Does anybody know what formula and/or the variables were that the steam locomotive designers used for calculating and determining the ratio of high to low pressure cylinder diameter?

Thanks,
Ray

> Does anybody know what formula and/or the
> variables were that the steam locomotive
> designers used for calculating and
> determining the ratio of high to low
> pressure cylinder diameter?

There are pages of formulas to cover what you ask, but for a real quick laymans explaination, the larger you make the low pressure cylinders in relation to the high pressure ones, the more power the high pressure cylinders will produce compared to the low pressure ones. It seems that most designs ended up with the LP cylinders being about 1.6 times the diameter of the HP ones to give approximately equal power.

With any given ratio, the actual power ratio will vary depending on how high the engineer has the reverser hooked. I understand that the french tried a mallet with seperate johnson bars for each engine to allow for optimum settings at different cutoffs. Wouldn't want to switch with that one!

It doesn't have any formulas but the new book
"The Great book of Trains" runs through a series steam locomotives and the fun they had compounding.
Inside, Outside and All around. If you read the different monkey motions that they used along with cylinder configuration, you will get some idea of the work done to salvage some of that steam shooting out the stack.



lamontdc@adelphia.net

Did any of the condenser locomotives compound and exhaust into an induced vacuum like marine steam?

Dave

irondave@bellsouth.net

Dave,

Most of the condenser locomotives were built by Henschel; the only main exceptions I can think of are the Swedish condensing steam turbine locomotives, of which I have little knowledge.

In the Henschel system, (applied to some members of the SAR class 25 and at least one "Kriegslokmotiv"), the exhaust steam was sent back to an air-cooled condensor in the tender. The condensed water was then returned to the tender tank.

The draft through the firebox was using a steam-driven induced draft fan in the firebox. This fan gave the condensing members of the SAR 25 class an unusual "inverted teardrop" shape, and engines a lack of any "chuff".

The trouble of keeping this fan running in such a dirty environment, along with all the "stuff" on the tender, practically nullified any efficency gains from running in condensed mode.

The Swedish turbine locomotive may also have had a condensor in the tender, but I am not certain about that.

BTW, the Class 25 and "Kriegloks" were all simple engines, not compounds. I am not aware of any compounds built with a condensor; it would have made a little more sense, but read above about the problems with condensor locomotives.

-James Hefner
Hebrews 10:20a

> Did any of the condenser locomotives
> compound and exhaust into an induced vacuum
> like marine steam?

> Dave


Surviving World Steam Locomotives
james1@pernet.net

In the book by Woods on compound locos the ratio is about 2.25 to 1 on cylinder volumes.

> There are pages of formulas to cover what
> you ask, but for a real quick laymans
> explaination, the larger you make the low
> pressure cylinders in relation to the high
> pressure ones, the more power the high
> pressure cylinders will produce compared to
> the low pressure ones. It seems that most
> designs ended up with the LP cylinders being
> about 1.6 times the diameter of the HP ones
> to give approximately equal power.

> With any given ratio, the actual power ratio
> will vary depending on how high the engineer
> has the reverser hooked. I understand that
> the french tried a mallet with seperate
> johnson bars for each engine to allow for
> optimum settings at different cutoffs.
> Wouldn't want to switch with that one!

> In the book by Woods on compound locos the
> ratio is about 2.25 to 1 on cylinder
> volumes.

In Baldwin's catalog for Vulclain compounds, they call for a 3 to 1 ratio.