The Steamboating Forum

thanks Bart

even in the static condition, the packing nut on the actuator side pushes the valve against the exhaust side. See the little taper on the end of of the valve? My plan is to make a brass ring with a matching taper and an OD to fit snug in the valve barrel. i am going to shorten a close nipple to receive a coupling that jams against the exhaust face. you can see in the pic that half of the outer thread has broken off.
its a pretty interesting design. i don't know if it is efficient. Have you seen something like it? The round valve itself would be a chore to make long ago but it is simply a D valve rolled in a circle. The port casting could not just be milled through. I have not removed the piston yet but the porting in there should be challenging to reason out.

wsmcycle wrote:thanks Bart

even in the static condition, the packing nut on the actuator side pushes the valve against the exhaust side. See the little taper on the end of of the valve? My plan is to make a brass ring with a matching taper and an OD to fit snug in the valve barrel. i am going to shorten a close nipple to receive a coupling that jams against the exhaust face. you can see in the pic that half of the outer thread has broken off.
its a pretty interesting design. i don't know if it is efficient. Have you seen something like it? The round valve itself would be a chore to make long ago but it is simply a D valve rolled in a circle. The port casting could not just be milled through. I have not removed the piston yet but the porting in there should be challenging to reason out.

The best rotary valves are tapered, so they can be readily adjusted for wear, or even be spring loaded. A straight cylinder is difficult to keep sealed properly. One can imagine spring loaded vanes and dividers in the ports to prevent the vanes from catching....

- Bart

If I recall correctly Corliss engines used semi rotary valves and steam pressure held them on the "face". Worked very well for long periods between overhaul. We only have to think of "Helen" and "Rina" at Trencherfield Mill, Wigan. Corliss valves are used on all four pots and it (they) ran from 1907 to 1968.

johngriffiths wrote:If I recall correctly Corliss engines used semi rotary valves and steam pressure held them on the "face". Worked very well for long periods between overhaul. We only have to think of "Helen" and "Rina" at Trencherfield Mill, Wigan. Corliss valves are used on all four pots and it (they) ran from 1907 to 1968.

Yes.

Corliss use separate valves for intake and exhaust, and the intake and exhaust were designed differently.



- Bart

It's a good thing I checked on the forum for information. Bart, you are correct. the valve is tapered. I measure 0.638 degrees. Poor little engine had someone tightening the packing on the actuator side against the taper until there was no more "take-up". It will probably run but to fix it, I will have to make a new valve. In 3.5 inches, the diameter changes from 1.336 down to 1.258. That's delta 0.078/2=.039" in 3.5". 0.638 degrees. Maybe this works to some quantitative hour minute second but i only work in degrees. .638 X 60= 38.28 and .28 X 60 = 16.8 so that would be 38 min 17 sec. Still queer.
By looking in the exhaust end down thought the valve slot, I see there is about 0.50" movement from the correct alignment with the valve slot in the female side.

wsmcycle wrote:It's a good thing I checked on the forum for information. Bart, you are correct. the valve is tapered. I measure 0.638 degrees. Poor little engine had someone tightening the packing on the actuator side against the taper until there was no more "take-up". It will probably run but to fix it, I will have to make a new valve. In 3.5 inches, the diameter changes from 1.336 down to 1.258. That's delta 0.078/2=.039" in 3.5". 0.638 degrees. Maybe this works to some quantitative hour minute second but i only work in degrees. .638 X 60= 38.28 and .28 X 60 = 16.8 so that would be 38 min 17 sec. Still queer.

That taper might have originally (supposed to have ) been 1/4"/foot on the diameter same as a taper pin; that would have been .073" per 3.5".

- Bart

It is hard to believe the male "lapped/wore" the female the measured 0.500". WOW!! I wonder how much clearance was designed? I can only guess "none". The male originally touched the female. (philosophically, that's been the problem of the ages).

I'm not sure where the .5" came from...

You said that

In 3.5 inches, the diameter changes from 1.336 down to 1.258. That's delta 0.078/2=.039" in 3.5". 0.638 degrees.

So in 3.5" the difference was 1.336 - 1.258, or .078 as you noted.

For 12", the difference would be

.078 * 12/3.5 or .26742857142857142857.

That's only .017" off from 1/4", and 1/4"/foot is a standard taper.

- Bart

You can align the slot in the valve with the slot in the valve block by looking through the exhaust. This alignment is rotational and linear. I measured the distance from the end of the valve in this aligned position to the outer end of the exhaust thread. I then pushed the valve toward the exhaust enc until the valve taper touched the valve block taper. The linear movement was 0.500".

I have taken a couple of pix of the valve which was made from a casting. I am curious as to the function of the small 0.173 hole that goes through the valve front to back. The slots in the case are at the top and bottom. The angle of the slots in the valve body is 120deg. I also made a sketch of the flow of steam through the valve and valve block into the engine. In this pic, the exhaust is out through the center of the valve out perpendicular to the plane of the drawing.