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Hi! Lynn
Thanks I have 3 or 4 housings that have less than an 1/8" of chrome missing( some less than 1/16"). Does anyone know how much you can move the thrust line with minimal effect?
Georges B
-------Original Message-------
Date: 04/01/06 16:27:44
Subject: [FlyRotary] Re: Very short intake manifold length
In a message dated 4/1/2006 10:41:54 A.M. Eastern Standard Time, echolakeresort@telus.net writes:
Thanks Lynn
I guess I should have asked first, I already got the Petersen 3.5 gallon tank & the Weaver 3 stage pump on Ebay this week (I'm more concerned about keeping the engine cool than the weight)I used that same pump for years when I raced in "B" sedan, never exploded an engine because on oil pressure, that's why I picked it . IVO came up with that prop size (electric control). Ken Weller uses a 4 or 5 blade prop but the float plane guys say the larger diameter the better. I can't find anyone who is using a large prop with a 13b.I have a Nitrous system if I really need it. The engine thrust line on the Christavia is only about 10" from the top (suitable for a Lyc.0-320) I don't know how much I can lower it without ill effect. An other question, I have taken 7 13bs apart & only have one rotor housing that doesn't have some chrome chipping on the edge, can any be used? Sure would like to hear from anyone using a large prop on a 13b. I appreciate your input, although I built race cars & piston engines for years I was never involved with rotaries (wish I had may have blown less engines with rotaries than piston engines). The Christavia Mk IV is designed to use a 150hp engine on wheels so 180 to 190 hp should be OK on floats
 Georges Boucher
2126 Creighton Valley Road
Lumby, British Columbia
Canada V0E 2G1
Phone:(250) 547-6434
1- 877-547-6434
Fax:: (250) 547-2342
The chrome flakes off from fretting as the housing moves around on the iron from high stress operation and just heating and cooling. By running over the very edge of the chrome with a diamond file nearly fat to the sides of the housing, so as to reduce the edge of the chrome so it will not touch the iron. Sealing is not dependant on the chrome layer. The chrome is also failed from the excess pressure of the small corner of the apex seal, that has more than enough pressure from the spring. One piece seals do no such damage. Note that later apex seals have the joint inboard of the corner.
Many engines die from OPM failure and or running filthy oil that cannot protect the chrome from wear. So long as the damage is with about 1/8" of the edge there should be no problems. Further damage will just appear as lowered power output and lowered compression.
The larger the prop diameter the more efficient it becomes. Also the drag at the tip is increasing faster than the efficiency is increasing right up to sonic where it all goes to hell.
Note that WWII fighters had propeller diameters close to 1/4 the wing span. And they all had reduction boxes. So there would be some logic in trying the largest diameter first.
The weaver is not a bad pump, but does not work well in the suction lift department. Better to have the oil level in the tank higher than the pump. The engine sump will over fill when parked as the oil leaks backwards through the pump gears. So a few seconds at idle is required, to allow the scavenge side to remove that oil and get it back into the tank before high power is needed. Also the scavenge side can build very high pressures, with no pressure relief system and blow off a hose, or collapse a filter element. A real treat if you have not done it before.
Sign onto the "Nopistons" list and check for used housings in the for sale area. Also hundreds of people asking questions and finding sources of supply. There is a huge Mazda only junk yard in Georgia but I forgot the name. I will find it and post it. Also the RX-7 list.
Lynn E. Hanover
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