Leaky Clacks

[ridleyian]

I've got a bit of a problem with clacks that refuse to seal completely. Anyone any thoughts / advice on the use of 'o'rings as seats? Anyone know where I can find drawings of same? There on a 5" 'Enterprise'
Thanks in advance.

[steamjohn248]

Try M.E. 10th Dec 2004 page 681 and or
M.E 22nd July 2005 page 87

Both about the same sort of thing basically a bobbin with an O ring under the head in place of the ball.

We use these on all our engines and they work a treat,

Regards

Steamjohn, Langford and Beeliegh Railway

[ridleyian]

Thanks John will give them a go

[Shawki Shlemon]

For standard clacks ,make sure the seat surface is flat and clean, ream the hole or clean with a reamer , then place the correct size ss ball ,using a copper drift ,one smart hit, if the ball sticks to the ball valve ,one tap and the ball will drop and that is it.For the other request visit the following
www.kinvermes.pwp.blueyonder.co.uk or see Priest & Sons web page on this board

[ukjimoo]

Or you could buy them from www.steamfittings.co.uk
Well made with viton o-rings, not expensive and delivered next day. Usual disclaimer applies.

[AndrewP]

On the link posted by Shawki there is a drawing of an O ring sealed clack
www.kinvermes.pwp.blueyonder.co.uk/clack.htm

Can anybody explain to me how that passes water, it would appear that the plunger is a good fit in it's 1/8" bore, I can see how water would get round the outside of the O ring and wide end of plunger as it runs in a threaded section but can't see how it gets that far in the first place.

Confused
Andy

[spurley]

Hi Andy

The normal way for this type of valve to work is for the 'plunger' to be made with flats filed or machined onto it generally leaving a triangle shape. These flats must leave some of the radius in place otherwise the valve will tend to 'cock over' and then stick as badly as the previously discussed ball type. The drawing doesn't show any relief on the plunger body which is maybe why you're confused! The name for a valve of this type is a 'wing' valve as the body has a resemblance to wings.

Hope that helped?

Cheers

Brian

[houstonceng]

Of course you could make the clack with a separate seating (turning outside of seat to a cone and reaming bore as usual to arrive at a near knife-edge).

Then place the ball to be used in the clack onto the seat, roll ball on a stack of newsprint (like a "biro") and it will burnish a good seat for itself. Screw seating part into bottom of fitting, normal "cap" or "outlet" in top of fitting - dependant on if fitting is 90 degree or straight-through clack.

Always worked for me. Was this a G Thomas or someone similar design in ME ?

[ridleyian]

Tonight I made a bobbin and new end cap to the drawing in Dec 2004 ME and converted the seating to a 60 deg taper. It seals beautifully against 100 psi of air, although I haven't had a chance to try it under steam yet. (between initial hydraulic and first steam test at the moment and just trying to seal up all the plumbing.) Two more to do!
Thanks to everyone for their advice.

[jones]

Hi,

I was just wondering if anyone had tried these clack valves:
www.whitetrout.net/Chuck/ShopStuff/CheckValve/Index.html

They look very easy to make. Does anybody know if they can be used with steam?

[Tel]

Given the right O ring I dare say they would. Don't think I'd use aluminium for the bodies tho'.

[ridleyian]

Looks worth a try. unfortunately if I try to expand the drawing it loses resolution. any ideas as to make it big enough to see?

[JohnP]

With IE7 I tried a right click on the picture followed by "Open Link". It worked for me!

JohnP

[modeng2000]

Thanks JohnP, that is something I didn't know.

John

[ridleyian]

yes, thanks John, but I still can't see how it works!

[steam4ian]

G'day all.
The valve seems to be similar in principle to an old time tyre valve. That valve had a hollow stem with circumferential holes covered by a piece of rubber tubing. The inflating air was pumped down the stem and expanded the tube to escape into the tyre; air pressure in the tyre sealed the tube back over the holes in the stem. I was given an old bike which had valves like that. It took a lot of effort to get the air through the tyre.
For clack applications you would need to consider the additional back pressure caused by having to stretch the ring away from the seat. (I'd better not say any more about clackers and rings; I could get thrown off!)
To make up one of these check valves would be a fiddly bit of turning; great for a CNC machine!

One good turn deserves another.
Regards,
Ian

[Tel]

johnp said:

With IE7 I tried a right click on the picture followed by "Open Link". It worked for me!

JohnP

Worked for me in Firefox as well, or here's the addy

www.whitetrout.net/Chuck/ShopStuff/CheckValve/Index.2.gif