CONWAY 0-4-0 3 1/2" GAUGE LOCO

[Firebird]

Hi

Richard, its bronze of some sort, not sure exactly what grade 

Today was somewhat disjointed, a lot fettling, making bolts of the correct length, cutting gaskets etc.

Made another spacer for the reverse lever, an extra 1/8"

Soldered the 2 stainless steel super heater tubes into the end piece

Fitted the exhaust T. Thread seal on the tubes that screw into the cylinders and gaskets in the flanges

Then I came across another problem 

I moved onto fitting the regulator into the boiler which first requires the drilling of 2 holes to hold it in place. Problem is the regulator won't go into the boiler 

Even with the bottom blanking plate removed it won't go in, it hits the super heater tube before I can hook it under the dome bush..

I have double checked all the measurements on the plans  and can find no fault so I can only assume another oversight by Martin Evans

<a href="https://www.youtube.com/watch?v=J0siMrAjorg" target="_blank">http://www.youtube.com/watch?v=J0siMrAjorg</a>

I can't machine anything off the top of the lug because that would make it sit too high in the boiler and so putting it out of line of the regulator control rod.

I am thinking of maching a littleof the bottom, say a 1/16" and silver soldering a plate on instead of the bolt on plate. Then with a little file work it might go in.

These things are sent to try us 

Cheers

Rich

[Firebird]

Hi

Machined a little off the bottom of the regulator with a 6mm cutter

Machined up a piece of bronze to a looseish fit and coated with flux silver soldered it in

Note the hold down gadget. Its something I have been meaning to make for many years. Took about 20 minutes to knock it up and it works just great. Should have done it ages ago

Back in the mill and machine down flush

With a bit more careful file work the little *+@@&$ just goes in

The 2 mounting screw holes (4BA) are drilled on a radius to match the boiler. I did a test drill on a bit of scrap brass before attacking the boiler

Then some careful marking out and drill the holes. A bit of scrap poked into the hole to protect the tubes when the drill breaks through

The holes need to be counter sunk. I have ordered some 4BA countersunk stainless steel screws

Cheers

Rich

[JC54]

Rich,
       Really like your hold down gadget. Just struggled with my first attempt at silver soldering, due to problem holding parts. Your gadget would have been perfect. Will make one tomorrow. Many Thanks JC

[Kim]

Hey Rich,
Sorry for your struggles with the regulator.  Honestly, I'm not fully following what's going on here. Clearly, your regulator doesn't fit. And you fixed it by cutting a slot in the bottom, the promptly filling that slot with another piece of material.

I'm sure it will become clear as you finish up this step.  Maybe part of the problem is I don't know what a 'regulator' is.  Does it regulate steam pressure?  But if so, I'd have thought it would be a pressure release valve.  I'm clearly still learning the terminology here!

Thanks,
Kim

[Firebird]

Hi

Thanks JC 

Kim, the regulator is the throttle. It regulates the amount of steam, not the pressure, that goes to the cylinders

It sits inside the boiler here

and is covered with a dome

It is controlled from the backhead

Steam passes through the regulator and forwards to the wet head where it loops backwards through the super heater tube, (the large tube in the boiler) into the firebox then loops forward again through the super heater tube and down to the cylinders

I hope I have explained that well enough

Cheers

Rich

[cnr6400]

Hi Rich, Looking at your pics and dwgs it occurred to me there may yet be an issue with Mr Evans' wonderful regulator design. I've attached a jpeg below. Worth checking I think.

If all else fails, and you want to solve this issue forever as well as get a regulator with much less flow restriction, I'd consider fitting a high temp Swagelok ball valve in the smokebox, driven by a rod thru boiler as you have. Many locomotives in the US and Canada have these Swagelok high temp valves fitted for regulators / throttles. They have some rated to 300 psi at 850 deg F / 454 deg C. There are a few articles about them in old Live Steam magazines.

Just food for thought. I really don't like seeing people struggling with Martin Evans' designs, but I've seen a lot of it. Always foibles like this in them, it seems.

[Firebird]

Hi cnr6400

Firstly I double checked all my measurements. The big dome bush is made to size as per the plans and the super heater tube is in the right place so it is the design of the regulator that is the problem.

Yes thats the plate. The plate I made was 1/8" thick but I did use countersunk screws, ie I gained 1/8"

I have checked the swing and the steam holes fully open and close

Cheers

Rich

[cnr6400]

Hi Rich, Glad to hear the swing is OK. I imagine you had a sigh of relief to see that the swing works, too! 

[Firebird]

Hi

Finally got the regulator fettled to fit so I can now finish the inner dome. Made a top from bronze and silver soldered on

I decided to pressure test the dome. Drilled and tapped the blanking plate and fitted a bit of 3/8" x 32tpi brass and silver soldered in. Fitted a gasket and used 8 M3 cap heads and nuts

Rigged up on the pump

Good job I decided to pressure test it

 

You can see the cracks in the brass tube

In the lathe to salvage the flange and cap

Start with another bit of brass tube this time a lot thicker

Silver solder the flange on then open out the inside with a boring bar until it just fits over the regulator

Silver solder the top on

Just got to pressure test it again

Cheers

Rich

[cnr6400]

Hi Rich, looks like you are on your way again despite the small setback leak. Good idea to test the dome as you go rather than wait until everything is together. 

[Firebird]

Hi

There are 2 stays that go from the back head all the way through to the smoke box tube plate. One is solid and the other is a 1/4" copper tube that doubles as a stay and the blower tube. The copper tube has to be threaded 1/4" x 40tpi at each end. Copper is difficult to thread being soft so I started with the die opened to its full extent then gradually closing up until the fittings screw on. The bushes in the back head and smoke box tube plate are tapped 3/8" x 40tpi. The fittings and blower tube are tricky to fit. The union in the smoke box has to screw into the bush and screw onto the blower tube at the same time, both having 40tpi threads.

At the back head the threads in the bush were not to clever so I made an adapter .010" over size ie .385" and screw cut it 40tpi which was then a nice tight fit in the bush threads. The adapter is tapped 3/8" x 40tpi. It just means the blower tube needs to be a bit longer and the blower valve will sit a bit further back. You can see the threads in the adapter and on the blower tube

The blower valve is likewise threaded 3/8" x 40tpi externally and 1/4" x 40 internally

I'm not fitting the blower valve just yet. I am going to make a cover for the back head to cover up my messy silver
soldering

Cheers

Rich

[Ye-Ole Steam Dude]

Hello Rich,

Coming along quite nicely.

Have a great day,
Thomas

[g0rph]

Hi Rich,

Is your boiler inspector OK with brass for the inner dome?   Mine wanted copper/bronze for that, when I re-made it, as it is "part of the boiler"   I know Martin Evans specified brass but times are changing!

The original on my loco was all copper, but the flange joint was dodgy, so i chose to remake the whole thing.

I made mine from 35mm domestic copper water pipe with a phosphor bronze top plate and gunmetal flange.   That passed the Club test with no problem.

On the stays, my hollow stay snapped at the blower valve during removal.   Those threads in copper tube are very weak!   I cut off the remnants of thread and silver soldered a length of 8mm phosphor bronze on, drilled it to let the steam through and reduced the extreme end to 1/4" for threading 40TPI.   I also cut off the threads at the smokebox end, bored the coupling !/4" and silver soldered it directly to the tube.   Internal/external threads are not necessary at BOTH ends!   The whole stay threads in from the smokebox end.

On my Rob Roy I silver soldered the blower valve to the (unthreaded) stay tube, fitted a couple of inches of bronze at the smokebox end with 3/8" x 40 external thread and screwed the whole assembly in from the backhead end.   A 3/8" locknut at the smokebox end helps to seal it.    Thats a much stronger solution than the double threaded design!   The far end of the bronze at the smokebox end can be reduced and made into a pipe fitting as usual.   (The external threads on Rob Roy stays are actually 5/16" but I quoted 3/8" in the above description to avoid confusion as we are thinking "Conway"!)

Its not an original idea of mine!   It came to me from Paul Wiese writing in Model Engineer 5th March 1982.

Hope that's of interest. maybe even help!

Richard.

[Firebird]

Hi

Thats a good point Richard 

Although the plans specify brass I might do that now. Once fitted I don't really want to keep removing it so it would make sense to do a copper and bronze one now 

Cheers

Rich

[Firebird]

Hi

Had a word with the club boiler inspector and he is perfectly happy with brass fittings.

But and heres the BUT I could be asked to remove them for inspection on subsequent boiler inspections so it makes sense to eliminate any future problems now. Some of the threads are quite fine and do not take well to repeated removal.

First up is the dome. I have made a new one from bronze and copper

Now for the hollow stay. I am following Richards tip  . The smoke box end has a bronze fitting made and threaded 1/4" x 40 which is perfect for the 1/8" pipe that connects to the blower. Why Martin evans has shown 5/16" x 26tpi on the plans I have no idea 

Need to make a bronze fitting for the backhead end of the blower tube/hollow stay now

I am making a new wet head from bronze, photos will follow

Also messing about trying to make some pipe bending rolls

Cheers

Rich