TFW’s workshop

[CF MRC]

Yes, they are 13mm diameter Simon.  Wouldn’t be room for bigger.   With temporary muffs in I noted that the centre axle was fractionally high - didn’t even try to make it so, but the gods obviously know best.  

 

Might be able to get the rods made in the next couple of days in the camper van, whilst we’re away.

 

Tim

Edited June 18, 2019 by CF MRC

[CF MRC]

After a few days in Lynton in the camper van, with zero internet and phone coverage, I have made the side rods for Valour using the kit etchings.  Nick Eason has designed these for a sprung / compensated chassis in 4mm scale, so they have a correctly articulated joint. This feature is not needed in 2mm FS, so I very carefully made the joint solid, taking care to maintain the inter - pin dimensions.  This paid off, because as soon as I had assembled the chassis with temporary testing muffs the rods worked with zero binding!  This is a first for me, but the chassis had been drilled on a new watch-making co-ordinate drilling  machine I am very lucky to have.

 

 

Not the most exciting picture. 

 

Tim

[CF MRC]

Valour’s worm gear housing has been fashioned from a lump of brass using my John Stevens watchmaking mill / drill.  It can be seen with the milling head in this picture, with a tooth brush for scale. 

 

The head was then changed for the drilling attachment to drill the 1.5 mm hole for the worm shaft.  There is zero backlash in the x-y table, although obviously one doesn’t rely on this when using it.  I find Roco RTD excellent drilling and tapping lubricant. 

 

The milling head can be tilted at all sorts of jaunty angles, as can be seen for making a clearance slot for the worm wheel. 

 

The brass block was filed to be a tight fit between the frames and then drilled through the frames for the fixing bolts at tapping size, with the worm positioned on the worm wheel at the correct meshing centre (the worm is over-long).   The frame holes were then opened up to clearance size. 

 

This photo includes part of my thumb for scale, with wheels just in place and not anywhere near the correct gauge: they will be hard up against the frames when completed.  The block was then milled back by 0.5 mm to avoid shorting out on the other side of the split frames. Finally the sharp corners were removed, as good engineers don’t like sharp edges. 

 

The last photo shows the two 16 BA bolts nestled into the frames.  The worm will be shortened and have a thrust washer between it and the bearing block. The universal joint from the tender motor drive will be at the right hand end. 

 

Tim

 

 

 

 

 

 

 

 

[bécasse]

Looks easy blown up like this! Or it would be if the fingers and thumb didn't increase in size too.

[CF MRC]

Quite a good view of Valour’s worm / worm wheel set up with one wheel removed.  

The worm has had been trimmed to length and thrust washers fitted. Whilst the 38:1 worm wheel is visible in a broadside view like this, it will not be such an issue when the engine is complete - and will certainly not show on CF!

The chassis was re-assembled with wheels set to Irish broad gauge: final gauging will follow chemical blacking of the frames and wheels.  It turned over by hand OK:

 

It was then put under power.

 

Good enough for government work. 

 

Tim

[garethashenden]

Is the black thingy a new form of universal joint?

[CF MRC]

No, Gareth, it’s a temporary acetal muff, that originally had 64DP teeth moulded on it.  These were turned off to make room to fit between the frames.  It will be replaced by a conventional wire loop UJ. 

 

Tim

[CF MRC]

The reason for making Valour’s front end removable was to enable the front end to be made independent from the main chassis as it is quite complicated, with an awkward motion support bracket.  As the etch has been made in 8 thou nickel silver, the slots or tabs need adjustment; I find a fine slotting file ideal for opening out any slots. Careful cleaning up of the etch cusp is also important to ensure a good fit of components, when dealing with a kit that has been reduced from four to two mm scale.  

 

The slide bars consist of two components that make up a Tee section.

 

The motion support bracket folds up into the required shape very well and it simply requires the slidebars soldering in place.  

 

Four hours later...

When people look at models they often say, “You must have a lot of patience”.  I think it’s actually more a case of perseverance. 

 

The outside cylinders are angled and so need to be lined up carefully with the centre driving wheel. This  was achieved with sighting rods which were also used to align the motion support bracket with the cylinders.

 

The L&R brackets are held in place with the two 16 BA bolts at the front with some PCB on top to stabilise them.  These brackets could be permanently soldered to the front frames when the detailing and mechanical bits are complete, if the PCB is too visible under the boiler. 

 

The next job will be to machine the rear cylinder covers and stuffing boxes, the piston guides to fit in the motion support brackets, followed by the crossheads and piston rods. 

 

Tim

 

 

 

 

[nick_bastable]

be jesus  thats clever 

 

Nick

Edited July 1, 2019 by nick_bastable

[CF MRC]

I really didn’t like the lump of PCB on the motion support bracket: it would have been too visible.  It was therefore replaced with another piece of copper clad, slipped in under the nickel silver cross pieces towards the front, where visibility is restricted by the frames.   At the same time, I made two dummy bits of valve gear for the inside cylinders which serve to strengthen the joint and show some ‘business’ in the area. 

 

The rear cylinder covers, piston rod guides and a temporary front cylinder alignment jig were turned up and fitted.  The rear stuffing boxes will need filing to a lozenge shape for the top and bottom studs. 

 

The alignment of all the assemblies has stayed true, as can be seen by the piece of pivot steel acting as an indicator.  The pistons will be made of this very useful material. . 

 

Crossheads will probably be made next.

 

Tim

 

 

 

 

[garethashenden]

What are the advantages of using pivot steel instead of "normal" steel rod?

[CF MRC]

It’s straight, hard and made with an excellent finish

 

Tim

[Atso]

Excellent work Tim. I can see that I'm going to have my work cut out for me when I get my hands on one of these! 

[CF MRC]

Crossheads are always quite fun to make.  Silver soldering is a good way of ensuring that at least the piston and inner crocodile are nice and solid.

The starting point is a piece of thick metal (0.7mm thick) to fit between the slide bars with a notch at one end to accommodate the 0.5 mm diameter piston. This also benefits from having some flats filed on to it to give a more precise location. 

 

The silver solder was in a paste form and very easy to flash the joint with a little gas flame.  

 

This was then placed in the vice and the socket for the piston filed into the end, rounding off the corners, taking advantage of the safe sided file.

 

Alignment in the slide bars was then checked: at this point - it should be a tight fit. 

 

Followed by a 1mm diameter hole to accommodate the little end of the connecting rod. 

 

This was then opened out rearwards to be able to take the connecting rod. The outer face of the cross head can also be seen resting against the slide bars. 

 

Making two of anything can be easily achieved by sweating two pieces of metal together and roughing out the shape, just once, then separating them. The little end pivot hole is 0.3mm diameter. 

 

The two components were soldered together using a tapered stainless steel pin (Jim will recognise it) to stabilise the outer face by holding it on a charcoal block whilst the inner face was held onto it with downward pressure on the piston.  This assembly was joined with electrical, relatively high melting point soft solder, as I didn’t fancy my chances at the whole lot not melting down into a blob if I tried to hard solder it.  I normally use steel for valve gear - which would be less likely to melt, but as this is kit is etched nickel silver, that is what I have used here. 

 

A tight but smooth fit is what was aimed for at this stage.  Subsequently, the mating surfaces of the cross head slippers were filed using a slotting file to give a running clearance with the groove locating the cross head on the slide bars. 

 

The outer cross head face was filed to represent the prototype and the piston socket dressed to look more convincing.  The little end of the connecting rod will have a pin silver soldered to it and the round outer boss of the cross head will be represented by a washer soldered onto this pin to hold it in place. 

 

It never ceases to amaze me what you can do with a phone camera. 

 

Tim

 

 

 

 

 

 

Edited July 5, 2019 by CF MRC

[Chris Higgs]

11 hours ago, CF MRC said:

 

It never ceases to amaze me what you can do with a phone camera. 

 

Tim

 

 

 

 

 

 

 

As I understand it (from CountryFile) they beat the pants off a full-sized camera for closeups due to the tiny lens.

 

Chris

[65179]

Informative and inspiring stuff Tim.

 

Can I ask how the crosshead arrangement works?  Am I right in thinking that the little end will be inserted from behind, and despite only being the width of the slidebars the rear face is in practice deep enough to stay in place in use?

 

Also where do you source your pivot steel? 

 

Many thanks

 

Simon

 

 

[CF MRC]

The little end pin will indeed be inserted from behind the cross head.  The slide bars are probably a bit skinny as they are only 8 thou thick, so the 30 thou original width of the inner crocodile allows plenty of scope to file in a groove to run over the slide bar. This gives lateral restraint from the medial side and of course the front face restrains it easily.  If that hadn’t worked I would have soldered a vertical piece of very thin wire across the back to restrain it.  However, with this engine, I don’t think the cross head would actually go walk about, as the piston is well restrained by the rear cylinder stuffing box as well as the long guide on the motion support bracket. 

 

I find Cousins very good suppliers of watchmaking equipment.  Pivot steel:

https://www.cousinsuk.com/product/pivot-blue-steel-assorted

 

Slotting files

https://www.cousinsuk.com/product/slotting-screw-head-1840-vallorbe-swiss-with-tang

 

Should become more clear when the con rod is made. 

 

Tim

[65179]

Thanks Tim,

 

Very helpful.  I wasn't thinking about how little sideways movement would be possible given the distance between the two points of support for the piston rod.

 

Thanks also for the links.

 

The copy of the B-P 9Q GA I have appears to state 5.5 inches across the slidebars.

 

Simon

[chrisveitch]

11 hours ago, CF MRC said:

 

Slotting files

https://www.cousinsuk.com/product/slotting-screw-head-1840-vallorbe-swiss-with-tang

 

The slotting file link is interesting - can I ask a couple of questions? They seem to be the same type of file that was once sold by the Association for slotting turnout check rails (and may still be, but I can't find it now). 

 

The file in your photo cuts on the edge only, whereas the the photos in the Cousins link show files with a cutting surface along part of the face as well. Is this the same type of file or is it just a slightly inaccurate stock photo? I notice that the Cousins page shows an icon of a file section which looks like a slitting file with a pointed cutting edge rather than a flat slotting edge.

 

The site lists Cuts 00, 2, 4, 6 and 8 but I can't find any reference to what widths these actually represent - do you know what these equate to in millimetres? The only reference I can find to these is this site which doesn't list sizes (but maybe I'm not looking hard enough).

 

Thanks,

 

Chris

Edited July 6, 2019 by chrisveitch

[CF MRC]

The file in the photo does cut on the side Chris. It is a very shallow V in section: I suspect that the camera software tends to exaggerate different textures.  I have other, much thinner files that only cut on their edge.  Not sure about the file number cuts vs widths relationship: probably, the finer the cut the narrower the file.   

 

A well aimed fine piercing saw blade could also achieve a similar result, but would be more difficult to control.  

 

Tim

[CF MRC]

C

 

Crossheads, connecting rods and motion support brackets now finished.  Looks nice and chunky, but clearances quite tight!

 

Tim

 

 

 

Edited July 8, 2019 by CF MRC
Added overall picture

[CF MRC]

After a day demonstrating fine scale stuff at the MRC, Keen House, yesterday, I now have Valour running with the connecting & coupling rods in place.  The wheels and chassis are chemically blacked, so they shouldn’t need to be removed any more. 

Demonstrating wheel quartering live, on camera, is surprisingly stressful; I can demonstrate dental operative procedures much more easily. 

 

 

 

Tim

[Atso]

Excellent work Tim. I'm gutted that I wasn't able to attend.

[justin1985]

Looks excellent Tim! And thanks again for running the workshop - super helpful!

 

How do you go about chemical blackening the wheels? When I tried this once, the blackening fluid (Birchwood Casey) made the steel rims rust like crazy. The same happened when I tried but used water to wash the blackening fluid off straight away. It didn't seem possible to sufficiently dry off either the fluid or the water from the inside of the spokes to before rust started appearing on the rims. After cleaning those wheel rims off with a fibreglass brush, they've always seemed prone to rust more ever since. 

[CF MRC]

I always found the Casey’s Gun Blue to be hit and miss.  This is what I use:

https://www.frost.co.uk/frost-metal-blacking-solutions.html

Much better and relatively cheaper.  It prevents corrosion.  If the metal is well polished up beforehand then the alkaline degreaser isn’t needed and the de-watering solution is a light oil, so again not really needed. 

 

Tim

Edited July 15, 2019 by CF MRC