flybyme

I'm trying to mount an os120 sur III on a dubro vibration dampening (688) engine mount. The regulator seems to be in the way, throwing off distance between firewall and thrust washer by 1/4" too long. Which vibration dampening mount would you suggest?

flybyme

Oh you may have figured it out, but it is a pumper.

Campgems

I ran into trouble with my OS 52 and the mounts. I had first had a Magnum 52 on the mounts, but the carb was hitting the right top, looking from the front. What I did was to take the outside aluminum hub out and counter sinked the front to burry a flat head machine screw in. That gave me the height of the head of the socket head that comes with the mounts plus the highth of the lock washer. If you are using the #8 screws, that should give you your 1/4". Just remember to give some clearance between the engine and the screws or with my mod, the aluminum hub. The engine will push back on the mount if you whack the runway and hit the prop, so you don't want the regulator getting whacked.

I personally really like the Dubro mounts. I use them on every plane I've built.

PS. The 120 mount uses #10 screws and the head of the #10 screw is 3/16" tall. If you use lockwashers like I do, that is another 1/16". The flathead screws don't use a washer, so you gain the full 1/4"

Don

Campgems

Another idea came to mind. If you have access to a mill, machine 1/4" off the back of the mounts. This will eliminate the semi circle for a landing gear wire. Then cut the aluminum spools down by 1/8 inch on the small end and also cut each of the rubber mounts by 1/8" This will give you your 1/4" also. If you still needed clearance, you could then use the countersink screws like I did.

Cutting down the mount won't really weaken it much due to the fact the semicircle is 1/4" deep.

Don

Bax

My Feedback: (11)

It would be difficult to determine which mount may work. After all, you have to consider the distance from the mounting surface of the airplane to the front of the drive washer. This will include the spacing needed for the engine mount and the carburetor/regulator assembly. Unless you have serious concerns about engine vibration getting to the airframe, you may want to consider doing without the vibration-dampening mount. Another place to ask might be the Pattern forum, where the flyers are extremely concerned about noise reduction.