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Hi Scott, Thought I would relate my engine mount situation. While there are rubber donuts between the parts of my engine and the mount, the first time I took the engine off, I discovered they were mostly cosmetic. The welder decided to have the center of the engine side of the mount made out of hollow tube (for bolt to go through) and the mount side simply had a hole (slightly larger than the tube) to go through. So basically once you put the two together (rubber donut around the tube) and put a bolt though the two (big washer over the hole) the center tube is in contact with the side of the engine mount. So there is really no insulation between engine and engine mount. I am certain I get more vibration than if I had the mount insulated with rubber - but have flown 300 hours like that (keep meaning to correct it but other things seem to come up). Certainly would not have wanted to do that with a Lycoming. So while that does not answer your question - that is my experience with engine isolation. Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com ----- Original Message ----- From: "Scott" <squiggles@yahoo.com> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net> Sent: Saturday, January 07, 2006 8:46 AM Subject: [FlyRotary] Why rubber engine mounts? Hello... If our engines are smooth and the entire engine is well balanced, why is it necessary to isolate the engine from the engine mount/airframe? Why isn't it appropriate to simply place a square of an old auto tire( or some similar material ) between the two points where I bolt the engine to the engine mount? What are we trying to protect the engine mount/airframe from the engine? I reached this point as I was diligently welding tubing to a plate to make cups for the rubber mounts which I purchased from Reid tool. After completing the two of the mount points I stopped and started questioning, is this really overly complicating the process, what am I really trying to protect the airframe from. Of course I identified a few, prop strike, loss of a rotor, among other out of balance scenarios. But, as those would ideally be minority do I need to over design for them? Any thoughts, opinions, and comments are very much welcomed... Thank You... -Scott Reference: https://reidecom.reidtool.com/xephr/edit/ITEM_GROUP_DETAIL?query=*CATALOG_ID=ARFF05&query=*ITEM_NO=VM-190-3&query=*GROUP_ID=73969&query=*START_WITH_ID=73969 __________________________________________ Yahoo! DSL - Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net/lists/flyrotary/