While building a crude wooden model with 2 large driving wheels of a steam locomotive and trying to figure out how walschaert gears work, I succeeded by trial and error just how that eccentric crank works, the model would be a 0-4-0 NOW the problem: when the 2 wheels are revolving the coupling rod, which would be connected to the connecting rod then the piston rod, what happens is when the coupling rod gets in linewith the axles of the wheels it locks, and if it moves at all it rotates the other wheel in the opposite direction for 1/2 a turn… what is my problem?? (other than not being to clear on explaining things)
On a steamer, the crankpins are 90 degrees apart on the two sides. That means that the piston on one side, on the “out” stroke, is pushing for just 1/4 turn. Then the cylinder on the other side pushes for another quarter turn. By that time, the first cylinder is pulling, again, a quarter turn, followed by the second cylinder pulling for another quarter turn. And so it continues.
Of course there’s overlap there, too.
What that means is that only one cylinder/wheel is “dead center” at any one time. The other side is perfectly positioned to start things in motion.
The valve gear timing will ensure that the proper cylinder is getting steam so as to move the wheels in the proper direction.
Sounds to me like you have the crank pins 180 degrees apart.
OOPS Sorry, It’s not the “quartering” What I have is 2 wooden wheels (only two) There is no other side it is mounted on a piece of wood that rotates with a crank on the other side to turn the wheel(s) I connected the 2 wheels with a coupling rod which connects the 2 wheels and they SHOULD rotate, but they lock at the centre line of the axles, this is a very crude model of the (supposed) working of a steam engine driving system, I did figure out the Walschaert puzzle,(the eccentric crank does not rotate on it’s pin)
So---- where the coupling rod is attached to the driving wheels seem to be my problem, but I cannot figure where they should be placed on the wheels. I would not try to figure out this system if there were more than 2 wheels, Yikes, 0-4-0 or more, I have looked up on many internet sites but they mostly assume I know how a steampropulsion system works (afraid not)
Rereading the "quartering’ Does that mean a steam locomotive will not function without an opposing set of wheels on the other side? so you could not have a one cylinder steam locomotive???
Right; if the main rod is all the way back or all the way forward, the pin is in line with the axel, and the piston in the cylinder is either pushing or pulling against the axel
At times it has been necessary to run a “one-legged” locomotive, and it could be started only if the main rod was not dead-centered. If it was necessary to stop anywhere, the engineer had to be certain that he stopped on a downgrade, so that gravity could pull the engine forward in the case that the main rod was dead-centered. There is an instance in which a 4-8-4 locomotive was run from Bristol, Va., to Roanoke, Va., on one cylinder because the valve gear on the other side had been destroyed. The engineer was very careful. (Trains, March 1999, pp. 47-48)
Speaking of starting a locomotive on one cylinder, a reprint of a locomotive maintenance manual that I have advises that when stopping a locomotive with one cylinder, you can put it in reverse when there are just a few revolutions to go, and the compression will ensure that it stops in mid-stroke
You may have a tolerance problem (with the parts of the model, not yourself!).
If the spacing of the holes in your rods does not correspond fairly precisely with the spacing of the pins at dead center, they will certainly bind.
Since you have no real momentum to work with, there is nothing to force the driven wheel(s) to continue rotating, as would be the case with a moving locomotive.
Since this is a demonstration model, your solution may be to mechanically couple the two wheels “behind the scenes,” either with a couple of pulleys and a rubber band on the back side, or possibly by adding a quartering factor on the back side. You could do this by replacing your current “axles” with longer rods and simply putting a couple of right angle bends in them, positioning them quartered, and adding a rod (much like a Diesel with siderods).
The pulley idea would probably be simpler and would serve the purpose.
A tolerance problem for sure, this model looks as if it were made by a 4 year old, it is pretty crude, if I run the 2 wheels on the floor it works (momentum for sure) a rubber band on the back on the axles solved the problem, I do plan to make a finer example of wood so will try for finer tolerances but will also add a pulley or gear system to make it operable, the Walschaert system works fine as that was my prime intention. There are some fine examples o