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George,
As you are probably aware the stock 13B eccentric shaft pulley is about 4.5 inches (114.3 mm)
in diameter and the stock waterpump pulley is about 3.875 inches (98.4 mm) in diameter resulting
in a overdriven waterpump.......Most of us are using an aftermarket (Racing Beat) aluminum
eccentric shaft pulley approximately the same size as the stock waterpump pulley.......Effectively
the ratio is now about 1 to 1........This is a good enough to keep the waterpump away from
cavitation if you are using the 2.17 to 1 redrive where inflight rpm is in the 6000 rpm or less
range........Those of us with Tracy's 2.85 to 1 redrive will be seeing 6500 rpm plus which puts us
close to the start of cavitation in the stock pump plus there is added load (HP) needed to pull
the pump at this rpm.......Tracy obtains well over 7000 rpm racing and Ed has seen 6800 rpm .....
I became aware of a larger diameter waterpump pulley used in Mazda powered race cars here
in the states........The race cars spend most of the time in the 7000 rpm range and are rpm limited
(they have sealed and blueprinted engines dynoed to have equal HP) to make the driver the main
factor in the race........This pulley is 5 inches (127 mm) in diameter and is as large as will fit using
the Racing Beat eccentric shaft pulley........I am not aware of any of the flying rotarys currently
using a larger waterpump pulley........I ordered one of these 5 inch pulleys today and will report
quality, fit, etc when it is received........
--
Kelly Troyer
Dyke Delta/13B/RD1C/EC2
-------------- Original message from "George Lendich" <lendich@optusnet.com.au>: --------------
Kelly,
I for one would be interested in that information.
Are you saying that the standard underdrive pulley ( I guess 15% to 20%) most commonly used is 5"?
George (down under)
Georges, Ed and all interested,
The following excerpt from Bill Jepson adds more info about the stock waterpump and
would seem to show the wisdom of reducing pump RPM for those of us using Tracy's
RD1C 2.85 redrive.......I will be ordering the 5 " diameter pump pulley today and when
received will report on quality, fit, etc as necessary for our needs......
--
Kelly Troyer
Dyke Delta/13B/RD1C/EC2
(Copied and pasted from eariler post)
Jim, I agree that 12-34 GPM is a big window. One of the items that always drove my skecptisim over the EWP is that in almost every thermodynamic text I've read turbulent flow is cited as helpful to heat transfer. This would be short of cavitation of course. Volume is always the second item, or sometimes interchangeable. I'm sure this is what drives the "other list's" refusal to believe the EWP will work. I AM willing to accept a actual test. Thanks Todd Leon and whoever has tried. Somewhere there is an incorrect assumption being made. I'd like to know where, so I'd be more comfortable, but I am always willing to believe my eyes, and my temperature guage! As a side item, when I spoke with Steve Wienzerl the designer of the newer PowerSport reduction drive, he said they tested the EDWP to max flow. The claimed volume was 55 GPM somewhere between 6500 and 7000 RPM. He was sure this was on the ragged edge of caviitation. He wasn't a EWP believer, in fact he wanted even more flow than they were getting!
Bill Jepson
-------------- Original message from "Ed Anderson" <eanderson@carolina.rr.com>: --------------
Hi Georges,
Not Tracy, but my alternator is underdriven by approx 40%. I have two Racing beat pulleys each 20% underdriven, one the main pulley on the eshaft and the other on the alternator. Kelly is looking into a underdriven pulley for the water pump. Running continuos at above 5000, even 6000 rpm make me decide to reduce the alternator speed and I would like to do the same for the water pump especially with engine rpms approaching 7000 rpm with the 2.85 redrive. I also use the best V belts I can find (Gates) which I change every two years and they have never shown any signs of stress such as cracks or grazing. Can not say the say of some cheaper belts I used in the past, including one which after 5 flights had the rubber "clogs" falling off the belt.
Ed Anderson
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