Steam-operated cylinder drains

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DianneB
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Location: Manitoba, Canada

Steam-operated cylinder drains

Post by DianneB » Wed Nov 21, 2018 8:30 am

I am trying to work out a design for a steam-operated cylinder drain cock that meets the following criteria:
1 - Must be "wide open" at zero pressure (assuming about 3/16 inlet passage)
2 - Must include over-pressure relief (if cylinder pressure > operating pressure)
3 - Must be physically small to suit a smaller 1.5" locomotive

I haven't found anything online.

I am considering a SS ball that is raised against a seat by steam pressure underneath a diaphragm but have no idea what would make a good diaphragm? Ideally it should lift at least 50% of the ball diameter. Any metal would have to be very thin or fairly large diameter to get sufficient lift. I don't think PFTE sheet has enough "stretch". A plunger under the ball would provide enough lift but whatever was used as a 'piston ring" would have enough friction that it would require a spring to ensure the ball would "fall open" at zero pressure.

There are some brilliant and inventive people on this forum so I am "fishing for ideas" in fertile waters! :mrgreen:

BClemens
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Re: Steam-operated cylinder drains

Post by BClemens » Wed Nov 21, 2018 8:31 am

Where's that Bill Shields guy?!!

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DianneB
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Re: Steam-operated cylinder drains

Post by DianneB » Wed Nov 21, 2018 9:01 am

I hope to hear from him! ;)

Asteamhead
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Re: Steam-operated cylinder drains

Post by Asteamhead » Wed Nov 21, 2018 12:14 pm

Hello DianneB,
Maybe a look on may topic A 1239 , page 9 on the `Build Log`will help:

viewtopic.php?f=45&t=103319&start=96

Width of bores is about 3 mm, piston (with 0-ring) diameter is 8 mm. Steam connection to the valve chamber.
Some more photos and scetches are available.
Good luck!

Best regards
Asteamhead
Attachments
A automatic cylinder cocks red.jpg
Automatic cocks ready for use
A cyl. cocks, preparation before being (silver-)soldered.jpg
dito, body made of bronze prepared for soldering
A cyl. drains, lots of parts,red.jpg
dito, parts

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Fred_V
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Re: Steam-operated cylinder drains

Post by Fred_V » Thu Nov 22, 2018 8:34 am

steam cock.JPG
here is an interesting design that would meet all your needs. You will need a 3 way valve to operate any of the steam operated types.
Fred V
Pensacola, Fl.

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Bill Shields
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Re: Steam-operated cylinder drains

Post by Bill Shields » Thu Nov 22, 2018 11:03 am

I am here...where are all of you on this cold and blustery Thanksgiving day (OK...not in Canada)….

I use the Nixon type of cylinder cock which are similar to what is above.

http://www.mehrs.com/misc.html : Steam Operated Cylinder Cocks

You need to check the fits of the O-rings shown in the drawing a bit so that the are a nice loose sliding fit. If the fit is too tight, they might stick a bit when you want them to just open to drain

You also need a 3 way valve the will dump pressure to the cocks when it is closed to the turret.

The designs with PTFE diaphragms are OK for a while but eventually fail and require rebuilding.
Last edited by Harold_V on Sun Nov 25, 2018 2:43 am, edited 1 time in total.
Reason: to correct provided link

little giant
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Re: Steam-operated cylinder drains

Post by little giant » Thu Nov 22, 2018 11:04 am

That drawing looks a lot like Ben Nixon’s drawing, which I have on my locomotive and works great. I don’t understand what the rear o-ring is for? This design will allow blow by and if you don’t turn off the air to the cocks when stopped can cause the locomotive to move. The Nixon design has the o-ring on the shuttle stopping steam from entering the cylinders.

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Fred_V
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Re: Steam-operated cylinder drains

Post by Fred_V » Thu Nov 22, 2018 7:58 pm

The rear o-ring prevents steam from getting around the end of the shuttle and blowing out the vent side of the 3 way valve.
I made some from Bill's design and they work well but you do have to watch the fit of the o-rings as Bill says. I've has some stick before.
Fred V
Pensacola, Fl.

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DianneB
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Re: Steam-operated cylinder drains

Post by DianneB » Sat Nov 24, 2018 6:28 am

Asteamhead: That looks like a nice valve but it's kind of complicated for a rube like me!

Fred_V: Interesting design but requires cylinder pressure or a spring to be "self-opening" at zero pressure.

BillShields: You link doesn't work for me :(

I haven't come up with anything better myself (yet).

I'd consider manually-operated drain cocks but my Little Engines American would require a complicated linkage to get the motion back to the cab.

Of course there is the possibility of using manual drains and having a steam-operated cylinder tucked under the pilot I guess.

I am still open to other ideas!!!

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Fred_V
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Re: Steam-operated cylinder drains

Post by Fred_V » Sat Nov 24, 2018 7:49 am

you could easily add a spring as there is nothing making the shuttle stick.
It would then be self opening.
Fred V
Pensacola, Fl.

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BAdams
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Re: Steam-operated cylinder drains

Post by BAdams » Sat Nov 24, 2018 7:02 pm

Here's Bill's link: http://www.mehrs.com/misc.html
I think the ".html" part was accidentally dropped.


Brook

Kimball McGinley
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Re: Steam-operated cylinder drains

Post by Kimball McGinley » Mon Nov 26, 2018 3:12 pm

So, in the "Heald" drawing posted by Fred V., is it possible for the steam applied to close the drain to leak past the plunger and get into the cylinders? If so, would the loco move, or would the pressure be equal on both sides of the piston?

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