stunthanger.com
Building Tips and technical articles. => Building techniques => Topic started by: ray copeland on January 17, 2010, 09:04:32 PM
-
What type and thickness motor pads are recommended for 35 to 46 size engines to help reduce vibration on profiles? Do these need to be on the outboard and inboard sides? I have had some fuel problems in the past that are helped with foam behind the fuel tank but i would still like to lessen the vibration if possible. Thanks, Ray
-
Everyone I've seen for that range is 1/8" alum. but I suppose you could use phenolic also. Usually placed under the lugs for crush resistance and to displace the load.
-
I use a different system. 1/2" square motor mounts and 3/8" square aluminium inserts that are drilled and tapped for the engine. They are removable so changing to different engine isn't all that hard. Works for me.
-
I use a different system. 1/2" square motor mounts and 3/8" square aluminium inserts that are drilled and tapped for the engine. They are removable so changing to different engine isn't all that hard. Works for me.
How do you secure the 3/8" aluminum inserts to the 1/2" wood mount ?
-
A solidly mounted engine has to shake the whole airplane, not just itself. I am well impressed that mounting pads cut down on vibration.
-
Allan,
I machine out the 1/2" wood for the 3/8" square block with the block sitting about 1/8" above the motor mount. Then I drill out the 1/2 motor mount and insert a carbon tube to prevent crushing. Then I usually make an 1/8" steel pad on the back of the mount that is tapped for 4-40 or 6-40 (depending on the screw size I'm using. Then bolt the block to the mount.
-
Allan,
I machine out the 1/2" wood for the 3/8" square block with the block sitting about 1/8" above the motor mount. Then I drill out the 1/2 motor mount and insert a carbon tube to prevent crushing. Then I usually make an 1/8" steel pad on the back of the mount that is tapped for 4-40 or 6-40 (depending on the screw size I'm using. Then bolt the block to the mount.
Any chance of some pix?
-
I lost all my pictures in a foolish error on a back a few months ago, but I think I have some pictures of the mounting system on my current PA. I'll check when I get home.
Sorry to take this off topic.
-
Maybe part of the dampening by balsa doublers, etc, is due to more efficiently transferring vibration to the whole airplane. Shaking the whole airplane wold be different from just shaking the nose. Different frequency, different energy required, etc. Whatever. Let us do what works for us to not have a vibration problem.
-
Today i did two different trials. On a Skyray with 35fp i made 1/8 aluminum pads, i could tell no difference, got good runs by adding foam behind the fuel tank and not squeezing it down so tight. Also used a venturi sized for the 25 and that seemed to smooth out the runs quite a bit. On my Twister with 46la i tried my neighbors advice and cut pads from a 5/32 thick piece of hard leather belting, still i could tell no difference. Again foam rubber behind the tank worked. Now i need to figure out a good tank mounting procedure with the foam besides using rubber bands and hooks. Next profile i do i may try the inboard tripler.