Mailing List flyrotary@lancaironline.net Message #19533
From: Barry Gardner <barrygardner@mindspring.com>
Subject: Re: [FlyRotary] under drive pulleys
Date: Mon, 28 Mar 2005 20:19:40 -0600
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Kevin,

Sign me up. I'm fitting them to '86 - '88 13B blocks but am not sure whether that's a 17mm or 19mm hole.

As for double pulleys, I have no idea whether that's good idea or not and am interested in other opinions.

Check my math: The ratio of the pulleys' diameters would determine the reduction. Assuming a 5" and 3.5" combo, the water pump would be going 70% of the speed of the engine, right? So at 8000 rpm, the water pump would be 5600 rpm, well below anyone's fears of cavitation.

Barry Gardner
Wheaton, IL

kevin lane wrote:

I spoke with a machine shop friend today about making pulleys.  He shows me his Mazda race car with a 400hp PP 13B, which I didn't know he had.  He believes that a single pulley with a deep groove should work fine, and that yes, often one belt will take out the redundant belt.  He runs his engine up to 9800rpm without belt problems.  His pulleys are 5 1/8 on the water pump, 3 1/2 drive, which just about touch.  He can make us sets for $110, a bit more for double pulleys.  He has an automatic tool changing mill with something like 27 tools available on this giant chain.  It is way cool to watch run.  Pulleys get made on the lathe however.  AL comes in 5 and 5 1/2" sizes, so a 5" pulley may be a better buy than 5 1/8".  He would make the pulleys to order, not as batches, so a 17 or 19mm center hole is no problem.  I wondered how many people were interested in getting some made.  I have not seen any for sale at these prices, although I may have missed some.  I saw some sets as high as $350.
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net <mailto:n3773@comcast.net>


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