Bob, Rob, Ed, et al

 

Further enlightenment is required.  This is to lift the bushel basket and incandescently illuminate certain Lancair secrets.

 

1. Let's say the motor mounts are about 15 inches apart vertically and the mount to spinner distance is about 30 inches.  1/4" added to a motor mount changes the height at the spinner about 1/2".  Note that the exhaust pipes also move so make sure that there is enough lower cowl clearance to survive such a shift and also handle the movement from the torque of starting the engine and/or rapid +/- G maneuvers.  Here is a pic of a soft isolator (320/360) after some time in use:

 

 

2. Adding area washers alters the bolt hole alignment angle.  You can expect to see a distortion of the rubber that encases the center bushing:

 

 

3. For ease of installing and removing the 1/16" thick large area washers, cut a slot that is the same size as the bolt hole so that the washers can be slipped on and off without removing the bolt.  Too bad, no pic.

 

4. This is most important aspect.  When the area washers are removed, remember that washers of the same thickness must be added to the bolt so that the nut is not shouldered on the bolt when it is torqued down.  You should see no more than 3 (three) threads when the nut is tightened.  I have a pic somewhere of hi temp nuts shouldered on a engine mount bolt that only shows 4 threads.  If you add the 1/4" inch of washers, you will need a longer engine mount bolt.  Bummer, I cannot find the pictures of such a shouldered bolt/nut that Grayhawk hid somewhere.

 

I chose to add 2 such washers to each mount at the bottom so that the spinner better matched the cowl.  Remember that in flight at 200 KIAS the interior upper cowl is highly pressured whilst the exterior top of the cowl is a low pressure area - thus, the cowl is both lifted and balloons upward.  Such lift can shift its desired orientation if one has used spring loaded Camlocs as fasteners.  Machine screws or hinge-pin cowl fasteners resist a major shift because of the increase in rigidity.

 

Also, I have a 60# Hartzell CS prop and an additional 12# damper on the flywheel - Yup, that's a lot of  extra weight on those soft isolators.  I have added phenolic blocks to the top cowl that provides a stop at the fuselage joggle so that the top cowl cannot move backwards (front cannot lift it then, can it?).  But it still can balloon and so I still get bug residue on the upper edge of the forward face of the upper cowl because that area is exposed slightly above the spinner at flight regimes in bug season. 

 

Go now, grasshoppers.  Be forewarned.

 

Scott AKA Grayhawk the ancient

 

 

Ed -

 

There is a well known tendency for the 320/360 engine to "sag" after 25 hours.  Or more accurately, after 25 hours the sagging is complete.  The reported solution is one of the following:

 

1)  Place two area washers on the upper mounts, pushing the engine down.  Set the cowl to match the spinner.  After 25 hours, remove the area washers and the spinner and cowl will once again be aligned.  If you do this, as I did, you may find very little clearance between the top engine mount tube and the cowling.

 

2)  Set the cowl to match the spinner.  After 25 hours, place two area washers on the lower mounts, pushing the engine back up.  The spinner and cowl will once again be aligned.  "They" say that it is harder to install area washers at the bottom mounts.

 

Hope this helps.

 

- Rob Wolf