Landing gear repair

Hangar > SBach 342 > Modifications > Landing Gear Repair

SBach 342 pictures


Damage Exposure Deconstruction Reconstruction Sheeting Covering

In the spring of 2013 after a winter of work in the shop I took my new-to-me 50cc SBach 342 to the field to maiden it. After a full stop landing I shot a touch and go, and was attempting to shoot a second. It was more of a thump than a touch - the port wheel pant broke and wrapped around the port main wheel, making a very effective brake. Unfortunately, the force of braking had to be dissipated somewhere, and that somewhere was the main landing gear mount. To the shop!

Damage

The external effect of the damage was easy to see:

Gear mount covering damage

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The gear itself got twisted by the force:

Landng gear bent

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Exposure

With some covering off I could get a closer look at the port side:

Gear mount - port leading edge

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Starboard side too:

Gear mount - starboard level

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There was a lot of filler between the joints, signs that this are had been repaired before. With the filler out the damage became more apparent:

Gear mount - port

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Here we see that the external mounting plate is a plywood block with tabs to engage the vertical structure:

Mounting plate tab

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This is a diagram of that mounting plate:

Landing gear plate

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I removed a bit of sheeting and some ribs and the damage on the port side was exposed:

The damage exposed

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The starboard side looked original (though why there's a small screw half buried there is anyone's guess):

Starboard side - closer

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Deconstruction

The canister runs between the outer fuselage and the inner deck. It was in the way of repairs so it had to come out:

Canister - a little beat up - 02

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Here we see the aluminum angle stock that provides the strength. Port side:

Aluminum bracket - port side

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Starboard side:

Aluminum bracket - starboard side

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At this point I removed more sheeting and ribs to get better access:

Port side again

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I removed the aluminum angle stock for both sides:

The starboard and port aluminum brackets

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The mounting plate had to come out, and I wanted to do that without damaging it. Some gently force and wiggling was called for:

Mounting plate separated, port side

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I did get it out, mostly intact:

The mouting plate is out

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The last step in the deconstruction was to remove the cracked outer section of the port side gear box wall:

Gotta get 'em separated

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Reconstruction

Here's the solid inner section of the port side gear box wall back in place for a test fit:

Port plywood block back in place

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With the broken parts out it was time for a test fit of the plywood gear block:

A test fit - now THAT looks right

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I wanted to tie the inner structure of the box together with some thin plywood. First I had to shim the recessed areas to align all the walls. Port side:

Shim size, port side

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Starboard side:

Shim size, starboard side

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With both sides ready I applied some white glue to the back and wedged them in place to dry with some scrap plywood:

Port shim - glued and wedged

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When the shims were dry I glued up and wedged in the inner braces:

Port inner brace - test fit with wedges

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Tri-stock adds a little strength at the corners:

Tri stock - glued up

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Now I could test fit the inner section of the port side gear box wall against the inner brace. I took this opportunity to mark and drill the holes that would pass through the gear box and the vertical plane of the aluminum stock

Port plywood block - test fit against inner brace

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I also test fitted the port outer brace:

Port outer brace - test fit

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My next step was to align the port side gear box wall with the inner brace, glue it up and clamp it to cure. I used Vaseline on the punch and bit to keep the epoxy off:

Aligned and clamped

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After the glue cured I glued and clamped the port outer brace into place. I would mark and drill through it from the back later:

Port outer brace - clamped in place

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I replaced the original aluminum angle stock with longer pieces and added a third hole where they could be bolted through the vertical walls of the gear box:

Third hole drilled on vertical faces of both blocks

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I added another layer of strength to the outside of the gear box by bolting through aluminum plates there:

Plates drilled

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Now all of the aluminum plates and angle stock were bolted in (loosely):

Port block - test fit commences

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Next, I clamped the original plywood block in place so that I could align the angle stock and tighten the bolts through the side walls of the gear box:

Original plate in place for alignment of port and starboard blocks

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Here are all the aluminum pieces tighly bolted in place. Note the right side of the photo where the forward bolt is visible:

Port install - outer

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Next I had to add a strip to the forward edge of the plywood block to support the longeron that spans to the next bulkhead forward:

Strip shaped

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I shimmed the plywood block to take up the gaps that previously held filler:

Closer look at the tab shims

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With the shims on the plywood block glued and cured I set it on the aluminum angle stock for a test fit:

Test fit, bolts from top

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The fit was good. I put glue on the block...

Glue on the mounting plate

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And, aligning it with bolts, placed a weight on top while the glue cured:

Center longeron glued in

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While the glue cured I had time to bend the landing gear back into place. First step was to wrap some masking tape around the jaws of my channelled pliers:

Time to bend some gear

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I taped up the jaws of the vise too, to avoid marking up the gear:

Clamped

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Sheeting

With all of the structure complete it was time to replace the sheeting I'd had to remove. Glued up and taped down:

Yet more sheeting in place

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Port side complete:

Sheeting complete - port

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Staboard side complete:

Sheeting complete - starboard

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Covering

Sheeting done, it was time to recover. Port:

Heat shrunk and fully ironed - port

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Centre:

Heat shrunk and fully ironed - centre

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Starboard:

Heat shrunk and fully ironed - starboard

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Then it was a matter of poking the bolts down from topside; a little tape keeps them from falling out:

Bolts through and held in place

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Here's the gear bolted back on. What a feeling!:

Gear on!

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I've had several flights on the plane since that repair and it's held up perfectly.