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Hi Gordon, I had to go out and reweigh my Ivoprop. I do not know if you are familiar with this prop? The blades are made of carbon fiber and do not weigh much. A metal blade (shaft) runs down the center of each blade. An electric motor applies force to the metal blades inside each carbon fiber blade, which twists the blades, changing the pitch of each blade. The term used is an in-flight-electrical adjustable pitch prop. The motor and contact discs on the center shaft make up most of the weight. All together the 3 carbon blades and motor prop system weigh about 7 lbs. Their placement is about a foot out further anterior than if I used a Lycoming engine. Ken Johnson
From: Gordon Alling <gordon@acumen-ea.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Monday, February 25, 2013 7:58 AM
Subject: [FlyRotary] Re: 13B weight and CG location
Hi Ken, Thanks for your info. You are correct that I am trying to determine the position of the engine for proper aircraft CG location. At the moment, I’m trying to design the engine mount truss for the design loads. If I know the weight and CG location of the engine/prop assembly, I can model the loading in truss analysis software and play “what if” games with different truss configurations. Your 300 Lb. figure for the engine/redrive
assembly and your heat exchanger weights is a start. What does your IVO prop weigh? Thanks again for the help. Gordon C. Alling, Jr., PE President acumen Engineering/Analysis, Inc. 540-786-2200 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Kenneth Johnson
Sent: Sunday, February 24, 2013 7:02 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: 13B weight and CG location Hi Gordon,
I am not certain what you are asking. It would seem you are asking if you can use a DIY engine mount, and therefore, you are asking how far from the firewall should you place your engine? This is what I found with my engine. I am using a 13B NA engine with a PowerSport redrive. The weight of my engine and redrive is 295 lbs. My radiator weighs 15 lbs and the oil cooler weights 7 lbs. I found that when adding the weight of the radiator and oil cooler fluids, that my engine system would come very close to the weight of a Lycoming 360. It was estimated that the average weight of the prop would be 27 lbs. My Ivoprop weighs less than that, but the prop is positioned much farther anterior than with a Lycoming because of the redrive. So, the arm is out there. Tracy's point on the cg of the engine being positioned just inside the
first end plate would be pretty accurate.
I am getting closer to finishing a Zenith 801, so I am yet unable to offer actual flight experience. Zenith did provide numbers for the installation of a Lycoming 360 and I compared my numbers to theirs. I had anticipated that I would be placing my engine a great distance from the firewall because everyone says the 13B is so light. However, after adding the weight of all the "extras," plus the fact that the arm of my prop is out a much greater distance than with a Lycoming, I actually had to move the engine closer to the firewall than if I used a Lycoming. I concluded that I needed to design and build my own engine mount.
I hope this is helpful.
Ken johnson I’m considering a DIY engine mount for my turbo 13B engine. Does anyone out there with an operating 13B (turbo or NA) have good numbers for the installed weight and CG location for his/her engine/redrive/prop combination? I want some ballpark numbers to get started. Gordon C. Alling, Jr., PE acumen Engineering/Analysis, Inc. |
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