Better suspension

I fly a cub with hydrosorb and bungee suspension. The thing is working ok. I was looking at AOSS suspension or homemade dye spring suspension. Untill I saw this video. Just getting out of the rockcrawler world, I think it would be a good way to absorb the earth.

Seem to work good for those guys.





With all aluminium shocks, I think it would weight about the same thing, or less. The only thing is the shocks would be working at a great angle... About twice the force. But I think they would handle it. But they are capable of jumping a 5000 lbs rockcrawling buggy.

Am I trying to reinvent the wheel??


Red are the shocks and orange would be the safety cables. With a X brace from the shocks to the front landing gear attatch, in the fuselage.

Take off and climb are important too. Weight and drag gets to be a drag at high density altitude.

piper L-14

Piper L-14 photo link 28 images
http://www.a2oxford.info/Pages/spain/pages/2005/piper/slideshow.html

Olibuilt, Take notice of the location of the upper attach point in the L-14 photos. It is different from where you drew it.

One of the downsides to the outrigger style of gear is all that flexing can make the airplane more difficult to control in a crosswind. It is like pushing a rope. Like everything in aviation, nothing comes free.

Bill

Oli give a call to Gilles Lalier from Sherbrooke he has came up with a hydrolic vertion of a hydrasorb with a die spring inside that work pretty good.

This is what I've been daydreaming about the last couple years. I'd borrow what Formula 1 cars are doing for front susp. but only have one A arm and the push rod going up through the floor with the shocks under the front seat. Move the pushrod to belcrank connection point to the other side of the pivot point and make the system work in tension rather than compression, and have the a-arm attach to the stock position of the fuselage. It's be easier with a wide body or a Maule frame to give you more room for the belcranks (which will have to set at an angle roughly matching the pushrod angle, heim ends would account for travel angle changes) and shock but you should be able to make it work w/ a super cub. (no under seat batt.) I'd also use streamlined tube for the pushrod like the F1 cars. Should make it pretty clean and using gas shocks it would be super light. We're just doing the stock setup on our project now though.
There, I published it 1/27/2013 so don't any of you try to patent the idea. :smile:
Chad Wirsig.

I have a PA12 that was modified in 1954 to include Fairchild style landing gear. It spent quite a bit of time in Alaska. It has survived over 50 years with this configuration. The struts shown in these photos have bungees inside the covers. I have since tried using Race Runner rock crawler air oil shocks. They are adustable with air pressure as well as the amount of oil that is placed in them. You can also adjust the rebound rate to be different from the compression rate. I like the set up so well that I am incorporatating the same design in my experimental PA14. Various companies sell air oil adjustable shocks with different travel lengths. They are about 10 pounds each and cost $300-400 each. They are made from steel. I had to put some blocks inside to limit the down travel. You adjust the air pressure to match the weight of the plane. I bought the 2" size but will go with the 2 1/2" on the new project so less air pressure is needed. I actually use nitrogen from a bottle. The landing gear setup is one of my favorite parts of this plane.

Jimbo, I've always thought that was a cool looking plane.

Some guys in ID working up an interesting approach using RAGE airshocks in 'cub-style undercarriage. Bet there's a Supercub market there, too:

http://www.backcountrypilot.org/forum/viewtopic.php?f=13&t=11744&p=157094#p157094

Thanks. cubscout

wirsig...im in the same thinking ass you. since i fly a tcraft we have a ton of unused space under the seat....i was debating on the use of shocks similat to a softail harley all in one airshock..also similar to the huskies but would need the bellcranks to dial in the progressiveness and change weight loadings

jimboflying said:

I have since tried using Race Runner rock crawler air oil shocks. They are adustable with air pressure as well as the amount of oil that is placed in them. You can also adjust the rebound rate to be different from the compression rate. I like the set up so well that I am incorporatating the same design in my experimental PA14. Various companies sell air oil adjustable shocks with different travel lengths. They are about 10 pounds each and cost $300-400 each. They are made from steel. o I had to put some blocks inside to limit the down travel. You adjust the air pressure to match the weight of the plane.

Click to expand...

Theese are the shocks I'm talking about. All aluminium, nitrogen filled airshocks.

http://store.tk1racing.com/searchresults.asp?cat=84


Any pics of you PA-14 shocks project??


Seems I would need to mount them higher, maybe at the middle of the door. Or like Jimbo...

The above shocks look to be prefilled with nitrogen. You could not adjust them for varying load conditions. You would have to get the right one the first time. These are the ones I have used. http://www.polyperformance.com/shop/Sway-A-Way-2.5-Air-Shocks-p-16815

I'm the guy doing some BETA testing for John using my Rans S-7S. The shock itself is made by this outfit www.foxracingsox.com He is using it in a way that hasn't quite been done before as regards cub style gear. He also makes a cub style bungee retro fit gear for the Rans S-7S which I installed some time ago. This new shocked unit simply bolts into place, replacing the bungee shock strut. Here's a test rig I made up yesterday to test the drag of the faired unit, even the ends are closed in. At 75 mph indicated (car speedometer) and with a estimated 10 mph headwind so about 85 mph wind, according to my digital fish scale..... it exerted a force around 10 to 13 ozs. This obviously was a pretty crude test, but as I was comparing it to the faired bungee unit I was replacing it was more comparative in nature.

I now have about 20 hrs on them, and am cruising at 95 mph, on wheel skis, at the normal Rotax 912S prop rpm of around 2300. (That's 12,000 engine rpm, but still less then 4 GPH, (just a little Rotax/Continental/Lycoming joke, the fuel burn is for real though, the actual engine rpm was 5200 which it can do all day every day though I usually cruise it at less the 5,000 and get the burn down to 3.2 GPH) The cabane and a-frames are also faired. So, not a big hit drag wise. I am still playing with the air pressure setting, which is as easy as setting the pressure in a tire. As you can see by the Fox site, these shocks are very trick.... and right now it is looking like somewhere between 100 and 125 psi is going to be the sweet spot. As far as handling improvements, it's been tough to extrapolate that due to the fact I'm on the skis, I mean on fresh fluffy powder anything or NO shock would feel great, but as I encounter varied types of snow I am gradually getting a feel for them. The plane feels real solid while taxiing and on sideslopes, overall "tighter", while at the same time just as squishy when you want it to be. Like getting vg's on an airplane, it takes a while, at least for me, to fully get a handle on the performance differences, one landing in particular stands out: I was setting down in what seemed to be a smooth mountain meadow, and on slideout and going maybe 15 mph I saw I was going to go over a drift or berm, whatever, and it looked like the kind of bump that would pitch you back in the air just enough to give the gear a good workout but not enough to be a problem. I went over it and after coming to a full stop and getting out and looking back, I noticed the ski tracks had never left the snow, this I believe was the shocks in action, they kept me glued to the surface as they get rid of the rebound/bounce back of the bungee gear.

For the next few weeks, rather then look for the smoothest areas to set down in I need to look for the roughest, if I am any kind of a BETA tester that is. If I was on my usual 29" Airstreaks the differences would be easier to pick up on, the changing snow conditions confuses thing a bit, but so far, I like them a lot.

jimboflying said:

The above shocks look to be prefilled with nitrogen. You could not adjust them for varying load conditions. You would have to get the right one the first time. These are the ones I have used. http://www.polyperformance.com/shop/Sway-A-Way-2.5-Air-Shocks-p-16815

Click to expand...

Thanks for the info about the shock you use.

But the all aluminium shocks sure weight less. And yes they are fully ajustable by putting more or less nitrogen in them to adjust ride height. I had those in the 4 corner of my rockcrawling buggy.





Seems to be a good setup CourierGuy. I like your testing rig.

Thanks for the correction. On closer review of the pictures I now see the inlet valve for the nitrogen. How much weight can they support and how much do they weigh?

My idea... I plan to build something like in the picture. The length of this gear is equivalent to 3" extended gear. I found a website called ridetec.com that has a large variety of air shocks with or without coilover springs. As of now, I think I would opt for the coilover springs because they are easy to adjust and there are lots of different strengths. I realize that changing the air pressire on an air shock may be a better way to go than coil springs. This website had a load calculator to help determine what size was appropriate.
I am of the opinion that pivoting the gear in the center of the fuselage is better than the sides because the angle allows the shock to better absorb the load and less of the impact goes into the fuselage.
The gear truss would have an aluminum leading edge and would be covered with fabric. The leading edge would be removable to allow for cleaning and inspection. I also think this arrangement would be more streamlined than the conventional cub gear.

Hello Super 11 xp has the idea now just need to make the gear kinda like just did , remove fabric and build up fuselage re inforce it and move the gear to the center just like they did make new longer gear

Here is another example of centerline gear attach and long struts
FrankenMaule
http://www.supercub.org/forum/showthread.php?29476-Franken-Maule

I started to check out the possible placement of the airshocks. Having already all the landing gear (6'' extended) and the landing gear attatch point at the fuselage, I wont change anything drasticly like attatching the gear in the middle.... So now working with 6 inch extended gear and stock fuselage...

Today, I placed some stock lenght landing gear and a 18 inch travel airshocks just to see.. Seems to be a working option for me, easy to fabricate. With the little longer shocks (20'' travel) and the 6'' landing gear, I think it would work...

The only think I am wondering is the working angle of the shocks... And the fuselage attatch point..

Do you think the fuselage can handle a shock placed at the middle of the door (with a brace bettween the fuselage at the lower portion of the dash panel)??

BTW, the all aluminium shocks weight about 6 pound each. Don't know the weight of the cabane V and the hydrosorb setup..

Maybe a rock-jumper cub on the way!



Figure a 3/4 or so tubing between the 2 doors, at the lowest point of the instrument panel

Here is some basic info...



23.471 General.
23.473 Ground load conditions and assumptions.
23.477 Landing gear arrangement.
23.479 Level landing conditions.
23.481 Tail down landing conditions.
23.483 One-wheel landing conditions.
23.485 Side load conditions.
23.493 Braked roll conditions.
23.497 Supplementary conditions for tail wheels.
23.499 Supplementary conditions for nose wheels.
23.505 Supplementary conditions for ski-planes.
23.507 Jacking loads.
23.509 Towing loads.
23.511 Ground load; unsymmetrical loads on multiple-wheel units.

You might look at the attach point used on the Great Lakes biplanes.

Oli, I'm not an engineer but on the horizonal tube at the instrument panel I would think you need a larger diameter than 3/4 and heavy wall too.

not too worried about the between door tube as you would the direction of force moving in the direction of your shock...it would want to open the windscreen angle.....but looking at the cluster of tubing coming from the gear attach up the side there is plenty....chances are that the bracket to attach the shock with will have smaller cross section than the structure in place....I do like the center attach for reasons of leverage but that is the area i would have most concern of....surely somebody here has the ability to run a fea side job of the structure using the numbers above....but why not tuck it all inside and lay the shocks down...even if they were external that would look cool......


http://www.hotrod.com/featuredvehicles/hrdp_1212_900_horse_power_on_propane_1970_chevrolet_chevelle/

jimboflying said:

You might look at the attach point used on the Great Lakes biplanes.

Click to expand...

The Great Lakes gear works awesome but I think the top attach point is a truss built into the front of the fuselage.




Glenn

Does anyone know how much tension is on the bungees at rest? Or how much force is required to keep the wheels from splaying out? How much travel is required?

The max travel on a bungee hydrasorb is 5".....Oli have you given any thought to safety cables. cheap insurance on a untested system.

DW

I made contact with Tony at TK1racing.com and found him to be exceptionally helpful. He went way beyond what is usual in answering questions and providing background information. He is a pilot who owns a couple of planes himself so he speaks airplane talk. He was so helpful that I decided to order a set of struts from him. He says they weigh 4.8 pounds each and are made out of high strength aluminum. You change the operating pressure by changing both the oil quantity and the nitrogen pressure.

Sound interesting Jimbo, would you post a pic of your struts when you can?