Ball operated Drain Cocks

[greensands]

Hi - I am a new member to the forum and this is my first thread. Can anyone please tell me the secret of making steam tight cylinder ball-operated drain cocks as described by Don Young? My current design calls for 5/32" diameter balls on a 1/8" diameter seating D-bitted in the usual manner and the seating then pre-formed by clouting a test ball into the body of the valve. I have tried both s/s and PB balls but to no real effect. Are viton balls of any use in this application? Any guidance or assistance would be most appreciated.
Drawings of my current design available if required.
Many thanks

[pondok]

hi, i made ones along these lines and went straight for "nitrile" rubber balls. Worked a charm and i got the impression that the balls were able to accommodate the occasional bit of gunk or residue and still make a nice seal, unlike steel balls that seem fussier
-andy

[greensands]

Hi - Thanks for the suggestion to use nitrile balls. My design requireds the 5/32" diameter balls to be pushed off their seating using a 3/32" diameter s/s operating rod. Did you have any problems of leaving indentation marks on the surface of the rubber balls in your arrangement?

[pondok]

hi, i seem to remember having to remove the drains at some point to repaint the cladding or something and I never noticed any indentations or scoring on the balls, as it were, but apart from that time I never needed to inspect them because they sealed so well. The loco is sold now and my new one has mushroom type valves in stainless, and these are more prone to sticking off the seat. The nitrile balls would occasionally not close at first, but they seemed easier to clear by flicking the drains open > shut a few times than the mushroom type. Previous to both of these I had the more conventional taper plug type but found they never sealed completely under high pressure, having always to compromise - either some play to allow smooth open/close, or the lock nut tight to improve seal (and the stiff working that results).
andy

[greensands]

Thanks Andy - I have placed an order for some trial nitrile balls and will give them a try. Incidentally, I now realise that the thread is out of place under "Model Engineer", it should have been put into "General Chat". Do you know how I can go about changing its location?
Regards
Reg

[pondok]

hi reg, 'fraid not, but i doubt anyone will ban you for some perceived rule transgression. personally i always just browse the 30 most recent posts - never a clue as to what section they're in unless i look specifically
andy

[greensands]

Progress report: I have now tried using a nitrile ball and it appears to be the answer, certainly performing well on the test rig. Does anyone have any experience or pics showing typical rodding and bowden operating cable set-up for drain cocks as recommend by Don Young?