Re: Kadee 158s and scale appearing coupler boxes

Dennis Storzek <destorzek@...>

--- In STMFC@..., Tim O'Connor <timboconnor@...> wrote:

But Dennis, you make polystyrene coupler box covers for
most of your kits, and nearly every other manufacturer
does the same thing.
So? We want to do better.

If the hobby isn't up in arms about
the boxes falling apart, don't you think that the glue
must be working? (Yes, I've had a couple dozen failures
over the years. I glue them back together.)


The Accumate box does more than just hold the coupler to the car, it also has to hold the parts in line. In our initial destructive testing of the full size Accumate, the common failure mode was to have the two shanks spread so far that the interlocking peg would come out of its mating recess and jam the shanks against the coupler box cover, which had to bend down to allow this to happen. The acetal coupler moldings would normally survive intact, and would work again when manually returned to centered. But, if the lid had taken a set, the couplers became more prone to doing this a second time.

Our full size coupler box covers are .044" thick, on average. In order to put the PROTO:HO parts in a box that fits within the outline of the prototype, the box needs to be .020" A quick look at typical physical properties of high impact polystyrene vs. acetal shows that acetal is two to three times stronger, stiffer, and more break resistant (less notch sensitive). If these were appearance parts on static models would be one thing, but they are not. People expect to run these in thirty or fifty car trains, and the occasional "oopsie" when a locomotive hits a standing train at a scale 50 MPH is a fact of life that people expect things to survive without suffering damage. The fact that the parts must be installed with screws just reinforces the fact that we INTEND the parts to be installed with screws, for the sake of durability. I'm satisfied that we are providing parts made of the material that is best suited to the purpose.


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