WurlyBird
Well-Known Member
Unfortunately this is my first post in quite some time. Unfortunately my plane laid in the garage in pieces in between and during a few government funded vacations and I have been stuck being that guy who is too busy with family to fix it. But now the wife wants to learn to fly planes so priorities around the house get to change a little. Wahoo. So here is what I am stuck on and hopefully this will not end in me being verbally beaten about the head and neck for being stupid.
I have a Kitfox 3 and decided to upgrade from a Rotax 582 to the HKS 700E. I found someone who makes FWF setups for this application including the mount. The problem is that the thrust line is higher with this engine and it looks ridiculous in the round "radial look" cowling. So I got a cowl from an Avid Mk IV which has a thrust line that is higher still. So now I need to raise the height of the engine mount 2". I came up with the mount extension design that I will attach pictures of made of 6063 structural aluminum channel that is 2"x1"x1/8". It has cross braces made of the same to prevent any torsional loads crushing the mount extension. The front brace has lightening holes drilled in it because the tabs on the front are where the oil cooler will be mounted and I did not want the air to stagnate behind it. I believe it would be best to bolt the engine to the mount extension and the mount extension to the existing mount since long one piece bolts would work to crush the channel. The other option I see if this will not work is to get 2" square steel tubing and weld that in place but that would be significantly heavier, on an engine swap that is already going to bring the CG forward initially.
So is this a mount extension that could work or will I be better off welding steel. I am nowhere near the ability to calculate the structural loads for an engine mount but I have studied several UL designs that had what looked to be very minimal engine mounts. Much less significant than this anyway. I certainly don't want to risk any damage or injuries so feel free to be brutally honest with me if you know better than I do.
I have a Kitfox 3 and decided to upgrade from a Rotax 582 to the HKS 700E. I found someone who makes FWF setups for this application including the mount. The problem is that the thrust line is higher with this engine and it looks ridiculous in the round "radial look" cowling. So I got a cowl from an Avid Mk IV which has a thrust line that is higher still. So now I need to raise the height of the engine mount 2". I came up with the mount extension design that I will attach pictures of made of 6063 structural aluminum channel that is 2"x1"x1/8". It has cross braces made of the same to prevent any torsional loads crushing the mount extension. The front brace has lightening holes drilled in it because the tabs on the front are where the oil cooler will be mounted and I did not want the air to stagnate behind it. I believe it would be best to bolt the engine to the mount extension and the mount extension to the existing mount since long one piece bolts would work to crush the channel. The other option I see if this will not work is to get 2" square steel tubing and weld that in place but that would be significantly heavier, on an engine swap that is already going to bring the CG forward initially.
So is this a mount extension that could work or will I be better off welding steel. I am nowhere near the ability to calculate the structural loads for an engine mount but I have studied several UL designs that had what looked to be very minimal engine mounts. Much less significant than this anyway. I certainly don't want to risk any damage or injuries so feel free to be brutally honest with me if you know better than I do.
