Weak motor X-mount

[Dad_flyer]

I replaced the X-mount for the motor on my foamboard spitfire.

After three gentle flights with what I would call good landings I noticed there was a good deal of downthrust. On inspection it is the motor X-mount that is bent.

There is not a mark on the prop or spinner so there cannot have been much force. The firewall is only mounted to foam too, so that would normally crush first. This is a replacement from the manufacturer, the material feels fine, but the design has no strength around the inner screw holes.

The countersink goes almost through and almost to the edge.

 

Does anybody know a source of better mounts? I think I shall have to make one that is square not X, if I can find a piece of aluminium.

Edited May 16, 2021 by Dad_flyer
Posted before finished

[Andy Gates]

That lower leg looks cracked to the right.

 

Never had that happen, just remanufacture with slightly wider legs / arms.

[alan p]

Agree with Andy, make your own, use existing as a template jig for the holes. those c/sinks look over depth as well.

If you can get away with it don't c/sink use cap or button head screws.

 

[leccyflyer]

I found that on a couple of ARTF foamies - cross mounts like that which had been manufactured from toffee and after a few landings, causing no other damage, not even a broken prop, the mount was deformed, just like yours. I replaced it and have had no further issues.

[Dad_flyer]

Thank you all. As I cannot find stronger versions anywhere, I shall make one.

[Dad_flyer]

Not very neat (or very not neat) but it will do.

Found some aluminium that is the right thickness and should be about the right grade as it was also for something expected to be stiff and flat.

It became rather less flat on 18th March 1995 I think it was. But we straightened it enough for the day and retired it when we could get a new one. I don't think I am likely to use it as a spare, so here goes.

And as I said, a rather less than square end result, but it will work.

[Zflyer]

I replaced one of mine with a rectangle of aluminium, beauty of which yo can have more than one motor mount set of holes.

So far so good.

All my depron models I use a 3d printed mount. I did use credit card cut to size and sandwiched depron between, however todate the 3d printed  option works well.