TFW’s workshop

[Tim Watson]

Making things from scratch is sometimes more straightforward than using components from a kit, as you can design the bits to be held whilst working on them. This was especially true when making the first cross head for the NER 4-6-2 class. The inner crocodile was filed up from 1mm steel sheet, drilled in the end for the piston rod (0.5mm pivot steel) which was silver soldered in place. It was adjusted to be an easy sliding fit in the slide bars with the piston originally being very long to give something to get hold of. The outer pivot and slide bar slippers were made from 0.5mm steel sheet, centred on the 0.4mm diameter pivot hole for the little end, but again with a long handle still attached.

Having the handle to hold enabled easier filing of the appropriate rebates and surface details.

The two components were soft soldered together and, once the main filing was complete, cut off from the handle.

The connecting rod will have a 0.4mm diameter pin silver soldered to its end which will be the little end pivot. This will be retained by a small collar on the outside of the cross head, representing the prototype little end retainer.

I now need to finish off the second cross head and then the connecting rods. I much prefer steel for valve gear, it is stronger and, being harder, is more forgiving when filing up components - it takes a little longer so you have time to think before you make a mistake - if you understand my strange logic.
Incredible what iPhones can do isn’t it?

Tim

 

[Susie]

Hi Tim,

Do I take it that the crosshead is held in line by the piston rod and the outside slipper: is there no inside slipper? Presumably there is no room for one.

 

[Tim Watson]

If it needs an inner restraint, then I will solder a thin wire across the back, towards the front of the cross head, spanning the slide bars. Can only do that once the connecting rod is made and fitted. That is what I did on the Baldwin 2-6-0. In fact the slightly concave sliding surface of the slide bars is acting a little bit like a trunk guide on this engine.

Glad to see someone is paying attention.

Tim

 

[Susie]

I always pay attention when watching a master at work! I did wonder if you had filed the slide bars flat or left them as a trunk guide; now I know. Thanks for your postings on this build, Tim. I think we are all learing a lot from you.

 

[Tim Watson]

The Raven NER 4-6-2 class now has an ‘engine’ with the connecting rods roughed out and the cross heads and pistons in place. The connecting rods will require fluting, amongst other things.


Tim

 

[Tim Watson]

Perhaps a bit crazy.
With such large big end bearings, it would have been churlish not to include separate brasses.

Tim

 

[Herb Garden]

Perhaps a bit crazy. View attachment 179782

With such large big end bearings, it would have been churlish not to include separate brasses.

Tim

Tim

You may say that's a crazy idea, and maybe it is....

What is a dead certain is that it downright brilliant!!!

You really have made me look at my scratch built con rods and valve gear and wonder how to do it better.

Really enjoying following the project and learning a lot in the process

Herbie

 

[Tom Mallard]

Perhaps a bit crazy. View attachment 179782
With such large big end bearings, it would have been churlish not to include separate brasses.

Tim

That's the spirit! Great stuff, Tim.

 

[Tim Watson]

Holding your work whilst working on it is one of the biggest challenges in 2mm scale (and others). The simplest way is to glue the component to a bigger piece of metal to hold in the vice. The holding area can be flooded with a puddle of fast setting cyanoacrylate and then the rod dropped into place: the glue is then ‘set’ with some accelerator liquid. The photo below shows how I set up the con rods for re-drilling the big end holes in the brasses. The measured position from the little end was marked with a fine marker pen and then the table shifted on the axis using the dial from the little end reference point: the drill more or less landed on the spot (I erred on making it a touch shorter). Removal and clean up with a scalpel blade is straightforward.

Once it all felt pretty free, the temporary plastic insulation collar was replaced with a steel version. The top of the cross head was coated with a black indelible marker pen, to act as an anti-flux. The steel collar was cut from a 0.4mm bore syringe needle.

A minuscule amount of this German flux was applied to the tip. This flux is excellent for steel, it is a bit ‘oily’ and very corrosive.

The iron is brought into contact with the pin and flux with just a small amount 145 degree solder on the tip. It boils up the flux and the solder immediately flashes into the joint, at which point the iron is removed, of course. I have never got on with cigarette paper washers when assembling valve gear as they make the joints too sloppy.

The con rods are a very close fit to the slide bars at top and bottom of the crank throw, but they just kiss past, I don’t think the bars will need any adjustment. The big end will probably have a turned collar made for it.

The alignment on the frames, wheels and valve gear is quite satisfactory, without any nasty bends anywhere: an advantage of working to a true scale / gauge.

The front steps will need to be robust and well fixed as they must not touch the connecting rod (at least on one side).

Tim

 

[Tim Watson]

Little & LARGE. The driving wheels on the Raven 4-6-2 class have been lined out, just awaiting the black axle ends. Meanwhile, I have started to fettle the cast lamp brackets for my 3.5” gauge King Arthur, Sir Sagramore, in a scale approximately an order of magnitude bigger, i.e. 1/152 vs 1/16 full size.


Once the Skittle Alley is re-assembled I’ll probably work on the KA (see separate thread) for a while.

Tim

 

[Tim Watson]

Measuring spot heights on locos / rolling stock can be achieved using surface plates and gauges / markers for model construction. My take on this is to use a piece of Tufnol with some PCB ‘rails’ set tight to gauge to locate a chassis very precisely (i.e. no side movement on the wheels). This block also has a coupling height gauge incorporated.

The way it is used is that a digital vernier is zeroed on the thickness of the block and ‘rails’. The block material needs to be of consistent thickness, but also quite hard and shiny to allow a vernier jaw to slide easily. The loco is positioned on the block, being held with one hand, and then the callipers used to make measurements or perhaps scribe a line for e.g. handrail stanchions.

The photo shows that the Skittle Alley boiler height is a fraction under, but should be about right when it gets a coat of paint…
Tim

 

[simond]

the “zero anywhere” function is very useful - I totally perplexed one of my staff the other day by zeroing the caliper in a hole, and then measuring outside to outside of a pair of holes, thus allowing a quick, if not hyper-precise, check on the centre distance between them. Only works if they’re the same size!

 

[michael mott]

Tim I can see how this would be a good way for some small parts as well as your application. It also shows just how precise and tiny your work really is.
Michael

 

[King Crab]

Measuring spot heights on locos / rolling stock can be achieved using surface plates and gauges / markers for model construction. My take on this is to use a piece of Tufnol with some PCB ‘rails’ set tight to gauge to locate a chassis very precisely (i.e. no side movement on the wheels). This block also has a coupling height gauge incorporated.
View attachment 180747
The way it is used is that a digital vernier is zeroed on the thickness of the block and ‘rails’. The block material needs to be of consistent thickness, but also quite hard and shiny to allow a vernier jaw to slide easily. The loco is positioned on the block, being held with one hand, and then the callipers used to make measurements or perhaps scribe a line for e.g. handrail stanchions.
View attachment 180748
The photo shows that the Skittle Alley boiler height is a fraction under, but should be about right when it gets a coat of paint…
Tim

I've been following the build, but seeing what you have produced, lying now in the palm of your hand,
shows just how much detail you have incorporated into such a small model.
Just amazing!

Peter

 

[Tim Watson]

The Raven 4-6-2 class is now mechanically complete. It slightly ‘stuck its elbows out’ on the slide bars when running and so a restraining wire was soldered across the back of the crocodile, using 145 deg solder.

The driving wheels are lined out at the hub but the rims are not yet black.

Tim

 

[Tim Watson]

Darlington works has been a bit quiet of late with a slight diversion into 4mm scale scenic modelling for the MRC’s OO layout. However, I did make the cab sides for the NER 4-6-2 class at the Missenden modelling weekend.

Subsequently, the spectacle plate was made from quite thick brass as well as the running plate top. This is 5thou steel shim, being stronger than brass or N/S and able to take a good chemical blacking. The cab sides were obviously made as a pair, sweated together for cutting and filing.

I decided not to put on the external cab window beading as it is very fine (in reality) and generally gets in the way of the black and white lining. The cab window frames are required, however, but only one is visible as the engines always ran with the rear window slid forward. Representing the rear slides was worthwhile and will also gave a greater surface area for soldering on the roof at eaves level. The window layer was aligned using a couple of stainless steel pins through the handrail knob holes whilst soldering.

Next stage was to get the cab erected and the footplate extension boxes in front of the spectacle plate.

The rear cab roof support was made from thick brass and the whole assembly held in place with two bolts - the engine is being designed with ease of painting in mind, breaking down into useful sub-assemblies.

The next job will be to make the styrene pattern for the back head, which substantially fills the cab, seats and cab floor. A good job for demonstrating at Ally Pally next weekend. The loco now looks that little bit more complete.

Tim

 

[Joe's Garage]

Amazing Tim as you do not realise how small this is until you see the picture with the tweezers!
All the best
Julian

 

[Tim Watson]

I had a conversation last weekend with a visitor at Ally Pally regarding drive shafts and UJs. He was adamant that the two ends of the UJ should be at 90 degrees to each other. I had a strong recollection that 45 years previously a very good engineer at the MRC, Alan Cruikshank, had told me that the yokes should be in line with each other - that is the way they were arranged on the Hymek diesels, as an example. The input and output shafts should also be in line or parallel to each other. Needless to say, all my previous engines over the last 40+ years have had this feature.

Wind forward to 2022 and I thought I would try making the UJ for the Raven 4-6-2 class at 90 degrees, as an experiment. It worked, but was perhaps a bit noisy. As is their want, this drive shaft was propelled in to deep space when I accidentally powered up the tender motor with the other end non-constrained. The next shaft was made in-line and performed much better.

This link & video shows why:
TECH CENTER: Does it matter which way the yokes face on a telescoping driveshaft? - RC Car Action

Hope this is of interest. When demonstrating at shows, it is always fun chatting to people who may / may not be knowledgeable.

Tim

 

[simond]

that demo was very nice.

Many years ago, I used to work for Spicers, I remembered the bit about equal angles, but to my shame, I didn’t recall the phasing bit.

 

[Kylestrome]

He was adamant that the two ends of the UJ should be at 90 degrees to each other.

As far as automotive drive shafts are concerned, the evidence is quite conclusive:

car drive shaft angle - Google Search