I am curious about a few aspects of steam locos and the way their drivers were quartered. I understand that the left and right drivers were out of sync, usually by 90 degrees. Was there any preference or rule of thumb for which side led - was 90 degrees ahead of the other? I have heard that some locos were run with a closer quartering - I have heard 80 degrees was used. What are the potential or imagined benefits of such an arangement? Finally, was there any effort to synchronize the quartering of the front and rear drivers on a Mallet? I can’t imagine that there was due to the possibility of slipping one set but not the other, but I have been wrong before.
Two cylinder locomotives always used 90-degree quartering; with this arrangement, the power pulses were more even than they would be with any other setting. They weren’t perfect, but as good as could be gotten.
Most railroads had the right side crankpins leading the left. In other words, when the right rods were at their lowest point (the “bottom quarter”) the left side was on front dead center. The Pennsylvania was the biggest user of left-hand lead locomotives. Someone theorized that it was because PRR had so much multiple-track territory; the most solid part of a multiple-track roadbed is toward the center, and since the side of a locomotive that has the lead is the side that pounds the track hardest, PRR wanted the locomotive to pound the most solid part of the roadbed - the left hand side.
Three-cylinder simple locomotives had the crankpins 120 degrees apart; the setting of the inside cylinder couldn’t be seen, but the two outside cranks were 120 degrees apart and the inside one 120 degrees from each.
Baldwin built an experimental three-cylinder compound 4-10-2 in which the driving wheels were quartered with left-hand lead. The center cylinder was the high-pressure cylinder and its crank was 135 degrees from the outside cranks. This locomotive exists today at the Franklin Institute in Philadelphia.
There was never any effort made to synchronize the two engines of either a Mallet or a Simple Articulated or a Duplex-drive locomotive. In simple articulateds and duplexes it was thought beneficial in some quarters if the drivers of one engine were a fraction of an inch different from those of the other so the engines wouldn’t get into synch.
On articulated locomotives, both simple and compound and including Garretts, both units always seemed to be perfectly syncronised. Should one engine unit go into a slip and get out of sync, it would always get back into sync within a few revolutions of the wheels after the slipping stopped. By syncronised, I mean four even exhaust beats for every revolution of the drivers. Why should this be? There was no mechanical connection between the two engine units. The only place where the two units were even remotely connected was in the blast pipe, and then not always as some locos had double blast pipes, one for each engine unit. I have never been able to find a satifactory explanation for this phenomenom, any Ideas???
Malc.
On compounds, they tended to stay reasonably close to sync because the exhaust from one engine fed the other engines. If the rear engine slipped, the back pressure from exhausting steam faster than the lead engine could use it would stop the slipping. If the lead engine slipped, the lack of steam from the rear engine would do the same.
My idea;
SCAVENGING
Kind of like “Hot Rod” headers where the four exhaust pipes come together in the collector pipe and as each exhaust exits, it tends to pull the next exhaust out of it’s pipe.
When people say articulateds get into sync, what counts as “in sync”? As far as exhaust-sync goes, 180 degrees out of phase would be “in sync”? And maybe 90 deg and 270 deg too?
Was the phenomenon alleged to happen even with the throttle closed?
Not true, Malcolm. Watch and listen to any video of N&W 1218 and you’ll note the two engines get in and out of synch - the exhaust, especially climbing a grade, tells the story.
Timz - I think for purposes of this discussion, we’re saying that “in synch” means when the two engines are exhausting simultaneously, whether their rod positions be identical, 90 degrees, 180 degrees or 270 degrees out of phase.
Many, but not all. And if you listen to a lot of other tapes, you’ll hear them getting in and out of synch. Listen to the 1218 on “Eighteen Wheels of Steel”. Listen to the dubbed 1200 on that tape of “The Big A and the Bigger Y”. Listen to “Thunder on Blue Ridge”.
The crews called it “hitting a double lick” and you’ll find it more often than not, Bud Swearer’s tapes notwithstanding.
Old Timer,
I’m not disputing what you said.
I’m just saying that from listening to Bud’s tapes many of A’s were in sync and stayed in sync for a long time. The fact that on his tapes, as opposed to Link’s, the canteens were in use making the sounds of the A’s very clear as the head Y passed and the A’s exhaust overpowered the Y’s as the train went further up the mountain.
One sound clip recorded as the train started after receiving the pusher clearly has the A’s double lick.
Not only did the A’s exhibhit the ability to be “in sync”, but the Y’s when in simple did too. Again this can be clearly heard on the tapes.
All of this goes to show the importance of Bud’s tapes and I hope that his masters can be preserved for future generations.