Hi Paul,
After all these months, I finally have most of the engine
accessories on so that I can measured the weight on the rear motor
mount. Paul, I believe you had estimated it to be around 50 lbs. I'm
using the motor mount plate, so the weight would be somewhat lower if I
had the s-beam. The prop is a 14 lb. carbon fiber composite with an
aluminum hub. It was made by Steve Hill who is a member of the Nemesis
crew and has a shop at Moriarty Airport. More about the prop after I
get the engine running. (I only have it on loan for now.)
Bottom line, the weight on the rear motor mount was 115 lbs.. I
measured the weight with a bathroom scale and a steel rod between the
rear mount and the scale. I wouldn't expect this to be too accurate,
but probably +/- 5 lbs or so. Also, the radiators were empty although
the block was full of 50/50 antifreeze.
Since the neoprene rod ends are only good to about 300 lbs, they look
marginal in this application. I will keep them initially, but inspect
after each flight. If there are any signs of deteriation, I will
replace them with the solid steel versions. Actually, I will put the
steel ones in anyway to see how much vibration dampening the neoprene
rod ends provide.
Bob White
--
http://www.bob-white.com
N93BD - Rotary Powered BD-4 (real soon)
That's static.
Since the thrust line is about 4 inches above the front rubber bushings
there is a moment about them. Lets say max thrust is 500 pounds so
the moment would be 2000 inch pounds. Lets say the rear mount is 18
inches back from that so there is an upload on the rear mount of
2000/18 = 111 pounds. 115 pounds download minus 111 pound up load
is 4 pounds down load. Your numbers may vary.
Worst case is 6 G pull up or dropping the airplane in at 6G (The
landing
gear will probably fail). In that case the down load is 690 pounds. The
rubber may fail (split) but it is unlikely the 1/2 inch steel rod end
will fail.
The front rubber bushings may also split.
Paul Lamar
Bob, are you using rod ends on both ends of the strut? If so, would
loads be shared between the two? That would bring the load bearing up
to 600 lbs. I don't know, but it seems likely.
You are right, if the neoprene turns out to be inadequate, a steel
rod end would take care of it. The McMaster Carr on line catalogue is
acting up today so all I have is an old print out of the neoprene page.
Above the neoprene isolated rod ends are "Thrust Rated Ball Joint Rod
ends." The 3/8 size is rated for 4,854 lbs radial load capacity and
1,765 lbs thrust. One half inch size not listed on that chart.
Jerry
If they were side by side and in parallel the load capacity would
be 600 pounds. Since they are in series both rod ends see the same load.
Therefore the load rating is indeed 300 pounds. Rather conservative I would
say. It is easy to build a test rig and use an engine hoist to lift something
heavy using a couple of rubber rod ends back to back.
Paul Lamar
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