Hi
I am building a KF5 and have been reading a lot of post on the landing gear option and I am leaning towards the Cabane/Roberts style spring or preferably shock landing gear. I have no problem fabricating my own but do not want to try to do it from scratch with no plans. Are there plans available to purchase and build your own gear?
I just want to put in my 2 bits, there are 3 important factors of the cabane gear 1) Front Down tubes should be 1.25" not 1" 2) Die springs are not a good idea mainly due to short travel 3) A cross tube should be used between the mounts of the cabane"V"
That said here is were I am coming from: I built my Cabane gear I used 1.25" for front tubes, used a longer travel die spring enclosed in a hydraulic dampener IE: Bearhawk design, did not use a cross tube for the Cabane "V"
I did a poor landing to a steep hill and hit HARD No damage to the gear but major damage to the Fuse Longeron twisting and buckling diagonal tubes.
Is it possible the front tube of the gear was originally sized at 1" so that it would bend before the fuselage gets damaged? (Easier to replace gear legs than a fuselage...)
The tube does not bend it folds and props hit the ground and it's a bad day. It was not easy to fix the fuse but I did not have to replace the prop or engine mount or .... Don't know for sure but that is why I think the horizontal tube at the top of the cabane V may have saved the fuse. The geometry of the gear mounts on the fuse are not correct for a cabane style gear and causes a twisting moment on the longerons. If you look at cub mount tabs you see the gear leg is inline with the center of the longerons.
I will see if I can find some pics to post.
Cabane "V"
I did a poor landing to a steep hill and hit HARD No damage to the gear but major damage to the Fuse Longeron twisting and buckling diagonal tubes.[/QUOTE]
I've often thought that if the center of the V of the cabane was connected to the center of the seat truss, it would take a lot of stress and twisting action off the longeron/landing gear mounts. When/if the V flexes downward, it has lots of leverage pulling in on the sides of the fuselage. By tieing the V to the strong seat truss, it wouldn't flex downward and would'nt then be pulling in on the longerons. Never had anyone come out and say they agreed with me, but that's what I think! :-) It would actually be pretty easy to do as well....JImChuk
Jim,
I agree there is an inward component to the cabane V loading but I believe the horizontal cross tube would take care of it. Also attachment to the fuse rather than a cabane V puts the tension bars at a steeper angle and increasing there load.
I find the drop tests on YouTube interesting, I intentionally did mine with small tires at high pressure and greased slide plates to see what the gear was doing without deceleration due to tire squish. So my test at 5.5" droop is probably equivalent to squishy tire drops of at least twice that. I designed my gear springs to go solid at 3 Gs I don't think they went solid during the drop test. Also note the lack of rebound which is what I was going for. The Beringer gear test shows rebound at first but I believe that is the squishy tires.
Dave
Re: Landing gear choices...
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