BigJim there is plenty of video and audio tapes around that prove that after starting, articulated locos will come in-sync and stay in-sync for long periods of time.
nicknoyesThe captions say, “Double exhaust stacks, one for each engine, is a characteristic of a simple articulated”.
CSSHEGEWISCH On most simple articulateds, there is no mechanical link between the two engines so they are rarely synchronized.
On most simple articulateds, there is no mechanical link between the two engines so they are rarely synchronized.
Paul,I think that you will find that a well maintained articulated will more often than not attain syncronicity on it's own. Obviously, if a slip occurs or one set of driver's tire diameter is different from the other then the engines will have that double-lick sound. But, there is plenty of video and audio tapes around that prove that after starting, articulated locos will come in-sync and stay in-sync for long periods of time. Even after a bad slip, if the two wheel sets are well maintained, the engine will shortly find it's way back into sync.
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CSSHEGEWISCH and selector,
Okay, I got it!! Thank you very much.
nick
Even compounds, those relying on expanded steam routed forward from the simple steam cylinders rearward, are often "out of phase", but it doesn't seem to affect them. If each set of cylinders has its own intake and exhaust porting, and each of those has pressure or vacuum as intended, then each bank of cylinders acts independently as an engine responding to changes in pressure. When a given valve passes a port in either engine, the condition of the volume at the port determines what happens to the piston ported. In the case of the exhaust, each cylinder exhausts spent steam which is routed through a conduit. In compounds, two of those ports route expanded steam, and two upward through the stack (single, as it happens, on the Y Class Mallets of the N&W). On Big Boys and Challengers, all cylinders route expanded steam directly up the two sets of blast pipes, converging to rise up a single pipe in each case.
But perhaps the front and rear engines of an articulated are out of phase to some degree. Pictures of articulated locos at rest may show front engine drivers up while the rear engine drivers down. Is this true?
It isn't just articulated engines that have double stacks. Some fixed-frame engines have them, too. Notably, UP's own 844.
-Crandell
As the picture shows, there are two stacks, and the blast pipes for the engines are positioned below them. The blast pipes create the draft by exhausting the steam from the engine up and into the stack, drawing the combustion gases with it, and providing draft for the fire.
The reason for using two stacks is simple: velocity. If the stack is too large, it would be difficult to draw the comubustion gases up and out. Which would mean a poor draft.
The blast pipes are what creates the familiar "stack talk" or chuff. Especially when they start to move, you will hear the bark and a large plume of smoke shoots out of the stack.
Two blastpipes in the smokebox. One for each engine.
Pictures I have of simple articulated steam locomotives show two exhaust stacks. The captions say, “Double exhaust stacks, one for each engine, is a characteristic of a simple articulated”. Overhead pictures show smoke coming from both stacks so both engines must be exhausting into the smokebox.
How is this double exhaust accomplished? If both the front and rear engines exhaust into the smokebox how can the individual exhausts be separated?
Nick
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