Scratch Building Darent in 16mm

[Hobbyhorse]

I've been posting occasionally bits about my Andrew Barclay Darent build in the workshop section, but its probably better to have its own thread. although the build is in the detailing stage I'll go back to the beginning. She was built in 1903 for the Provan Gas Works in Glasgow as a wing tank, and worked until the late 50's, some restoration did commence but sat in different locations until we purchased it bits.
I started the build after I sold the full size loco in 2012, I was one of four who owned the locoI purchased the loco in 1999 and spent the next four years restoring her. Originally built as 2' 6" gauge, our restoration was to re-gauge to 2' and add a saddle tank to run on a private line in Kent.
With my interest in garden railways 16mm gauge would be the ideal size, and as we had the loco running originally without a cab, then added the cab after a visit to the L&B in Devon I would construct two models.
The first bits made was the wheels using cast iron, a pattern was made that had both versions on using a removable section. With the first stage done on the Pantograph and finished on the lathe.

Simon




The bits after bringing them home to Kent.



Construction under way.

 

[Hobbyhorse]

I spent quite a lot of time on the drawing board setting out the frames with all the holes needed, also woking out the bearings as space is very tight with all the valve gear and motor that's going to be fitted. The frames are cut from .9 nickel silver, with a jig used to part drill the holes required for the rivets to be pressed in. I've using roller bearings which with the framework of the bearing are only 4mm thick, no springing or compensation is used just allowing 2mm downward movement in the horns. The square spacers are temporary and will be replaced as the build progresses.

Simon

 

[Hobbyhorse]

The next stage was constructing the the saddle, buffer beams, cylinders, weight shaft and making some patterns for the lubricators and weight shaft bearings.
As I wanted to fit some automated couplings I've been doing some development work on it, the couplings are the ones we use at Bredgar which I made a while ago. Using a spare ESU chip, servo driver board, and some small servos it does work, so next stage is to make it smaller to fit inside the saddle tanks.

Simon

 

[Hobbyhorse]

Some work on the brackets that support the running plate, cab floor and coupling pockets.
Spent quite a lot of time drawing up the boiler, smokebox, saddle and back plate. The first bit I'm going to do is the backplate, so made the pattern for it.
Simon

 

[Hobbyhorse]

The construction of the boiler, smokebox and saddle tank used was fairly straightforward, using cages over which the 10 thou nickel silver is soldered. Most of the time was spent drawing and cutting out the cage parts, accuracy is key with all the parts screwing together.
Simon

 

[Tom Insole]

What a stunning work of art. Really look forward to watching this come together! Keep up the good work.

 

[Hobbyhorse]

Making the motion and valve gear is one of my favourite parts of model making, as it certainly makes you think about the various setups needed to produce the parts, especially the rods that are cut on two planes, the photos should give you the idea.
Most of the rods and links are cutout on the pantograph miller, with the vertical miller and lathes also playing a part, I prefer using machine tools as much as possible as it gives a crispness to the work, hand work is used mainly on the cleaning up of the bits.
It's taken quite a time making all these bits so I'll let the photos tell the story.

Simon

 

[Tom Mallard]

Really great work, double thumbs up from me. Quite a different approach for you on some of the parts though.

Tom

 

[Hobbyhorse]

It's been a while but I've been thinking about how to manufacture the clack valves, so over the course of a couple of days these are the results. Other than the hand wheels which took the longest to make everything else was straight forward.

Next on the list is the injectors.

Simon.

 

[Hobbyhorse]

Time to get on with Darent as it's been three years since the last post. I've been working on the chimneys, it's one of the things I really enjoy making.
Using various jigs and tools speeds up producing them.
The shorter chimney was the easiest one to make because I've got the works drawings, but the taller one just relies on some notes and a few photos.
The reason for the taller chimney was because of a visit we made to the Linton & Barnstable line, shortly after finishing the restoration. The weather at the line was extremely wet and windy, so the decision to fit an enclosed cab and tall chimney was taken. We used the original base but cut off the tapered top, replacing it with a tube which came from a lamp post, and fitting a top which one of us had.












Simon

 

[Frank1958]

Really impressive, real thing and model.
Where is the full size loco now?
Frank

 

[Scale7JB]

My workshop enthusiasm far outweighs my knowledge of tools and processes sadly. All part of living in a flat in East London, so if I may ask, what is the type of cutter used in the collet in the third photo of your most recent post?

It looks like it has a taper on it, is it home profiled/cut for the job?

JB.

 

[Hobbyhorse]

Really impressive, real thing and model.
Where is the full size loco now?
Frank

Hi Frank

Darent is now at the Kempton Waterworks Railway.

Simon

 

[Hobbyhorse]

My workshop enthusiasm far outweighs my knowledge of tools and processes sadly. All part of living in a flat in East London, so if I may ask, what is the type of cutter used in the collet in the third photo of your most recent post?

It looks like it has a taper on it, is it home profiled/cut for the job?

JB.

The cutter is a standard bullnose 2 flute cutter, the size was chosen to suit the radius require.

Simon

 

[Hobbyhorse]

Cutting the backplate was a bit time consuming with a multitude of different holes sizes required for regulator, gauge frames, washout plugs, rivets etc, from 2mm down to .7mm. Those above 1mm used the cutting tools on the engraver, but the .7mm for the rivets used a slightly different approach. Firstly the location is spotted then drilled to size on the drill press.


The frame for the firebox uses two endplates and three spacers, with access holes to enable fixing to the saddle and boiler. The backplate is fixed to the endplate using 12ba screws located in the recess that is the fire hole, and two other points that are stays with hex headed fixings. The fire hole fixings will be hidden by the doors.


The wrapper uses the same rivets as the back plate, so with a lot of holes to drill in thin nickel silver a drilling template in brass was made first. Rolling the wrapper did cause a bit of distortion because of the holes, but was easily removed with some emery cloth.
The radius on the back plate was hand filed with a small guide to help.




Before applying the rivets to the backplate the small additional thickening plate that allows the blowdown valve to be fixed to the bottom was made. The rivets required two different methods of fixing, those on the wrapper are soldered in, and the backplate ones glued in from the rear. A little bit of cleaning up is needed with solder around rivets, bit other than that I'm well pleased with the result.



Next is the firehouse runners and doors, these will hide the two fixing points.

Simon

 

[Hobbyhorse]

After a very wet and windy trip with Darent to the Linton & Barnstable Railway it was decided to fit a cab. So with one model fitted with the cab it would portray her in both guises, although I do prefer her without the cab.
Using the drawings we made for the cab it was just a case of reducing the scale to produce the patterns for the miller. Cut from 10 thou nickel silver these folded up easily, and when soldered with the bottom fixing strips and to the roof made them quite robust. Small bolts are used to fix the cab to the cab sheets. The small slot in the back sheet angled piece was to allow the coupling to be seen while coupling up. The cab windows are simple turnings that incapsulate the glass when both are fitted, after painting is completed.









Simon

 

[Hobbyhorse]

After deliberating which way to make the safety valves, I decided to follow the prototype exactly which meant some quite small parts, especially the buckle at the pivoting end of the valve. In the end I made the actual valve drop into the housing, this gives the correct shape to the valve tops. The rest of the part are straightforward machined parts, except the springs which took the longest to make. The cover plates have also been made, but not fitted yet as the hand rails need to be made.





Simon