• Old passenger car diaphragm as a shock absorber

  • General discussion about locomotives, rolling stock, and equipment
General discussion about locomotives, rolling stock, and equipment

Moderator: John_Perkowski

  by VPayne
Old passenger car diaphragm as a shock absorber
I have heard the comment made that the old heavyweight cars used a lot more pressure on the between car passage diaphragm striker plate, is this the correct term, up until the time that more modern tightlock couplers and rubber draft gear were employed. I suppose the increased pressure was to prevent slack from developing in the connection between cars, or at least to keep all the components consistently pressed against one side of the tolerance. Is this correct?
I have also heard that the contact pressure and friction between adjacent car’s striker plates helped to brace one car against the other so that the effects of roll and bounce were lessened as each car had the adjacent car to use as a rolling reference. Is this true and is the effect beneficial to the overall ride of the train? I am currently in Japan for the remainder of this week, where I can observe that both the regular express trains and the shinkansen trains use a link above the between car passageway on ordinary two truck, drawbar connected, stock that is tied off to one rotary shock absorber mounted on opposite sides of the adjacent cars end sheets. So the rotary shock absorber arm is vertical, it axis is in line with the length of the car, and the link connects a shock absorber on the left hand side of the leading car with one on the right hand side of the trailing car. The ride is noticeably better for such cars on the same track but I am comparing swing link, coil spring cars, to air bag primary suspension cars equipped with the link.
Now the application to North American practice is that I can think of a lot of ways to achieve a similar effect in cars that could be joined by a knuckle coupler and separated with no additional work. Once such a link is created you might as well put Head End Power connection points on it and make the HEP an automatic connection, leaving just the reservoir and train line air to be connected. The coupler could even be made to be self-centering. Any thoughts on such an idea? I will hopefully be able to get pictures up when I return as well as a sketch if anyone is interested.
Virgil Payne

  by steemtrayn
The spring pressure on the diaphragms keeps them in contact with each other, thus sealing out the elements.
it has no effect on slack control that I'm aware of. Also, tight-lock couplers do not prevent slack, they jusy hold the train together in case of a derailment.
  by VPayne
I thought that it was the early steel heavyweights that had a bit more pressure on the stricker plate. Once the lightweight cars were coming into being advances in draft gear had lessoned the need for slack control. Of course the tightlock coupler's main function is to prevent disengagement in the vertical direction, but I thought that the tolereances at the knuckle became tighter with the adoption of tightlocks or perhaps in the standard coupler before them. Please correct me if I am wrong on the historical aspect.
However, what I really want to know about is if any attempt has been made in North American passenger cars to brace on car against the next car so as to prevent roll and bouce. Of course the Turbotrain had some intercar links as does the Talgo, but to my knowledge no bracing link has ever been created between coupler connected stock in N.A. Do the new VIA cars have couplers that are braced in some way back to the carbody? Of course most of the intercar couplers are not knuckles but some other form.

  by txbritt
I do know that diaphram pressures can keep passenger equipment from coupling at slow speeds. We were switching out the equipment at the museum a few months back with a railking. At every joint we made we would have practically slam the cars ( 4 or 5 mph ) to compress the diaphram assembly. When uncoupled, the diaphram frame extends so it is even with, or exceeds the length of the coupler. It was a pain in the butt.

The tightlocks we had showed no slack that I could detect. When pulling a cut that had been sitting with the slack run in, the only movement was in the drawbar/frame connection, and that was very slight.


  by cb&q bob
One of my books on Union Pacific steam locomotives talks about early applications of diaphragms on the rear of locomotive tenders. In this book it states that the purpose was to help stabilize the tender from verticle and lateral swaying. Apparently they were'nt really needed or were'nt all that successful because the railroad discontinued their use after not too long but it shows that the mechanical departments did hold some value in using the diaphragm as a motion dampening device.