
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Just spoke to the Rexnord engineer about the pressure fed
Tuflite Teflon journal bearings and he was enthusiastic
and encouraging. He is sending me some samples.
It is also known as Rulon. Same stuff not mil spec however.
We both agreed that engine makers should be using the technology.
Most wear takes place during start up when the oil pressure is low.
The Teflon handles that fine and prevents metal to metal contact.
Also during aerobatic maneuvers when the front and rear of the prop
shaft journal bearing may be momentarily over loaded the Teflon will
prevent metal to metal contact. The rest of the time there is
no contact between shaft and bearing due to a high pressure
dynamic oil film with extremely low friction.
Here are some more pictures of the Sprint Car aluminum parts I will
be using for the prop shaft and flange. These parts get tremendous
abuse in Sprint Car racing with cars cart wheeling occasionally.
No sign of fatigue breakage.
I call it the Sprint Car PSRU for short.
Paul Lamar ...No rotor no motor.
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