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26#’s vs 42#’s. Was the 26#’s just the hub or did it include the blades? Yeah-- I know you may not have gotten that far into the conversation J There are some used Egginfeller electric MT’s available from time to time. Not sure about HP for each model. Steve B. may have more information since he converted from fixed to electric a little while back. Bobby From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Friday, April 05, 2019 9:47 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Electric constant speed props Went to Sun n Fun and talked to a Aeromaster representative to collect information and data on their Electric constant speed prop combinations. After waiting a little while a representative of the company approached as asked what he can do for me. I replied that I am extremely interested in their design and would like further information. I was asked about my aircraft engine installation, I explained to him about the Rotary and what my RPM requirements would be. His response went something like this " Do you know how much this cost? it will probably double the cost of your installation/plane" I immediately took this as an insult and replied " you know nothing of me, my finances, nor my plane" as I walked past him I padded him on the arm and said " keep your freakin prop, you just saved me a lot of money" but I didn't say freakin. One thing I did find out is that it would be around 26lbs, well worth the trip, wouldn't you agree? On Tuesday, April 2, 2019, 07:27:12 PM EDT, Bobby J. Hughes bhughes@qnsi.net <flyrotary@lancaironline.net> wrote: Correction 6000/ 2100 rpm. Bill, Most takeoffs have been at 7000/2400 rpm with MP between 34-38” to pattern. Cruise at 5200/ 1824 or 4800/ 1624 rpm depending on my desired fuel burn and airspeed. Most cross country flight are at 28-30” MP and with F/A 15.8. Or 13.5 for higher MP. Bobby, You push it fairly hard with your supercharged engine too. What cruise RPM are you running? P.Sport always tried to tune for lower RPMS and higher power to avoid the torsional vibration problems. With boost you can make more power at lower RPMs which is a plus in this case. The rotary is tough, the engine will tolerate a lot, but the high revs for long periods is what causes the need for attention to torsionals. BTW I moved and had to take a break from my redrive efforts, but am getting back to it. Got some good ideas today from Mark Hatch, Everett's son. My MT weighs 42#’s. The hub is heavy, blades are light weigh. Gear lashing appears to have increased a little over the first 500 hours. End play is about 5 thousandths with original snubber. Sam, I am working with some originators of Powersport. The weight of your build makes a big difference on the use of a constant speed. Also in the case of the rotary the quality of your muffler! Sound levels really effect your comfort on longer flights. Mufflers for rotaries are tough, I already have 1 failed design to my (bad) credit. The original Powersport designs used the light weight and flexibility of a wood prop to their advantage. Those engines were tuned for max power at 6500 RPM. The reductions were about 1.85 to 2.2:1. suitable for the lower power peak. Torsional vibration issues also favored a wood prop. How heavy is the electric Airmaster? MOST engines including the rotary are helped by a variable pitch prop. Whether the combination is safe depends on the reduction drive, ratio, and weight of the prop on the output shaft. Powersport's owners noted significant torsional vibration problems with every planetary gear set, (even their own custom made straight cut planetary). Their later stiff model internal ring gear reduction gearbox put the resonances out of the normal range for the rotary. Prior to that the only problem free build with a planetary was when they built a pendulous damper system (like a big radial engine uses) which worked great but was so expensive they figured they would never sell an engine. So if you are running a planetary reduction you need to keep the weight down as much as you can. Find out what the Airmaster weighs. The amount that it exceeds your wood or carbon fixed blade prop is your risk factor. The advantage is to use a low cruise rpm that takes advantage of the props flexibility. As a thrust producing device it is better, there is no doubt. If it is very heavy though it may cause problems that aren't obvious as to origin. Torsional problems may take hundreds of hours to develop, or something may break the first week. Just be wary. Always keep track of things like changes in output shaft end play and backlash. You can make the change, and see excellent results but go in with your eyes open. Lots of people will tell you this is nervous nelly stuff, but the guys at P.S. probably had more hours running and testing rotaries AT HIGH OUTPUT levels than anyone other than Mazda. Lately I have been considering an Airmaster electric constant speed prop to help achieve the rotaries true potential. I am asking for insight to help me make this decision. I'm not sure if the benefits of a constant speed out weight the cost, please help.
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