Torsion Spring Landing Gear

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DaveK

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The Heineken HE 222 is the only plane I know of that has a torsion spring based landing gear. Curious if there are any others? Torsion springs can store more energy per pound than a leaf or coil spring so you’d think there is potential in using them on aircraft.
 

wsimpso1

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I think you mean Heinkel 222...

While that bird did use a torsion bar spring set up, I suspect it was used there for a combination of reasons.

Let's check some thinking.

Going to the spring design chapter of Shigley or other spring industry design guides, you will find that the biggest part of stress in a coil spring is also torsion. They are also torsion bars, but without having to put carefully designed and applied splined ends and mounts to make them work. The issue of getting the loads in and out of torsion bars usually results in significant fractions of each bar either being much less springy and/or expensive.

Designing for low weight is designing to make the whole airplane lighter. Making one piece lighter whil driving weight up in other parts can result in an net weight increase. You must include the associated components of a system. Each type of landing gear system is not just its direct pieces, but its effect on the rest of the airplane too.

Telescoping strut or an articulated/trailing arm type of gear with an oleo pneumatic absorber is usually the lightest system for any given amount of landing gear energy, and they can be tailored for low rebound too. Interestingly, the air spring has a very low mass spring per unit energy storage. The air spring also demonstrates very nicely the fact that the system to make it work is important - it can carry no load without its pressure vessel and sliding seals...

Other systems that are part torsion bar are any Wittman type gear that puts the tread patch significantly forward or aft of the mount at touchdown- this stores significant energy in torsion during the landing stroke, but also results in significant scrubbing of the tire on pavement, reducing rebound. Others are the nose-gear of the single engine Grumman/American - a pair of horizontal torque tubes take the moment from the strut and transmit it outward to the edges of firwall. There is significant energy stored in these torsion elements during landing strokes.

Billski
 

DaveK

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Spell check to the rescue again!
My thought was a torsion rod spring could be run near the bottom of the fuselage and take the place of the bulky bungees or stacked rubber disks used on many aircraft (Cub types). Since the rods are small in diameter if oriented fore-aft they’d fit inside the fuselage without greatly impinging on the cabin space. Either aligned with the rotation axis of the gear legs or react the load via tie rod to a centrally located spring in a Cub like arrangement.
Really I’m just curious if an arrangement like that has been tried.
 

TFF

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So an articulated gear but a flex rod it reacts against? Wittman round and flat gear is pretty easy. What do you see the advantage?
 

Hot Wings

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What do you see the advantage?
Don't know about the OP but I can envision the advantage being able to easily attach an absorber to the non-fixed end. Tire scrub on the Whittman gear has a similar function.
 
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don january

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I think it may have been torsion Bar landing gear that came to mind instead. If a builder was to take a wish bone off a 66 VW Bug and by way of the works of the swing arms tied into the degree and spacing of gear need it may just ride along nicely in ground effect. There is 2 torsion bars per wish bone on the v dubbs. I'm sure weight would be an issue on a smaller craft. ???
 

wsimpso1

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Spell check to the rescue again!
My thought was a torsion rod spring could be run near the bottom of the fuselage and take the place of the bulky bungees or stacked rubber disks used on many aircraft (Cub types). Since the rods are small in diameter if oriented fore-aft they’d fit inside the fuselage without greatly impinging on the cabin space. Either aligned with the rotation axis of the gear legs or react the load via tie rod to a centrally located spring in a Cub like arrangement.
Really I’m just curious if an arrangement like that has been tried.
Ah, aligned axially like a Chrysler product from the 1970's. Issues are several fold. In cars, the torsion bars aligned this way are tied into structures that are already designed around enough stiffness (plenty strong) and so add little weight penalty to surrounding structures. Try this with a steel tube truss or aluminum semi-monocoque, and you will have to add a bunch of material to spread the anchor end loads out into the fuselage. On top of that, the gear legs will either have to carry the torsion or have a push rod transmit loads to the end of the gear legs. Everything on this is added weight to be tallied and compared to other schemes.

Have fun!

Billski
 

DaveK

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Meglin1 thanks, exactly what I was looking for.
wsimpso1 I’m not proposing anybody do this. I can see situations where it could work and it is pure curiosity if anyone has done it. Obviously the structure would need to be designed for it; you can say the same for any other type of landing gear.
 

wsimpso1

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Meglin1 thanks, exactly what I was looking for.
wsimpso1 I’m not proposing anybody do this. I can see situations where it could work and it is pure curiosity if anyone has done it. Obviously the structure would need to be designed for it; you can say the same for any other type of landing gear.
Let's remember that a forum is way more than a "party line" for your question. It will live on for years, can be found in online searches, etc. Many of us will try to write for the broader audience. When you ask about a scheme, it is then a proposed scheme in many readers minds, even if not in yours.

As to "the structure would need to be designed for it", while that is true, waving it away as equivalent to others is to seriously underestimate the weight impact. The places where the suspension arms mount to the fuselage will be close to equivalent, but then you move off the length of the torsion bar, and must make another hard point and beef up the fuselage in places where we commonly do not have big local torque loads.

It can work. It might be heavier than a simple analysis would indicates.

Billski
 

opcod

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Those type of tail gear are very common on many stol plane. Work great and perfect for large load absorbtion. But as writen over and before.. An ultralight don't need this. Just look at any glider, the wheel is even embeded into the rudder, so while they do real tail landing.. not much is needed in that area. Sure 2-3 extra ply of carbon, but nothing more.
 

Riggerrob

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What about the main landing gear in Bushby Mini Mustang?
The main gear legs are typical Cessna flat springs, but they are bolted to a long tube that penetrates the main spar and is bolted to the rear spar. That helps distribute point loads to the rear spar. The tube is oriented straight fore-and-aft, I am not sure if the tube is rigidly bolted to the main spar.
 

proppastie

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What about the main landing gear in Bushby Mini Mustang?
The main gear legs are typical Cessna flat springs, but they are bolted to a long tube that penetrates the main spar and is bolted to the rear spar. That helps distribute point loads to the rear spar. The tube is oriented straight fore-and-aft, I am not sure if the tube is rigidly bolted to the main spar.
That flat steel gear leaf is seriously heavy,.....The telescoped welded tube is bolted to the caps of the main spar and a socket at the rear spar. When I crashed the tubes absorbed lots of energy as they twisted like pretzels.....Its probably best they did that rather than a bounce to a cartwheel or worse......I would guess if there were problems with normal landings we would know about it.
 
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