Custom shims for engine mounts
I noted that for all four engine mount points, secured by M5 bolts, a small gap is visible between the engine mount surface and the upper and lower firewall mount channel. Tightening the M5 bolt I suppose to close this gap by flexing the channels along their centre line. I am not so keen on this unneeded introduction of stress risers into the channel. Instead I fabricated shims from 0.4mm 6061-T6 to fill such a gap.
Engine
An additonal effect is to remove a slight interference between the nominally flat welding along the edges of the engine mounts and the folded corners of the firewall mounting channels.
Custom shims. The rightmost shim is covered in a separate posting
From the left of the previous image, the first shim is a shim that will sit against the upper left hand engine mount, matching the 0.4mm parachute box sheet
The second and third shim are for the upper engine mounts
The fourth and fifth shim are for the lower engine mounts.
RH shim approximately in position. These shims are extended to match two 4mm rivets so as to ensure correct orientation owing to there being only one bolt. Unwanted rotation could cause interference with the channel fold and consequent stress risers
Upper engine mount shim visible
Author
This post is from Adam Dickson
