Minimum alternator / cowl clearance?

[tx_jayhawk]

I am curious if there is a generally accepted minimum clearance between the alternator and the cowl. I am not close to the pulley, but I am pretty close to the body of the alternator. 0.5", 1", 2"?

Scott
7A Cowling

[Mel]

1/2" should be absolutely minimum. This could still be marginal during acro. The engine moves around considerably.

[kentb]

But then I don't do acro with my plane.

After the first flight, I discovered the mixture linkage (located on the left side of my throttle-body in my installation) was starting to wear a hole in the cowl. I cut out a hole around it and fiber glassed a bubble over that area. There was about 1/2 inch clearance here before the first flight.

After 65 hours I am starting to get my fairings ready to paint and would be repainting the bubble on the lower cowl. When I took it off I found that it still hit some times and the glass had a couple of small cracks in it. I how have increased the bubble some more. It has more then and inch of clearance now.
I guess that it depends where on the engine that the clearance is needed, but these things really shake when they are shutdown and started.

Kent

[gmcjetpilot]

Originally Posted by tx_jayhawk

I am curious if there is a generally accepted minimum clearance between the alternator and the cowl. I am not close to the pulley, but I am pretty close to the body of the alternator. 0.5", 1", 2"?

Scott
7A Cowling

Consider getting more clearance by modification of the tension arm. Not sure what alternator or mount hardware you have. Some times you can get more room. I cut the end off that attaches to the engine and re-drilled it. It changed the geometry and adjustment so I could get the alternator tighter to the engine.

[N941WR]

Originally Posted by gmcjetpilot

Consider getting more clearance by modification of the tension arm. Not sure what alternator or mount hardware you have. Some times you can get more room. I cut the end off that attaches to the engine and re-drilled it. It changed the geometry and adjustment so I could get the alternator tighter to the engine.

Consider getting an O-290. Lots and lots of room, they even give you two more inches between the firewall and the back of the engine.

Oh, that won't work in a -7. Sorry about that.

[Bob Axsom]

The only problem I had was with the pulley and the exhaust pipe from cylinder #2. I cut off the blade of one our stainless steel kitchen knives and glued it to the inside of the cowl at the ocassional pulley contact point with structural adhesive. It works great with ocassional contact marks. The exhaust pipe had to be cut off at the slip joint for engagement to permit maximum clearance. A new mechanical link (shorter) had to be made to facilitate the new coupling and I had to glue the very expensive aluminum backed woven silica thermal blanket to the inside of the lower cowl with 3M weatherstrip adhesive. We won't talk about the cowl repairs that had to be made before these fixes were incorporated. RV-6A, O-360-A1A, new style cowl (when they were first being sold by Van's). B&C 60 Amp. alternator and Skytech starter.

Bob Axsom