Denny Anspach <danspach@...>
I have noted Tony's caution that within bounds simply measuring breaking coupler breaking strength may not be too useful in judging coupler quality, if for the only reason that this kind of stress would be experienced only in a true minority of real-time model operating climates.
In this regard, Dennis Storzek told me a number of years ago that he tested the original Accumates by hanging a weight to the end a small string of cars equipped with Accumates that were in turn held on a sloping section of track attached to the ceiling of his basement (where he would leave them). The Accumates were in industry-standard Kadee/Athearn boxes, presumably the ones moulded on Accurail cars. He conducted the experiment both with reference to time, and to weight. The Accumates did finally fail over a certain length of time and with a certain level of weight, but the failure was not in the knuckle, the coupler head, or in the coupler shank per se, the failure was that the coupler shanks eventually twisted within the relatively loose box, opening the coupler halves in the process. Although I do not know this for certain, I have a feeling that it was the observation of this type of failure that persuaded him to design his new Accumate Protos to be engineered with the box as a true integrated system (the AccProto cannot twist or droop in its box).
I have heard before of the occasional scissors-like splitting of the Accumates when being pushed. I have had some occasional issues with Kadee 5s under the same circumstances (the coupler knuckles are pushed open, and for some reason do not close fast enough when the pressure is released) but this is has not been a memorable issue for me.
I have thought up a simple experiment in this regard with the Accumate Protos, and will report my results.
BTW, take a good look at a photo in Don Fiehmann's recent RMC article on maintenance where he depicts graphically the potential problems posed by couplers with draft angles drooping out of loose coupler boxes. That one coupler is higher than the other is only a part of the problem.
Denny S. Anspach, MD