Bob White wrote:

Hi Paul,

I have attached some photos of my rear motor mount for critical
analysis.  I cobbled this together just to see how it would look.

The two bolts on the left (pilot's) side are 8 MM.  The three on the
right side are 1/4 inch.  Both support bolts are 1/2".  The spacing
on the top bolt is about 6 inches, and the bottom about 3 inches.
The 1/2 inch washers are being used temporarily for spacing, and
will be replaced with smaller diameter tubing.  The rod used for the
mount is 1/2" mild steel, and total length is about 13 inches.

The top plates are 1/4 inch thick, and the bottom are 1/8 inch.
(It's what I had laying around.)  The angles at the bottom were
originally part of the landing gear and this area is very well
supported.  I forget what the spacing was on the front mount, but I
think it is 28 inches. If I grab the rear of the engine and shake
it, the whole plane moves, and it seems very solid latterly.

Assuming a final weight on the rear mount of about 60 lbs., will
this support 300 lbs for my typical 5 G landing, or is it woefully
inadequate?  Do I need any lateral support?

Thanks,
Bob White

- - - - - - -
http://www.bob-white.com
N93BD - Rotary Powered BD-4

That is almost good enough. You need a bracket between those two
flanges on the 2nd gen front cover you are using. I'll draw something
up. Do you have somebody close by that can tig weld?

BTW you can get rubber rod ends from, McMaster car that would be
better for this purpose..

Paul Lamar

Bob, make something that looks like this out of 1.25 or 1.5 sqaure 4130
steel tubing .065 wall. Same for the bracket that goes on the firewall.
You can cut one inch holes in the back wall of the tube to get to the
nuts inside the tubing.

Paul Lamar

Thanks Paul,

I can make something like that, but I'm not sure it will bolt to the
left side quite like that.  The back side is partially taken up by a
casting for the plugged hole you see in that photo.  The top bolt is a
blind bolt.  It cuts into the space on the back side of the flange.  I
will take another look when I get back out to the airport.

Bob White

- - - - - - -
http://www.bob-white.com
N93BD - Rotary Powered BD-4

What you don't want is a cantilevered load on those front cover ears
as the force could rip them off. Keep the square tubing in there as close
as possible.

Here is a modification of one of your pictures to illustrate what
I am talking about.

Feed the load right into the bottom of the square tube.

Paul Lamar
 
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