Help! > Specific Engine Help

Crank operated lever controls rotary valve and fries brain!

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Zephyrin:
this arm fixed on the crankpin is the "return crank", present on numerous steam locomotive, as being a part of the Walschaert distribution...
it is also visible on many hot air engines, to set the length of the stroke of the power cylinder.

PaulR:

--- Quote from: Zephyrin on December 25, 2024, 07:00:10 pm ---this arm fixed on the crankpin is the "return crank", present on numerous steam locomotive, as being a part of the Walschaert distribution...
it is also visible on many hot air engines, to set the length of the stroke of the power cylinder.

--- End quote ---

Yes, I thought it looked similar to Walschaert valve operation although I don't really understand how that works... I've got a loco book that explains it but it's a bit above my pay grade  :Lol:

PaulR:
It also occurred to me that the piston rod (dark green in this clip) could be attached anywhere along the line from the axle to the original crank pin position provided that the long side of the v-shaped link is raised to clear the big end.

Jasonb:
It will just alter the stroke of the engine.

Do watch your timing, the latest video does not have the piston and valve pins 90degrees apart.

Also I have noticed in the last few simulations that you have the valve rod on the pin that is on the shorter radius and the piston on the larger radius.

Drawing shows piston pin at 7/32" radius and Valve pin on 1/4" radius, you have the opposite which will give less angular movement to the valve.

PaulR:

--- Quote from: Jasonb on December 26, 2024, 11:38:06 am ---It will just alter the stroke of the engine.

--- End quote ---
Yep, I realise that - could prove handy!

Re the accuracy of the animation, well spotted! I'm not getting to using as a basis for building yet, just fiddling with the components and learning how the software works. I did notice you could swap the valve pin inside or outside the crank's radius and the mechanism still works although I didn't spot any change in the valve lever movement while playing around with it - good catch!

I'm guessing once things are set up ok I can get some measurements and just scale them to suitable dimensions provided everything is kept in proportion?

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