I've always used bolts and hex nuts when mounting engines, both in the fiber filled and wooden mounts. I recently bought a Great Planes adjustable mount for a kit and it came with the machine screws.

My first inclination is to drill out and use bolts, but I was wondering if anyone had any opinions on bolts vs. screws, or drilling and tapping. It seems the machine screws will be the easiest and quickest, but I'm concerned about the security of the engine. I'm mounting an OS 46FX.

Thoughts?

Until my last build, I've always used bolts with lock washers & self-locking nuts. I bought a used plane from a buddy & it had just the machine screws into the motor mount. He said he has been flying the plane like that for over a year,no problems. I don't think I would trust that to a big gasser motor but for the smaller nitros, that's all I'm going to do from now on.

In nylon mounts I always drill, tap and use machine bolts. They won't ever back out, no nut needed.

Dave

I use [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD979&P=0]socket head sheet metal screws [/link] with washers into fiber filled mounts. Works great, just drill a pilot hole the size of the minor diameter of the screw thread. Used it up through a Saito 100 with no trouble.

Stan

would that work in aluminum too? ive got a dubro mount, and dont like the hassel of drilling and tapping. do u lock tite them in, or do they hold as is?

I dont think I would try it on an aluminum mount.

I think the reason the screws work well in the glassed filled is because you drill the hole a bit smaller than the screw and its a nice snug fit. With aluminum you wont get that.

I normally drill and tap all my mounts but all my flying buddy use screws and I have never seen one come loose (although I have had bolts in a tapped aluminum mount come loose)

The important question about taping screws into the mount is how would they hold if you need to take the motor out and install it back again.....
i know that with hex nuts there are no problems.

Alex

The tapped holes hold up fine under many mountings and unmountings.

Dave

I have used self tapping screws and machine screws. I have never had any trouble with either one. However, being slightly paranoid, I still use a nylon hex lock nut on the machine screws even if they are tapped.

I have used nuts and bolts, machine screws in taped hole and coarse pitch screws to hold smaller engines without any problems. Currently I have a shaking Saito 100 with 6-32 machine screws taped in a nylon mount. Its holding well. Above 120 I use nuts and bolts. I run the Saito 100, OS 108, Laser 120, Webra 120, OS 160fx, Saito 180, Saito 325 and 450r

On smaller engines in fiber filled engine mounts I have used self tapping plenty of times and never had trouble. In would engine mounts I use regular screws into blind nuts on the bottom.

On engines larger than 91 4 stroke I use regular screws into nylon lock nuts. I have used self tapping on 91 4strokes without trouble before but generally that is where I draw the line.