Author Topic: Globe valve and Handwheels  (Read 31096 times)

Offline smfr

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Globe valve and Handwheels
« on: December 26, 2012, 07:06:27 AM »
Here's my first attempt to make a globe valve for my Stuart No. 4 (for the 5/16" inlet piping). I followed George's build here, http://www.homemodelenginemachinist.com/f31/small-globe-valve-how-make-4377/, but scaled it up 1.5X to better suit the size of my engine.

First step was to take some 5/8" brass and cut the profile for the main body:



followed by some freehand turning then filing of the globe:



I had a template to work to, but this was way off spherical which did cause some problems later. After this experience I'm eyeing one of the toolpost ball turners  :naughty:

The next step was to drill through with a drill the diameter of the valve seat (the smallest of the diameters), then drill with the tap drill size down to the valve seat level, which is around the bottom of the globe. Then I used a small home-made boring bar to remove the angle left by the larger drill, leaving a flat around the valve seat:



The last step in this setup was to tap for the top, screw-in portion. I used the same thread for this as the pipe fittings (5/16" 26 TPI BSB). I suspect that a Model Engineer (ME) 32- or 40-TPI thread would be more appropriate, but I don't have taps or dies in that size.

Then came the screw-in cap part, which consists of a threaded end, a flange which will be cut into a hex, and a profiled neck:



I left drilling the center until I had it parted off, and then screwed into the body. That way, I know the bore is aligned with the body after assembly:



This cap is drilled through with the tap drill size for the thread used on the spindle (I used 5BA, and a 1/8" spindle), then drilled and reamed about half way down for the spindle. An external thread is cut on the end for the gland nut (I think I used 1/4" 26 TPI here).

The third part that makes up the body is the side arm, here being profiled to fit the globe:



While still attached to their parent material, the body is put in the rotary table to drill the side hole. I had a minor boo-boo here:



The rotary table wasn't securely bolted down, because I can't easily get a clamp on the front side. When cutting this hole, the drill caught as it broke through to the bore, and pulled the part up, tilting the rotary table up with it.  :wallbang: The result was a somewhat oval hole, but luckily it's covered by the side arm.

Then I cut the hex flats on both side arm and body:



A final small part is a collar which locates the side arm onto the body when soldering, so here's where we're at:



Here you can just about see the valve seat, which was, luckily, unmarred by the side-wall drilling incident:



The parts were then parted/hacksawed off their parent stock, and put onto a mandrel to drill and tap the newly exposed ends, as well as put a slight 30? profile on the hex flanges:



Time for silver soldering now! All fluxed and ready to go:



and post-solder:



That went into the acid bath for a while.

Not shown here was some threading of the spindle. I used 1/8" stainless steel for the spindle to avoid rust, and threaded the bottom portion 5BA, and a section at the top 6BA to give the handle a flange to sit on.

The handle started live as a bit of 1-1/4" brass bar. I left a generous boss in the middle to give me something to put in a collet later:



then trepanned out a bit from the lower face with a boring bar meant for internal threading:



While still attached, it was partially parted off, and the outer rim profiled:



then parted off completely, and flipped around and held in a collet to trepan the upper surface. I may cut holes or spokes at some point if I decide that this valve is a keeper.

So here's what we end up with:



which, when assembled, looks like:



It's missing the gland cap part that screws onto that top thread, which I haven't made yet.

Blowing through the valve while turning the handle indicates that it seems to form a pretty good seal.

Here's a trial fit on the engine:





I'm quite pleased with how the valve went together, but I'm not sure that it looks quite right on the engine. The globe part seems a bit small to me. Or maybe it's the mixture of styles of the lubricator, T-piece, copper piping and globe valve. It could be time to think about flanges everywhere   :insane:

So, things I'll do differently next time:
  • Make sure the body is spherical. Preferably use a ball turner.
  • Maybe give up on trying to profile the side arm to match the sphere. It would be easier to have it just be cylindrical, with just a solder fillet where it joins the sphere.

After this I also have questions!
  • How the heck do you choose an appropriate thread for parts like this. So many choices! (BSB, ME, BA, English....). I *think* ME is most appropriate for mating brass parts like this, but 32 or 40TPI?
  • What's the best way to get the valve bit fixed to the end of the spindle? Can I silver-solder stainless? Or maybe just center-punch the end of the spindle to lock it on?

Thanks for reading!

Simon
« Last Edit: December 29, 2012, 04:04:29 AM by smfr »

Offline Jo

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Re: Globe valve
« Reply #1 on: December 26, 2012, 07:30:05 AM »
Simon,

Nice valve, your questions:

Ball turners will not help here, you have not got the clearance between the flanges. What you need is a profiling tool. A simple piece of gauge plate (or any bit of steel that you can later harden) drill a hole in it, shape up around the hole to suit your valve and harden, will work well ;)

Threads: 40 TPI is normally chosen when you have an application where things have to line up.

Valve spindle: I am not sure what the problem is....Is it that the handle is threaded on and it is taking the nut off when you try to loosen the valve? This is why handles are normally mounted using a square on the shaft and secured with the nut.
-----
Edit: The trick for drilling the valve seat is to do that first on the round bar and then do the valve body profiling around the hole. ;)

Jo
« Last Edit: December 26, 2012, 09:17:33 AM by Jo »
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Offline Jo

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Re: Globe valve
« Reply #2 on: December 26, 2012, 07:46:24 AM »
 :facepalm: Looking again at the photo's I have just realized the problem you have with the spindle: you have made the end separate to the spindle. It is normally all turned from one piece.

Yes go and silver solder it on. Careful with the flux stainless is a little different to SS and demands a higher temperature to take which is why they do a higher temperature flux (Tenacity) specifically for that job.

Jo
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Online Jasonb

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Re: Globe valve
« Reply #3 on: December 26, 2012, 08:31:54 AM »
Like Jo I would go for 40tpi on these or 32 at a push. It gives you more turns of full engagement in a shorter length and also not having such a small root dia means you can get a larger bore to the pipe. And lastly on the ME series the tappings size is generally 1/32" smaller than nominal which means the often blind tapping hole can be drilled with a milling cutter to get a flat bottom without having to resort to small boring bars.

Regarding drilling the globe out, again a milling cutter to open out the dia would have been better than a drill plus ad some support to the overhanging end to stop it flexing and then snatching.

The spindle from solid would have been how I would do it but the equivalent to Tenacity or HT5 flux which removes the chromium oxide from stainless will allow you to silver solder it.

Offline tel

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Re: Globe valve
« Reply #4 on: December 26, 2012, 09:15:28 AM »
The 40tpi ME series gets my vote as well

Nice job on the valve tho - really looks the part
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Offline steamer

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Re: Globe valve
« Reply #5 on: December 26, 2012, 10:12:56 AM »
I think flange connections would screw up the scale Simon.    The 4 has those 2 bolt flanges that would look way out of scale with a 4 or 8 bolt flange.

Right now it seems like a large model of a small engine...and looks right as far as I can tell
Maybe spoke and slightly dish the handwheel and put the bonnet gland on.....I think you've done a  great job!

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Offline tel

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Re: Globe valve
« Reply #6 on: December 26, 2012, 10:56:47 AM »
By sheer coincidence, I did a 180? flanged one last week - it's a bit bigger scale tho, 1" 'globe' and 8BA screws in the flanges. For your size you would need to go down to 12 BA perhaps, to get it looking right.

I'll try and get a pic tomorrow if I finish spraying early enough.
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Offline zeeprogrammer

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Re: Globe valve
« Reply #7 on: December 26, 2012, 11:36:04 AM »
Nice valve Simon. Excellent post too. I have a project in mind and found this very useful.

Re clamping the rotary table. When I did the hub for my spinning wheel the other day, it was the first time I'd used the RT in vertical mode. The whole thing flexed when I took a plunge cut. I added a long clamp to the top (side) of the RT down to the table to fix it. Don't know if this is the same issue you had or if this helps. (I should have pointed that out in my thread.)
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Offline vcutajar

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Re: Globe valve
« Reply #8 on: December 26, 2012, 12:04:38 PM »
Simon

Your engine is getting nicer and nicer.  I believe these small details make it stand out from the crowd.  :ThumbsUp:

Vince

Online Jasonb

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Re: Globe valve
« Reply #9 on: December 26, 2012, 01:23:28 PM »
I think for the type of small launch engine that this represents then the screwed fittings look fine and certainly not out of place on an American installation where screwed pipe & fittings are more common. If it were a large marine engine then flanges would be better.

One thing I would say is the valve should probably be mounted with the spindle horizontal, that way it works like a stop cock and the pressure of the steam from the boiler will help to hold the spindle onto its seating rather than the steam trying to lift it off as you have it now.

J

Offline Don1966

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Re: Globe valve
« Reply #10 on: December 26, 2012, 03:04:57 PM »
Looks good to me Simon, and I would add spoke to the valve handle. i would also do as Jason suggest and us the steam pressure to your advantage. I have the same problem with my RT and I put two clamps on the back side this helps greatly. Unfortunately the RT has no room to secure it on the front.

Don

Offline smfr

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Re: Globe valve
« Reply #11 on: December 26, 2012, 05:33:38 PM »
Oooh, so much good information :)

Ball turners will not help here, you have not got the clearance between the flanges. What you need is a profiling tool. A simple piece of gauge plate (or any bit of steel that you can later harden) drill a hole in it, shape up around the hole to suit your valve and harden, will work well ;)

Good point, though I was thinking something like this:



with maybe a 1/8" cutting bit could be used (with care!) for the final profile. I do have some some oil-hardening gauge plate, though, and a Dremel with a conical grinding wheel, so I can try that next time. I'm worried about chatter, though.

Threads: 40 TPI is normally chosen when you have an application where things have to line up.

Good to know! Time to stock up on ME taps and dies!

:facepalm: Looking again at the photo's I have just realized the problem you have with the spindle: you have made the end separate to the spindle. It is normally all turned from one piece.

Yes go and silver solder it on. Careful with the flux stainless is a little different to SS and demands a higher temperature to take which is why they do a higher temperature flux (Tenacity) specifically for that job.

The reason I didn't turn it all from one piece is that I don't feel confident that I can get a good, smooth accurate finish along a length of skinny rod. I should probably buy or make one of these:



George mentioned that he used bronze for this spindle. Any reason to choose that over SS?

Thanks for the feedback, Jo!

Simon

Offline smfr

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Re: Globe valve
« Reply #12 on: December 26, 2012, 05:39:22 PM »
By sheer coincidence, I did a 180? flanged one last week - it's a bit bigger scale tho, 1" 'globe' and 8BA screws in the flanges. For your size you would need to go down to 12 BA perhaps, to get it looking right.

I'll try and get a pic tomorrow if I finish spraying early enough.

I would love to see that, tel!

After completing this valve, I found a reference to a German gent (store here http://www.modellbau-niggel.de/?sid=pn1440drsgp3cqibgeut49tot4) who makes smaller ones, like this:



which look like they'd be slightly easier to make. Gotta love the sand/bead-blasted finish, too. It's a bit odd that his direction arrow suggests that it should be mounted in such a way that the steam would be trying to lift the valve, though.

Nice valve Simon. Excellent post too. I have a project in mind and found this very useful.

Re clamping the rotary table. When I did the hub for my spinning wheel the other day, it was the first time I'd used the RT in vertical mode. The whole thing flexed when I took a plunge cut. I added a long clamp to the top (side) of the RT down to the table to fix it. Don't know if this is the same issue you had or if this helps. (I should have pointed that out in my thread.)

Probably; this is the little 4" table. I should make a clamp that extends out far enough to the sides that I can get in to tighten the hold-downs. Seems like we all have the same problem!

Simon

Offline tel

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Re: Globe valve
« Reply #13 on: December 26, 2012, 06:42:56 PM »
Yes, some form of box tool is well worth the effort of making for jobs like the spindle. Mine is quite a simple affair, but works very well.





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Offline tel

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Re: Globe valve
« Reply #14 on: December 26, 2012, 11:18:32 PM »
And here is the valve - not finished yet, as you can see!


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