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Steam & Excursion > Walschaerts and Baker valve gear difference

Date: 01/05/21 18:27
Walschaerts and Baker valve gear difference
Author: NYCStL776

I was reading through some of the dimensions of the Wabash O-1 4-8-4s when I noticed that the weights listed for 2900-2919 (walschaert) and 2920-2924 (baker) were different, with 454,090 pounds listed for the walschaerts equipped engines, and 459,290 pounds listed for the baker equipped engines. What about the valve gear would account for such a difference in weight? Thanks

Date: 01/05/21 19:39
Re: Walschaerts and Baker valve gear difference
Author: wcamp1472

I'm guessing here...

Baker valve gear operating mechanisms are identical moving pieces..
According to the BEST location, the 'support frame' ( Gear Frames) 
can be either of two types....

The Gear Frames can be the ' short frame' and the 'long frame'.

Walschaert gears use a modest, one-piece casting to support the trunion pivots
of the Walschaert swinging link.   The support carries one pivot point, and can be 
located between any two drivers ... and allowances are made in the lengths 
of the radius rod ( operates the valve stem) and the eccentric rod
( connects to the eccentric crank).

( Note: There are also 'long supports'  brackets--- reaching around a driver --- used with many
Walschaert reverse link pivots.   But the weight of those brackets was not vendor-provided 
part of a Walschaert  valve gear.    If you bought  Baker Gear, you specified the type of
bracket you needed.   The bracket is in the crate with the gear links when sold to the builders).

The Baker bracket has two major pivot points.... their relationship in spacing is the same :
for either the long frame vs, the short frame ( gear frame).  

Long fame Baker gears typically reach over one of the drivers, like the #2 drivers 
on 4-8-4 locos.  The gear frame is soecific to the location of  gear, and the long frame
would be of considerable weight,  with one in each side.

Typically, 2-8-X locos use the 'short frame',  Four wheel pilot truck locos, 4-6-X & 4-8-X 
use the 'long frame' Baker gear.

Long frame vs. Short Frame is where the weight difference lies.
The Baker yokes , levers and bell cranks are the same, identical 
parts, regardless of the supporting frame style.

A loco carrying two long-frame Bakers will weigh more than a loco carrying 
a simple, one-pivot Walschaert link,  on each side.


Edited 4 time(s). Last edit at 01/06/21 04:13 by wcamp1472.

Date: 01/06/21 06:14
Re: Walschaerts and Baker valve gear difference
Author: bigmc83

This website provides some information on your question at hand, also mentioning that the piston diameter was slightly different depending on the valve gear type, which may have also attributed to the weight difference.



Date: 01/06/21 07:07
Re: Walschaerts and Baker valve gear difference
Author: wcamp1472


( a technical clarification...).
The reference you made talks
about the piston (spool) valves’ dimensions; i.e., larger valve sleeve bores, NOT the cylinder bore
of the power pistons.

One advantage of larger diameter spool Valves is the greater area
( larger bore circumference ) of the port opening, compared to the smaller Bore, listed for the Walschaert equipped locos, of this order.

The opening( “lead”) of the spool valve would be the same for both the Walschaert & and the Baker
‘Gears’, since the “combination lever” is the controlling lever at the
beginning of the piston stroke
( ‘dead center’ ).

The larger valve bore ( on the Baker ) should primarily benefit the more rapid release of the exhausted steam, especially at very short cut-offs;  important to reduce
cylinder ‘back pressure’ during
steam release and exhausting.


Posted from iPhone

Edited 2 time(s). Last edit at 01/06/21 07:24 by wcamp1472.

Date: 01/06/21 08:01
Re: Walschaerts and Baker valve gear difference
Author: wabash2800

I don't have references handy, but I believe if they were like the M-1s, there were some other hardware differences within the class. Wabash railroaders said they were great locos. As Baldwins, and with their all-weather cabs, they were beefier looking than many other 4-8-4s with the exception of some others like on the Santa Fe and Union Pacific, IMO. Surprisingly, a Wabash president at the time is quoted as saying (who had been a bean counter) that the M-1 and O-1 were locos not needed. He seemed to suggest that the "Big Mikes"  on the roster would have sufficed. But the 4-8-2s and the 4-8-4s were greatly appreciated and needed during the war years. First-hand accounts exist of Wabash engineers accelerating and running fast with these locos. 

Victor A. Baird

Edited 1 time(s). Last edit at 01/06/21 08:06 by wabash2800.

Date: 01/06/21 08:15
Re: Walschaerts and Baker valve gear difference
Author: bigmc83

Thank you for the great description and clarification.  I am by no means a steam expert but I learned something!

Date: 01/06/21 09:47
Re: Walschaerts and Baker valve gear difference
Author: wcamp1472

I appreciate the effort that you made in researching the issue.
Your comment allowed others to benefit from your research, and 
they, too, can learn.

After 1970, there are no 'steam experts' .... we are all at different 
points on the  'steam learning curve'.....  compared to the steam professionals 
from before 1960...

Make no apologies.... even today, I learn something new about steamers...
the field is so vast,  and I'm so 'new' to the field....

I'm very enthused that Gary has encouraged new students to become involved...
wuth hand-on experiences and support for curiosity-hungry future mechanics.

Passing on the mechanical learning-experiences is the most crucial aspect of Loco preservation.
These 'newbies' are so lucky to be able to access the steel and steam of producing a 'live',
operational steamer..

Thanks for your contribution.


Edited 1 time(s). Last edit at 01/06/21 09:51 by wcamp1472.

Date: 01/07/21 09:02
Re: Walschaerts and Baker valve gear difference
Author: NYCStL776

Thanks to all for the knowledgeable replys, it is greatly appreciated.

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