Hi,
I'm putting together an ARF trainer, the firewall came pre drilled for the engine mount,the engine mount is a standard 2 piece nylon mount,i bolted it to the firewall and tried to fit the engine in (TT46 Pro) but it wont fit,the tow mounts are to close so the bottom of the engine wont go thru. I guess i can use some force to pry the mount open or maybe grind it a bit, but i wanted to ask for advice first.
TIA
Eran

You could grind the existing mount, but it it will eventually break -- however, that will get you going for now. A better solution is to get an adjustable mount (Great Planes makes a good one -- you need a 40-70 size & can order it from Tower Hobbies). You will have to drill new holes for the mount.

if its not too far off, you can just file off the upper inside corners of the two arms to get a snug fit. the crankcase bottom is round and only the widest part of it next to the mounting flanges needs to be cleared. a dremel with a sanding drum will do the job.

peter

I was going to give BirdNest's suggestion. But next time mount the engine first. With the engine still mounted, mark the mounting holes on the firewall.

A good way to do it is to put the mount on your bench near the edge and clamp it down so it's flat. Then mark the engine mounting bolt holes. When the engine is bolted to the mount, sand the back of the mount to make it perfectly flat and then mount it to the firewall.

You would be surprised how much time you save by taking the time to get things right in the first place. It just takes some building experience to learn all this kind of stuff. Best thing you can do is meet some experienced guys in the club and find someone who's a good builder. Ask him to stop by and help you out with mounting tasks because any time you mount something to an airplane it's probably important to get it right.

I had the same problem when I switched from my LA46 to a Tower 46 in my LT40. I just use the Dremel to cut out a tiny amount from the inside of each of the mounts, and drilled new holes. It worked fine until I decided to return the plane to kit form!
Glen

He's going to have to grind the mount, as his firewall mounting holes were pre-drilled. I ran into same problem with an ARF, and it had an adjustable engine mount. I wound up taking material off teh upper inside edges of the mounting rails, and the mounts were find for the life of the plane.... although it only had a .40 sized engine mounted, it was used as my basic low wing trainer and aerobatic trainer (rough life)

Andy

Thanks for all the advice guys,i ended up grinding a tini angel from the mount arms and it did the trick