How exactly do Accucraft reverse valves work? (Edrig, Ruby, Caradoc etc.)

[DannyTheElfman]

Hey everyone,

Sorry a bit of a silly question. I'm well familiar with the workings of locomotives with standard valve gear. Every steam valve I've seen has got a single steam inlet, and two exhaust ports. As in the diagram below.


Yet seemingly on our Accucraft locos, they make do with a single steam inlet, and a single exhaust port, leaving me wondering where the gasses are disposed of on the side of the cylinder without an exhaust? You can see below, only two ports on the valve gear, where is the third?


I've had a bit of a think, and the only way I can make this work in my head, is if the valve has a hollow centre and allows gasses to pass through, effectively allowing the cylinder to exhaust through both the inlet and exhaust depending on where it is in the cycle and where the reverser is set. I have mapped out my thoughts below. The central steam chest is placed at the top of the diagrams, with the valve gear and cylinder below.


Is this correct or am I miles off the mark? I have no reason to actually need to know how it works. Just pure curiosity!

Many thanks
Dan

 

[Charles M]

Your drawing is exactly how the valve system works. This kind of valve has been in use for over a hundred years. German steam toys used this very early on.
After I replaced the 3/8ths cylinders with 1/2 cylinders on my Accucraft Mimi I opened up the passage in the valve body to allow more steam to pass through to cylinders. Engine runs better after the modifications.

 

[Paul M]

Hey everyone,

Sorry a bit of a silly question. I'm well familiar with the workings of locomotives with standard valve gear. Every steam valve I've seen has got a single steam inlet, and two exhaust ports. As in the diagram below.
View attachment 339299

Yet seemingly on our Accucraft locos, they make do with a single steam inlet, and a single exhaust port, leaving me wondering where the gasses are disposed of on the side of the cylinder without an exhaust? You can see below, only two ports on the valve gear, where is the third?
View attachment 339300

I've had a bit of a think, and the only way I can make this work in my head, is if the valve has a hollow centre and allows gasses to pass through, effectively allowing the cylinder to exhaust through both the inlet and exhaust depending on where it is in the cycle and where the reverser is set. I have mapped out my thoughts below. The central steam chest is placed at the top of the diagrams, with the valve gear and cylinder below.
View attachment 339301 View attachment 339302

Is this correct or am I miles off the mark? I have no reason to actually need to know how it works. Just pure curiosity!

Many thanks
Dan

Part of the dark arts to me TBH! The reverser can also be the speed controller too. Some thing I would leave well alone!

 

[maxi-model]

My Accucraft L&B Lyn, like other Accucrafts it's fitted with a piston valve arrangement, and can be controlled from its reverser quadrant alone. I only have leave the regulator cracked open and the reverser does the rest. So, only have RC servo on reverser. I do not know why I have never given this a go on my other Accucraft locos. Every other supplier though has fitted servos to both reverser and regulator on those. Some say it gives better control, I beg to differ, even with the inclines/declines on my line (tip add a touch of reverse going downhill).

Once tried to advise somebody who's regulator servo had failed on their Lyn that their day's running was not lost. They were having none of it and stalked off saying their trip to the CFR was wasted. Ho, hum. Max

 

[DannyTheElfman]

Your drawing is exactly how the valve system works. This kind of valve has been in use for over a hundred years. German steam toys used this very early on.
After I replaced the 3/8ths cylinders with 1/2 cylinders on my Accucraft Mimi I opened up the passage in the valve body to allow more steam to pass through to cylinders. Engine runs better after the modifications.

Excellent, thank you! I can't say I've ever seen this setup before, but I've never had a live steamer before either. It's quite the interesting system!

 

[Paul M]

Some say it gives better control

I find my Caradoc, speed contrlled by reverser, will stop dead in an emergency when put into neutral, my other locos controlled by the regulator will take a second or two. Actual speed control doseem much different