Landing gear concept

Hey guys, my buddy had a gear collapse on his Skyraider II Monday evening:( I observed the landing and it wasn't a hard landing so there must have been some damage left over from a previous GL incident. His SK II had no suspension to begin with (other than the tires) just fixed tubes. Looked like the previous owen cut the bungies off to make room for the oil cooler:confused:. Anyway, this leads me to looking at all the options for "bush gear" out there and other designs. So far the options on the table were either the die spring set-up (conventional cub style replacement), or some type of retrofit that would require modification of the fuselage. I may be violating some kind of code here, but I don't see why we can't take advantage of the compression and dampening benefits of coil-overs? I've attached a concept sketch of some ideas I'm toying with and working on the math to ensure I have a good factor of safety in the stress points. My initial thoughts were to build a "cradle" that utilizes the existing LG attachment points and provides a place for the oil cooler to mount. This should not eliminate, but greatly reduce the forces applied to the airframe, and keep the failure point out on the LG leg. This should also alow for some suspension adjustability based on load and potential landing environments. I'm planning to mock up a set this weekend from either PVC or 1" pipe to see how it looks. Btw, I'm leaning towards the shorter shock post (bottom right) and a more vertical shock mount with a lower saddle in the LG leg near the 1/3 mark, this should give plenty of travel and adjustment with a 6"-8" shock travel.

Thoughts anyone?

Jay P
N627C

Quote:

---

Originally Posted by Greensuiter86

Thoughts anyone?

Jay P
N627C

---

My only thought is that you will need some serious engineering on the upper and lower attachments of the shock device. The bending moment on the gear leg where the shock attaches would be very problematic. 4130 is designed to bend rather than break. I worked a little bit on making a stinger type tail wheel spring with very heavy 4130 and it deformed very easily with the 45 lb. weight at the tail wheel. The Highlander design similar to your idea has the shock device connected near the axle and at the wing root.

The spring bush style gear for kitfoxes and cubs have been around awhile and have been tested to work.

I quess if you want to be a an experimenter and also someone to be a test pilot , then you can do what ever .

Don't you have to follow any modification rules on a skyraider for the certificate of airworthiness ?

I personally would stick with the spring bush gear that is available.

A Cub type gear is pretty hard to beat, using a die spring as opposed to bungees, however, bungees are very forgiving and do offer some shock absorbing function as the rubber bands slide over one another. The use of the Cub type cabane keeps all the stresses outside of the airframe. If you don't have the capability, you do need someone to do a little arithmatic and check if the loads versus structure are acceptable.

Cheers,

His plane is registered as Experimental. It will have to be taken back to Phase I operations and flight testing done, then returned to Phase II. No issues. I work in an engineering department...so where I was asleep in school:cool: there are others here who were clearly awake and can help on the math;). I do like the die spring mod gear, but have read a few concerns about limitations regarding travel and end stops.

Jay