I'm the guy that had the double ACME Gen 1 shock failure.
See the "ditch" that caused the failure in the picture. I was rolling with the tail up when I went across the "ditch", perpendicular to it, right to left. You can see the bare dirt on left side from the 31" Bushwheels and tail far left in same picture. It was a very short and soft "landing". Didn't even pull the shoulder straps. Speed was rolling, not at flying speed but faster than normal taxi speed.
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My point to Acme was shocks had to be too weak because nothing else in the whole landing system was damaged. All bolts where straight as new. Reused all parts except cabane vee and lower wing strut forks even though all where straight my mechanic didn't want to risk it.
When I purchased the shocks it was advertised on Acme web site and verbally as able to fail in tensile or pull test at 19,000 lbs. When in fact it failed at close to 9,000 lbs in the DER report and a later actual test by Acme.
I paid for the DER report which concluded the below summary. Acme did the actual pull test after I had had the DER test done. They used the wrong type metal and not enough material in the design.
The failed shock caps are made out of aluminum, not steel.
From DER report;
In Summary,
The ACME end cap will fail at a calculated load of 17,068 Lbs.
The OEM end cap will fail at a calculated load of 48,899 Lbs.
According to this analysis, the
OEM end cap is capable of supporting 2.86 X the load of
the ACME end cap. In addition the OEM upper end cap is manufactured out of a ductile
non-brittle material much more appropriate for the type of loading.
I'm fully aware I'm the test pilot when experimental. But in the pursuit of a better off-road ride I wanted to believe what I was told.
Also was told verbally by dealer that shock travel was close to 6"+ and safety cables wouldn't be long enough. So I didn't have cables on. I do now. Turns out travel was/is closer to stock 3". Dealer later said I misunderstood the 6", he meant 3"+3"=6" right, now I understand!
In the end the, dealer sent me a replacement prop and a hard time. The dealer is an attorney and the repair bill I was asking help with was $10K
No point in court to force the issue as $10k in attorney fees is about 4 days and 3 letters worth of fight.
I'm not willing to have Acme warranty the shocks for lack of trust. I have the stock bungees from Cubcrafters on our Carbon Cub, working just fine.
We had a great mechanic get us back in the air, made our trip with a week delay and got a very nice mountain caribou in spite of the setback.
At this point I just want everyone to be better off after my learning experience. That includes all parties.
I do feel good that my incident (that nobody got hurt in) caused Acme to make changes and "recall" all Gen 1 shocks.
This was Aug 2016, I'm past expecting anything to happen except the learning.
Fire away with thoughts.
Peter