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50cc - repairing a main gear mount

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Old 05-02-2013, 01:53 AM
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grosbeak
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Default 50cc - repairing a main gear mount

I flew my new-to-me 50cc Slipstream SBach 342 for the first time yesterday. An amazing flight with a greased full stop landing and takeoff and a greased touch and go. The final landing did not go so well, though.

It was a hard landing. I don't know if I caught a hole in the grass runway but the port side wheel pant broke and wedged against the port side wheel, resulting in a sudden stop, a nose-over and damage to the main gear mount. Amazingly, the prop did not break, though the main gear did twist.

A similar accident has occurred in the airplane's past and has been repaired - I've emailed the previous owner for any information he might have. And after remounting the gear I can move the mount back to its original position with a fair degree of carefully applied force but it reverts to the damaged position when the force is removed.

Here are some photos of the damage (I stripped away some covering for a better look). Advice on the repair would be appreciated.

Bent gear and split covering




Port leading edge




Port leading edge exposed




Port side - note that filler along trailing edge of mount is undisturbed

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Old 05-02-2013, 03:11 AM
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Default RE: 50cc - repairing a main gear mount

Dang dude,,at some point ya gotta say is it all worth it??, I feel for ya,,, What is this,, the 8th thread on this plane??

Most of these planes have an aluminum bracket that supports the gear block to the fuse sides,, does yours??

Break out the epoxy,,


Pics of the inside please
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Old 05-02-2013, 03:22 AM
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Default RE: 50cc - repairing a main gear mount

Yes some pics of the inside would help. I would add a big piece of plywood inside or at least two wide strips running fore and aft over the mounting holes to distribute the load. Otherwise it's just going to continue to tear out  in the same place if not reinforced.
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Old 05-02-2013, 04:05 AM
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Default RE: 50cc - repairing a main gear mount


Quote:
ORIGINAL: scale only 4 me

Dang dude,,at some point ya gotta say is it all worth it??, I feel for ya,,, What is this,, the 8th thread on this plane??

Most of these planes have an aluminum bracket that supports the gear block to the fuse sides,, does yours??

Break out the epoxy,,


Pics of the inside please

Whoa, now! This is different - when I bought the plan it was a little tired and I wanted to refresh it... but this is damage I caused!

Yes, I believe there is an aluminum bracket on each side - I can see it looking down into the fuselage from above. I have some pictures from when I first got the plane:



Quote:
ORIGINAL: flyinwalenda

Yes some pics of the inside would help. I would add a big piece of plywood inside or at least two wide strips running fore and aft over the mounting holes to distribute the load. Otherwise it's just going to continue to tear out in the same place if not reinforced.
I think I'm going to have to remove the mounting plate to get at the brackets.
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Old 05-02-2013, 04:23 AM
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Default RE: 50cc - repairing a main gear mount

Yeah, the system in theory adds strength, but what happens is, the cheap light ply breaks right where the bolt holes go into the fuse sides and it all comes loose with the gear plate,, in order to get epoxy where you need it, you'll have to open up access removed the aluminum plate and see where it is all broken. It's a pita believe me

I have a 50cc Raven on the bench that the gear were ripped out,, and I've fixed a 50cc Pitts with the same issues,, Surgery is needed to fix it right,, a band aid will not do.

Good luck
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Old 05-02-2013, 04:32 AM
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Default RE: 50cc - repairing a main gear mount

,,,,,,,
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Old 05-02-2013, 02:23 PM
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Default RE: 50cc - repairing a main gear mount

I got more if it open tonight and here's what I found.

The damage




It's hard to see in this picture, but the mounting plate has tabs that engage the plywood former aft.




Here's a diagram for a clearer look



I'm assuming I have to remove this but I'm not sure how. My best guesses are a dremel cutting wheel, an oscillating multi-tool and a fine back saw. Before I proceed I'd like more input.
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Old 05-02-2013, 05:40 PM
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Default RE: 50cc - repairing a main gear mount

I removed the canister from the tunnel and stripped off a lot of the sheeting forward of the damaged area.



Got the bolts and the aluminum brackets out too.



A closer look at the port side damage.



At this point I think everything associated with the last repair is going to have to come out; when I redo it I'll spread the load around.
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Old 05-03-2013, 01:30 AM
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Default RE: 50cc - repairing a main gear mount

When I put mine back together I'm using nylon bolts, it's redicules how weak these ARFs are @ the gear plate,, PITA
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Old 05-03-2013, 01:55 AM
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Default RE: 50cc - repairing a main gear mount


Quote:
ORIGINAL: scale only 4 me

When I put mine back together I'm using nylon bolts, it's redicules how weak these ARFs are @ the gear plate,, PITA
You're not the first one to suggest that... it's a pretty radical departure. Would they be up to the stress of regular use, you think?
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Old 05-03-2013, 02:40 AM
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Default RE: 50cc - repairing a main gear mount

Not so radical really,, most old school kits came with nylon bolts for 3 reasons, 1- break off in crash/bad landing, 2- don't vibrate out. 3-weight

The new school way isn't turning out to be the better way now is it

Tell ya what, you bolt that gear to a 2x4 with 4 8-32 nylon bolts and try and bust them off with just your hands, then tell me if you think they are strong enough or not.

When mine goes back together I'm loosing the aluminum piece and installing tri-stock for added support in the joint,, then I'll thread the gear plate to receive the nylon bolts
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Old 05-03-2013, 06:11 AM
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Default RE: 50cc - repairing a main gear mount

Quote:
ORIGINAL: scale only 4 me

Tell ya what, you bolt that gear to a 2x4 with 4 8-32 nylon bolts and try and bust them off with just your hands, then tell me if you think they are strong enough or not.

When mine goes back together I'm loosing the aluminum piece and installing tri-stock for added support in the joint,, then I'll thread the gear plate to receive the nylon bolts
Easy now! Just asking!

If the bolts won't break, doesn't that defeat the point of their use?
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Old 05-03-2013, 06:46 AM
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Default RE: 50cc - repairing a main gear mount

A note on Nylon landing gear bolts.  I had a beater (Hot Stik) that I used to fly very hard.  I was doing a low pass for a knife-edge and instead of changing rates I flipped the CROW switch.  It instantly did a 90° dive towards the ground.  I reacted just quick enough to pancake in.  The gear - held on with Nylon bolts as I had seperated them once before - pulled off smoothly . . . and punctured one wing before flipping up under the tail and yanking out the pull-pull cables and with them both horizontal stabs and elevators!  Who says CA hinges don't hold?

It was MUCH easier to fix a missing belly section than redo the whole tail.
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Old 05-03-2013, 07:00 AM
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Default RE: 50cc - repairing a main gear mount

No good deed goes unpunished

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Old 05-03-2013, 07:11 PM
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Default RE: 50cc - repairing a main gear mount

Lots of progress tonight...

Mounting plate removed intact




Shims glued in




Port inner bracing glued in




Port plywood block reattached




The way forward is clear. There's plenty more to do but I know what it is, and that's a relief.

The complete set of photos: SBach 342 - Damage 2013-05-01 - Hard landing
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Old 05-04-2013, 07:52 PM
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Default RE: 50cc - repairing a main gear mount

About eleven hours into the repair. I can see the light at the end of the tunnel and have confirmed it is not an oncoming train.

Lots of progress again tonight.

New aluminum angle blocks marked and drilled.




Blocks installed and aligned




The hard stuff is done and the finicky stuff is about to start - repairing longerons, sheeting, recovering, bending the gear back into place and remounting it.


SBach 342 - Damage 2013-05-01 - Hard landing - 134 photos and counting.
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Old 05-06-2013, 04:09 AM
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Default RE: 50cc - repairing a main gear mount

Just about complete.

Shimmed, sheeted and shaped.




Covered.




Straightened.




Remounted.




Just a bit of reassembly left - I hope to finish tonight.




SBach 342 - Damage 2013-05-01 - Hard landing - 199 photos and counting.
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Old 05-08-2013, 02:33 AM
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Default RE: 50cc - repairing a main gear mount

After putting the whole thing back together I got it onto the scales. What the... I'd lost 100g and the CG, which was perfect before, was now 7mm further back! I expected to gain a little weight with this repair given the larger angle brackets and the braces. I looked around to see if I'd left anything off and there they were - the wheel pants. I added yet more weight to the motor box and that got me to 3mm back of the CG - I'm happy with that.



Yes, that's a lot of lead. But the CG of this airplane is almost an inch forward of all of the other 50cc SBachs I've seen - and when I flew it, short as the flight was, it was perfect.
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