GORDON SMITH SAFETY VALVE

[firebird]

Hi

I'm interested in an article written by Gordon Smith about safety valves in Engineering in miniature magazine in Feb/Mar/Apr of 2001

Has anyone got those articles or magazines that I could get a copy of

Cheers

Rich

[Jim]

I think I may have the article by Gordon Smith and if so will copy and send it to you.

I made the safety valves for my Britannia to Gordon Smith's design and they work well.

Jim

[Jim]

Hi Rich,

I've just sent you an PM with the two page article by Gordon Smith on Safety Valves. Hope you find it useful

Jim

[steamer5]

Hi Rich,
Here’s another thread on Gordon’s safetys

modeleng.proboards.com/thread/12077/select-correct-gordon-smith-safety

Cheers Kerrin

[firebird]

Hi

Thankyou gentlemen, that's a good start

Cheers

Rich

[stevep]

Drawings and the appropriate springs for a range of his designs for various locos are available, IIRC, from Polly.

Usual disclaimer.

[chrisb]

I got balls, springs and drawings from Polly when I replaced the safeties on my Wren

[firebird]

Thanks everyone

I'll post my progress when I get onto it

Cheers

Rich

[oldnorton]

Rich

I agree with the suggestions to contact Polly. It is well worth getting a drawing from them and the spring. You can change the external appearance and dimensions but a most important distance is that between the bottom of the ball carrier and the main body land around the steam hole. It needs to be within a few thou of the drawing - it affects the amount of 'pop', semi-pop' or no hysteresis at all.

Norm

[stevep]

I agree completely with Norm - you must keep close to dimensions. When I made replacement valves for my Rob Roy, I made 3 sets of guides (the bits that hold the balls) with the depth a few thou either side of nominal. I then tried each set in turn to determine how much hysteresis I was comfortable with.

[firebird]

Hi

Thanks for the info gentlemen.

A bit of news about Polly

You may or may not be aware that the directors here at Polly are retiring
and the business is in the process of being sold
Completion of the sale should be within the next few weeks

I have heard that they will no longer be manufacturing loco's

I understand that all in house manufacturing has stopped

Cheers

Rich

[simon6200]

That is terrible news, not for me but for beginners and non model engineers who want to buy a new loco that will actually run as it should. Two members of my club bought commercial locos, not Polly, and one needed new fittings made (turret fittings with zero% thread engagement) and the other had to be stripped and re-engineered. The second never re-surfaced. I thought locos were Polly’s core business.

[chrisb]

I had a look a the Polly website after reading the post about the business being sold. There was a statement about retirement and sale of the business but no mention of the cessation of Polly loco production.

[andyhigham]

I hope they continue the safety valves. They just work, don't dump all your water, don't scare the children, reset before pressure drops too far and don't hurt the wallet

[firebird]

Hi

I totally agree about Polly's safety valves.

My first loco build Conway would reach its working pressure of 80 psi then dump the contents of the boiler down to 50 psi before the safety valve would close. I purchased one from Polly and that cured the problem. Just a gentle fizz at 80 psi and pressure would be maintained.

My mate spoke to Polly a short while ago and they confirmed that they had finished manufacturing

Cheers

Rich

[kipford]

Post deleted.

[firebird]

Hi

Finding myself at a loose end I have had a go at making 2 of the Gordon Smith safety valves.







A question if I may

I didn't have any 5/16'' stainless steel balls but I did have some nitrile 5/16''. Is it ok to use them in safety valves or should I order some stainless steel

Cheers

Rich

[chris vine]

Hi Rich,
They look great!

I guess there is a risk that the rubber/nitrile balls might stick to the seat and raise the blow off pressure.

Roger, of this parish, will certainly advise the use of silicon carbide balls. Much rounder and harder than stainless. He and I have got them from Ebay for a few pennies...

Chris.

[firebird]

Hi Chris

On Ebay I can see the silicon carbide but mostly from America and quite expensive.

The ceramic silicon nitride are a lot cheaper, are they the ones

I'm interested in having a look at them

Cheers

Rich

[steamer5]

Hi Rich,
From my experience using nitrile balls in clacks / non-returns I wouldn’t use them in safety valves! They will get an impression of the seat & under spring load likely to deform.
Keep looking on EBay I got my silicon carbide balls out of China at a most reasonable cost. They seem to pack them in packets of los, if you hunt you can usually find them in smaller numbers

The safety looks great!

Cheers Kerrin