Steam Dome Throttle

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daves1459
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Steam Dome Throttle

Post by daves1459 » Sun Nov 18, 2018 5:55 pm

Has anyone seen a design for a steam dome type throttle that offers good speed control particularly during starting and low speed but doesn't have the heavy handed operation and stick/slip characteristics of the common flat metal disk sliding back and forth over a flat metal body yet doesn't have the complexity of a prototype poppet valve? I'm not asking for much am I. Anyway if there is a design that offers what I described I'd appreciate having a look at it.

Thanks, Dave

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Builder01
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Re: Steam Dome Throttle

Post by Builder01 » Sun Nov 18, 2018 6:36 pm

I don't know if this will work for you or not, but a screw down type works well, at least for me. The throttle valve rod comes through the back head terminating in a handle that can be turned to open it. No leaks with this type either. (Just remember to open the throttle at the end of the day).
Super Simplex Regulator - JPG.jpg
DSCN1369 - reduced 8.jpg
DSCN1381 - reduced 4.jpg

Ken Schroeder
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Re: Steam Dome Throttle

Post by Ken Schroeder » Sun Nov 18, 2018 11:00 pm

Use a ball valve in the steam dome, makes a great throttle. That is all I have used in 45 years and have never had to replace one.

daves1459
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Re: Steam Dome Throttle

Post by daves1459 » Sun Nov 18, 2018 11:22 pm

Builder01 wrote:
Sun Nov 18, 2018 6:36 pm
I don't know if this will work for you or not, but a screw down type works well, at least for me. The throttle valve rod comes through the back head terminating in a handle that can be turned to open it. No leaks with this type either. (Just remember to open the throttle at the end of the day).
Super Simplex Regulator - JPG.jpg
DSCN1369 - reduced 8.jpg
DSCN1381 - reduced 4.jpg
My throttle actuation uses a push-pull actuation rod. However, I see a possibility with "latch" to hold the throttle closed. I imagine a lot can be done with the taper on the plug. Making the taper much more shallow would allow better modulation in my case. Thanks for the idea.

By the way, nice work on the boiler construction. The silver soder joints are excellent.

Dave

daves1459
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Re: Steam Dome Throttle

Post by daves1459 » Sun Nov 18, 2018 11:38 pm

Ken Schroeder wrote:
Sun Nov 18, 2018 11:00 pm
Use a ball valve in the steam dome, makes a great throttle. That is all I have used in 45 years and have never had to replace one.
I was looking at ball valves this evening. I can fit one in with 1/2" npt up to 3" long. But, so far cannot visualize a linkage to the "handle" that will offset sideways to the centerline of the throttle rod so not to cause any binding. Any suggestions?

Also does the valve have to be one designed specifically for steam service? They can be rather expensive and relatively large. Will a simple Teflon seat valve due working in a 340 degree F environment?

Dave

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cbrew
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Re: Steam Dome Throttle

Post by cbrew » Mon Nov 19, 2018 6:42 am

morning dave,
I also have been using ball valves.
I run this one the smoke box and it will run great in the dome
https://www.mcmaster.com/4485K31
just need to machine up a new handle that will clock correctly


daves1459 wrote:
Sun Nov 18, 2018 11:38 pm
Ken Schroeder wrote:
Sun Nov 18, 2018 11:00 pm
Use a ball valve in the steam dome, makes a great throttle. That is all I have used in 45 years and have never had to replace one.
I was looking at ball valves this evening. I can fit one in with 1/2" npt up to 3" long. But, so far cannot visualize a linkage to the "handle" that will offset sideways to the centerline of the throttle rod so not to cause any binding. Any suggestions?

Also does the valve have to be one designed specifically for steam service? They can be rather expensive and relatively large. Will a simple Teflon seat valve due working in a 340 degree F environment?

Dave
If it is not live steam. its not worth it.

Pontiacguy1
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Re: Steam Dome Throttle

Post by Pontiacguy1 » Mon Nov 19, 2018 8:53 am

Bend your throttle rod so that it has an offset in it, or either move your throttle rod position over a little bit so that it lines up. I've done both and they've both worked good. I also like using a ball valve in the dome. With it in the dome, it won't get hotter than about 350 degrees, which will extend its life a whole lot. There are those who say they don't like the throttle opening and actuation of the ball valve, that it admits too much steam to quickly and such. That's a matter of personal preference, and I haven't had problems with it myself.

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TEAMTSM
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Re: Steam Dome Throttle

Post by TEAMTSM » Mon Nov 19, 2018 12:45 pm

http://www.tsmtrains.com/PROGRESS%20JUNE%202015.htm
you can scroll down about half way and get a view of my ball valve in my dome and the linkage. for 1-1/2 i would not use a valve bigger then 1/4 npt.

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Fender
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Re: Steam Dome Throttle

Post by Fender » Mon Nov 19, 2018 3:18 pm

Ken Schroeder wrote:
Sun Nov 18, 2018 11:00 pm
Use a ball valve in the steam dome, makes a great throttle. That is all I have used in 45 years and have never had to replace one.
Ken, did you use a “garden variety” valve from a hardware store, or something special?
Dan Watson

Pontiacguy1
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Re: Steam Dome Throttle

Post by Pontiacguy1 » Mon Nov 19, 2018 3:32 pm

. for 1-1/2 i would not use a valve bigger then 1/4 npt.
I would say it depends on the locomotive. For something with an 8" boiler or smaller, then a 1/4" ball valve will do. If you have a Pacific, USRA Mikado or something with a 10" or larger boiler, then a 3/8" ball valve will probably be your best bet. For most small and medium size locomotives, a 1/4" will do fine and deliver enough steam.

Rebuilt a 4-4-0 with a 3/8" line and big sliding plate type throttle valve and all that, and it seemed to me to be a waste. With that big of a valve and piping, it was very touchy on the throttle and would slip easily if you opened the throttle a little bit too far, despite it having a lot more weight on the drivers. That's the downside of having a throttle valve that is too large.

My 2-10-0 has 2 3/8" X 3" cylinders, a 10" ID boiler, a 3/8" ball valve in the dome, 3/8" dry pipe, and it has worked out very well indeed. Have made several Allen boilers with a 1/4" ball valve in the dome, and they've all worked out good too. Use the big-body bronze 1/4" ball valve with teflon seats. They make some 1/4" valves that are really small, but those are more-or-less a 1/8" NTP valve with 1/4" threads in each end. They have a smaller hole through them and will not flow as much as the bigger bodied valves.

Hope this helps.

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FLSTEAM
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Re: Steam Dome Throttle

Post by FLSTEAM » Mon Nov 19, 2018 4:19 pm

Here is a 3/8" Jamesbury stainless ball valve in the Shay. Works very well.

JOHN B
Attachments
Throtle.JPG
http://www.ngshay.com/
Shay drawings and castings

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johnpenn74
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Re: Steam Dome Throttle

Post by johnpenn74 » Mon Nov 19, 2018 10:58 pm

John B,
How does one get the valve stem through the side of the dome and bolt the dome down at the same time?
John Pennington

Project
2 Mich-Cal Shays
Allen 4-4-0 Narrow Gauge Conversion
Reading A5a Camelback 0-4-0
USRA 0-6-0
Clishay
4 Western Wheeled Scraper NG Dump Cars
N&W 4-8-2
ICM 2-10-2
4 Modern Stake Cars
L&N Caboose
4 Big Four Conversion Gondolas

Like I'm actually gonna build all this stuff :-P

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