Adams "O2" Calbourne in 5" gauge

[flying fox]

Greeting Steve, very nice, what pressure are you thinking of using for air brakes?

[springcrocus]

Greeting Steve, very nice, what pressure are you thinking of using for air brakes?

I've no idea, Brian, but as Don Young's drawing calls for testing at 100psi, I assume that working presssure is half of that. It's all moot, however, if I can't make a working compressor and that appears to be quite a daunting challenge at this size. 

Regards, Steve

[flying fox]

That's the tricky bit Steve, I had some success using Schrader valves from car tyre as valves and a stem driven pump, but the volume of air produced was low, although it seemed to have a fair pressure.  My experimental system suffered from leaks.  I have a crosshead driven pump fitted on a GER loco I have now put aside, but I might finish it sometime.
Regards
Brian B

[springcrocus]

I've been completing various jobs around the loco but none of which warrant an individual write-up and one of those jobs was to reduce the height of the safety valve bushes. When I tried to fit the manifold to the rearmost bush, the outermost connections of the manifold fouled one of them. The boiler was removed from the loco and set up on the mill with a very light clamping arrangement to hold it in place. The copper is still very soft and I didn't want to risk distorting anything. Ten thou cuts with a very sharp tool being the order of the day. I made a pair of threaded brass bungs to block the holes and stop a load of swarf falling into the boiler.



With the manifold screwed into place, I was able to finish the front spectacle plate and get that fixed into position. Also, the tanks have had the filler caps and the front footstep assembled.



At the rear, the buffer stocks and the drawhook plate have been fitted. The roof is just resting in place at present while I work out how best to make a removeable section to allow access for driving the loco.



A pair of pressure relief valves were made from brass stock, starting by making the threaded end first, then screwing into a mandrel and turning the outer form and boring the internals.



The spring adjuster nuts were made by threading a short length of brass rod, then milling four slots down the sides.



An adjusting spanner was made by milling a cruciform shape on the end of a length of steel bar. One of the parted-off adjusters is sitting on the collet.





The brackets for the air reservoir were made and the assembly fitted to the top of the left-hand tank. Also seen in the next picture are the two pressure relief valves fitted to their bushes.



Calbourne has flatted rivets around the running plates, rather than the more common roundhead rivets so these have all been filed down to suit. The smokebox door has also been completed, along with the hinges.



The last picture today is an overview from the left-front quarter. It's starting to look like a loco now.



Regards, Steve

[wagnmkr]

This is coming along very nicely! 

[Kim]

I would say that is great progress!   

Kim

[Admiral_dk]

What a lovely Tender Lokomotive 

Per           

[Prowler901]

Wow, what a beautiful locomotive!  You're doing great work.

Todd

[flying fox]

Looking good Steve, well done.
Regards
Brian B

[springcrocus]

Wagnmkr. Kim, Per, Todd and Brian, thanks for following along. 

The boiler clacks are quite prominent because they have a fancy spacer between the valve and the pipe flange. I made all the parts for these assemblies from phosphor bronze, starting with the two main body parts. These are just straightforward turnings that get silver-soldered together.



Previous experience has shown me that they never line up properly when assembled in place so, this time, I made sure I had a means of tightening them into the clack bushes before soldering. After screwing into a stub mandrel, the two branch pieces were drilled 4.3mm diameter for about 20 thou, followed by drilling through with a 4mm drill. A hexagon shape was formed in the ends by pushing in a cut-off Allen key with the end ground flat and square , then forcing deeper in the bench vice. This was followed by turning the O/D with a radius tool. I was able to remove the parts from the mandrel without damage.



The branch pieces were then screwed tightly into the bushes, complete with a gasket washer, and the top marked with a line. They were also noted as left or right. Having the hexagon for an Allen key really pays off in this situation.



The four bolt holes in the body were drilled next, a four-jaw self-centering chuck proving ideal for holding the work in this operation. Sorry about the poor out-of-focus picture. The auto-focus sometimes chooses the wrong detail to highlight.



I made the two spacer pieces and the two flanges next so that I could drill the bolt holes while the 4-jaw chuck was still mounted on the mill. The drawing says to make the spacers 1/4" wide but this looks too chunky to me and I have made mine 3/16" thick. The grooves were cut with a 4mm ball-nosed endmill and the outer radii formed with files, although they could do with a bit more work. The flanges are 3/32" thick, the same as the flange on the body. Then it was the main body, drilling and counter-boring the side hole for the branch piece to be soldered into. A pair of 10BA threaded studs were screwed into adjacent holes and rested on the vice jaw for alignment purposes.



The two parts of each valve were joined together using a ring of 0.5mm silver-solder wire on the stem of the branch. The work was held in an engineers clamp so that heat could be applied from below and avoid directly heating the solder. Correction fluid has been painted onto the threads to protect them from stray solder. Edit: I forgot to mention that the alignment mark on the branch was used to ensure accurate positioning in the body of the valve.



This is the collection of parts needed to make a single clack, with an assembled one to the left. The sealing ball is a silicon nitride one; these are extremely hard and even more spherical than traditional steel or stainless steel ones. The only disadvantage is that they are half the weight of steel balls and have a slight tendency to float off the seat when not under pressure. You can give them a damn good whack to bed them in, though, and you won't damage the ball.



After cleaning up and assembling the various parts, they were fixed to their respective clack bushes using the same gasket washer as before. Nice and tight, and perfectly aligned. The body is a bit too long compared to the prototype but this is one of those situations where things won't scale properly. If the clack valve was scale size on the outside, the inside would be too small to let enough water into the boiler.



Regards, Steve

[Kim]

Very nice looking clack there, Steve.  Does the other one go on the opposite side of the boiler?

Kim

[Keith1500]

Still following your build Steve, enjoying it too.

Yes that’s my technique. I like the fitting to tighten nicely and be in the right position without the need to pack with copper or fibre washers. I like to use liquid Ptfe on the treads. It seals nicely and doesn’t look unsightly.

[Prowler901]

Nice!  Excellent reproduction of the prototype.

Todd

[Kim]

Still following your build Steve, enjoying it too.

Yes that’s my technique. I like the fitting to tighten nicely and be in the right position without the need to pack with copper or fibre washers. I like to use liquid Ptfe on the treads. It seals nicely and doesn’t look unsightly.

OK, I had to re-read Steve's post a second time to catch that.  That's a very clever way to set the orientation of the valve prior to soldering!  I'll have to file that away.

Kim

[Mike R]

Steve,  I'm following along.  I'm keenly interested in your steel cab and tank work, as the cost of brass is prohibitive in this and larger scales.
Carry on please and great work so far.

Mike