Steam engine drive wheels

[Modelcar]

Kenneo: All your points are well taken....I wasn't sure if the design had them out of phase as you said from side to side. And for sure at 1/4 position, it would have the most advantage to turn the wheel. One other thing....on a Mallet I doubt if the front engine and rear engine are in any phase...Separate from each piston / wheel position, etc...so that would always provide a way to move as it would have one in position to start the movement. But it is an interesting subject....[:)]

[kenneo]

Modlecar: You are correct. What was being talked about at the steam trap (excuse, rr excursion) was the practice of quartering. If you look closely at a steam locomotive with rods (normal configuation) you will see that the main rods and wheels are 1/4 turn apart and not 1/2 turn (or revolution). The comment about not being able to start the locomotive with "halved" rods is correct. It won't start by itself. The rods need to be off-set and the most efficient placement is 1/4revolution, or 90 degrees off. When you hear the locomotive in operation, there is a power stroke for each 1/4 revolution, so you hear four "chuffs" per revolution.

[irmspc1]

QUOTE: Originally posted by Modelcar

....Would it possibly be if the engine main side rods happen to be in the exact parallel position to the rails...Perhaps then the piston could not effect any movement of the wheels with out something getting them off dead center...I imagine if this was possible, the engine would also have to be on absolutely flat grade so gravity woudn't move the engine.

[:)]I think that you are right Modelcar, the pistons would get "centered" and the loco could not move, without a push on the train to get the pistons off center. But in the old days, with friction bearings on cars, even if the train was on a slight grade, it wouldn't move very easy.

[Modelcar]

....Would it possibly be if the engine main side rods happen to be in the exact parallel position to the rails...Perhaps then the piston could not effect any movement of the wheels with out something getting them off dead center...I imagine if this was possible, the engine would also have to be on absolutely flat grade so gravity woudn't move the engine.

[Mikeygaw]

ok, now like years ago i was on some tour at some steam tourist trap, excuse me, i mean excursion, and the guide was talking something about the drive wheels jamming up if they were set in the same position. Anyone know anything about this?

Hey, first topic of the year!