David Andrews Princess Chassis Assembly

The last few days have been spent assembling the chassis frames ready for detailing.

I had to trim away sections of some the frame spacers to accommodate the thicker cast spring hangers, the horn guides and the gearbox. Most of this adjustment was done prior to assembling the frames but the cut out for the gear box was done afterwards. The mill came in handy for removing the bulk of the cut out, I just needed to square up the round corners of the slot with a file.

David Andrews Princess Frame Spacers
David Andrews Princess Rear Frames
David Andrews Princess Front Frames
David Andrews Princess Assembled Frames
David Andrews Princess Assembled Frames

David Andrews Princess Driving Wheels Springs and Hangers

The rest of yesterday was spent fitting the replacement driving wheels springs. Due to fitting Alan Harris wheels, I thought it necessary to make the springs and hangers removable so that the horn blocks can be dropped out for maintenance. With Slaters wheels it’s easy to loosen the screw and ease the wheel from the axle to wiggle them out around the brakes. When using telescopic axles there isn’t the flexibility to wiggle the wheels so alternatives need to be sought.

Replacement Driving Wheels Springs
Replacement Driving Wheels Springs

David Andrews Princess – Home Made Castle Nuts

A little more miniature madness this morning. The LG Cross heads are supplied with really nice cast castle nuts on pins for attaching the connecting rods.

The David Andrews castings have something similar but it’s a plain nut (I would guess that the pattern maker used either a 14 or 16 ba nut) rather than a castle nut specifically.

A quick search online for photos of castle nuts and off I went. These are very cruel close ups but I am happy with how they have turned out and now I know how to make them knocking more up in the future will be relatively simple. To give a better idea of scale the pin through the nut is 0.8mm. You will note that one of them has a thick stem to the pin? That’s because I made the first one with a 0.8mm pin right through but it’s a bit sloppy in the cross head hole and it’s well and truly stuck so the other two I made by turning a piece of 1.2mm rod down to 0.8 for a couple of mm on each end.

Home made Castle Nut
Castle Nuts
Castle Nuts
Home made Castle Nut
Home made Castle Nut

David Andrews Princess Inside Motion module

After a bit of fiddling about I got the cylinder front and motion plate for the inside motion made and assembled.

The fiddling about was my own fault, I initially made the motion plate too shallow and therefore it would only accept the slide bars at their very ends and I needed to mount it further along. I was also considering adding the valve guides and after spending some time fettling the rather misshapen castings I realised that they wouldn’t actually be seen so decided not to go any further. After considering them I had started to remake the cylinder front plate in order to accept them but in the end used it for the replacement motion plate so it worked out perfect in the end if a little convoluted getting there.

One beauty of having a mill is that cutting out the centre section of the motion plate was so much easier than using a piercing saw and files as I have done in the past.

Princess Inside Motion
Princess Inside Motion

I may yet need to cut the ends off the slide bars but I won’t know for certain until I start assembling the chassis.

David Andrews Princess – working on the frames

Since my last post available time has been spent finishing tapping the horn guides, cutting the springs and hangers from the other side frame and then cutting out and modifying frame spacers.

Like most kits many of the provided frame spacers are either flat or L shaped plates. How ever there has been some attempt at replicating the actual frame spacers of the prototype albeit it in a very 2D form.

I have taken these 2D spacers and made then more 3D by adding framing to openings making them look a bit more like they do on the real thing. I still have some to go but this is a flavour of what I am aiming for.

David Andrews Princess Modified Frame Spacers

This model is also going to have the rudiments of inside motion. In so much as there is a large hole in the frames where the crossheads of the inside motion are quite visible. Due to the axles being telescopic I cannot fit a proper crank axle so what I plan is to use eccentrics to impart a small amount of motion to the crossheads/pistons giving some visible movement behind the frames.
Before moving ahead to assemble the frames I need to make a motion plate and cylinder front for these.
I started this by cleaning up the David Andrews cross heads and slide bars (I have a set of more detailed Griffin castings for the outside motion).

David Andrews Slide Bars and Cross Heads

For anyone who is planning on fitting outside or inside motion time spent fettling the parts to get them smooth running without any hint of hesitation will pay dividends when you come to assemble the various rods etc. to them.

The piston rods on the DA casting were tapered getting noticeably thicker at the crosshead end but reasonably straight. I have come across quite a few castings even from the better kits where piston rods have been like a banana. To remove the taper I put the end of the rods in my Dremel and making sure that it was rotating centrally I gently filed the crosshead end until the rods slid cleanly through the piston glands.

If you do this make sure that you don’t have the drill set on too high speed or the weight of the cross head spinning if slightly out of balance may bend the piston rod.

David Andrews Princess Chassis preparation

I am currently working on preparing the chassis for assembly. Due to the provision of cast driving wheel springs and hangers I had to cut of the etched versions from each side of the chassis. Here I am half way through the process. I am also cutting out for the horn guides at the same time

David Andrews Princess Chassis

The horn guides and blocks are Finney and consist of an etched backing plate with a fold up guide.Time spent making sure that they are square and free moving at this stage saves loads of hassle down the line.

Finney Hornblocks and Guides

Previously I have soldered a 12ba nut on the top of the guide to allow the screw to set the ride height later in the build. I found myself short of 12ba nuts so rather than wait I cut some strips of 0.7mm nickel and drilled them 0.8mm I then soldered them to the top of the guide and then drilled through both sections 1.0mm finally tapping them 12ba. I still have three to finish tapping this morning. The replacement springs will serve to retain the horn blocks once fitted. and I am considering making them removable as the Harris wheels on telescopic axles need more movement to allow them to be removed.

Scratch Built Side Control Unit

The last bit of the bogie puzzle is a side control unit.

I started with a short length of 1/4″ square brass rod. I drilled a 5mm hole through the centre and then milled 2mm off the side of each end to create the main central block.

I don’t plan to do anything more with it now until I have assembled the chassis and can confirm if it needs any further adjustment to fit it.

Scratch Built Side Control Unit
Scratch Built Side Control Unit
Scratch Built Side Control Unit

David Andrews Princess, The Bogie

The bogie as supplied is a fold up box to which additional end pieces are soldered. I forgot to take a phot of this so I include a snip from the instructions to show what it consists of.

I have some very nice castings in place of the etch parts B6, but sadly as you will see not much of them is visible on the finished bogie.

Replacement Bogie Springs

I built up the bogies frames to create the I section where needed, as with the trailing truck. I also added some rivet strip along the top. Parts 164 are white metal castings which were passable, but I chose to remake them from brass

DA Princess Bogie Frame modifications

You will also note parts B10, this is where period photos are essential because these were not fitted until the 1940’s which is later than this model is to be depicted (around 1938). There were location marks half etched into the spring plates so I reversed them to hide the marks.

DA Princess Bogie Frame modifications
DA Princess Bogie Frame modifications

DA Princess Bogie Frame modifications
DA Princess Bogie Frame modifications

I have also elongated one pair of holes so that I can provide some basic springing of one axle.

David Andrews Princess Completed Bogie
David Andrews Princess Completed Bogie
David Andrews Princess Completed Bogie
David Andrews Princess Completed Bogie

Once it’s all assembled you can see what I mean about the visibility of the springs.

David Andrews Princess, starting the loco from a different position

Usually when I start a loco build, I start by making up the coupling rods in preparation for aiding with the assembly of the chassis. On a whim, I decided to build the trailing truck and the bogie first.

First the trailing truck.

Basic Truck as Supplied with extra details started

The truck is in two parts an outer and an inner which holds the axles/wheels. As it comes in the kit it’s a fold up frame with the front yoke as separate etches that you assemble to create the I frame.

Basic Truck as supplied

I am working from the Wild Swan Loco Profile book N0 4 The Princess Royal Pacifics and aside from photos and historical information about the development and changes to the locos over time it also contains a number of General Arrangement Drawings. One of sets of drawings is for the trailing truck and shows the differences between the first two and the main production batch. 6206 is from the latter. What is clear from the drawings but not from photos (because you only see the sides not the ends) is that the front and back of the truck is also I beam type construction. I decided to add this from 10 thou nickel sheet cut with the guillotine. You can see the first piece in place on the photo above.

Main truck with castings and extra plates added
Main truck with castings and extra plates added
Main truck with castings and extra plates added
Main truck with castings and extra plates added

The inner truck is a basic fold up box that you add a couple of nuts to and then fit bearings. Although it cannot be seen from any angle unless you turn it upside down the drawing shows that there is some kind of side control mechanism so I decided to turn a basic representation of it from a couple of pieces of brass rod.

Inner Truck detailing – representations of the side control mechanism

Lastly the truck assembled and ready to fit to the chassis at some future point.

Trailing truck assembled
Trailing truck assembled

The additions have also added a little more weight to the truck so with luck I may not need to try and find room for some lead later on.