The Home Machinist!

The header says it. The rear beams of some tenders do and some don't. Why do those that do not, have not?

Greg,

I've never seen a written rule, but I would suspect that locomotives over a certain weight were given draft gear on the tenders to alleviate shock loads as slack ran in and out.

Heavier the engine, heavier the train, the harder the slack action was on the tender coupler. A small engine won't pull a train heavy enough to damage itself or the couplers, but with big engines pulling the throttle too fast could break a knuckle, pull the draft gear out from under a car, or even rip a car in half. The weakest link would be found.

I've seen the option for couplers with draft gear on Shay's of 50 tons and heavier.


Cheers,

Curtis F.

Hmmm, Curtis, makes sense. But then even cars in the link-and-pin days had draft gear and those most certainly were relatively light and short trains.

Please can you explain to a Brit what you mean by draft gear? Sounds like you are using the term to refer to a particular piece of equipment rather than generally.

Peter

The draft gear is the connection between the coupler shank and the car. Sometimes just springs for pull and compression and some wedges for fiction damping. Modern cars may have hydraulic units to minimize shock to cars from coupling forces.

The first image below is a cutaway of a coupler with draft gear.

The second image is a drawing (end-for-end compared with the first image) of one brand of draft gear from about 1922. Inside the gear you will see springs that, as mentioned in the post above, serve to soften the impact of starts and stops.

The third photo is of a rather sorry tender. You can see that the coupler is attached to what's left of the rear beam solely by a pocket that is bolted to the beam. This pocket is rather rough; looks homemade.

The fourth photo is a coupler and pocket without draft gear.

Greg,
Once again, don't know if I have a proper answer to your original question...

But, during steam days, steam locos would back up to take the slack out of all the couplers on the train. Then, as the loco pulled ahead, it would start the 1st car moving and then the 2nd car and so forth. This way, the loco wasn't trying to start the entire train all at one time. Perhaps any spring action in the draft gear would have created a "slinky" effect and be counter-active.

When the steam loco engineers started converting to diesel locos, some continued the same practice of "taking up slack". All too often they would end up pulling the coupler and draft gear out of the ends of the cars. I guess that says something about electric transmission!

Don't know if that helps you...take it FWIW. Maybe you could ask Cal T. the next time you cross paths with him. I believe he fired the cab forward mallets on the SP before they were retired. Carl B.

Interesting question and probably no correct answer except for the decisions of the Chief Mechanical Officer of the railroad making the order to the locomotive builder. He would certainly have to consider the weight and tractive effort of the locomotive. The tonnage the locomotive was expected to pull under normal operating circumstances was also of big concern. Even more so, cost was a big issue with new locomotives. It is common knowledge that wood running boards and cabs were good enough to get the engine off the builders floor and operational for a few years. The first major shopping might see a home made steel cab and steel running boards. Another way to cut costs was to order a wood tender frame with no fancy draft gear and run it until rot and the forces of everyday operation destroyed the frame. It could then be replaced with steel and maybe an improved draft gear. In the case of the V&T, it seems that economics had generated history and you have just a simple coupler pocket to deal with. A good reason to select a small engine to model.

It was also common to have a wood pilot beam from the factory as it too could be replaced in the future when the need came to pass. Many of the engine crews in the days of small steamers liked the way the wood pilot beams acted as a pseudo shock absorber during the many rough switching joints being made. The steel pilot beams and tender end sills were certainly stronger but transmitted the shock to the cab and crew in a big way.

Of further note, when the Sierra Railroad put #34 back to work in excursion service during the early 1970's, the wood end sill on the rear of the tender was done for. Rather than replace the big timber with more wood, they simply welded a few pieces of large channel iron together. The slightly warped weldment was strapped down to the big planer table and trued up in a few hours. The new steel tender end sill served well until the end of Crocker Family ownership of the Sierra.

Robert

Carl, your thought is an interesting conjecture but as I think about it, the result would only apply to half the action on the first connection, between the tender and the first car. By the time the forces got to the second car, both connections would have draft gear.

Robert, I think you may have an answer although I wonder how much would be saved by dropping the draft gear from the bill. But then, by adding that to all the other stuff, the total could be enough to think about. (I wonder if Baldwin could provide cast iron bells and tin whistles?) Sort of like buying a car. Slightly over a half century ago, you could get what was known as the "factory model." This was essentially a stripped down vehicle without arm rests in the door panels, no radio, no extra trim, plain cloth upholstery, and in some cases, not even a heater. Back in the 1950s when the middle class was very status conscious (perhaps they still are) we felt sorry for the folks down the block who could only afford a Hudson factory model. We had a Chrysler New Yorker Deluxe with two-tone paint (red and white -- stunning), white wall tires and power windows. Being the first kid on the block to ride in a car with power windows, I enjoyed demonstrating them to my jealous friends. So perhaps the Baldwin owners were jealous of the Alcos!

Thanks for the explanation guys.

Peter