Eames Train Brakes - Official Work Thread

[Tom Casper]

Very good news indeed!  Can it be scaled down to work on our 3 3/4 scale locomotives?

Tom C.

[Jeff Schumaker]

Congratulations, Jason & Jonathon. Your hard work has paid off.

Jeff S.

[John Kokas]

From the sound of it, it looks like you guys have made some improvements to the original patents.  I hope you will pursue applications for new patents on your work.  Who knows - there are lines in the world that still use vacuum brakes and you actually might be able to sell new systems based on your patents.

[Bob Holmes]

Super!  SO much work has gone into this for a long time.  This is a major step to working train brakes!

[John Kokas]

I certainly hope that #10 will also be equipped in the coming year.

[ALAIN DELASSUS]

Well done you both. That breaking system will definetely improve the safety when you'll roll down the mountain.

[Mike Fox]

Johnathan machining a guide for part of the vacuum brake chamber

[Joe Fox]

Just watched the test video, very impressive. Well done to everyone involved with the design and implementation.

In either case, I am excited to see the continued development of the vacuum brakes.

[Mike Fox]

Jason is doing some welding on the brake pots to keep the project moving..



Meanwhile, Jay Wiley is helping clean the new drill big in the foreground.

[Benjamin Richards]

I do have a question: Why only 21 inches?

One of the disadvantages of vacuum brakes is the relatively low working pressure. (Contrast an air brake, which can be operated at as high a pressure as one wishes to design for.) Wouldn't it make sense to try to squeeze as much power out of the measly 14.7psi as possible?

[Alan Downey]

A couple reasons.
Firstly, it's not measly. I'll let Jason chime in on results of testing the cars, but having been in the cab of #9 plenty of times when the engine brakes were applied, I can assure you that 10-15"Hg is actually quite sufficient for a rapid stop. You have to remember that (like 2 ft narrow gauge) vacuum brakes have a range in which the tradeoff of simplicity for pressure differential is best suited. Mile long freight trains at 60mph is not that application. Lightweight narrow gauge rolling stock? It works splendidly. Simply by increasing the size of the brake cylinders compared to what you'd see on a positive-pressure system, you're able to use a smaller pressure differential to achieve a desired application force.

Secondly, with any kind of system that has an absolute limit governed by natural laws (absolute zero, speed of light, perfect vacuum), it gets exponentially more difficult to achieve that limit as you approach it. It is not reasonable to have a system in this application that can both draw down the pressure in the train pipe from atmospheric pressure to vacuum both quickly, and "completely" to -14.7psi. The steam powered ejectors have a functional limit of about 21 inches (10.5psi), but they are able to make that pressure change relatively quickly.

It's not fair to just look at the pressure differential of a vacuum system and call it "measly". It fits within the context of a system which is designed around that differential to make use of it as is needed. In it's intended application it fits the bill quite nicely.

[Benjamin Richards]

Thanks. It was that second bit, the asymptotic limit, that I wasn't thinking about.

I meant no criticism by my question. It was not a, "Hey I think you missed something here," but rather, "I see this is standard practice and I wonder why."

[Gordon Cook]

Another thing to remember is that the actual pressure applied to the brake shoe is dependent upon how the force is transferred from the vacuum cylinder to the brake shoe.
On #9, if you look at the leverage that is gained by the arrangement of the brakes between the drivers, you can quickly see that the force from the vacuum cylinder is multiplied many times.

[Dag Bonnedal]

Good summary by Alan.

Could also be added that 21" vacuum is/was standard by most railways using vacuum.
Only Great Western Railway in Great Britain used 25" (and mechanical pump instead of small ejector) with a lot of compatibility problems.

Dag

Added:
Going thru half-a-dozen steam loco manuals from Sweden, Denmark and India, non of them states a nominal value. But mention 19.5 - 21.5 inch as normal.

[Bill Reidy]

Reviving this project thread, as a lot of work has moved this project forward, largely hidden because progress reports have been embedded in the forum's monthly Work Reports, or as part of the J&S Truck Rebuild thread.  The May/June 2023 WW&F Newsletter did include a detailed project report by Jason Lamontagne.

Some of the latter posts this year in the J&S Truck Rebuild shows the vacuum brake hardware installed on the trucks, starting about here.

As noted in the Newsletter report, Jonathan St. Mary and Joseph Gilbert constructed a cycle tester to verify the long term integrity of diaphragms and bellows, which have exceeded 30,000 cycles without failure in both warm and cold temperature testing.  Before work started on the B&SR flatcar No. 34 trucks, Jason restarted the testing unit yesterday, Saturday, December 30th, explaining its operations to those of us present.  The testing on this cylinder, set up a while ago, surpassed 23,000 cycles yesterday.