7mm David Andrews Princess - 6206 Princess Marie Louise

Rob Pulham

Rob Pulham

Western Thunderer
Steeping back slightly, I was asked by a fellow GOG member on the forum how I planned to tackle the front crank pin 'nut'. Initially I hadn't a clue how I was going to do it other than probably reversing a crankpin bush. As I was pondering on how to reply to the enquiry I had the germ of an idea.

I had a go at a proof of concept this morning after my lightbulb moment when replying last night.

This is what we are looking for (just in case you needed a reminder;))

51915939734_e5d4945ce6_w.jpg



This was my first attempt, I think that there was a slight bend in my bit of spare 8ba stud as it didn't machine each face evenly and the nut/stud portion was far too big

51917706999_00940ebc6c_z.jpg



After a coffee break I reversed the short length of stud and had another go.

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And yes it should have a cotter/split pin....
 
Dave Holt

Dave Holt

Western Thunderer
The BR version of the hand book was published by Ian Allen. Mine is the 1957 edition and was published in 1977. It has the brake system and LMS brake valve diagrams, together with various BR and other regional systems.
Dave.
 
Rob Pulham

Rob Pulham

Western Thunderer
Now that I have a proof of concept on the front crank pins, I returned to the brake linkages.

The linkage that connects the cylinder with the brake pull rods is supplied as a pair of etches that are laminated together. - Parts AA/AB in the diagram below.



I decided to see what I could come up with as an 3D compromise. So I butchered the etches and then laminated them together with some additional parts turned/milled from rod.

Which gave me these:





Next, I added strips of nickel to the two etches which support the brake linkages behind the brake cylinder.



I did need to cut one of them to accommodate the motor, but I preferred to cut it after I had made them up. You can see that there is a half-etched cut line to allow for this.

Next, I went to fit them and that's where life got interesting again. If I soldered them into the slots in the horizontal plate as intended, I lost access to the screws which hold the rear springs on. I am pretty sure that during the course of fitting the motor and get it running, that I will no doubt need to remove the rear springs at some point.

My solution was to make a small plate from scrap etch which could be soldered in between the two frames and then drilled for a 10ba screw. I had to make a little jig from the 10 BA screw and a piece of spare rod and some washers to space the top part of the frames the right width to allow me to solder the plate in at the bottom. I made it slightly trickier for myself by electing to make it precise enough that the frames still located in the slots. Soldering the base plate on took a couple of attempts before I was happy that it sat correctly.





Then it was a fairly simple matter to drill 10BA clearance (1.8mm) and solder a nut on the frame. This allows for the screw to screw in from the top of the chassis on the basis that it's less likely to drop out in motion that way.



As an aside I was really surprised that the stub on the base of the brake cylinder was a really snug push fit in the hole snapping into place when I pushed it home. I was surprised because I hadn't thought to measure the hole prior to assembly of the frames and measuring it accurately was quite difficult with the tools I have.





In the view from the top of the frames above you can see the screw and the tabs of the frames located in the slots tightening the screw makes them snap into place quite easily.
 
3 LINK

3 LINK

Western Thunderer
Hi Rob,

Quick question, what flux are you now using? If I remember correctly you were having trouble with the fumes. I am using the so called “ safety flux “ at the moment, but I’m sure it’s giving me a sore throat, so today I had a fan running next to the work bench to dissipate any fumes and so far I would say, yes it looks like either the solder itself or the flux was to blame.

Martyn.

P.S. Enjoying the build and the extra details your adding..
 
Rob Pulham

Rob Pulham

Western Thunderer
Thanks Martyn,

Your must have a good memory, I was having problems with flux fumes but I have been using Building O Gauge online safety flux for over 10 years.
The only reaction that I have to it is that my hands sometimes itch if I have had a long soldering session.
 
Rob Pulham

Rob Pulham

Western Thunderer
This week has mainly been more lathe work. After a suggestion elsewhere I remade the two front crank pin bearings in steel and then because I had worked out a technique to make them much finer, I remade bearings for the other wheels as well. Hopefully my first efforts will come in somewhere for something.





With those done to my satisfaction I turned back to the chassis and the cylinders/motion brackets. More on the latter in another post but first the cylinders.

I used the David Andrews Slidebar/cross heads for the inside motion and the LG Miniatures pair that I will use for the outside motion don't come with the cylinder back plate.

Timing being perfect, just this week I acquired some assorted thickness Nickel Silver bar ends. They weren't cheap overall, because I bought quite a few. But they worked out as a one off, about half the price I would expect to pay for similar lengths/thicknesses from my regular supplier.




Then I turned (if you will pardon the pun) to the fronts of the cylinders. The castings with the kit are nicely detailed but sadly both the cover plates and valve guides are oval, presumably as a result of shrinkage in the casting process.


51935584024_712d64fc22_h.jpg


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51935583289_fc954c9768_h.jpg


They still need a few more details adding before I solder them to the cylinders fronts but I am happy with them so far.

There is a gent, whom I have met a couple of times. Who posts superb builds over on RM Web under the username of Jazz. His tag line in his signature is, "Learning by doing" and I couldn't agree more with the statement. I have learned a great deal this week while twiddling the knobs on my lathe...
 
Rob Pulham

Rob Pulham

Western Thunderer
Another productive session yesterday afternoon saw the parts above detailed ready to fit.

Although I have the Milling machine and a rotary table for it, I kept my Proxxon mini Pillar drill and dividing head which I use for drilling out the small stuff.

This is the set up when I lift it onto the bench.



This is partway through drilling out the valve guides



Once drilled, I did my usual trick of wire and microbore tube filed to a hex for the head. I also fitted the rather nice brass cylinder relief valves that came with the kit.





 
michael mott

michael mott

Western Thunderer
Wow rob that is some really nice machine work and filing, I like the little rotary table as well, I have not seen one like that before, is id just rotated by hand the clamped with the black handle?

Michael
 
Rob Pulham

Rob Pulham

Western Thunderer
michael mott said:
Wow rob that is some really nice machine work and filing, I like the little rotary table as well, I have not seen one like that before, is id just rotated by hand the clamped with the black handle?

Michael
Click to expand...
Hi Michael,
Yes, there are a couple of pins to tighten the chuck and then as you say, rotate it by hand and lock in place with the handwheel.

It's all I had before buying the lathe etc. And its too useful to let go.
 
MarkR

MarkR

Western Thunderer
Hi Rob,
Could you tell me please, the manufacturer of the rotary table?
Many thanks
Mark
 
OzzyO

OzzyO

Western Thunderer
Hello Rob,

I know that you like putting the nuts and bolts on the parts that you have made but I'm sorry to say that the bolts on the front valve spindle covers don't work for me as they are way to big. You would be better to just use some 0.6mm or 0.7mm wire to represent them. Please see the attached photo of 46206 at Crewe in 1962.
46206 Crewe 1962 - Copy.jpg

ATB

OzzyO.
 
Rob Pulham

Rob Pulham

Western Thunderer
Thank Paul,
You succeed, where I failed to find a photo that you could make the details out in gloom.

I am inclined to agree with you, so will add it to the list.
 
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