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Ernest Christley wrote:
Ed Anderson wrote:
Looking good, Ernest!
Not quite certain I understood your pan attachment arrangement, but you
want to make certain that the Pan is structural quality steel - which being
an oil pan it may not be. You may need something like the 1/4" plate to
carry the load.
Ed
Having cut a slice from the pan, I can vouch that it cheap steel. But it is THICK and it is steel. A picture should clear any confusion. The red areas of the attached sketch would be the 1/4" plate. The arms would be long enough to catch a reasonable number of bolts.
The way I'm seeing it, the block sits on a plate that sits on the mount pads. Because the mount pads are not directly under the block, there is a torque moment on the ear with the fulcrum at the corner of the block. As long as the ears don't bend (I'll have to run numbers to determine if 1/4" is enough to meet that demand), then the arms simply have to counteract that torque moment. I just don't see what all the metal in the middle is doing except weighting the aircraft down.
Paul Lamar's sight has a tutorial that quotes 800ft.lb. as the maximum torque pulse from the engine. I'll need to add that to the maximum 10G load limit (situation: trying to pull out at the last second with full power, but slamming the nose in anyway). It's too late tonight, but I'll take measurements and try to run some numbers tomorrow to see if this is even worth pursuing, but it sounds good at this late hour 8*)
In the likely chance that I'm missing something, I'm all ears 8*)
What are you trying to accomplish by NOT using a sandwich mount.. save money? Save weight? If you aren't conducive to using a sandwich mount like the others, I would err towards using the original mounting hardpoints on the engine block, or use some of the other 10x1 stud holes... AND perhaps the pan based mounts for some sort of torsional stability.. but NOT the proposed pan mounts as sole support. You are dealing with not only torque (which you appear to be cognizant of) but also G-loading (both positive and negative)... I would be interested in seeing what this sort of pan mount would withstand with regards to ultimate g-loading.. Normal Category is 3.8 g if I remember (and thats considered normal bounds.. I dont recall what the design factor is above and beyond that. Aerobatic is something like +9 and -3 or -6... it would be interesting if this 250 pound motor on a pan mount will remain in position without deformation at loading approaching 1000 (normal) or 2000 (approaching aerobatic) pounds of load x factor.
Engine mounts are a major structural item, and failure WILL likely mean loss of the aircraft, and landing in an uncontrolled manner (engine comes off and then you have a really unfavorable CG).. this is where you want to OVERBUILD (if you are going to err), not underbuild.. a stamped oil pan is hardly a structural item....
Fly SAFE,
Dave
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