Skybolt + Marquart Gear + Repair

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DC_Wolfe
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Skybolt + Marquart Gear + Repair

Post by DC_Wolfe » February 24th, 2018, 5:53 pm

Well, we decided to purchase the Skybolt with the Marquart gear. During the prepurchase inspection, we found the expected cracks...

Below, I tried to take some pictures of the cracks, but you can't really see them. The first photo shows just how easy they are to miss - on the right side, you can see the crack we first saw if you zoom in. If you didn't know what to look for (thank you biplaneforum!) you'd totally miss it.

Without everyone here, I could have easily collapsed this gear without every knowing. As it is, we saw the problem and we're trying to fix it.

In my reply, I'll show you some of our strategy going forward... And no, we're not converting to another gear. I wanted to make this work. Yes, yes, I saw the bungees (ugh!), and the aluminum Grove gear (icky look), so we're hoping to make the idea work with some re-engineering.
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DC_Wolfe
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Re: Skybolt + Marquart Gear + Repair

Post by DC_Wolfe » February 24th, 2018, 5:54 pm

So the airplane is located at Valkaria airport, near Steen Aero Lab. Mike Hughes mechanic and fabricator, who helped build the Steen Aerolab Skybolt (The 350+hp Skybolt Awesomeness), along with Paul (Engineer) from Aerolab, and Tim, an Aeronautical Engineer, and a couple of other 30+ year mechanic veterans all looked over the Marquart gear situation and we came up with a plan to try and finally "solve" the issues of cracking. We'll find out next year if it will all work or not, but it involved some new gussets, lubrication, rotation, and bracing.

If this all works I'll make sure everyone knows what we did. So far, I replaced the 30+ year old pucks with new Ercoupe pucks... Just realize that if you do replace, you'll need a press or something to get them together for the first time... they're a bit thicker at the start..

In the first photo are the old pucks, with the new pucks lined up with them..

The next is the pucks reinstalled.

After the pucks is the original "sleeve" or bar that the gear rotated on. Notice the groves. This wasn't done by us. Theory is that the bar freezes due to lack of lubrication, which in turn transfers much of the forces into the structure. I'm no mechanic or engineer (I'm just a dumb pilot), so I may not have that exactly right. Either way, that's definitely the sign of a problem.

My aircraft had 535 hours in 30 years, and maybe as many landings. Being in Arizona for a good portion of it. Additionally, it was evident additional undocumented "repairs" were done on the airplane, as the sleeve (which is supposed to be hollow) was replaced on the right gear by a... bolt.

Yes, a bolt.

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DC_Wolfe
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Re: Skybolt + Marquart Gear + Repair

Post by DC_Wolfe » February 24th, 2018, 6:22 pm

When we did the pre-purchase inspection, we noticed the cracks along the attach points (both fore and aft) on the gear. After ferrying to the shop, we discovered those cracks didn't really display the REAL PROBLEMS.

The gear didn't have many more landings before collapsing. Don't take ANY crack as something MINOR! They were indications of serious buckling in the support shaft, and things were torqued/bent in ways we didn't realize until taking the thing apart. If you find any cracks around the Marquart gear... Do a FULL inspection! We thought the major issue was the right gear until we pulled it apart and realized the left gear was twisted so bad it took half a day just to get the old sleeve out.

Don't just weld the crack. It'll be back.

Here's some photos of the plane in it's current repair state. I'll send more photos of the completed repair when I get them.

Without the support of Steen Aero Lab and a good fabricator this would have been a major problem, but after talking a lot about forces and vectors and cotterpins and other things, I think we may have a good solution for this. Time will tell, but I'll keep "yah'll" up to date.
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