Fascinating pictures
Notice how the gear just bent at that one spot, fairly skinny section near the axial end. It clearly exceed the tensile / bending strength of that cross section.
My suggestion, theory, SWAG (Scientific Wild A** Guess) is making the gear stiffer both in deflection side to side, forward to aft, but rotation of the axial or twisting down where it plows the retainer nut into the dirt.
The tell-tail ground scar shows it hit and built a berm up until the force exceeded the strength of the skinny part of the gear. No matter what skid plate or fork you have, if you snag and the plane has enough forward momentum to carry the plane over, its a done deal.
The photo evidence is almost better than an experiment (sympathies to the owner/pilot); and I find it fascinating just as a technical challenge. Van should hire a guy to do FEM (finite element analysis - computer modeling of the structure) or do some practical test with the gear leg on a test rig mounted to a sled being pushed in a soft field, to get a grip on any design improvement possible. I'm not a great designer like Van, but I think the gear could be stiffer towards the axial end.
Compromise:
Van has said publicly and in writing (RVator) that his gear is a compromise of design goals, with the aside that may be he made it too much of a compromise (in so many words). That is why we like Van, he is a straight shooter. If he knows for sure he says, and if he does not know, he does not say anything.
You will never have a nose gear on a light fast sport plane that is as rugged as say the gear on a "bush plane". You could make a gear that could never get snagged or bend, but it would weigh a lot more and cost airspeed. The question is, is this a good compromise. I still think it is, but I could see Van adding a "heavy duty" nose gear option, with a 5x5 tire.
My band-aid idea stop gap would be to wrap the existing gear with a carbon fiber structural fairing, especially at the skinny end, which would make is stiffer/stronger. It would cause a little more drag due to larger (thicker) frontal area and add weight but not much. Look at a Grumman trike nose gear, it does not get super skinny at the axial end does it? For sure they use larger tires.
There is no doubt that the gear is strong enough for normal operations, takeoffs, landing and taxi but that snag load is too great sometimes and the gear is too springy, meaning defects in a way the deflection and than loads go unstable. That means the more deflection the less load is required to bend it, so it bends more until it yields (breaks).
It's a complicated dynamic problem. One solution is OVER BUILD, but than it is not the RV way. The reason our RV's go +200 mph on 160HP and not 110mph are these compromises. A U2 and SR71 are planes that have incredible performance but great compromises.
It's a stiffness thing not strength. Not sure a Titanium gear leg would help since we use pretty high tensile steel already. Again taxi slow, normal or fast walk speed, 8 mph or less may keep you safer. If he was doing 10-15 mph, it looked like he went over fast. No offense to any A-model drivers, we just care and not a A-model basher, stuff happens.
History: A friend who is a structural engineer owned a famous but ugly Piper Tri-pacer. The Tri-pacer, "flying milk stools" or toad-stool has a massive nose gear/tire and was one of the first widely produced trikes. He researched the history of the plane for his amusement and came up with some old historical pictures. The engineers didn't know what loads to design to. Yes there where FAR's so to speak, drop test and so on, but what is the real world loads. So one of their test was to drag and tow the plane across a plowed field, perpendicular to the furrows. Of course it has a steerable fork in-line with an oleo strut (ala almost every GA plane since). Well they ended up with a nose gear the size of a main gear. Of course the RV tapered spring gear and castering trailing axle design is different but may be the plowed field test might be a good idea? (or has that cow left the barn already)
May be the grumman is not that stout
is that a
rub or skid plate on the bottom of the fairing? (or repair)
