Spring Gear Replacement for Charger?

Discussion in 'Marquart Charger' started by Meadowlarkfield, Dec 12, 2017.

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  1. Dec 12, 2017 #1

    Meadowlarkfield

    Meadowlarkfield

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    Halfway through the annual we found that the gear leg pivot bushings had again deformed and bent the pin that goes through the gear leg - same on both sides. It is not a new problem for the Charger design and not a new problem on this particular aircraft. We went through the repair five or six years ago (I haven't bothered to look it up) which was probably less than 100 flight hours. We assumed that first repair was due to faulty original work or "some other guy's" bad landing. We went in (original builder and me, current owner) and beefed it up and increased pin size by a couple of steps of wall thickness. So seeing the damage again after a short time was disheartening.

    I have a new team to fix it this time as original builder is no longer around and since I am a fine owner but I am not a builder. I had the team study Glenn's wonderfully detailed thread on his repair of the exact same problem. When we got the legs off today it became clear that the gear legs will have to be rebuilt. I had hoped we could 'fix' them and add Glenn's third gusset.

    Since this is the second time around with same fix on this plane we are thinking hard about design change. It is not my first choice as I would prefer to stay with the original configuration. But as it has become clear that this is a weak point of the design and in an effort to manage the cost of the repair, we want to consider the options.

    Jake, my A&P/IA on the project has seen good work done with Grove Landing Gear (http://www.groveaircraft.com/landing_gear.html ) they make custom or ready-made spring aluminum gear in one or two pieces. We are exploring what it would take to mount a one-piece spring gear on the charger. It would also give us a chance to update wheels and brakes. We'd like to refit the wheelpants and make some new fairings to complete the job.

    I know there has been a lot of discussion of Charger landing gear. Anybody have knowledge of a switch to spring gear? Or worked with Grove? What do we need to consider? What have we forgotten about? What can of worms will this plan open? Help us make an informed decision. Fill us in.

    2015-05-30 11.41.12.jpg
     
  2. Dec 12, 2017 #2

    Lotahp1

    Lotahp1

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    I’d look very hard at Glen’s fix and rebuilt the gear using it. The issue with spring gear is you will have a lot of structural changes to make the load paths not crack the lower longerons. In my opinion you’d be trading one issue for another. Even if you need entire new gear legs...and I bet you don’t. I’d still rather do that than add spring gear to a design not made for it. Look at the issues Eagles have had with spring gear. And...this is very important...the Charger gear is a key design element that give the plane its “look”. Take away the gear and it changes the whole look. Now maybe it would change it to something you like. Or maybe it changes it “to a charger with spring gear”
     
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  3. Dec 12, 2017 #3

    IanJ

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    What is the empty weight of the plane? I've been assured over and over that the original design is sound, but it isn't up to heavy planes (particularly the Firebolt). On the other hand, I can find someone who hates the design for every person who told me it was awesome. I know Glenn went to solid pivot pins with the extra gusset and seems pleased with that choice.

    I think for simplicity, going to spring gear makes a lot of sense. But then, I also don't know how much that would complicate a rebuild, since I think the fuselage would want a change or two to really do it right. I know that at least one or two Chargers were set on spring gear, by looking through the gallery, so it's definitely doable.

    I find myself torn between sticking to the plans for my build, and going to a spring gear. I would have the advantage that I could make the fuselage for the gear type from the start, though. If I did go for spring, I'd be working with the Grove folks to make sure my engineering was sound. You could presumably do the same, to at least get an initial read on what you might be letting yourself in for.
     
    Last edited: Dec 12, 2017
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  4. Dec 12, 2017 #4

    EAABipe40FF

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    In one of Ian's recent threads(I think?) I bad-mouthed the original gear(with zero personal knowledge BTW) and suggested a spring gear. When the fuselage structure picture was posted I quickly changed my mind!!!

    I suppose you could come up with an adequate new design but a retro fit would give you enough worms to fish forever.
     
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  5. Dec 12, 2017 #5

    cwilliamrose

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    I'm going to have to do major surgery on my unfinished S-1 fuselage to convert it from what I had originally planned for the spring gear mounts to the newer mount design as done on the Super Stinker and the M12. If you plan to do the spring gear from day one using the best and most proven design your life will be much easier. A retrofit is many times more difficult, my chore will be somewhere in between.
     
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  6. Dec 12, 2017 #6

    AaronS

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    Did you replace the biscuits last time? The rubber gets hard and compressed over time (think about it, the airplane spend most of its time sitting on the gear). Stiff compressed biscuits transfer all the loads directly to the airframe. On the Beech Mice you see wrinkles in the top wing skins because of this. The rubber is good for about ten years.
     
    Last edited: Dec 12, 2017
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  7. Dec 12, 2017 #7

    EAABipe40FF

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    In another thread Ben Morphewb said,


    "Andye, good job. Hardly much left to do except make the gear solid. Just two landing gear ''V's'' with the axle and the drag strut from the axle to the fuselage can be a bolted on strut. You'll add a little metal for upper drag strut attachment but you'll be taking off some heavy duty tubes on the upper portion of the landing gear. With the gear ''solid'' you can get really creative with the the bottom firewall and exhaust area since you won't have bungees or a gear flapping around.

    Seems like new bungees on an S1 make it like the gear is welded solid anyway. I never used to see any movement for at least a year on that first Pitts and I was operating off of a grass runway. Steve Wolf and the Younkins have operated the Samson models for years with solid gear. If there have been any difficulties I haven't heard what they were. My landings won't be any worse if the gear was solid but there definitely would be the incentive to make them better."


    Ditto on my S1C with new bungees. My AD2 is the same. With it's non stock HD bungee truss the "softest" bungees that fit are still almost solid.

    Maybe just WELD IT?

    Jack

    (Of coarse I suspect Ben makes consistently better landings than I do.... I must admit I did feel the bungees give once:cool: on the Duster)
     
    Last edited: Dec 12, 2017
  8. Dec 12, 2017 #8

    IanJ

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    On that point, I've heard nothing but good reports of swapping over to Belleville washers to replace the rubber donuts. They won't suffer the same aging issues, though I suspect they're a touch heavier. I haven't seen a clear description of what exactly goes into a Belleville washer conversion, but it's possible that this is common knowledge that I just haven't come across yet.
     
  9. Dec 12, 2017 #9

    freerangequark

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  10. Dec 13, 2017 #10

    Meadowlarkfield

    Meadowlarkfield

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    Thanks for the input. The aircraft is not particularly heavy and has an O320. Not a lot of hours (~450) but plenty of "once around the pattern" days mean quite a few landings during those hours. Only 2 pilots have flown it since last repair - no beginners. And we have kept it on the pavement not landing on the grass. This is why another gear repair is so disappointing.

    We did not replace the donuts. That is a good point and the Belleville washer suggestion is a good one.

    Glenn, I will follow up w you.

    The collective experience here on the Forum is impressive and valuable. Keep the input coming. We will advise what we learn as we go.
     

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