7mm David Andrews Princess - 6206 Princess Marie Louise

[Rob Pulham]

As I mentioned in a previous post, in between working on the cylinders, I was also working on the motion bracket.

There are two options in the kit depending upon whether you are building one of the first two engines, or the production batch. I am building the production batch so chose the appropriate etches.

They are designed as a main fold up with addition folded sections to create both sides of the cast bracket.



As etched when placed together they don’t fit, because the thickness of the metal pushes the etched slots out of alignment.



The simple answer to this is to carefully break of the wo sections at the fold line. File down the edge cusps so that the pieces align properly then solder them on in two pieces.

This is the bracket ready to fit after making sure that the slide bars fit in the slots.

 

[Rob Pulham]

The extras included with the kit include some very nice LG Miniatures castings for the rear valve guides. The only issue was positively locating them due to the nature of how they have been cast there is a very thin spigot to fit in quite a big etched hole.



My answer was to turn up a couple of locating bushes.



There are only two I just combined two small photos to show the detail.

This made them easy to locate into place.

 

[Lancastrian]

Rob,

An observation. The piston valve fronts and rears should be virtually at the edge of the cylinder block at the top.

https://media.gettyimages.com/photos/the-lms-william-stanier-designed-princess-royal-class-460-express-picture-id681557705

I found a similar issue with the two Schools, as well as the Black 5 I built for JohnK.

Ian

 

[Dave Holt]

I agree with Ian, but are the valve chests in the wrong place or the cylinder formers the wrong profile? I'd say the key dimensions are the centre distance height between piston rod and valve spindle and the widths between the rods/spindles across the loco. The others aspects are cosmetic and the cylinder formers can be dressed to suit, if necessary.
Dave.

 

[spikey faz]

Hi Rob

Whilst I don't have access to the same sort of machine tools that you have, the solutions you come up with to resolve some of the inevitable issues are very inspirational for me. I will endeavour to do better in my own builds!

Can't wait to see more.

Mike

 

[Ian@StEnochs]

The extras included with the kit include some very nice LG Miniatures castings for the rear valve guides. The only issue was positively locating them due to the nature of how they have been cast there is a very thin spigot to fit in quite a bit etched hole.



My answer was to turn up a couple of locating bushes.



There are only two I just combined two small photos to show the detail.

This made them easy to locate into place.

For those without access to a lathe similar bushes can be built up from telescopic brass tube. However, cheaper and quicker with a machine.

Ian.

 

[Dave Holt]

Another possibility, which I failed to consider earlier, is that the cast valve chests are too small in diameter?
Dave.

 

[Rob Pulham]

Another possibility, which I failed to consider earlier, is that the cast valve chests are too small in diameter?
Dave.

Hi Dave,
Showing my ignorance here, which bits are you describing as the valve chests?

The GA 's that I have access to, in the Wild Swan loco profile. Only show the cylinder castings themselves without the valvevguides/ covers. So for the replacement fittings I have had to take measurements from the David Andrews castings which may well be undernourished.

 

[Lancastrian]

Rob,

14.75 inches diameter for the valve chests/covers. 12.25 inches for the cylinder covers.

Ian

 

[Dave Holt]

Rob.
By "valve chests" I meant the circular parts of the valves which protrude from the main cylinder block, each end.
Ian has given the diameters, although I rather think the cylinder cover should be 21.25" not 12.25. Those are the casting diameters, so the cladding would be 1/8" or 3/32" bigger on the outside.
The top corner radius of the cylinder block formers is a much greater radius, 10.125", struck from a centre inboard and lower than the valve centre-line. Looks to be 1.5" inboard and 1.75" below, but the drawing dimensions are rather indistinct, so these might not be quite right. Anyway, you could just make that radius tangential to the existing top and outer edges of the formers.
Dave.

 

[Rob Pulham]

Thanks Gents, I will see how what I have compares to those measurements.

 

[Lancastrian]

Hi,

Yes, 21.25 inches....I'll have to admonish my fingers later !! Lol

Ian

 

[Rob Pulham]

Thanks for the feed back Gents, I was a way for a couple of days but I have now had a chance to measure the LG castings and my turnings. Remarkably to say the rather crude method of arriving at the sizes they are not a lot out.

They are follows

Valve chests - 0.39mm under size
Valve covers - 0.36mm over size

Cylinder cover rear - 0.1mm under size
Front - 0.31 under size

I now need to check the sizes against the GA for the cylinder block to see if I can work out where to make amendments

 

[OzzyO]

Hello Rob,

looking at my G/A drawing for 46202 over the outsides of the cylinders should be 8' 10 7/8" so approx. 62.35mm.

Hope that helps,

OzzyO.

Edit to correct the metric size.

 

[Rob Pulham]

Hello Rob,

looking at my G/A drawing for 46202 over the outsides of the cylinders should be 8' 10 7/8" so approx. 6.35mm.

Hope that helps,

OzzyO.

Thanks Paul, I hope to be back to it later in the week. At minute I am preparing for my first demo session at a show for a couple of years.

 

[Dave Holt]

Rob,

Best wishes for your demonstration. What is the subject matter? I'm scheduled to do one on loco construction at Scaleforum, in September, assuming it all goes ahead.

Regarding the cylinders, looking again, it is clear that the top corner radii on the front and back cylinder formers is wrong - they are too small and centred on the valve chest centres. Assuming that moving the valve chests is too big a job and might cause issues with the valvegear, the solution is to file/grind. etc, the corners to a larger radius, to the dimensions previously stated by various people. This will affect the length/position of the cylinder wrapper but should be easily rectified.
Dave.

 

[Rob Pulham]

Hi Dave,

That's pretty much the conclusion that I had come to after studying the drawings that I have.

The demo will be loco building, not that much actual building will take place. Or so I have found at previous shows, you mostly end up chatting and listening to a few life stories of course.

I also demo the Silhouette cutter but not at this particular show.

 

[Rob Pulham]

Returning this today to the Princess I tackled the cylinders as discussed up the thread.

I have filed quite a bit off but being careful not to over do it. Easier to take more off than to add it back.
Looking at the photo above I am not sure that you can really tell that I have taken any off but I have.

I have also dry fitted the cylinder wrappers again I won't be soldering them in place until I am sure that they don't need adjusting.

 

[Rob Pulham]

A little more work last night, had me fitting a couple of pieces of tube to fit between the front and back plates.

Use of the lathe allowed me to cut them very precisely and fitting them has made a very sturdy unit, which without them was quite flimsy.



I have a vague feeling that I might have swapped the covered over as I picked them up off the bench. The good news is that it seems to have resulted in an even better fit than I had yesterday.

 

[Rob Pulham]

While still deciding whether to take a little more off the cylinders (which I am leaning towards) I decided to do a dry fit of the cylinders, slide bars and the inside slide bars/ cylinder front to make sure that all fitted snugly but freely.

The outside cylinder unit, screws in place and I had deliberately not fitted the frame spacer that it fits to, until I was at a point where I could determine whether or not I needed to modify it to allow the inside slide bars to fit.

As it turned out I did. I needed to cut a slot out of the middle of the spacer between the two nuts.

Now I could have done it with the piercing saw but knowing that I would never have used the piece that I cut out, I found it far easier to pop it in the vice and mill it out.

Next, I added a representation of the bottom to the inside cylinders and then assembled all the parts to the frames to check the fit.