have about 35 hours on my 320 and have the traditional 1/4" – 3/8” sag at the spinner.  The engine is mounted on the Barry vibration isolators that Lancair sells.  My intent was to align the cowl with the sag in mind in hopes that the engine would eventually match up.  Well, the way the cowl turned out it was aligned perfectly before the first flight.  Within the first 10-15 hours I got all the sag I’m going to get.

 

My question for the group is: how many area washers should I put under the lower two dynafocal pads to shim the engine up?  From past postings that I can find I am guessing at 2.  What say you all

Dan,

 

I am surprised that you have that much sag so soon on the stiffer Barry mounts.  This is usually more of a problem with the softer Lord mounts. 

 

In any event, consider the engine mount to spinner linkage much the same way the leg bone is connected to the knee bone and the knee bone is connected to the foot bone, Dem Bones - Dem Bones.........  Think about a lazy ell (L) with the right angle as the pivotal upper engine mount, the end of the short leg at the bottom engine mount and the end of the long leg at the spinner. If the short leg is 1 foot, the long leg is 2 feet and a spacer is used to move the short leg forward 1/8", the long leg would move up 1/4".  So, measure the distance between the mounts and from the top mount to the spinner bulkhead and compute how thick a spacer is needed to return the engine to its' faired position.

 

A common problem is to use the wrong length bolt or to torque the nut onto the shoulder of the bolt.  The heat-proof steel locking nut is longer than others and you should see no more than three threads showing after torqueing the bolt.  Use as many washers as necessary to satisfy this condition.  If the nut is torqued onto the bolt shoulder, the internal bushing is not tight to both rubbers and the mount "floats" the engine which can result in excessive sag and harmful vibration.