Correct landing gear for Super Baby Great Lakes?

Discussion in 'Tube and Fabric' started by birdus, Jan 8, 2016.

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  1. Jan 8, 2016 #1

    birdus

    birdus

    birdus

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    The short version is that I bought a fuselage for my Super Baby Great Lakes. It came with spring landing gear (among other things). As an aside, I'm the fifth (!) owner of this fuselage. It needs some work, but I think I'm ahead by buying it. Anyway, I have a question about the spring landing gear it came with (the plans call out gear more along the lines of what a Pitts has). I actually e-mailed Grove twice about this, but they never responded, so I'm asking you guys here.

    The gear seem like they massive positive camber (excessive?). I realize that some of that will be squashed out after everything is on the plane (e.g., engine, full fuel, etc.), so its stance on the ground should look more normal (i.e., wheel more or less vertical). However, of course, when landing, the gear will have this major positive camber. Is this correct? Is this landing gear correct for my plane? (NOTE: I will plan on buying and using radius plates for mounting the gear.)

    Here are the measurements:
    • Depth (front to back at top where it attaches to fuselage): 6”
    • Width, wheel to wheel: 48”
    • Width (flat along top): 25”
    • Height: 19”
    • Bolt pattern: 1.375”, center to center, square pattern
    • Thickness: 1/2”
    Thanks for any thoughts and advice.

    Jay

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  2. Jan 9, 2016 #2

    Turd Ferguson

    Turd Ferguson

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    I'd be curious if the gear will straighten out without a reverse bend in the long leg? I guess you could load it up with sandbags to the design gross wt and see what it looks like....

    Looks like each builder added his own touch - I noticed quite a few deviations from the plans just from the pics. Not that it matters, some of the baby lakes components seemed to be overly complicated.
     
  3. Jan 9, 2016 #3

    TFF

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    Until the plane is finished or you ballast it to see if it will flatten out, you will not know. It will be carrying another 500 lbs just on the empty weight. Make sure the conversion is well thought out. The spring gear put a lot of torque on the lower tubes and the reinforcement needs to be done right. Spring gear usually lands easier than the standard and is usually faster too. Are you going to keep the cable brakes?
     
  4. Jan 9, 2016 #4

    birdus

    birdus

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    I guess I figured it will straighten out some under load. My concern is hitting the ground on landing. Will that angle do anything funky, or will the gear simply settle in?

    Yeah, lots definitely not done to book. I plan on cutting off station zero and adding the 3" fuselage extension which the newer version of the plans calls out. Also, I plan on doing the brake pedals according to plans. There are some other things, too, that are not stock. Most or all of them I plan on bringing in accordance with the plans.

    Thanks,
    Jay
     
  5. Jan 9, 2016 #5

    BJC

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    Check with some Pitts builders in your area that used a spring gear, and learn about how they reinforce the longeron, just above the spring gear, to keep it from cracking.

    Might also ask on the biplane forum.


    BJC
     
  6. Jan 9, 2016 #6

    birdus

    birdus

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    I figured what you said--that there will need to be some good bracing to support those gear. As mentioned in my other reply, I'll be redoing station zero. At that time. I'll put some more bracing in place which will help transfer the load from the rear of the gear to the upper longerons. Any thoughts on that are welcome. By the way, what did you mean by the torque from the spring gear? The landing gear are not directly attached to the fuselage. The mate via the radius plates, which will allow the gear to "spring" without any twisting on the lower longerons. Is that what you were referring to?

    In answer to your question about the brakes, I'm actually planning on getting magnesium wheels and disc brakes by Grove. The tires are brand new, so I'll keep those.

    Thanks,
    Jay
     
  7. Jan 9, 2016 #7

    Turd Ferguson

    Turd Ferguson

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    From the pics, there looks to be too much camber. In addition to tire scrub, if the toe angle varies as the gear "springs" it could make the plane difficult to control.
     
  8. Jan 9, 2016 #8

    birdus

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    That was precisely my big concern and my main question. Would it be reasonable to take it to a metal shop and have them remove some of that bend at the...well I guess there are two places they could do it. What do you say?
     
  9. Jan 9, 2016 #9

    birdus

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    Something just occurred to me. This landing gear would have the exact same shape when the plane touches down no matter what plane it was on! So, unless they are defective or someone bent them beyond how they were made, they are normal this way. Hmmm. The only difference (between this gear on planes of varying weight) would be their stance when the weight of the plane is on them.

    Jay
     
  10. Jan 9, 2016 #10

    Turd Ferguson

    Turd Ferguson

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    All true except maybe the normal part. If you look at inflight pics of planes with slab sided spring landing gear, positive camber is usually evident but none seem to have that much camber. A purpose built plane, like an ag plane that carries a huge payload. a STOL plane or plane that operates off airport may need a lot of positive camber because of gear flexing.

    Again, this is based on your pic which can be deceiving depending on camera angle, etc. With the fuselage in level attitude is all that matters.
     
  11. Jan 9, 2016 #11

    Rockiedog2

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    I installed a Grove gear on a Pitts I built way back. You can go here and probably find any info you need to decide what else you're gonna do to it.

    Steen Aero Lab - Pitts Special Construction Gallery - Index

    I doubt you're gonna need any additional diagonal type brace tubes but you may want to add a doubler type tube to the the bottom of the longeron where the gear is clamped...the radius plates you mentioned. I see a couple things...from the pics I can't tell for sure if there is a lateral fix of some sort to keep the gear from shifting L R. If not, I wouldn't consider the clamps to be good enough for that. The Pitts usually uses an 032 AL plate bolted thru the clamp keeper bolts on each side and extending across the the top of the gear with a bolt thru the gear and plate at the center of the gear. There are pics in the link. And it looks like the aft edge of the gear leg is resting against the square tube. Is there a similar tube contacting the front of the gear leg? The gear leg needs room to flex upward when it rebounds. That aft tube looks to be restricting that. And if none to the front now we got a tendency to torque the install type thing as the rear of the gear is stopped well short of the top of the reflex upwards and the front isn't. Even if there is a tube fore and aft the gear doesn't need to contact either. That gear looks to be so massive you may can trim it for clearance. If that's a wide angle pic of the thing sitting on the gear we may be getting an exaggerated view of the camber. It "looks like" it may be ok once loaded. I would run some ballast tests like somebody mentioned. You can get a good idea with barbell plates etc. Load it up and push it around. Easy.
    Don't believe you said if it was AL or steel. Either way it's a weight penalty over a well done tube and strut braced gear(not a Cub gear stuck on it like a Baby Ace; that's terrible!...but a gear that's stout enough and no more. Probably like what's in the plans?) On a plane that small/light a big beefy leaf gear is a big percentage of what the EW should have been. And the drag advantage on a slow little plane like that isn't enough to justify the weight penalty IMO. I know it it's steel I would be cutting all that out and going with a tube gear. If it's AL I can't tell from here but would look at it really close to see what the weight penalty is and then decide. Personally I couldn't accept much. And I know that wasn't the question you asked, sorry...I think you're gonna find the camber to be OK. Have fun

    Joe
     
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  12. Jan 9, 2016 #12

    Pops

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    I would save a lot of weight by sticking with the plans gear. On such a small airplane a small weight gain is a large percentage of the EW and make a large difference.

    Dan
     
  13. Jan 9, 2016 #13

    birdus

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    Good tips. Will do. Thanks.

    Jay
     
  14. Jan 9, 2016 #14

    birdus

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    I was thinking the exact same thing. I should've taken a photo more in line with the gear (i.e., closer to the ground). Thanks for your other thoughts, too.

    Jay
     
  15. Jan 9, 2016 #15

    birdus

    birdus

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    Don't apologize for the extra info, Joe. I appreciate it! I definitely don't want extra weight if I can avoid it (relatively easily and cheaply). I suspect I'll wrap up the wings within the next week or so (yay!). Then the fuselage goes into the garage. At that point, I'll remove the gear. Then the material should be obvious. I assumed it was aluminum, but I don't know. I'll check out your photos. Thanks for those. I'm sure they will be helpful.

    You mentioned lateral movement. I had thought about that. I figured the downward bends in the gear should be close to up against the radius plates, so I concluded that this spring gear was a little too wide for my fuselage, but I suspect that's not an insurmountable problem. It's something I have in mind, though. If the radius plates are tight, it might inhibit lateral movement adequately.

    I've only ever been to my local EAA once (a couple years ago), but maybe this is a time to visit them again.

    Thanks,
    Jay
     
  16. Jan 9, 2016 #16

    birdus

    birdus

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    How much lighter would the plans-built steel gear be than this spring gear? I'm assuming these are aluminum. Keep in mind, too, that the firewall will be lighter/simpler using the spring gear, as there is nothing required there for absorbing landing impacts.

    Jay
     
  17. Jan 9, 2016 #17

    TFF

    TFF

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    A single seat Pitts can put on 75 extra pounds.
     
  18. Jan 9, 2016 #18

    BJC

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    Two S-1S, same propeller, engine, except for pistons:

    Spring gear, no battery, no starter 756 pounds.

    Bungee gear, battery, starter, no alternator, spades 800 pounds.


    BJC
     
  19. Jan 9, 2016 #19

    birdus

    birdus

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    75 would be a lot more to my Baby Great Lakes than it would be to a Pitts. Empty is supposed to be 480 and gross is 850.

    Jay
     
  20. Jan 9, 2016 #20

    birdus

    birdus

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    Are you telling me that the spring gear adds 75 pounds on a Pitts?
     

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