Regulator Help please

[GWR 101]

Hi I have put this in this section, I hope it's the correct place. I am as you can probably gather building a Juliet in 3 1/2 gauge and have got to this stage, the boiler has a boss at the firebox end with a plain bore and there is a tapped boss at the smoke box end in the centre is the dome. The drawing shows a disc type regulator, basically a 3/8" tube connected to a 5/8" tube and then a 1/4" tube. The 5/8" tube contains the disc which is operated via a stainless rod from the cab end. The questions are :-

1) The static part of the regulator with two holes I am using PB, would the disc be best in stainless.

2) Should I fit a boss to the top of the 5/8" tube where the 1/4" pipe comes out of the top into the dome.

3) I think I have read somewhere that for safety reasons the gland at the cab end should have some retaining device to prevent it coming out at the driver.

Any help would be gratefully appreciated. Regards Paul

[ejparrott]

I think we need a bit more info. What size is the hole in the backhead boss and the smokebox boss? At the moment I'm struggling to see how you can have three different tube sizes, so I can't really help with whether you should have a boss for the upstand or not. If there's room I'd say you should.

My Hunslet has a bronze regulator body and a bronze disc, that's been fine for the best part of 20 years now. One thing I will say, relieve the center of the disc on the mating face. Make sure the holes have a good sealing face, and relieve below the diameter for a 1/64". After some considerable use we had trouble getting the hunslet to seal for boiler test, even after lapping the valve several times. Relieving the middle cured it.

The regulator handle will stop the gland coming off the shaft should it unscrew. Whenever possible I prefer a gland with studs to secure and a O ring to seal.

[GWR 101]

Hi Ed, thanks for your interest. I did wonder if a sketch might be a better option so please see my attempt, not much better than the back of a fag packet but hopefully it will give some idea of the layout.

The left hand end is the smoke box end which screws into a boss screwed into the boiler. The cab end has a flanged boss which is bolted to a boss in the boiler and has a gland. The disc which is in the 5/8" tube has a peg and slot to restrict the angular movement, the connection of this to the handle is a 5/32" stainless rod. Hope this helps, regards Paul

[ejparrott]

Looks like a fairly good design, the regulator rod appears to have a support bush too, usually just relying on the valve itself.

I assume the hole in the backhead bush is 5/8" bore or larger and the whole assembly is screwed in from that end? If the hole is no bigger you'll struggle to get a bush in for the pickup pipe.

[GWR 101]

Hi Ed, just realised after reading your post I have potential problem.  Yes the hole in the back head is 0.625" dia. and I have just brought some 5/8" copper tube and it will not go in. What worries me is that once it is in if there is any scaling or distortion it will not come out, I can possibly polish the hole to get the tube in but how much clearance should I allow. I have got some domestic copper tube that is about 0.605" so I suppose I could use that, but I don't think either option is going to let me put a boss on. I have attached a couple of photos showing the boiler ends, which may be of help, the drawing states a bronze spring to put pressure on the disc I assume stainless would be the preferred option but how strong. Regards Paul 

[ejparrott]

It doesn't need to e very strong, steam pressure will help keep it there. Mine is of very fine wire gauge.

You might want to try opening out the boiler bush in the backhead with a small flap wheel. I'd recommend pressurizing the boiler though with only that bush open so it encourages the dust outwards. At a guess the boiler maker has just reamed the bush, or maybe bored it, and only measured it with a verynear. This could quite easily be 8 thou undersize. Failing that, reduce the pipe diameter, but that will reduce the amount of thread for the pickup pipe.

[jma1009]

hi paul,

most of my locos have disc in tube regulators, but inserted from the smokebox tubeplate end. that doesnt help your current predicament! (mine are also bolted in place rather being threaded into the boiler bush on the smokebox tubeplate).

the bit of tube for the steam collector doesnt require a steam tight seal - and can be screwed into quite thin tube - the boss if you want to add one can always be added to the inside of the tube.

you obviously have to have a piece of tube that will fit through the backhead boiler bush - find out the max clearance size and let us know!

i would suggest that the regulator rod works on a square in the disc (i would make the disc of bronze rather than stainless) - then there is more room for the steam ports on the disc. so think of a flat disc with a just under 1/8" square in it. i add a spigot hole in the body of the regulator as well for a round end of the regulator rod to fit into.

spring can be phos bronze or non magnetic stainless but needs to be strong and relatively stiff, and i fit a PTFE seal/tight washer inside the tube at the other end from the rotating disc.

dont worry about the backhead gland. if made to a good standard it wont work loose.

i make the ports/holes in the disc 'pear shaped'.

cheers,
julian

[GWR 101]

Hi Ed, thanks I was thinking of opening the hole using a small sanding drum on my Dremel with a vacuum cleaner in close attendance, but I will now add an air line as well.

Julian I will make the disc out of bronze with a square, yes the most forward bush in the 5/8" tube will have a spigot hole to accept the stainless control rod. The tube I have is 0.625" + .001 -0 so I will open the back head boiler bush up, does +.005" seem ok. Regarding the bit of tube in the collector, I think I will screw this straight into the tube initially, as surely the pressure is equal on both sides.
I assume that this is fitted last via the inner dome bush after it's position has been decided ?. The picture I have shows pear shaped holes so I will do my best. You mention a PTFE washer in the end of the tube, how do you secure this in place as I am not clear how the bush this end is secured (the other end could be brazed) but surely I need access for maintenance. As always many thanks, I bet you will all be relieved when I get this build finished, thanks to you all for your patience Paul

[ejparrott]

You are correct, the pressure will be equal. You need to cut a screwdriver slot across the top of the pickup tube so that you can screw it in through the dome aperture

[GWR 101]

Nice one Ed, off to the workshop now to make a start. Hopefully I will not hit too many problems, only time will tell, watch this space. Regards Paul

[runner42]

Hi Paul,

I like your boiler, you have done a sterling job. That firedoor is mighty strong and well made it puts a lot of flimsy ones I have seen to shame. Your backhead appears to be uncluttered I assume that a lot of fittings will be connected to the manifold?

Brian

PS Good luck with drilling the regulator bush, standing the boiler on end generally makes it difficult to use your pedestal drill or mill because of height restrictions.

PPS Not wanting to teach grandmother to suck eggs, but make sure your water gauge blowdown valve and pipe clears the firedoor hinges.

[runner42]

Found this, every little helps. Yours didn't include a spring which is necessary to keep the faces together, although you are aware that it needs one. Yes notice the end stop fitted to the shaft just forward of the backhead bush to stop the shaft coming out.

Brian

[GWR 101]

Hi Brian thanks for your input on this, I am afraid I have to come clean I didn't make the Boiler. (blushes in embarrassment).

It's beyond my skills and equipment, and I decided that if I was ever going to get the loco completed I would get it made. I did make the fire hole door to a pattern very kindly loaned to me by Alan (aka Hagley). When I visited the boiler maker we discussed the problem of the water gauge being very close to the door and if it was mounted the conventional way that is handle on the left there would not be enough room. So we temporarily fitted the water gauge elbows and found that reversing the door was a workable solution so the bosses for the door were positioned accordingly. Apologies if this flies in the face of convention, but it is a freelance design so I have assumed some license in its construction. Yes  the whistle, pressure gauge and feed to the injector will come from a manifold.

I haven't decided (built up the courage) of how to drill the regulator bush yet but will probably make a jig to make sure that the holes are in the correct place. I have encountered one minor problem after increasing the bore slightly and making the end piece I have found that the end face of the boss is not at right angles to the centre line of the boiler so I need to decide how I rectify this.

Many thanks for the sketch far more detailed than anything I could find and I will definitely incorporate a lot of the features, it helps me resolve how to fit the right hand end of the large tube to the end closure (8 BA screws), the other end I assumed is brazed. I take your point about securing the control bar, on my version the stop pin is located at the valve face and works with a segment so not sure which way to go. One thing I am going to try is to experiment with part punching the hole for the top feed pipe to see if I can get more meat for the thread. Regards Paul

[ejparrott]

You should always have a quadrant for the regulator handle. As well as serving as a stop for the handle and the assembly, it also serves as an indicator to the driver as to what position the regulator is in and which way it opens! There's a Glen runs at our club, and it doesn't have one, and I never know which way to open it

[uuu]

Which reminds me of an American regulation in the 1970s, that required motorcycle contols to be labelled. So if you were wondering which way to move the pedal to change down, you could stop, and crouch down beside the bike to remind yourself. I was so grateful that the big pedal sticking up was captioned "kick starter" it avoided many an embarrassing mistake.

Wilf

[andyhigham]

That could be confusing on a CZ 175 or Jawa 350. The kickstart and gear lever were the same pedal, you push it in and rotate it backwards

[GWR 101]

Ed thanks, then that's the way I will go with a quadrant in the cab. Not much progress today decided to experiment punching the hole for the top feed pipe thread to give it more meat prior to taping, not a success.  Also got side tracked into some gardening, understand rain forecast for tomorrow  so more workshop time. Regards Paul

[runner42]

Paul wrote "I have found that the end face of the boss is not at right angles to the centre line of the boiler so I need to decide how I rectify this."

I am no expert so if others have an alternative view then go with that. I would do nothing and you are probably being ultra cautious. The regulator is a long assembly and probably exaggerating the mis-alignment of the regulator boss with the boiler centre line. Construct your regulator, assemble it in the boiler and if when this is done the regulator bush and the boiler boss are not mating correctly then consider doing something. But I would imagine that the backhead would be sufficiently annealed to allow some judicial give and alter the plane of the boss to be aligned to the regulator bush. If in the very worst case scenario that this cannot be achieved then some annealing of the backhead could be carried out to allow this self aligning to occur.

Brian

PS I offer this based on the fact that my backhead bush, the same off axis was apparent and it didn't take much with the soft copper backhead I was easily able to correct this.

[GWR 101]

Thanks Brian, it may be that I haven't machined (emery clothed) the bore evenly, as I push the bush in on it's own the faces do not sit flat. I only took a few thou out and because of the use of an air nozzle and a vacuum cleaner it was a bit crowded (that's my excuse anyway) so I will try and take a bit more of one side of the bore. I assume a gasket is not normal practice ? for this location. Back off to the workshop to undertake some more work on the other end where the disc is. Regards Paul

[ejparrott]

I would most likely use a liquid gasket for this, Stag jointing compound being my favourite. There is no reason not to use an ordinary klingersil gasket for it as most probably will.