Landing Gear Front Mount

Sig Skyray Fri May 08, 2015 7:21 am

I met a guy a couple weeks ago who turns out to be an AMA control line TN state champ from the late 50's and a national champ in the scale class for his 15 year old age back then and he gave my son and I a 1/2a stunt trainer with a black widow attached. Cool! I've run the BW and it runs well. I ordered a Turnigy tach so I can see how my small and growing collection of engines are performing.
He had several speed and combat CL planes hanging from his ceiling in his garage and lots of dusty trophies.

He did not build this plane, it was given to him and it needs a little sprucing up and adjusting before I fly it. I'm questioning the landing gear mount. The wire gear is simply sandwiched between the plywood firewall and the *plastic* black widow back plate.

Wouldn't this make the back plate screw mounts susceptible to breakage in a nose landing? I was thinking maybe sandwiching the wire between a couple pieces of thin rubber, like a bicycle inner tube, with some longer engine mounting screws. That would cushion things somewhat.

If there's not a good way at this point to mount the gear I could always fly it gearless like my Skyray will be but I prefer wheels at this point.

I know I've been looking for a lot of advice lately and very grateful for all the input and tech support guys. I'm looking forward to giving back one of these days, somehow. Greg

KariFS Fri May 08, 2015 8:39 am

I'm guessing the engine mounts will fail with that installation eventually even without a hard landing. The design of the backplate (in my humble opinion) requires support for the mounts to prevent them bending.

You could glue some plywood pieces around the landing gear and then add another piece on top of it to sandwich the landing gear into the engine mount. Hard to explain but I hope you understand what I mean Smile

pkrankow Fri May 08, 2015 10:11 am

Rubber will make the problem worse. It will pre-load the back plate and allow the wire to move. Cut a piece of thin aluminum like flashing, or steel sheet metal like air duct, to the size of the mount and sandwich that in between the wire and engine.

Phil

Mark Boesen Sat May 09, 2015 12:06 am

This type of LG mounting has been around as long as the Babe Bee, its by far the most common and works well. If your worried about strength, maybe use longer screws?

GallopingGhostler Sat May 09, 2015 5:27 am

Can't speak about the later Cox plastic tank mount. My only experiences are the metal ones. That is a common mounting way used by Walt Musciano (Scientific) and Sterling. Instead of the rectangular bend you used, they both used a simpler Vee bend.

On the Scientifics the ply was factory indented to recess the wire. The Sterling motor mounts, earlier being aluminum and later nylon had a groove formed for the wire, which the engine held in place.

You'll need to recess that landing gear wire. Simplest may be using 1/16 inch thick plywood or basswood with section cut away to recess the wire. Glue firmly to ply bulkhead.

Wood or sheet metal screws with wider diameter portion of thread passing through the ply firewall should be sufficient to hold the engine in place without failure except for the most violent of crashes.

pkrankow Sat May 09, 2015 7:02 am

GallopingGhostler wrote:Can't speak about the later Cox plastic tank mount. My only experiences are the metal ones. That is a common mounting way used by Walt Musciano (Scientific) and Sterling. Instead of the rectangular bend you used, they both used a simpler Vee bend.

On the Scientifics the ply was factory indented to recess the wire. The Sterling motor mounts, earlier being aluminum and later nylon had a groove formed for the wire, which the engine held in place.

You'll need to recess that landing gear wire. Simplest may be using 1/16 inch thick plywood or basswood with section cut away to recess the wire. Glue firmly to ply bulkhead.

Wood or sheet metal screws with wider diameter portion of thread passing through the ply firewall should be sufficient to hold the engine in place without failure except for the most violent of crashes.

I agree and I have several like this. I suggested the flashing because I don't trust the plastic bee backs with landing gear, I've broken enough plastic backs WITHOUT landing gear!
Phil

roddie Sat May 09, 2015 12:47 pm

I just reinforced a radial mount firewall for a Babe Bee powered model having that same gear strut shape. My gear is 1/16" music-wire.. so I cut some 1/16" plywood plates and glued them all around the gear sides and top.. inside and out, to create a slot having 90 degree corners. I will use #4 wood-screws to mount the Babe Bee I'm using.. and they'll only need to retain the engine.. rather than keeping the gear from moving out of position. I may make a ply spacer.. to cover the wire.. but not glued on. This will make removal of the gear possible if needed.

Landing Gear Front Mount 5-1-1513

I've done similar bracing with an inverted "V" gear too..

Landing Gear Front Mount Dsc02631

Sig Skyray Mon May 11, 2015 8:47 am

Thanks guys. That's what I'll do... surround the LG wire with 1/16" ply and glue to bulkhead/firewall. I'll probably make the outer piece an inverted "U" shape and extend it to the edges of the firewall.
Greg

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