dem132
Seasoned Member
Posts: 122
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Post by dem132 on Jun 13, 2014 16:31:36 GMT
Hi all,
I would like to make my first ever clack valve, and would like to have article / drawing to follow as I've never made a valve before. Advice and guidance would be welcomed before I start cutting metal etc. I hope to use a nitrile ball type valve, I recall reading an article saying that flat valve seats are not ideal for nitrile but ok for stainless steel balls. I have a couple of pieces of SAE660 - assume that's ok to use? I won't be using brass at all.
Thanks in advance.
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Post by ejparrott on Jun 15, 2014 10:45:18 GMT
If I may suggest? Buy a copy of DAG Brown's book on injectors. There's some really great pointers in there about clack design, plus loads of really good stuff about injector design and manufacture, pipework design and troubleshooting. It'll prove it's worth in the long run.
For legal, I have no affiliation to DAG or TEE publishing, I just think it's a damn good book that needs to be read more!
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dem132
Seasoned Member
Posts: 122
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Post by dem132 on Sept 20, 2014 8:25:44 GMT
Hi ejarrott, Apologies for not responding. I did already have a copy of DAG Brown book, I agree is a good read. Loads of big words in it! I've manage to make a bronze clack valve with a removable seat for better maintenance. I'll attach a photo of it in a bit (if the attachment works!). I've had a few problems with making the clack valve, mostly around machining bronze and rushing!
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dem132
Seasoned Member
Posts: 122
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Post by dem132 on Sept 20, 2014 8:30:29 GMT
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jma1009
Elder Statesman
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Post by jma1009 on Sept 20, 2014 9:44:48 GMT
hi dave,
the check valve looks very nice indeed and very well made and i especially like the added detail of the dummy bolted flange.
how are the dummy nuts and studs fitted/secured?
cheers,
julian
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Post by ejparrott on Sept 20, 2014 14:16:45 GMT
Lovely job  |
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dem132
Seasoned Member
Posts: 122
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Post by dem132 on Sept 21, 2014 18:49:08 GMT
I really appreciate the positive comments, it's the first time I've made something like this. I've learnt a lot, and slowly improving my engineers skills. Julian, the 10BA bolts are C/S from the rear, and I've reduced the length the brass bolts to suit. The design is a bit a mixture from a drawing someone in the Basingstoke MES give me, but it was for 1/4 x 40, but I required 5/16 to suit a 3/16 pipe for my L1. The drawing didn't include the removable seat either. The passageways are 9/64, which should provide the 3/16 stainless ball the best seat arrangement. I haven't tried it under steam yet.
I'm going to keep it the stainless ball design for the moment, but I've read an interesting article from Dave Noble regarding rubber type balls.
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jma1009
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Post by jma1009 on Sept 21, 2014 23:06:30 GMT
hi dave,
many thanks for the explanation of fitting the dummy studding and nuts.
if you burnish your bronze seats with a hard steel bearing same size as the stainless ball you will get a perfect very durable seat.
im not a fan of nitrile balls. john cashmore of commercial injector fame attributed them to many failures. last week i took apart a whistle valve fitted with same and the state of the nitrile ball was simply horrendous. ive never used them on my own locos. however i do test thoroughly all check valves on air before fitting to a loco, plus throw away any stainless balls that are magnetic.
cheers,
julian
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dem132
Seasoned Member
Posts: 122
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Post by dem132 on Sept 24, 2014 13:43:03 GMT
Hi Julian,
Thanks for the advice. I'll try that method using a steel ball, does sound like a much better way of creating the ball seat. I've been testing the valve using air, discovered that my bike pump accepts the 5/16 diagram nicely. I'll provide an update later on in the month, and hopefully have it installed on the L1.
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Post by Roger on Oct 18, 2014 8:42:53 GMT
Check out Ceramic Ball Bearings on eBay, they are harder than any steel ball and won't rust. They're available in any size, imperial or metric. Silicon Nitride are the ones I'd go for, I don't know whether the White Zirconium Oxide ones are harder or not. Those are the ones used in the food industry.
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robmort
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3.5" Duchess, finishing 2.5" gauge A3 and building 3.5" King
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Post by robmort on Nov 6, 2014 20:13:47 GMT
The nitrile balls are not only expensive compared with stainless, but not suitable for clacks as nitrile does not withstand boiler temperatures. A better, cheaper, and more reliable design, is to use a viton or silicone O-ring as a seat and a stainless ball. This does not leak, does not suffer from sticking and does not require forming a seat. Courtesy of John Baguley:  |
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Tony K
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Post by Tony K on Dec 1, 2014 8:33:53 GMT
The nitrile balls are not only expensive compared with stainless, but not suitable for clacks as nitrile does not withstand boiler temperatures. Beg pardon sir, yes it does, but nitrile is right on the spec. That said, they do work very well which means the spec is generous. If you are worried about this aspect then use viton which is well in spec. |
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robmort
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3.5" Duchess, finishing 2.5" gauge A3 and building 3.5" King
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Post by robmort on Dec 1, 2014 11:09:47 GMT
Beg pardon sir, yes it does, but nitrile is right on the spec. That said, they do work very well which means the spec is generous. If you are worried about this aspect then use viton which is well in spec. Sorry, but you are wrong. The facts, which you can easily check, are these: a boiler at 80 PSI has a temperature of 156degC (higher if at 100 PSI). Nitrile has an upper limit of 108deg C - totally out of the range. Try it and see! Many have seen their Nitrile disintegrate at boiler temperatures. Viton balls are even more expensive. Rob |
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Tony K
Elder Statesman
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Post by Tony K on Dec 2, 2014 14:34:06 GMT
Rob, I was thinking along these lines.
NRB has a max working temperature of 108 deg C
I think mostly the balls on sale by model eng suppliers are HNRB with a max working temperature of 165 deg C, which is just on the spec. at 100psi.
I think Viton has max working temperature of 220 deg C and, at about a quid each, are not expensive compared to other model eng components.
You think differently.
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dem132
Seasoned Member
Posts: 122
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Post by dem132 on Dec 3, 2014 15:13:52 GMT
That's what I've always been told, use Viton for clack valve in the hotter areas of the boiler, like the back head etc. My new clack valve has been fitted, and the second injector has been fitted. Now I have both injectors (No.3 and 4) feeding water into the front clack valve (LH and RH) and the hand / axle pump feeds the back head clack, which I rarely use. Pleased to say it's all working fine, and has been a interesting project, as I had to re-done most of the pipe work and fit a new filter to the tender. Only task remaining is to make a new valve handle for the water feed from the tender. Julian has provided me with guidance on making square ends. Hopefully I should have this completely shortly and back on with the Black Five!
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robmort
Hi-poster
3.5" Duchess, finishing 2.5" gauge A3 and building 3.5" King
Posts: 174
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Post by robmort on Sept 11, 2015 14:27:57 GMT
[quote
I think mostly the balls on sale by model eng suppliers are HNRB with a max working temperature of 165 deg C, which is just on the spec. at 100psi.
[/quote]
Don't know why you think that....... wishful thinking?
Why would suppliers undersell their products??? You can always ask them anyway.
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Post by fostergp6nhp on Sept 11, 2015 18:08:11 GMT
These rubber balls would be no good then in the boiler clacks for my Road Loco which has a WP of 200psi.
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Post by runner42 on Sept 13, 2015 3:05:50 GMT
The nitrile balls are not only expensive compared with stainless, but not suitable for clacks as nitrile does not withstand boiler temperatures. A better, cheaper, and more reliable design, is to use a viton or silicone O-ring as a seat and a stainless ball. This does not leak, does not suffer from sticking and does not require forming a seat. Courtesy of John Baguley: how is the O ring attached to the clack valve body, ideally the flat bottomed seat needs to be achieved?
Brian
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Post by 4fbuilder on Sept 15, 2015 11:52:30 GMT
Good afternoon,
At a recent trackside discussion on the subject of balls a fellow member mentioned something I had suspected for years, are the stainless balls truly round? Personally I have used bronze balls for many years and never had a problem, also I'll always make my check valves from drawn bronze with both the bore and seats finally sized and finished after silver brazing, perhaps a little longer in the making but always give success.
Regards,
Bob
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Post by fostergp6nhp on Sept 15, 2015 17:03:51 GMT
Stainless balls not round, that might explain why my boiler clacks leak even after reforming the seats and fitting new balls. I will have to try bronze balls next.
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