Author Topic: B&SR Question Two  (Read 3503 times)

Herb Kelsey

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B&SR Question Two
« on: February 09, 2012, 01:02:04 AM »
This question concerns the vacuum brakes used on the B&SR.  Were they "automatic" vacuum brakes or the older straight version?

Why do the locos sometimes have the can (muffler?) on the ejector pipe and sometimes they don't?  Were the brakes on the engines vacuum also or were they steam rams?

OK, more than one question but that happens sometimes!  :D
Herb

Mike Fox

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Re: B&SR Question Two
« Reply #1 on: February 09, 2012, 01:49:36 AM »
Hope someone knows the answer. Seems interesting. I never gave that a thought.

I know some had the muffler where you could see it, above the cab, and others were not in such a noticeable location. I never studied up on the workings of the vacuum brake system.
Mike
Doing way too much to list...

Jeff Acock

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Re: B&SR Question Two
« Reply #2 on: February 11, 2012, 03:12:05 AM »
I am far from an expert on braking systems, so take the following for what it's worth....
To my knowledge, there really wasn't an "automatic" vacuum system to correspond with the more common straight or automatic air brakes.  The Eames vacuum brake (the most common type) operated comparably to a "straight air" system.  It was a simple and cheap technology, which is why so many narrow gauges used it.  Briefly, steam under pressure was ejected through a venturi connected to the train's brake line creating a vacuum in the line which acted on a diaphragm on each car (usually the engine as well).  The diaphragm was connected to the brake linkage, and acted by pulling on the linkage rather than pushing as the Westinghouse system did.

The chief advantage to the Eames brake, aside from low cost & simplicity, was that brakes were instantly available any time steam was up.  There was no lag time between brake applications as with air brakes where the air reservoirs must be refilled after release before brakes can be re-applied.  The disadvantage was that there was no fail-safe feature.  A reduction in steam pressure, vacuum leakage in the line, friction on the brake rigging could all have a deletrious effect on stopping ability.  The system was not considered adequate for trains of more than ten cars.

Some later versions of the Eames brake placed the ejector nozzle in the smokebox, which might explain the apparent lack of a muffler.

If you happen to have a copy of Hilton's  American Narrow Gauge Railroads there is a fairly good description of the Eames system, with machine drawings, beginning on Page 187.
J

John McNamara

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Re: B&SR Question Two
« Reply #3 on: February 11, 2012, 04:16:35 AM »
Ellis Walker's 2-Foot Musing No. 43 in the July/August 2009 WW&F Newsletter has some additional information and some diagrams.

-John

Richard "Steam" Symmes

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Re: B&SR Question Two
« Reply #4 on: February 11, 2012, 04:31:16 PM »
The late Charles A. "Carl" Purinton, an early advocate of the live steam locomotive building hobby in America, used vacuum brakes on his 1-1/2" scale trains.  He built the whole system from scratch, and they worked very dependably, were reasonably simple to maintain, and many other builders copied them. A simple piece of rubber tubing between the cars was all the connection you needed. Keith Taylor may be able to add more to that aspect of the live steam hobby.

Richard Symmes

Keith Taylor

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Re: B&SR Question Two
« Reply #5 on: February 12, 2012, 02:54:37 AM »
To my knowledge, there really wasn't an "automatic" vacuum system to correspond with the more common straight or automatic air brakes. 

I don't know if it was ever used on this side of the Atlantic, but there were certainly "automatic" vacuum brakes in use in Europe and Great Britain. You can read about this type of brake here: http://en.wikipedia.org/wiki/Vacuum_brake
Keith

Steve Smith

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Re: B&SR Question Two
« Reply #6 on: February 12, 2012, 04:51:21 AM »
Here's a further source of info on the basic principle of operation of the automatic or "fail safe" type vacuum brake used in the U.K.
http://www.railway-technical.com/vacuum.shtml

Herb Kelsey

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Re: B&SR Question Two
« Reply #7 on: February 12, 2012, 05:12:42 PM »
Thanks fellas!  I have access to Ellis' write up and will go do some study.  Thanks again.  This is a great board! :)
Herb