Trailing Link Landing Gear

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roverjohn

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I wonder if you couldn't use motocross forks to get close for testing purposes. They might not be too heavy if converted to air spring.
 

Rienk

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I think I did look into the Foxx shocks. It would be the equalivalant to what might go onto a dune buggy. But of course to get it optimized you need to do the math on weight, decent rate, max g, suspension travel and angles.
We designed our own trailing link gear for the main gear on the Envoy (six seat turboprop) and we used custom built Foxx shocks... length, diameter, piston size, wall thickness, orifices, etc... all custom.

However, even though it is lighter, stiffer, less expensive - a lot of potential customers were put off by the "different" look.
 

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DarylP

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AAK's Hornet has a neat system that works for them... you may be able to do something similar on a trike.

 

MadRocketScientist

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We designed our own trailing link gear for the main gear on the Envoy (six seat turboprop) and we used custom built Foxx shocks... length, diameter, piston size, wall thickness, orifices, etc... all custom.

However, even though it is lighter, stiffer, less expensive - a lot of potential customers were put off by the "different" look.
Put some gear doors on that and it would look more conventional, a lower weight and associated increase in baggage allowance should help you sell the gear.

If its lighter and stronger, I like it.:gig:

Shannon.
 

orion

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We designed our own trailing link gear for the main gear on the Envoy (six seat turboprop) and we used custom built Foxx shocks... length, diameter, piston size, wall thickness, orifices, etc... all custom.

However, even though it is lighter, stiffer, less expensive - a lot of potential customers were put off by the "different" look.
Not to be an armchair quarterback but if I were to make a cursory comment regarding that gear I'd say that it looks flimsy at best. For proper behavior, a landing gear's design requirements must include not only those associated with strength but also with stiffness. In some cases the latter may actually drive the design more than the strength. I've attached the two pictures of a gear I designed for a project about the same size as yours - this gear was tested and fully certified.
 

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LArzfromarz

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Orion-
Just a thought, for trailing arm fixed gear arrangement it is probably next to impossible to "pants" it due to the travel correct?
Larry

Love the design tho...
 

autoreply

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Just a thought, for trailing arm fixed gear arrangement it is probably next to impossible to "pants" it due to the travel correct?
I've though about this for my own design as well. It's no problem to fit pants, but either the wheels stick out of the pants quite a lot, or the pant drags through the grass/over the concrete.
A setup where the pant can tilt up much more than the suspension will ever compress could solve this.

A much simpler way though is to have the pant such that - when the landing gear is unloaded the pants are in the ideal position and mounted to the part where the wheels axis is fixed to. Once you put weight on them, you will tilt the rear of the pant up and - as long as you keep the front of the pant relatively short, which it should be anyway - that actually might work.
 

orion

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The trick in trying to fair in a trailing link gear is to figure out how you can do a pivoting pant leg. I've only seen it done once (don't remember where although I think it was the Arlington Fy-In some years back) but the result was attractive and seemed quite functional. But yes, it does require a bit of thought to get everything moving right.
 

bronkk

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Inspired by Orion on this post I think I found a solution for my landing gear at:

Double Convolution Springs - Timbren Aeon Hollow Rubber Springs

They are light and would be very simple to implement and you don't really need a shock. A720-65 has a standard load of 650#'s and goes up to 1800#'s for max deflection of 2.75 inches. Seems a pretty good fit for a 1300# airplane. I e-mailed and they sell for $80 bucks each.

Kelly
 

Dan Thomas

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Googling the Beech Musketeer (trailing link fixed gear) I could find no pictures of any wearing wheelpants, suggesting that it would be something of a headache to make work. Lots of airplanes used trailing-link gear, among them the Ercoupe (on all three wheels, and which which I found to be too easy to land), the Mooneys, the Cessna 404 and 441, and the PZL Wilga. Of the fixed-gear versions, here's an Ercoupe with pants:


What angle would those pants fly at, seeing what happens to the gear once in flight?

Dan
 

Hot Wings

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Off the wall idea - let the pants pivot on the axle center line and add a horizontal stab?
 

GESchwarz

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A simple 4-bar linkage can keep the pants pointed into the wind. Or design the pants for lowest drag at cruise and allow for clearance on the ground. Sure it might look a little different than a conventional wheel fairing, but so what.
 

Rienk

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Not to be an armchair quarterback but if I were to make a cursory comment regarding that gear I'd say that it looks flimsy at best. For proper behavior, a landing gear's design requirements must include not only those associated with strength but also with stiffness. In some cases the latter may actually drive the design more than the strength. I've attached the two pictures of a gear I designed for a project about the same size as yours - this gear was tested and fully certified.
Are you talking about the mains or the nose?
Of course, the mains are the ones that are trailing link - and the whole point of the triangulation is stiffness - purportedly much more than the single post gear style like in the sample picture.

As to gear doors; this gear is locked down until we do enough flight testing, and then we'll finalize the gear (that's why the wing skins aren't cut out yet - avoiding the extra drag).

We too are looking for an elegany solution to putting pants on TL gear.
 

Tom Nalevanko

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Perhaps 'flimsy' is not the best word? I would characterize them as 'spindly' which may be perfectly fine. However I am influenced by the spindly Lionheart gear and the video of their spectacular collapse. People expect something to also look sturdy to feel comfortable. That's why they attach a big thick rope to the end of a 1/4 in. steel rescue cable.

A long time ago, I was involved with an optical sight with an exposed moving mirror. It was an elegant French design but the mirror looked like it would break when banged up against its stops. It simply looked flimsy. However the French had banged it 'full-force' over 10 million times with no problems! My compadres insisted that it be covered up so our military would not worry about it. Go figure.
 

orion

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I understand the issue of triangulation however as you do the calculations for side force (turning, skidding, skewed landing, etc.) there are quite significant loads imposed upon the tire that will create secondary deflections, especially with trailing link gear. As such, torsional stiffness becomes as important as the basic vertical impact.
 

GESchwarz

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My design provides 13.5" of travel at the main gear tires (from 0 to 3 g's). With that much travel on a forgiving trailing link gear, can I afford to go with a 5" wheel as opposed to the more standard 6" wheel? I would be saving weight and aerodynamic drag. The plane will have a gross weight of about 1800 lbs and is a tricycle gear with differential braking.

What are the down sides to going with a 5" main wheel.
 

Lucrum

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My design provides 13.5" of travel at the main gear tires (from 0 to 3 g's). With that much travel on a forgiving trailing link gear, can I afford to go with a 5" wheel as opposed to the more standard 6" wheel? I would be saving weight and aerodynamic drag. The plane will have a gross weight of about 1800 lbs and is a tricycle gear with differential braking.

What are the down sides to going with a 5" main wheel.
I hope so, I'm anticipating a max landing weight just a little higher than yours and I'm looking at 5" wheels.

I'm a long way from buying wheels but these are my current first choice when the time comes.

http://www.matcomfg.com/W51LTRIPLEPISTON-idv-2382-33.html
 
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addaon

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When I last looked at this problem, the only issue I found with going to 5" wheels (besides minor things like tire selection, availability) was that brake sizing means less energy per break, or external brakes which kill any drag advantage. I ended up deciding that 15x6-6 made more sense for me.
 

pwood66889

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"Googling the Beech Musketeer (trailing link fixed gear) I could find no pictures of any wearing wheelpants, suggesting that it would be something of a headache to make work. Lots of airplanes used trailing-link gear, among them the Ercoupe (on all three wheels, and which which I found to be too easy to land), the Mooneys, the Cessna 404 and 441, and the PZL Wilga. Of the fixed-gear versions, here's an Ercoupe with pants:"

There are many `coupes with wheel pants. I'll see if I can get some feed back if any one is really interested in pants on a trailing link landing gear.

Percy in SE Bama
 

GESchwarz

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I'm very interested in pants on trailing link, and I won't leave home without them. I haven't really put much thought into how I'm going to attach them, but I imagine it will utilize a 4-link mechanism to keep from dragging the trailing edge on the ground and keeping them pointed forward at cruise. It really has to be streamlined only when the gear is unloaded.

Yes, I would appreciate the feedback.
 
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