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Cylidner drain cocks

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Dan Jones08/04/2015 20:50:32
73 forum posts
314 photos

I've got a 3" Plastow Burrell and I'm having consistent failure with the cylinder drain cocks.

I bought the engine part built and in the set of bits were some drain cocks so initially I installed those but they didn't last long, they just kept clogging up and leaking. So in a rush I made some new cocks of the same type with a slightly larger hole through the middle in the hope they wouldn't clog. These cocks worked averagely for a time but now just aren't worth bothering with.

Does anyone have a 3" scale engine with well working drain cocks?

If so, could you let me know where you got them or if there's a drawing available if you made them?


Harry Wilkes09/04/2015 07:08:16
676 forum posts
59 photos

Hi Dan

I have a 3" Burrell and the drain cocks work fine, they are not home made but ones that are available from supplies such as Poly Models / Maidstone Eng. The hole in them is not that big however my thinking is you have to much solid material in your boiler so I would start by giving it a good flush out and take it from there.


Phillip Hancock09/11/2018 09:29:40
4 forum posts

It might be that you are using too much cylinder oil, is the chimney oily?

Paul Kemp09/11/2018 11:00:41
282 forum posts
9 photos

I made mine for my 4" Ruston Proctor with parallel plugs and PTFE liner inserts. Never made a drawing, just had a back of an envelope scrawl for my design. They have worked fine since I first ran the engine, about 2010 I think off hand. There are some pictures on my thread on Traction Talk for the Ruston, difficult to post them here as I don't have easy access to where they are stored. Basically the body was profiled from brass hexagon bar. The hole for the plug and liner was drilled from one side, top end of hole tapped for the back / retaining gland nut the portion for the liner was left tapping size for the thread chosen. PTFE liner turned up a couple of thou over the drill size and pressed in with a purpose made dolly. Bar transferred to lathe and profile turned (form tool) and threaded each end and drilled through for the steam passage. Plugs turned from stainless, cross drilled in the right place to match the steam passage when fitted, OD turned to be a fairly tight fit in the liner (it nips down on the bore when pressed in so rather than faff about trying to work out how much I used the shanks of number drills to gauge the finished size of plug required). I put a thread on the ends of the plugs and left a small shoulder to file a square for the operating levers. The plugs have a shoulder so when the back nut is screwed in (looks like a short bolt with a hole in it for the plug spindle) the threaded end of the 'nut' bears on the end of the PTFE sleeve providing some compression adjustment and retains the plug in the body. Not hard to make, probably took me about 4 hours for the pair, more difficult to describe than to do it!

I made the three cock gauge frames in a similar manner, that was more difficult and time consuming but again they have been working without issue for the same period. I do find they leak a bit on the cold hydraulic test but they are 100% tight when in steam. They operate freely too unlike the taper cock designs which always seem to leak or sieze!


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