NSW 'B' class mogul

[David]

Thanks for the info guys. The website blurb says 0.15" but that can't be right. Glad to know the primer doesn't do anything except improve setting time.

At about 6:30 this morning I thought I'd made another mistake on the regulator, so I got up and had a look given I wasn't going to be able to let go of it until I knew.

Here is the part out of the pickle.



That groove in the bush on the left is for for a 3/4" OD viton o-ring. It had not occurred to me that perhaps I should have put the o-ring on the pipe before soldering the bush on. The body on the right is 3/4" and the smaller dia of the bush is 3/4". All I could do was stretch the o-ring over the body and roll it along, then over the end of the bush and into it's groove. The o-ring still seems tight so I'm hoping the long journey over the body hasn't stretched it.

I looked at the next bit that needs attention and it is a threaded cap that goes at the rear of the body. It looks suspiciously like brass, and given I made it two years ago I can't remember if it is brass or very yellow bronze. I think I'll make it again so I know it's bronze. It's only 3/4" OD so I should have some 25mm bronze around for that.

[Deleted]

Hi David, perhaps it's 0.15mm and not 0.15"..IIRC loctite give their dimensions in metric.

Cheers

Pete

[Roger]

The 'O' ring will be just fine, you can stretch them a long way before they are permanently stretched or split.

[David]

To be fair the instructions said something like this might happen trying to thread the copper.





I was at about 3/4 depth on the thread when it jammed on the tool and went up and over.

That's the only piece of 3/8 tube I have so it had to be recovered. I turned up a bronze part to solder onto the end. This will act as additional support for the regulator operating rod so it's not all bad.



I convinced myself the threaded cap was bronze after all, so did not remake that. The fact I no longer had the 3/8 x 26 tap helped the decision. I took it out of the pickle this morning to take the photograph for this post, and the soldered joint to the threaded cap hadn't taken.



After redoing this, the next job is to silver solder the stainless valve spindle and operating rod together.

In his Stirling Single thread John pointed to a Beeson Stirling Single in a museum in Sydney. I had a look at that model a couple of years ago and it is very impressive. You may be interested to know Mug Builder was commissioned to make a model for that same museum: collection.maas.museum/object/99548

[David]

Resoldered the rear tube to the cap and soldered the stainless bolt to the spindle.



I used Tenacity flux for the stainless, no idea if it helped. I did a test on two pieces of 1/4" stainless butted together and the solder flowed well and it looked ok but I was able to snap it with my fingers. Being an optimist I put that down to butt joining rod that wasn't clamped in place probably wasn't a great test so press on.

The spindle shot out of the bolt twice when the flux boiled! Eventually I had one end of the spindle pushed against the bench vise and the bolt being held in place by a firebrick and even that moved as the steam had to come out where the spindle was, there being no other escape for it. It got done and I bent it straight as best I could. It seems like a good joint, or at least stronger than my hands.

The thread where the riser screws into the body is loose enough you can probably see through it in places so that will have to be sealed with some sort of gloop. I assume just letting the water through would be a bad idea.

I didn't get the hole for the riser lined up as well as I'd hoped, it's somewhere like 20 - 40 deg off vertical but that won't matter. It just irks me because I did try to get it right.

So, having soldered everything at least twice and remade a quite expensive bush we're nearly there. Five days in - elapsed time - and all the parts had already been made when I started last Saturday!

Still have to solder the rear fitting into the body with some high-temp soft solder, make sure I can screw the rear tube into the backhead bush, and fix up the spindle to take an operating lever and nut.

[suctionhose]

when silver soldering something into a blind hole, drill a cross hole to let the flux out. Unless, you do this the solder can't penetrate down the hole and a) it pops out as you found and b) the solder is merely a fillet around the outside.

[David]

I thought about it, but couldn't see how to drill a hole cleanly through the thread of the bolt.

Here I'm trying to figure out how to model a clack valve from a flat drawing. Given I had no idea where to start to make that curved pipe a couple of hours ago I think it's good progress.

[David]

No 'real' work, but I did find some 965 solder to do the last soldering operation on the regulator and spent tonight fiddling about with the dummy top feed clack model. I'm hoping it isn't too fine to preferably cast, or 2nd choice 3d print. With luck the threads as modeled can be cleaned up with a die from the cast/print.

If the threads are a bad idea I guess those parts can be made separately and soldered on.

[kipford]

David
I would not attempt to cast the thread or the internal cone, even with a 3D printed lost wax you will not get either the form or surface finish you require. Leave some meat on the casting and machine it. Then 3D print the machining fixture(s) to hold it as Adam does. 3D metal printing is hideously expensive unless you have a nice friendly local company.
Regards
Dave

[David]

A shame. Given the corners in the pipes the bores can't be machined. You don't think a die would clean the threads up? I could remove the pipe beneath the body and the thread beneath the flange but at that point I may as well turn the body and use the tiny German screws to decorate the flange with the stiffening gusset having to be added later.

Finally got the last soldered joint on the regulator done today. A lot of easing of the clearance holes in the superheater header with a long 2mm endmill and it all fits, even at the backhead end where the bush simultaneously screws into the backhead and onto the end of the regulator.

[David]

Last week saw the handbrake column and handle done. The column is tapered and the bosses at the top and bottom have different diameters so the turning operations had to be done in a very specific order. The only thing I should have done differently was drilling the cross hole before tapering because it ended up off-centre.

I then started on the seats last night. They're a folding design on the real thing but fixed on the model. The folding mechanism isn't apparent on the bits I've made so far.

Taking it easy with the seats. There's a few things I could have done that would have made the next steps easier but I'll muddle on with what I have. I'll print out some drilling guides for a set of 4 holes on a 3/4" pcd that would have been better done before parting the seat discs off. A hole in the middle of the disc to aid assembly would have been trivial on the lathe but I had to punch and drill it afterwards, when I had the idea. It doesn't matter they're a bit off.

With luck the most tricky bit will be a pair of 29mm dia 1mm thick wooden discs that sit on top of these brass ones. Can you part wood with a parting tool?

[ettingtonliam]

You certainly can part off wood with a parting tool just make sure its really sharp. When I'm pattern making I use a piece of broom pole or wooden rolling pin (no, not the one from the kitchen, she will notice) because they are dead cheap from the local thrift shop. Problem then for you is that it will be end grain, and I'm sure your full size seats would have shown long grain.

[David]

The seats are progressing. They've taken about 8 hours over the course of last week. A few more parts need making (or reattaching) but they're about the right size and shape.

Very tricky to solder together because the seat is cantilevered from the bracket that screws to the cab with no easy way to hold it all in alignment. It's pretty weak too but there will be a diagonal support rod that goes from below the seat to the bottom of the bracket.

[Roger]

Hi David,
That's looking good, very neatly done. I find that it's worth desiging the individual parts so they lock together with tabs which can be peened over before soldering. It does take more time, but it's so much easier when you come to solder them. You can also Silver Solder them if you do it that way, which is much stronger.

[David]

Thanks Roger. I agree with what you say but in this case I was hoping I could just cut and file the parts up by hand and not take too much trouble about it. We know that always leads to making life harder down the line but hope often trumps experience!

I certainly had tabs and slots in the front of my mind while I was trying to hold things in place during the soldering... Even a little angle would have helped. If I was willing to take more time then the dummy hinge - not yet present and represented by nothing more than a 1.6mm rivet shank - could have been built up as a support structure, albeit a very thin one.

I used tin/silver solder to hold the seat 'bar' to the angle and it will be strengthened when a further support rod goes underneath.

[David]

The tricky parts of the seats were finished the other day. Many parts came unstuck in the process which is why one of the angle gussets looks wonky. I'll have a look at that this morning and see if it really is that bad.

[David]

Today was handrail brackets for the cabsides. I was able to come up with a sequence which allowed machining to the numbers in all the cases that mattered to it went pretty easily. Having two 1/4" 5C collets allowed me to save time by not having to constantly swap one between the lathe and the square block. The square block was indexed against one side of the vise jaws or the other so no measurement was required after the first part was setup for the operation. It still took about six hours to get to the point seen in the last photo, so a bit less than an hour each. I can't think of a way I could have done it faster.

First up turn the stock to 6BA major diameter for about 5mm, and 4.8mm for about 10mm after that. Put the thread on with a die.



Next it goes in the mill to be flattened top and bottom, to 3.3mm thick. Then cut the blank off with a hacksaw. All 8 were taken to this size so the endmill height didn't need to be changed.



To drill the hole through I made a threaded tophat arbor that fit in the 1/4" collet and could sit tight up against it repeatably, then calculated the height under the blank when it was screwed into this and sitting horizontal. I machined a block to this height and used this an both a means to set the blank flat in the block and as a drilling support.







Then some stainless steel filing buttons and a fitted bolt got the radius on the end.

[Roger]

Hi David,
Those came out really well, I'm sure you're pleased with those. I'm wondering why you chose Brass though, wouldn't Steel have been just as satisfactory and easier to paint?

[David]

Thanks Roger. I chose brass because I thought it would be easier to work. In hindsight steel would have been just as easy. There are other brass bits all over the place so that cancels out any issue with painting.

I've fitted these little brackets today after buying some 2.6mm welding rods yesterday afternoon. The handrails aren't at their final lengths but now I know they fit.

I checked the gussets on the seat brackets and they're both straight, but one of them is slightly below where it was when it was first soldered in place. I'm going to leave it because it's facing the front of the can so can't be seen.

I also trimmed the reversing screw bracket back by the same amount I moved the screw to make it look more tidy.

[mugbuilder]

G,day David, don't forget the alterations to the rear drag beam for clearance for the blow down valve and operating tool. Easier done sooner than later. All is looking really good and mostly neater than mine. Barry.