Landing gear struts without scissor links

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cpatelaero

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Hello,

I am working on a tube-in-tube (Tony Bingelis/AR-5/CA-65) landing gear strut for a custom homebuilt that is a mash-up between a KR2 and a Gazaile II, with EZ-like construction methods. 1125 lb gross, Rotax 912iS. I'm considering designs that do not have a scissor link. Would greatly appreciate inputs from anyone who has firsthand experience with the following designs:

- Parker Teeny Two: Has a simple implementation with a spring and concentric rubber hoses. Torsional constraint is provided by a ~quarter inch bolt riding on a slot in one of the tubes. The contact stresses do come out to be high for a heavier airplane. Did the Teeny Two have any problems with the bolt-in-slot arrangement, esp. with wear/plastic deformation?

- Tipsy Junior: Seems like a square tube inside a circular one. Not sure if something like Phenolic/Delrin or wood is used as the spacer, but there seems to be a reasonable bearing area. Any experience with this design?

- Jodels: Some of them seem to have streamline struts with no scissor links, but I don't have any further info. Did they work well?

I will be able to do the structural sizing, so just need inputs on how the designs worked in general.

Thank you!
 

TFF

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I would think the now standard spring or rod gear is the usual answer. I imagine that’s what the Jodel has. A T2 is a rather crude airplane. It is charming that way, but it’s not an example of elegant design. Mine was a damaged project that wasn’t going to fly again. The Tipsy Jr gear doesn’t seem much better from the description.
 

TFF

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Square has a lot of drag as it is torquing in the housing. It is probably the crudest. Is there a reason for not having scissors? Still with small planes spring or rod is easiest unless you really need the gear straight up and down.
 

cpatelaero

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Don't have a major reason for not having scissor links. Just a few extra welds, but I do have some welds planned for the top of the strut. I had not thought of adjustability in the Teeny-two-like gear. Thank you for the inputs. Back to circling around a nearly stalled project!
 

Riggerrob

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"I would think the now standard spring or rod gear is the usual answer. I imagine that’s what the Jodel has. ... "
Chris Falconar's variations on Jodels got Wittman leaf spring main gear, but the originals had what looked more like oleo struts. I only flew once in a European-made Jodel and did not take a detailed look at the main gear legs. I suspect that stock Jodels have steel coil springs or rubber shock absorbers.
 

TFF

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Oleos have a cool factor for sure. If you look at older homebuilts, one could always see if or how someone was trying to avoid the Wittman patent. Same with certified. A lot of plane that would have been naturals with a spring gear, couldn’t. Of course Wittman had the middle digit at him with the Cougar because of that. Marquette Chargers and Firbolts had gear that looked like spring gear but were coil or bungee. I had a recked T2 in high school. While I hold the design in high regard for its inventiveness, did it really need springs in the gear? The springs are valve springs from a Cadillac.
 

karmarepair

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And the earlier ones used a pear shaped piston running in a similarly shaped outer leg, compressing hollow cylinders of rubber.
 

Pops

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I used round Cessna 150 gear legs on my Falconar F-12 . Worked out very good. Plans show the round tube leg with scissors.
 

Dan Thomas

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Wittman gear is the tapered rod. The Falconar adaptations of the Jodel used the flat leaf, and it's terribly heavy.

At the flight school I had two main gear legs from Cessna 150s. A flat leaf gear leg from an older model, and the tapered rod from a newer airplane. Same gross weight for both airplanes. The leaf weighed, I'd guess, twice what the rod weighed.

The Jodel oleos would have been 4130 tubing, fairly thin wall, and would be lighter than either the rod or leaf.
 

Pops

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Wittman gear is the tapered rod. The Falconar adaptations of the Jodel used the flat leaf, and it's terribly heavy.

At the flight school I had two main gear legs from Cessna 150s. A flat leaf gear leg from an older model, and the tapered rod from a newer airplane. Same gross weight for both airplanes. The leaf weighed, I'd guess, twice what the rod weighed.

The Jodel oleos would have been 4130 tubing, fairly thin wall, and would be lighter than either the rod or leaf.
My plans were an early set of Falconar F-12 plans, Before the A model that had the sweep fin and rudder. The LG plans is a round strut with scissors like the Jodel and also retract gear plans that folded to the rear with part of the wheel below the bottom wing skin. Also the fuselage is 2" narrow than the A model. I still have the plans.

Added-- Plans also shows two , 9 gal wing fuel tanks in addition to the fuselage fuel tank if desired.
 

Tiger Tim

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Wittman gear is the tapered rod. The Falconar adaptations of the Jodel used the flat leaf
Wittman designed the single leaf first, then the tapered rod. See the later iterations of Chief Oshkosh, the big V12 Bonzo, and the earliest version of Buttercup which I believe had a different name.
 

TFF

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Wittman had the patient on either. He was showing his plane with the rod to Cessna. Cessna was interested but someone said the upcoming 195 would look racier if it was streamlined, could the gear be flat? Wittman said of course. Then he went home and had the patient amended before anyone knew.
 

Marc W

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I looked at a Falconer project several years ago. The plans were for the Jodel D11 with additional sheets for the Falconer changes. It showed the gear legs made from streamlined tubing. The plans showed both tails and the only major change was in the wings. The wings and fuselage were built but were uncovered. The workmanship looked good but the wings had hung in a leaky hanger and were coming apart. The fuselage was in good shape but I discovered that I would have to shorten my legs to fit so I passed.
 

Pops

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My plans are just for the Falconar F-12 , not Jodel D11 with add on plans for the Falconar. Engines from the Lyc- 235 to the Lyc-360. With or without flaps, with or without the wing fuel tanks, fixed or retract LG. The fixed LG designed like the Jodel. With or without the 3 rd rear seat. Also one piece wing or outer bent up wing panels bolted on for a 3 piece wing. I built the one piece wing. Spar attach fitting and bolts add a lot of weight.
 

Dan Thomas

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Wittman designed the single leaf first, then the tapered rod. See the later iterations of Chief Oshkosh, the big V12 Bonzo, and the earliest version of Buttercup which I believe had a different name.
Thanks for correcting me.
 
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