3-cylinder locomotive

[Anonymous]

I'm looking for details on how 3-cylinder locomotives work, can be quite technical (electromechanical engineer in past life).

[Anonymous]

The only 3 cyl locos that I am aware of were steam. Shays, and 4-10-2's. There may have been a few other wheel arangements, IHB 0-8-0's come to mind too, but they only had 3 of them.
I might be wrong here, but as far as I know, the major diesel-electric builders ( EMD, GE, ALCO, Baldwin, Fairbanks-Morse, etc.) never made a locomotive with less than 6 cylinders. That 6 banger title would go to EMD's SW-1. 6 cyl 567, with 600 hp. GE, had the U-18-B, 8 cyl. FDL engine. ALCO, of course, was a pioneer with their 6- cyl. 539 engine used in the switchers of the '40's and '50's. Unless you get into small critters made for industrial customers, I think that is about it.
For great info on the 3-cyl. steam locos, I would suggest the book " Three barrels of steam", by a fellow named "Boyington" published in the early "70's. I have not seen that book in a very long time, it used to be in the public library in my old hometown. But, seek and ye shall find.
Hope this helps ya.
Todd C.

[sooblue]

Hi, I'm not expert enough to go into minute details but I do know that the third cylinder was between the frame and connected to the main drive axel which was formed like a crank. I belive that the valve gear was shared with an adjacent cylinder but 180 degrees off so the steam entered the piston opposite each others stroke.
I've never heard the exhaust of a three cylinder engine but I've been told it was quite off beat.
I can't imagine rebuilding that third cylinder It must have been a bear to do.
mike

[Anonymous]

Here in the UK the majority of Locos designed by Sir Nigel Gresley for the LNER wre three cylinder. an earlier reply was correct in saying that the third cylinder was between the frames.
The valve gear used was normally Walschearts on all three cylinders with separate geaers for each. however the grsley locos used a system that operated form the two outside cylinders via a 2 to 1 combination lever situated in front ob the cylinders. The calsses inclusde the A4 A3 for main line expresses. However due to expasion the middle cylinder sometimes 'overran' an caused damaged to the middle big end. Two classes the D49 and the B17 had the lever at the rear of the cylinders and thus negated to expansion problem. i sam building a 5in gauge B17 and watching the middle cylinder operate is a joy to behold. The cranks ( if the cylinders were parallel to each other) and had divided drive, ie the outside drove the middle axles and the inside drove the leading axle,were set at 120 degrees thus giving 6 beats per revolution. On the A4 and A3 locos the middle cylinder was inclined as all three sylinders drove the middle axle and therefore the middle connecting rod had to miss the leading axle. In this instance the spacing was slightly different in being 120 114 126. The Peppercorn classes A1 and A2 had diviided drive with three sets of WEalschearts gear.
The sothern had 3 cyl locos as did the LMS 'Royal Scot 'class
Any other questions email me off line. hope this helps

Ron

[BR60103]

Ron left out the other weakness of 3 (and 4) cylinder locomotives - the crank axle. The driving axle was split in the middle and the driven part was offset (as far as the rods on the outside were) from straight with 2 large metal castings holding it in line. This introduced a weakness right at the place where the most stress would be put on it.
--David

[Anonymous]

I forgot to mention the 4-6-0 designed by Sir Vincent Raven for the NER. They were also 3 cyl but had three sets of stephensons valve gear between the frames... that must have been cramped!

[Anonymous]

If the first axle was `U' shaped to rotationally clear the center rod, can I assume it didn't turn with the wheels? If it did, wouldn't there have been a huge vertical wobble plus on the upswing, wouldn't it have destroyed the valve gear there?

[BR60103]

Only the driven axle was U shaped. Sometimes it was the first axle, but I think second was more common; to match with the outside drive. The centre cylinder was mounted high so that the rods would pass over the first axle.
--David

[aussiesteve]

Over here in Oz the Victorian Railways built 4 Pacifics based on the Gresley model in the 1920's, later streamlining them to haul the Spirit Of Progress Express Pass. In 1941 they built a 4-8-4 with the center cylinder driving the 1st axle in order to overcome maintenance dificulties the experienced with the Pacifics. When diesels arrived in the 50's the pacifics where scrapped but the 4-8-4 (H220 Heavy Harry)survives in the ARHS museum in Melbourne, Victoria.