Making Safety Valves.

[Tony Bird]

Hi,

Having constructed several boiler, fittings for them need to be made. Normaly these fittings are made in batches but none are left. Some months ago I bought an inexpensive Chinese tail stock turret. The last time I used one was when I was an apprentice! The turret was modified to suit my Myford lathe and has had some use producing boiler bushes and gas regulator valves which now means that it is now up and running. Yesterday a start was made making the bodies for safety valves, this is the first time that all 6 stations of the turret have needed to be used. The turret though fairly cheap to buy costs a lot more to fill ith Jacob chucks and tool holders. I have found the turret very useful and quick but I make all of my own fittings usually in multipules. The following photographs show the sequence used making 12 safety valve bodies each body took about 10 minutes to make and the set up of the turret about 40 minutes.

Turret set up.

Marked out.

Centre drill.

Tapping drill.

Drill for steam entry.

Drill to make bottom of hole flat.

Tapping.

Turning sholder.

Parting off.

Turning shoulder for thread.

Threading.

Finished.

For those interested the internal thread is 1/4"x 40tpi the exrernal 3/16"x 40tpi. With the bodies finished its the srew that holds the spring in next.


Regards Tony.

 

[Herbiev]

Thanks for sharing that Tony. I have never seen one of those turrets. Where did you get it?

 

[Tony Bird]

Hi Herbie,

It has no brand name. I got it from a company called Arc Euro Trade in the UK. They do have a web site.

Regards Tony.

 

[Tony Bird]

Hi,

Finished making 12 safety valves adjusting srews. The photographs should show how they were made if not please ask.

Rods to be made perhaps tomorrow.

Regards Tony.

 

[lee9966]

Tony, can you comment on the depth stops on the drills? Do they have just one locking screw? I would have thought that could just happen to land on a position on the drill where it would just catch an edge on the spiral and tightening the locking screw would move the stop a bit off where you want it. Am I dreaming up an issue that doesn't ever happen?

Thanks for showing the turret, quite nice.


Lee

 

[Tony Bird]

Hi Lee,

There doesn't seem to be an issue with the 3mm locking screw, it either does or doesn't fit into the slot of the drill or tap. It is possible that there might be a problem with when it just doesn't go into the slot but as yet I haven't had a problem.

Regards Tony.

 

[SilverSanJuan]

Great stuff Tony. Thanks for posting this.

Todd

 

[Tony Bird]

Hi,

I managed to complete and test one safety valve yesterday. Decided to try and make a semi 'Pop' type. One of my larger locomotives is a 5" gauge saddle tank with one safety valve. In recent years with more stringent boiler testing regulations being applied it was a mute point whether the safety valve would keep the boiler within the 10% increase in pressure allowed. In the UK safety valves on model boilers above the 3bar limit must not allow the boiler pressure to increase more than 10% above the boilers normal working pressure. This is done with the locomotive stationary and the blower full on. I was about to make a new safety valve for the boiler when a member of our model club said that he had seen an article in the ME on altering a standard safety valve to a semi 'Pop'. These valves release more pressure more quickly than the standard designs. They open and close very quickly with a 'Pop' and do not allow the pressure to drop very far. The alterations to the safety valve of the large locomotive worked very well its working pressure of 90psi only increasing by about 5lbs during tests not the 9/10psi of the original valve.
Not that I think a 'Pop' valve is necessary for small boilers but it would be a bit of fun to see if one could be made to work. Results in video below, more of a phut than a pop but it is quite a low pressure.




Regards Tony.

 

[skyline1]

Hi Tony

Those safety valves look familiar are they the old "LBSC" design from many years ago. They are very reliable and just do the job. I have made several of them myself.

Great example of how to mass produce things like this I might investigate one of those turrets myself. I presume that it is not self indexing like a capstan turret.One of these would be great for doing union nuts as they are getting pretty expensive now. Anyway it's much more fun to make your own especially if you can mass produce them like this.

Regards Mark

 

[Tin Falcon]

Thanks for sharing that Tony. I have never seen one of those turrets. Where did you get it?

IIRC most of the tool importers sell those. enco, LMS, shars cdco, ..... not expensive. they do require some time and tool making to set up .

you can use bushings instead of drill chuck to save z axis space.

a nice set up saves time changing tail stock tools easier than building a capstan or turret. .
tin

 

[GVH]

Tony....nice post....thx

 

[Tony Bird]

Hi Mark,

Those safety valves look familiar are they the old "LBSC" design from many years ago. They are very reliable and just do the job. I have made several of them myself.

They are a similar design to LBSC's and many other peoples, they are my own design as much as it is possible as it to design a safety valve. I did do the volume calculations and probably came to the same results as many others.

Great example of how to mass produce things like this I might investigate one of those turrets myself. I presume that it is not self indexing like a capstan turret.One of these would be great for doing union nuts as they are getting pretty expensive now. Anyway it's much more fun to make your own especially if you can mass produce them like this.

The turret does idex but not like a lever operation like on a Capstan lathe. A lever is pressed and the turret moved around by hand. I am very happy with my purchase because I sometimes make a lot of the same bits. I have a long bed lathe which was an extra £27 when it was bought a long time ago. The turret does take up quite a lot of room and would take up quite a lot of room on a standard length Myford. But as has been suggested bushes could be made up to replace Jacobs chucks which would shorten it but the tap and die holders are quite long. As a draw bar cannot be used in the tailstock so I have fitted a set screw to stop the turret rotating on its Morse taper.

Regard Tony.

 

[Tony Bird]

Hi,

This is the difference between most safety valves and the semi 'pop' variety. The usual valve is on the right and the recently made 'pop' on the left. As can be seen the ball is in a cup on the pop valve and in the open on the other. The ball in the cup is a good rotating fit. When the ball fits in the hole in the valve body the edge of the cup is only a few 100ths of a mm off the valve body. It works (I think) as the steam pressure increases the ball lifts slightly and instead of going directly to atmosphere the steam acts on the inside of the cup and given this extra area opens the valve quickly with a distinct 'pop'. The valve also seems to close quicker and doesn't seem to weep as much as the usual type of safety valve.

Regards Tony.

 

[Tony Bird]

Hi,

Marked out.

First cut.

Second cut.

Third cut.

Forth cut.

Parting off.

Needing facing and drilling.

Facing.

Drilling.

Adjusting ball depth.

Adjusted.

Ball depth jig.

Maximum amount of clearance.

Seven of the twelve safety valves used.

The tailstock turret has now been used to make Goodall water filler valves, gas poker burners, gas control valves and now safety valves for the above boilers with a couple of each components spare for other models. Still to be made are gauge glasses and steam regulators. But a little time off on other jobs first I think!


Regards Tony.

 

[ChooChooMike]

Nice collection of boilers !!

 

[pandy]

I see you are using a vertical hold tool bit holder for this project. Is there any chance that you could post details of source, dimentions or even a photo

Many thanks

Pandy

 

[Tony Bird]

Hi Pandy,


I see you are using a vertical hold tool bit holder for this project. Is there any chance that you could post details of source, dimentions or even a photo

I have used what is known as a Diamond Tool Holder for more than twenty years and I am am very happy with it. Mine came direct from Australia but there is now a UK importer. See.

http://www.eccentricengineering.com.au/index.php?option=com_content&view=article&id=2&Itemid=17

I wish they made a right hand version of it and a square on one would be useful as well.

Regards Tony.

 

[Tony Bird]

Hello again,

Just had a look at the DTH site they now do make a right hand version which I will order.

Regards Tony.

 

[pandy]

Thanks for the info, Tony, I have had a look and will be placing one on my Christmas list!!!

Pandy

 

[skyline1]

Impressive collection of boilers Tony. Now I know why you need so many safety valves If you fired up all of 'em at once I'd see the cloud of steam from this side of the Severn.

Regards Mark