Hello ; I just bought a new Brison 2.4 to put on my Hanger-9 cap. I'm wondering what is the best way to mount this engine, should I soft mount it & if so where do I get the stuff to do it with, or would just bolting it to the firewall be OK? Seems to me if it was hard mounted it would shake the plane apart. Thanks for help, Rob

I'm interested in the discussion as well. I believe I'm going to be converting my Stinger with Brisson 3.2 to a soft mount.

The vibes are shaking everything apart. The sheet metal screws holding my fiberglass on are either falling out in flight or wearing big holes in the glass parts. I even converted the main screw holding my cowling on to a 1/4-20 nylon wing bolt to try to dampen the vibration. It's threaded into a 1/2" think piece of hard ply that was tapped for it. It backed out less than 10 minutes into the flight and the wing cover/canopy flew off. I've also had glue joints holding my hinges in break loose, but that could just be me.

I think alot of the problem is that the Stinger fuselage is a C-channel design - that is, it has only 3 sides. The firewall is only supported on 3 sides. Structurally, the top is not restrained, although covered by a fiberglass piece. That really allows the fuse to twist all the way back to the wing mount bulkhead.

After having done a search here on soft mounts, it seems to me that using a soft mount subjects the airplane to less vibes but increases the vibration load on the engine. I think I'll need to go with that.

The Stinger fuselage is quite narrow, only a little wider than the mounting flanges for the Brisson. I'm considerinig ways to soft mount it in the available space and would appreciate feedback on the different systems and would like to see pics, web site links, etc, if anyone has them.

Right now I'm thinking I will drill the firewall out and install the J-tec rubber grommets thru the firewall. The engine would be mounted directly to the grommets with the same bolt that holds the grommets into the firewall, using large washers on the face of the grommets. Suggestions?

PS - roadhor, didn't mean to hijack the thread. Hopefully we'll both get usefull info.

I think your going to get people on both sides of the fence here. I personaly do not use soft mounts on gas engines, I own several and have not had a problem. If you look at the paperwork that comes with a Bisson muffler it say's the warranty is void if you use a soft mount. Johng, what you are experiancing with the stinger is nothing out of the ordinary, they have that problem even with soft mounts, I think its because the airframe is not as rigid as most. Rubber grommets stuck through the firewall don't seem to do much and they don't last very long, lord style mounts allow way too much movement, even the large 1.5" ones. I am however sure there is a system out there that will work, but I've never found it.

I knew about the muffler thing, but I'm not really too worried about that. I understand why Bisson would do that, since they build some intricate wraparound designs where the muffler is cantilevered quite a bit off of the motor. I'm using the stock Brison muffler which is very compact. I'm not really worried about the rest of the stuff on the motor. The Brison lit mentions soft mounts, but neither recommends them or condemns them.

I will probably be trying some stuff to stiffen up the fuse in front of the wing as well.

Thanks

I have one that is soft mounted and I had another that was hard mounted. I saw no difference.

I am fairly new to the sport but I don't think hard mounting is ever the answer. I think mounting gently is always the way to go. But if you insist on hard mounting ole speedracer said he would be happy to help you out ...............Your wing is half done.....Rocket

Ok you soft-mount advocates think about this, the engine,prop, spinner and muffler weigh around 4.5 pounds give or take depending on size and manufacture, its not at all uncommon for our planes to see +/- 12 G's and sometimes more. That means the mount must support around 50 pounds plus without too much movement. Sounds like one freek'n hard hunk of rubber to me. Also remember that its not the low frequencie vibrations that hurt parts and radio gear its the highs, so to work the mount would need to be soft enough to absorb these small movements. In most real planes the mounts are installed at angles, I wonder if they know something we don't?

I have that plane with a Fox 2.4 hard mounted, no problem. I have the sig 300 with Brison 2.4 hard mounted, no problem. I have the big stik with Quadra 35 hard mounted, no problem.One thing I have learned since switching to gas is to try and keep it simple.

OK Speedracer ; I'll let you help me hard mount the Brison. Is there medication for cranial-rectumitus? If so you need a big ole dose! Thanks to all for the help.

if you insist on soft mounting-you can go to the (b&b specialty web site)they have soft mounts and bolts