I have a new .40 hangar 9 twist with a lot of vibration. I have a question about the engine mount.

From the factory, the engine mount fingers leave about 1mm of space between themselves and each side of the engine compartment on my Twist. However, I have an oversized engine in the twist (mvvs .77 2 stroke) and the engine is a bit big for the mount and is pushing/stretching the mount fingers against the wooden sides of the engine compartment. Does this cause excesssive vibration because i'm getting a lot of vibration. My engine is used but its the first time i've ran it so i'm not sure if something is wrong with the engine or if its the way its mounted.

Ryan

It's not a good idea to force the engine into the mount such that the mount has to be spread. This puts a lot of load on the mount, and can cause it to fail. It's better (if you can't use a larger mount) to trim out clearance on the mount itself so that there's no stress just holding the engine when you're not flying.

The vibration is probably caused by the bigger, heavier engine. It is one of the common problems when overpowering those ARF's. I've seen planes loose their firewall, and bend nose struts due to heavy metal up front.

You did balance your prop, right?

Well you could reduce vibration, by useing "Well Nuts" in stead of Blind nuts. well nuts are nuts incased in rubber and act like a molly when tighten the rubber of the nuts expands and holds the mount fast.... I have used them all the way up to my OS 91 FS... found mine at "Lowes" if you want pics of them let me know i can post them

DOH_Blk_Adder, if its not a hassle, i'd like to see pics, but if it is than thats ok.

Thanks for your inputs. None of you have addressed if the mount touching the sides of the engine bay is contributing to extra vibration?

Ryan,


Power is not what you should be worried about.

An MVVS .49 with the tuned silencer is more than enough power for this plane.

Sure the .77 can make more power, but the added weight of the power system, which amounts to about half a pound, is more weight for the plane to carry. This model should be sharp and responsive at its .40-.50 engine weight.

Putting a bigger engine on it could reduce the performance, making it respond more slowly and land faster.

Dar,

I considered the smaller/lighter engines. Most .46-.52 weigh about 17oz with muffler. The mvvs .77 weighs 21.4 oz with muffler . At a quarter pound sacrifice, i thought it was worth it.