YASVQ: yet another safety valve question (australian design)

[johan]

With all those safety valve related threads lately I thought about drawing the safety valves for my boiler. I wanted to use a design I found -I think- here that did NOT use a ball as the valve.

When I first joined I read around a bit on the forum and found a thread where someone mentioned an Australian design of safety valve. This was not the typical UK design with a ball but it was a type that used a valve like a "wing valve" and had "pop action". I do not remember if the link to the original article was directly here or if there was a link to another forum where there was more info but I found it a very well thought out design. And the commentaries on it were also favorable. Sadly I did not save the thread or linked article at that time. So if anyone can point me to the thread or original article I'd be thankful.

I really don't like the idea the use of a ball as a valve. I can see the attraction of it in the '50's but not now. So I'd like my engine to be free of such valves. I know, probably just an "idée fixe" but why not?

[John Baguley]

A similar design is shown in the AMBSC boiler code booklet along with details of the springs etc. for different bore safety valves.

John

[ettingtonliam]

Many years ago I made a pair of safety valves for a 3" scale road roller, and that design had wing valves. Try as I might, I couldn't get to seal very well. Most likely my incompetence, I was only 21 at the time, but I've stuck to ball valves ever since.

What convinces you that the vast majority of us are wrong when we use ball valves?

[mbrown]

I made wing valves (3/16" dia seats) for the Ramsbottom valves on my "Lyn". I cribbed the design from a traction engine designed by Malcolm Frost and serialised in EIM in the 1980s.

They seal fine - but go up very violently and tend to lift the water. I'm not sure if that is because they are wing valves or for some other reason. But they work and were easy enough to make.

Malcolm

[oldnorton]

Personally, I think that 'pop' action safety valves are nasty things. If the driver also likes to generate too much steam the valves are banging on and off all the time - very annoying. And the sudden rush of steam can easily lift the water and if you are unlucky can nearly empty the boiler.

Far better to have a semi-pop whereby the valves will quietly start to hiss at the red line, then quickly lift to release pressure. For shut-off they will start to slow the steam release but then quickly 'pop' fully closed.

Norm

[davewoo]

I'm with Norm above, I made a pair of Jim Ewins disc safeties for my Simplex, work brilliantly but I've lost count of the number of times I've thrown coal everywhere when they have lifted and made me jump!. I once belonged to a club that was very big on passenger hauling and the violent pop action reduced several young childrem to tears, one poor little girl was so traumatised by the noise and column of hissing steam she refused to board the train to visit Santa, eventually the hysterics stopped and she boarded one hauled by a nice safe electric shunter.Recently returning it to use I cheated and bought some Polly valves to the Gordon Smith design, much more tranquil!

[johan]

Oct 9, 2024 22:27:37 GMT John Baguley said:

A similar design is shown in the AMBSC boiler code booklet along with details of the springs etc. for different bore safety valves.

John

Thanks, I'll see if I can get my hands on that.

Oct 10, 2024 7:46:48 GMT ettingtonliam said:

Many years ago I made a pair of safety valves for a 3" scale road roller, and that design had wing valves. Try as I might, I couldn't get to seal very well. Most likely my incompetence, I was only 21 at the time, but I've stuck to ball valves ever since.

What convinces you that the vast majority of us are wrong when we use ball valves?

It's not about right or wrong. It's that if in 1:1 they did not use balls, then I'd like to go the same way. Within what is possible in a model and the current design rules for boilers of course. And it is not that this is an irreversible decision, it is always possible to replace the safety later on if problems arise.

Thanks as well for all who shared personal experience.

[davewoo]

Johan
If you don't mind the sudden pop then the jim Ewins valves incorporating a flat disc work extremely well, with a differential that can be adjusted to around 5psi, I have not got a copy of the drawings and construction article given to me by Jim years ago, but at one time they were available on the Maidstone MES website. Exacting but not too difficult to make and extremely reliable without any buzzing noises. Worth a look if you can find the article, I believe they were adapted from a design by H.W " Bert" Holmes, not too tall in height I made some for a 5" Brit recessesed into the boiler and they looked very to scale, but care was needed not to overfill the boiler to avoid a shower.
Dave

[suctionhose]

Oct 9, 2024 19:36:13 GMT johan said:

With all those safety valve related threads lately I thought about drawing the safety valves for my boiler. I wanted to use a design I found -I think- here that did NOT use a ball as the valve.

When I first joined I read around a bit on the forum and found a thread where someone mentioned an Australian design of safety valve. This was not the typical UK design with a ball but it was a type that used a valve like a "wing valve" and had "pop action".

This may be presumptuous but are you referring to an article I wrote for the Australian Model Engineering Magazine in 1990? It was not so much a 'design' as an attempt to provide a methodology to follow if one wanted the pop action. Many ways to skin a cat as evidenced by the far superior articles by Gordon Smith, Jim Ewins etc. With some understanding of the principles I hoped people would feel more confident to tune their valves to meet accumulation standards, tame the volume of discharge, pressure drop etc.

The article could certainly do with a makeover with more contemporary prose and additional information, however it was written 35 years ago following a concerted effort in my shed to come up with a 'system'. It came out in the Jan/Feb 1991 issue of the magazine and I was promptly put in my place by a more qualified author in the following issue! Still I think we all learnt something from both...

I find the high-lift quite fascinating and delight in the ability to manipulate the action! I've enjoyed finding different ways to apply the principles and making good valves in many shapes and sizes. It's just one of my things!

So, if this is what you're looking for, here it is. Do with it what you may. Happy to correspond on the subject.

[johan]

Oct 12, 2024 22:04:10 GMT suctionhose said:

Oct 9, 2024 19:36:13 GMT johan said:

With all those safety valve related threads lately I thought about drawing the safety valves for my boiler. I wanted to use a design I found -I think- here that did NOT use a ball as the valve.

When I first joined I read around a bit on the forum and found a thread where someone mentioned an Australian design of safety valve. This was not the typical UK design with a ball but it was a type that used a valve like a "wing valve" and had "pop action".

This may be presumptuous but are you referring to an article I wrote for the Australian Model Engineering Magazine in 1990? It was not so much a 'design' as an attempt to provide a methodology to follow if one wanted the pop action. Many ways to skin a cat as evidenced by the far superior articles by Gordon Smith, Jim Ewins etc. With some understanding of the principles I hoped people would feel more confident to tune their valves to meet accumulation standards, tame the volume of discharge, pressure drop etc.

The article could certainly do with a makeover with more contemporary prose and additional information, however it was written 35 years ago following a concerted effort in my shed to come up with a 'system'. It came out in the Jan/Feb 1991 issue of the magazine and I was promptly put in my place by a more qualified author in the following issue! Still I think we all learnt something from both...

I find the high-lift quite fascinating and delight in the ability to manipulate the action! I've enjoyed finding different ways to apply the principles and making good valves in many shapes and sizes. It's just one of my things!

So, if this is what you're looking for, here it is. Do with it what you may. Happy to correspond on the subject.

That is indeed what I was looking for, I recognise it from the drawings. Thanks a lot for that. This time I'm going to save it for reference.

[suctionhose]

You're most welcome!