When hearing the exhaust of a steam locomotive, you can hear a repeating pattern in the chugs. One is chug is always louder than the others.
What causes the rhythm? and why is one chug louder than the other 3?

and is this correct? you hear one exhaust from one piston and the next chug is from the opposite side, and repeating?

thanks

adofmsu@aol.com

> When hearing the exhaust of a steam
> locomotive, you can hear a repeating pattern
> in the chugs. One is chug is always louder
> than the others.
> What causes the rhythm? and why is one chug
> louder than the other 3?

If the valves are set properly this will not happen. There should be four identical exhausts. An engine so set is said to have "square valves", or to be "square". The sound is very pleasing when you understand what it represents.

This having been said, it is difficult to accomplish and frequently an engine will be off slightly. It takes great skill to set valves for a perfect 1-2-3-4 rythem. In the old days this work was only done in the back shops, not the roundhouse and one man was assigned to this work AFTER he had proven to have the special skill necessary to set valves.

An engine that is badly out of square sounds sick and will not pull maximum tonnage.

> and is this correct? you hear one exhaust
> from one piston and the next chug is from
> the opposite side, and repeating?

> thanks

A steam locomotive is actually two steam "engines", one on each side of the locomotive and capable of independant operation in the event of failure on one side. Of course hauling capacity will be reduced, but you can at least get into a siding and not tie up the mainline. Just don;t stop on the dead quarter!
One is set a quarter ahead of the other side.

There are 4 quarters to each revolution of the drivers. 1-2-3-4 1-2-3-4 Then on a 3 cylinder engine you get 123-123-123 123-123-123 or 6 chugs per rev. On geare dengines its 10 (?) chugs per very small diameter drivers, so it sound like 80mph instead of 8 mph.

A compound engine sounds 1-2 1-2 1-2 1-2 in same time space of 1-2-3-4



Railway history and stories
oldtimetrains@rrmail.com

If you didn't click on the above link to Raymond's website, it is worth a look. Lots of Canadian railway information there!

ryarger@rypn.org

Consider that since the front half of the piston usually did not have a piston rod in it's steam space, but of course the bore was the same, the force (and sound) of the front was greater than that of the rear half. The area of the piston rod subtracted from the area available to steam presure in the rear half of the cylinder.
In other words, the rears were usually slightly less powerful than the fronts. If you add to that the usual situation of one cylinder having a slight leak in a piston ring or valve rod packing, etc. it is easy to arrive at at a "1-2-3-4" beat when logic tells you they should all be the same.

The locomotive that had full piston support via the piston rod going through the front cylinder cover? Are any like that still operating or preserved?
S'
David D.

djdewey@cncnet.com

The locomotives I've seen that have a rod through the front cover usualy have the valve stem traveling all the way through in order to provide timing for additional cylinders, (such as the gresley valve gear.) There are two gresley valve geared three cylinder simples preserved in the U.S. One, U.P. no. 9000 is in California, (in a Sacramento park, I believe.) The other, A&S no. 12 is a lowly 0-8-0 in the collection of the Museum of Transport in St. Louis. Baldwin no. 60,000 was also a three cylinder locomotive, but she was a compound, with a single low pressure cylinder between the frames. She may alos be similairly equipped, but I am unfamiliar with her valve gearing pattern. (Probably not Gresley, as ALCO built them under permission from L&NER since Gresley was a personal friend of an ALCO bigwig of some sort, and Baldwin probably did not have a similair agreement. Both UP 9000 and A&S 12 are ALCO products built under this agreement.) It strikes me as possible that you might extend the piston rod out the front in order to power some auxilliary or other, but I don't recall having ever notived that. There are several Gresley's opperating in Brittian. There are a number of three and four cylinder starights of various sorts opperating in continental Europe. None of the U.S. examples opperates. (After about 1910 very few locomotives with more than two cylinders were built in the U.S. save for "Mallet" types so popular in mountain divisions. Those that were built with more were generally converted to two cylinder opperation before they were retired.)
Sincerely,
David Ackerman

david_ackerman@yahoo.com

> The locomotives I've seen that have a rod
> through the front cover usualy have the
> valve stem traveling all the way through in
> order to provide timing for additional
> cylinders, (such as the gresley valve gear.)

David,

How does a longer rod out the front of the cylinder affect the valve timing?

Thanks.

BLW 60000 has two sets of Walschaert's valve gear on one side, the second to work the inside cylinder. Some Gresley 4-12-2's were rebuilt with a third set of Walschaert's also.

PRR used extended piston rods around 1920; I wouldn't be surprised if K4s 1361 were once so equipped. I believe the Germans continued the practice.

Electric City Trolley Museum Association

I believe the term you are looking for is "tail rods". Their purpose was to provide support for the piston so that the wear on the cylinder lining was reduced. Since the weight of the piston was not being supported by the cylinder wall, and only the rings were riding on the bore, wear was much reduced.

Tail rods fell out of practice on locomotives in the 1920s. They were very common on large stationary engines such as our Tod Engine. With a piston 68" in diameter and a 11" piston rod that would be alot of weight bearing down on the cylinder bore. So a tail rod was used to support this weight, and after 65 years of service the cylinder bore is still in good shape. For a pic click on the link and look for the photos of the engine.

Tod Engine Foundation

todengine@woh.rr.com

Perhaps this would also be called a tail rod. On a locomotive with three or more cylinders on one frame valve timing must be provided for all cylinders inside the frame. The most conventional way to do this was with something similair to a Stephenson valve gear between the frames, along with the relevant cylinder or cylinders. The shop crew of the L&NER devised what they felt was a better solution, where the valve timing of the third cylinder was the "inverse sum" of the outer two. This timing was supplied by a series of links in front of the locomotive, affixed to the "tail rods" that extended forward from the valve pistons. (assuming that that is the correct name in this case. I appologize, as I'm unsure.) It's something of a historical curriosity that Gresley was apparently opposed to the use of this valve gearing arrangement until it was demonstrated to him by his mechanical department. I gather that it was a symptom of Brittish shops that the superintendant or foreman, (Gresley was in charge of locomotive designs and shops for the entire road. I forget what his title was according to Brittish practice,) received all credit for any inovations on that road, whether he instigated or even approved of them. The same accusation has been bandied agaist the Edison laboratories, in as much as Mr. Edison apparently received credit for designs created by his employees. In any case, that's about the best I can describe it without recourse to a picture. As has been noted in a previous post, the Gresley valve gear fell out of favour in U.S. practice, and was replaced with an independant set of Walschaerts valve gearing leaving one side with two sets. (That would be something to behold in opperation.) I believe that the center cylinder was prone to overtravel if the timing was out of adjustment, leading to an unbalanced work load, and undue wear on the center cylinder, (cooincidentaly the most difficult to maintain, due to it's position between the frames.) It remained popular in Brittish practice however, possibly due to the advantage it would provide in a modest reduction in axleload by eliminating the need for much heavy machinery. (European axleloads were consistently much lighter than their U.S. counterparts. Brittish weights were particulairly so.)
Sincerely,
David Ackerman

There's a good book out there titled "Locomotive Valves and Valve Gears" you can get to learn everything you ever wanted to know about locomotive valves. It's got great line drawings and detailed descriptions of different valve configurations. Lindsay's Books sells copies for about $20.

And some from Slovakia


http://mercurio.iet.unipi.it/pix/cz%2Bsk/steam/477/477sl01.jpg
lamontdc@adelphia.net

The British steam engine at Green Bay, "Dwight D. Eisenhower" #60008, has tail rods. The link below shows the engine, but you can't really see the tail rods.

Frank Hicks

Photo of #60008
frank@gats.com

The Northern Pacific W-3 Mikes had tail rods as built, and although most of them had them removed over the years, the sole survivor of the class, SP&S 539 (ex-NP 1762) still has hers.

SP&S 539
rjenkins@railfan.net

> The locomotives I've seen that have a rod
> through the front cover usualy have the
> valve stem traveling all the way through in
> order to provide timing for additional
> cylinders, (such as the gresley valve gear.)
> There are two gresley valve geared three
> cylinder simples preserved in the U.S. One,
> U.P. no. 9000 is in California, (in a
> Sacramento park, I believe.) The other,
> A&S no. 12 is a lowly 0-8-0 in the
> collection of the Museum of Transport in St.
> Louis. Baldwin no. 60,000 was also a three
> cylinder locomotive, but she was a compound,
> with a single low pressure cylinder between
> the frames. She may alos be similairly
> equipped, but I am unfamiliar with her valve
> gearing pattern. (Probably not Gresley, as
> ALCO built them under permission from
> L&NER since Gresley was a personal
> friend of an ALCO bigwig of some sort, and
> Baldwin probably did not have a similair
> agreement. Both UP 9000 and A&S 12 are
> ALCO products built under this agreement.)
> It strikes me as possible that you might
> extend the piston rod out the front in order
> to power some auxilliary or other, but I
> don't recall having ever notived that. There
> are several Gresley's opperating in
> Brittian. There are a number of three and
> four cylinder starights of various sorts
> opperating in continental Europe. None of
> the U.S. examples opperates. (After about
> 1910 very few locomotives with more than two
> cylinders were built in the U.S. save for
> "Mallet" types so popular in
> mountain divisions. Those that were built
> with more were generally converted to two
> cylinder opperation before they were
> retired.)
> Sincerely,
> David Ackerman
The two main examples of the Gresley valve gear in America, Alco built 3 cylinder locomotives U.P. 9000 (4-12-2) and S.P. 5021 (4-10-2)are both well preserved and displayed at Los Angeles County Fair Grounds in Pomona, Ca. (not Sacramento) The 5021 was actually steamed in the San Bernardino Santa Fe yards before being moved to the current location.

edwinsinclair@hotmail.com