Grove 7075 spring gear too stiff, kitfox damage????

Regarding the 7075 spring gear problem with High-Wings aircraft (see his destroyed kitfox pics under “Kitfox IV Speedster & learning to fly” for details of the accident) . The question raised was that it appears 7075 aluminum gear may just be too stiff and unbending for a kitfox, and cause induced airframe damage, as outlined by Hi-wings kitfox in his blog.
I looked up ALCOA brand 7075 specifications, and compared it to their 2024 aluminum spec (which is the typical type used in experimental landing gear). They are indeed different, the 7075 has a greater Tensile Strength and Yield strength, however, it does flex and if flexed far enough, it does permanently bend. Looking at other spring gear, 2024 has been the most popular choice in the past, with some being made of 6061 too, mostly because it’s cheaper and very corrosive resistant. In general, 7075 just is not very popular for anything in homebuilt planes, maybe because 2024 is cheaper and available in many more sizes than 7075 and perhaps better understood by the general homebuilder or designer, even though making structural parts out of 2024 will typically weigh more than something made of 7075
With landing gear, really you want it to flex and return to normal position during normal landings and such. But, in a hard landing, or certainly in a crash landing, you would like it to flex and bend and deform permanently, thus absorbing energy. The last thing you want it to do is bend and spring back transfer the load to the airframe (as we can see the results from High-Wings picture below). So what’s the solution here? Go with proven 2024 aluminum gear or the Grove 7075 gear (which is lighter for the strength)? Well I am thinking the Grove 7075 gear can be a great landing gear choice, but the width of the gear and the thickness must be chosen correctly. Too thin and it bends to easily, too thick and it just transfers the load to the airframe and the pilot.
For the Kitfox model 3 & 4, Grove specs a 4” width gear made of 7/8” thick 7075-T6, which is stiff stuff. (I’m thinking 3/4” might be a better thickness, but don’t really know how to analyze this options). Fortunately, Gove also offers help in designing the specific gear needed for a client’s particular application. So perhaps working with Grove on a specific aircraft application will provide the best gear thickness for a flyers particular application. In my case, Tri-gear model 4 with a proposed Gross of 1250 lbs (and maybe some extra weight in the noise making it somewhat nose heavy).
Well that’s really just my take on it, next week I might just give Grove a call and see what they have to say about my specific kitfox application, and whether their 7/8” 7075 gear is indeed too stiff for the model 4.
Roger

Hi Roger, in your choice of landing gear, and depending on the type of terrain you plan on flying onto and off of, match your tire and suspension to meet your need

rogerh12- seems like lots of effort for a problem that doesn't need solving. The Grove gear is on hundreds of Kitfox's world wide and working great and performs exceptionally well. They are already model specific in design.

Grove gear have also worked perfectly on rv's for years, as well as tons of other types.

I'm pretty sure the Grove gents know their game and will have applied a suitable strength and weight of material for the application. I love Grove gear and think it is the very best upgrade that anybody can give their Kitfox.

Robbie Grove designs and sizes the gear for the aircraft gross
weight plus allowance for those of us that misjudge the distance
from our wheels to the runway surface. The gear on my 1320#
SS is 4" wide as opposed to the 1550 gear width of 4.5".

Phil Laker