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Steam operated drain cocks

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ed milton04/03/2013 22:02:45
7 forum posts

Dose any one know if there has been an article or drawings for steam operated drain cocks in ME mag?

Stewart Hart04/03/2013 22:14:56
662 forum posts
354 photos

Hi Ed

Quite a few members at my club use them, I've drawn them and made a few sets and passed them on, so far they seem to have worked, if you PM me with your email adress I'll pass the drawing on.


Frederick Michael WICKENS 116/01/2020 14:51:05
1 forum posts

Dear Stewart

I have been trying to sort this out, steam operated drain cocks for ages, I would be interested with any drawing.


Kind regards

Mick W


Edited By JasonB on 16/01/2020 15:41:42

Essm16/01/2020 21:52:18
28 forum posts
8 photos

Hi Guys

Search in Wikipedia for steam drain cocks for a drawing and then you can also follow various links

Edited By Essm on 16/01/2020 21:55:03

Sorry - search should be for Automatic cylinder cocks and not as previously shown

Edited By Essm on 16/01/2020 22:03:19

Please disregard this post altogether  - I am searching for correct link

Edited By Essm on 16/01/2020 22:10:52

Nick Clarke 316/01/2020 22:00:09
1221 forum posts
49 photos

Looking at the index to Model Engineer at **LINK**

There are two references to 'Steam Operated Draincocks' but that doesn't mean there are not others under references to particular model designs.

Model Engineer 2007 Volume 198 Issue 4292 Page 143
Model Engineer 1985 Volume 155 Issue 3758 Page 165

Essm16/01/2020 22:26:52
28 forum posts
8 photos

Hi again - please try this link for a drawing


Fowlers Fury16/01/2020 22:47:19
378 forum posts
87 photos

In 2015 there was a short article on Steam Operated Drain Cocks in David Carpenter's Model Engineers Website. I like the design and eventually plan to make a set as described by Peter Squire.

Usual "for personal use only" applies to downloads, so check the website:-

Doubt there's a problem with me showing the article's heading:-

(You could PM me if interested)

fizzy16/01/2020 23:32:40
1798 forum posts
120 photos

I tried some a few yrs back....wasnt impressed

Paul Lousick17/01/2020 06:09:59
1789 forum posts
644 photos

My preference is for manually operated drain cocks.

If the engine starts to prime , you can open a manual drain to release pressure and prevent damage to the cylinder, piston, etc.


Brian Baker 117/01/2020 07:49:32
162 forum posts
34 photos

Greetings Paul, I have been using steam operated drain cocks for some time, and they are completely controllable, just like taper cocks, just close the steam valve and they open to clear condensate, but with the added bonus that they will open automatically if you get a hydraulic lock.



Hans Hogendoorn11/06/2021 14:45:42
3 forum posts
17 photos

Maybe someone can help me, I downloaded some time ago this picture from a steam operated drain cock. This is all I have , is there someone recognize this part ? And maybe can help me with the rest?

Kind regards Hans

Daggers13/06/2021 11:06:49
26 forum posts


sorry but I don’t recognise that image.

when i was looking for information on this subject I found this website, might be worth a look.

fizzy13/06/2021 12:57:59
1798 forum posts
120 photos

1. drain in

2. drain out

3. valve head

4. O ring

5. Gland nut

6. ferrule

7. Out of shot - live steam line

Simples - perhaps all that time spent trying to get them to work wasnt a complete waste! Whats not shown is that you will also need a steam relief valve to release pressure to operate the valve.

Hans Hogendoorn13/06/2021 14:14:00
3 forum posts
17 photos

Thanks !

Hans Hogendoorn13/06/2021 14:14:04
3 forum posts
17 photos

Thanks !

duncan webster14/06/2021 00:37:53
3354 forum posts
61 photos

I think it would work better with 2 connected to the cylinder and 1 as outlet. The drawing shows the OD of 1 not threaded, which agrees

John Alexander Stewart14/06/2021 02:27:49
803 forum posts
53 photos

I made some from the US model engine maker from a long time ago. I made my copies about 10-15 years ago now.

Work great! Piston valve engine, so wanted something that would act as a relief valve if required.

The one Hans shows above would be better than the ones I made; rather than annealing brass disks, the o-ring makes it simpler.

Great little addition to a locomotive.

John Olsen14/06/2021 05:01:57
1178 forum posts
92 photos
1 articles

Sorry Duncan, 1 is the end that should connect to the cylinder. The pressure from the steam on the other end holds the valve on the seat. When there is no pressure there, any pressure in the cylinder can open the valve, allowing it to drain. The ones on my steam launch are just like the one shown, and they work fine. If the pressure in the cylinder gets high enough, say from trying to compress water, it can overcome the steam pressure on the other end and vent anyway, so they act as a relief valve, although I have also provided separate relief valves as well. The operating valve should be a changeover type, so that in one position it connects live steam to the valve, and in the other it connects the cylinder end of the valve to atmosphere.

The operating cylinder part needs to be big enough to hold the valve on its seat, but not so much bigger that it won't act as a relief valve. The ratio of the areas will approximately determine the pressure at which it opens.

I don't have drawings of mine, they were made by eye from a sketch, and they would be a bit big for all but the largest of model locos.


Martin Johnson 114/06/2021 13:03:08
131 forum posts
1 photos

I cosidered this type of design for my steam lorry - a large piston valve engine. I was cocerned that they would be rather poor at pressure relief because you would get the live steam line full of codensate. In the event of hydraulic lock on the engine, you have to shift a load of condensate in the actuation line - with it's own inertia. So I concluded it would not prevent damage to the engine. If someone has evidence to the contrary, I would be pleased to hear it.


fizzy14/06/2021 18:00:17
1798 forum posts
120 photos

Duncan - I opted for no.1 as it has a much lower surface area when closed so whould require less pressure to hold it shut, but either way should work.....I think

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