Hi Is there here somebody knowing somebody who would have a Tracy
Crook PSRU for sale? I'm looking for one on the web but can't find
one. Or is there a company which will re manufacture Tracy's PSRU?
Thank you for any kind of help.
Best regards Pascal
I am working with Randy Kempf on a copy of the Ross. Randy will
manufacture it and sell it. The Ross design is ten pounds lighter
than Tracy Crooks design. I'll have more time to do that now that my
patent is filed on the new ignition.
The ratio will be 3.12:1 to take better advantage of the rotary.
Paul Lamar
Pascal, I will have a brand new tracy Crook PSRU for sale in about
1 months. Currently using it to form a new cowl and nearly finished.
Price I do not really know, I think this one cost me $4500 or
thereabouts, but I cannot remember if that was AUD or USD. Make me
an offer and I will try and remember what it cost, but I believe it
was in USD plus freight. Neil.
Neil Unger
All those who have a unit for sale please specify the reduction
ratio as the 2.2:1 rotates backwards. Those buying make sure you
check this detail. Tracy built two. 2.12:1 and 2.85:1. The 2.85
rotates in the correct direction.
Paul Lamar
1. For which engine type was the 2.12:1 REVERSE reduction used for ?
Why is 3.12:1 better than 2.85:1 (difference of 0.27 of turn, a quarter
of turn) ?
Regards,
Zahid Rahman
It was used for a 13B engine. Tracy Crook did not fully understand
the Mazda Rotary. The rotary is a small displacement engine comparred
to an aircraft engine. It is only 2.6L. A O360 Lycoming is 5.9 L. Over
twice
the displacement. To get the same power (180 HP) the rotary must
run at twice the RPM of the Lycoming. The prop diameter limits the maximum
direct drive RPM of the Lycoming to 2800 RPM. The prop tips hit the Mach
One
brick wall at 2800 RPM. Therefore the geared rotary must run at least two
times the RPM or 5600 RPM.
The side port 13B rotary does not generate very much HP at 5600 RPM
so it must be run even faster. To get the most HP out of a rotary you must
run them at 8500 RPM or above; hence the need for a 3.12:1 gear box.
The rotary loves RPM and it is not happy at low RPM unlike a piston
engine. You must drive an RX8 to fully understand this. Tracy crook
never owned an RX7 daily driver let alone an RX8. I have owned
seven Rotary powered Mazda's including an RX8.
There is another factor here and that is the volumetric efficiency (VE).
That is the ratio of the amount of air getting into the engine relative
to it's displacement. Believe it or not the old Lycoming has a very good
VE. The large diameter piston allows large diameter intake valves.
There for to get a better VE out of a rotary you must use peripheral
ports rather than side ports.
Paul Lamar
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