Hi everybody,
It's time now for me to install my engine in my plane (an OS 160 FT twin cylinder).
But, if I fix my engine directly on the firewall, it's too deep in the engine cowling.
My idea to bring forward (about 10 centimeters) the engine fastening is to fix this one on :
- 4 threaded screws, screwed in the original firewall
- 1 aluminium plate where the engine will be fixed.

My questions are :
What do you think about this technique ?
Which threaded screws diameter do I have to use ?
Which aluminium plate thickness do I have to use ?

Thank you by advance for your help

Thierry

I think you may be pushing your luck with straight bolts at 10cms long? Have you considered maybe 6mm dia bolts set inside aluminium tube spacers - say 10mm - 12mm OD?

How about a transverse length of aluminium box extrusion - one side bolted to the firewall and the engine bolted to the other side? Something like 100 x 100 box section with 3mm wall thickness. You could carve great lightening holes out of all sides to keep the weight down?

Good luck,

Alan W

Even though 10cm isn't much, that setup you describe will wobble. I'd build out a ply box glued to the original firewall, and use socket head caps screws with lockwashers and blind nuts.

Dr.1

10 CM??? that's about 4 inches.

If that's the case, I would go with DR1's suggestion

Hmmm, you're right, Minnflyer!!! I thought he said mms.

Dr.1

Thank you guys for your answers
Yes 10 centimeters is almost equal to 4 inches.
If I well understand, my "threaded screws" first idea is not the best ...
Which plywood thichness do I have to use ?

Thierry

Use whatever thickness your existing firewall is.

Dr.1

So I will build a box with plywood.
Thanks once more.

Thierry

Hello Thierry
I am sure yoy now have the solution. I have exactly the same "problem": Cessna 2.10 m and the OS 160 Twin boxer. I only need to move the engine around 6.5 cm and plyvood
is the perfect solution . Maybe you have ansver on the next problem....how can I/we move exhaust on my Cessna 182 to exit the cowling in a scale location ?
Good luck with your plane
Flemming

This is what I have done.

I use a 1/4 thick piece of plywood as a firewall
and then mount that firewall on standoffs. It's the
same way most gas engines are mounted.

I make my own standoffs but someone offers them
commerically but I'm not sure who.

I usually use aluminum for the standoffs but if I need
some weight in the nose I 'll make one out of steel.

Regards,
Roby

Hobbyking supplies standoffs