Ian_C's workbench - P4 and S7 allsorts

[Ian_C]

This goes back to 1998. A Dave Bradwell WD kit that was started and then put to one side. Goes back to the days before children and dogs, and when modelling was done on the kitchen table. In fact that was all that was done on the kitchen table back then. The workbench clutter spread out and stayed there for months at a time. Basic tools only in those days. No lathe or mill. I'd just built a Gibson 04 kit in EM, converted it to S4 and thought I'd nailed the kit building thing. Not lacking ambition, I thought the WD would be a good next project. In truth it was a bit beyond me. I struggled to a powered rolling chassis, built the tender body because it looked easy-ish, then a bit of footplate, and then...it gathered dust while house renovation took up my time. Today I dug it out from under the bed and opened the box for the first time in 22 years...

...all pretty much as I remembered it. Brass somewhat tarnished, but no rust on the wheels or axles, which surprised me. Reams of instructions and loads of handwritten notes. I'll have to read through the lot to see where I got to. No Wild Swan book of drawings for this project, but a lot more photos available now than there were back then. More towards the model making end of the spectrum than the model engineering end. First job is to clean it up in the ultrasonic tank.

 

[Dave Holt]

Ian,
That's a lot further advanced than mine! Looking forward to seeing it develop and, no doubt, learn a few things.
Dave.

 

[Ian_C]

The plan was to put a large Mashima in tender and drive a gearbox on the rear axle through a driveshaft. I think the small gearbox is an Exactoscale specimen. The electrical collection was to be American (I think it's called?) style, with loco live to one rail and tender to the other, and drawbar insulated. To that end I'd shorted out the drivers on one side with fuse wire, and defeated the insulation on one side of the tender wheels with silver conductive paint. Surprisingly it worked - well it did 22 years ago. I remember a huge amount of messing around with the drive shaft. Starting with a variety of rubber tube type couplings that didn't work well, and ending up with a UJ type shaft (Exactoscale again I think) that had to be arranged almost straight between motor shaft and gearbox input. I might re-engineer the driveline, but for now I'll make a start on the loco body.

A lot of reading instructions, looking at diagrams and checking what had been removed from etches to figure out where I'd got to. First job was to fit the front buffer beam and associated parts. The basic cab was next, to serve as a location for the back of the firebox. Having spent so long working on the 7mm 8F I'd forgotten quite how small some 4mm parts are. The cab roof in particular was a fiddle. It took a while to recalibrate from 7mm to 4mm.

Boiler and firebox next. The boiler and firebox is built up as a basic shell with overlays...well...overlaid. The smokebox is built up as a separate unit with an overlay added over a length of brass tube. The smokebox was easy enough. The boiler and firebox were not so easy.


Since the boiler barrel and firebox are from one etched part, the boiler can't be rolled. It was formed by hand around lengths of 7/8" and 3/4" bar held in the big vice. I can't ever get a perfectly round boiler shell this way, so it does rely on being pulled up tight onto the internal formers before soldering.


The kit has two etched round formers for the boiler, and two for the firebox. They're quite thin and it's not really possible to pull the boiler shell tight around them. They're also prone to flip out with much pressure on them before they can be tacked in position . The other challenge is that the smokebox slides inside the front of the boiler, so the first boiler former has to be a way back from the front edge, and the smoke box to the rear of the overlay has to be built up in diameter to fit inside the boiler and represent the step in diameter on the prototype. The kit has a couple of etched strips that are to be wrapped around the rear of the smoke box to make up the diameter. I couldn't see that going well, and I did want a good fit of smoke box to boiler. I turned some more robust formers from brass bar. The rear former is simply a ring. The front former combines a ring to form the boiler and a thinner extension that the smoke box slides into.


Here's the front former in place with the boiler shell pulled up tight with twisted wire. The smoke box slides into this end.


Here's the rear boiler former in position. The wire tension was cranked up a bit more before soldering to close the gap you can see at the top of the boiler. The frontmost firebox former sits up against this boiler former which helps to keep it in position as the firebox is formed.


The rearmost firebox former was remade in thicker material, from a scrap of 1/16" brass sheet. Once the fit and location of the cab , boiler and smoke box had been checked, the boiler was soldered up. The boiler's a great heat sink and the turned formers have some mass, but the 100W soldering iron makes it quick and easy.

The kit provides a boiler barrel overlay, and two alternative overlays for the firebox depending on which arrangement of boiler washout plugs the loco had. Earlier boilers have a straight handrail, whereas later boilers have the upper washout plugs so positioned to necessitate a cranked handrail and ejector exhaust pipe. Therefore it's at this point you have to decide which loco you're modelling. Usually I like to model locos with some kind of local connection, but the 8Fs kept the WDs away from Midland lines for the most part, although photos show the odd WD made it as far as the mighty Toton on occasion. After browsing 'The Book of the WD 2-8-0s and 2-10-0s' (Irwell Press - ISBN 1-903266-96-3), I decided on 90361. It was at Wakefield in 1966 before moving on the a last posting at Sunderland. The Irwell book shows the earlier firebox type in 1952, but another photo taken at Wakefield in 1966 shows that by then it had a boiler with a later pattern firebox.


Here's where it gets tricky. If the boiler and firebox shell does not end up as geometrically perfect the overlays won't conform fully to the shell at all points. I thought I'd done a pretty good job, but even so, the firebox wrapper had a couple of small areas that didn't want to sit on the shell. It was rather like chasing air bubbles around under wet pasted wallpaper. In the end I had to nick the edges of the overlay in two places with a scalpel and let them overlap to relive the wrinkles. When soldered over, the tiny overlaps were smoothed out with a file and some wet & dry. We'll see how that looks under a coat of primer - at some time in the distant future. The boiler overlay was straightforward by comparison. Cleaned up in the ultrasonic tank, and that'll do for today.

Decent progress considering that my conscience made me go and do some gardening this afternoon as well.

 

[john lewsey]

It looks good already. An apparently mundane engine that is so appealing.
John

 

[Ian_C]

It looks good already. An apparently mundane engine that is so appealing.
John

I always quite liked the WD, even before Dave Bradwell invented one. I have to say I'm hooked again after re-starting this kit. The Roxey/Snowhill WD in 7mm has some appeal. I reckon you could really capture the essence of the WD in 7mm.

 

[Ian_C]

Chipping away at my usual pace. Glaciation happens faster. Thought I 'd dress up the boiler a little. It always feels like progress when the boiler fittings are on.

The top feed is a lovely little brass casting. It looked a little squat to me. The top feed on the WD did stick up a bit. I turned a small disc to represent the fitting flange and raise it up a bit. The disc was silver soldered to the casting and blended in with a needle file.



There's a hole etched in the boiler overlay to show the top feed position. There are also a couple of holes in the boiler shell, beneath the overlay that can be used to locate where the top feed pipes enter and exit the cladding. Except they're now buried by the turned former. Planning ahead is so over rated. The holes had to be estimated from photos, marked and drilled.


Safety valves, dome, snifting valve and chimney were located and sweated on...

I wonder if the top feed is a bit too sticky uppy now? I feel more able to take a few more dimensional liberties in 4mm than 7mm, even so I really ought to check it against the drawing. Looks a bit Super D like this. It needs the cylinder wrappers and the pony truck to balance it up. Maybe they're next. I think Webb might have appreciated the WD, but I can't imagine what language Samuel Johnson would have used if he'd lived to see one!

In passing , here are the oil boxes that are scattered along both sides of the foot plate.

I did wonder if it was worth fitting the oil pipes. I soldered one box in position with no pipes. They're not very visible tucked away under the curve of the boiler, but you do notice the empty space beneath where the pipes should be. There's no chance of drilling out the unions on these tiny castings. Instead I filed the back of the unions flat to about half the diameter, and soldered copper wire looted from domestic flex to the flat. Very much of a fiddle & faff. Soldering them in place on the footplate brackets was tricky. Linger too long with the iron and the pipes become unsoldered. A couple of them had to be removed and done all over again. Also fitted the sand fillers while I was there.

After the last episode I realised that the tender and pony truck wheels were too large. I'd bought 3'8" wheels back in the day instead of 3'2" wheels. Goodness knows why. Fortunately Alan Gibson Workshop had 3'2" wheels in stock, so I can re-wheel the tender now.

 

[Ian_C]

Very much an example of humans as the ultimate tool using creature. Clever as they are, chimps, crows and dolphins couldn't have successfully mounted Gibson wheels on the axles and got the B-B perfect and no wobble. Previously, getting wheels like this onto axles in the correct position was a stressy struggle, and usually ended up with a little wobble and a loose/tight B-B. And the more you twist and tweak and adjust, the lower your odds of success.Doing it this way takes a little effort initially, but you end up with consistent B-B and no discernible wobble. The conclusion I draw is that the process of pushing the axle into the plastic wheel centre very much determines the quality of the outcome. Perhaps no surprise. Here's a way of doing it...

1. Do your sums if you only want to press the wheel on once with no adjustment. The Gibson wheels measure 2.11 mm over tyres. At 25.93 mm the axle is damn near a standard 26mm pinpoint. If I take 17.7 as the B-B then it follows that I need 2.00mm (near as makes no odds) of axle projecting from the front face of the tyre on each side. An odd end of brass bar was faced parallel and a flat bottomed 2.00 mm hole was sunk into one face with an end mill. The usual small run out on the mill gives a clearance size for the axle. Sure, the pinpoint of the steel axle will indent the brass slightly, but not enough worry about.
2. The pressing block was set up on parallels in the mill vice (itself set perpendicular to the spindle). The table was positioned so the spindle centre was directly over the hole in the pressing block.
3. Wheel placed face down (!) on the block and approximately over the hole. The pinpoint on the axle will centre it. The axle is gripped in a 2mm collet (or should that be Collet on WT?) in the ER11 collet holder. I should add that the wheels were rubbed gently both sides on wet & dry on a flat surface to remove any plastic flash that would prevent the wheel sitting flat on the block or the B-B gauge.
4. Bring the quill down gently (chimps please note) to press the axle through the wheel until resistance is felt. The axle can be carefully released from the collet. Bring all the axles to the same stage.
5. Wheel and axle placed back on the pressing block, and the B-B gauge is balanced on the back of the tyre, having made sure wheel tyre and gauge are free of gubbins.
6. Place the other wheel over the axle pin point, approximately level.
7. Bring the quill down again to centre and press the wheel on until it contacts the B-B gauge.
8. That's job done. It's really quick and consistent once the tool is made. I won't be doing this by hand and eyeball any more.

You could do similar if you have a small drill press, or a mini arbor press. That said, if the job had required flippers and echo location I'd have struggled, although if food was involved I'd place a small bet on Grey Squirrels working this out.

 

[Ian_C]

This has been the most demanding stage of construction so far. A lot of small parts, and a requirement for some accuracy in the fit of moving parts. The order of doing things is a bit mixed up in the photos, but a thousand words is worth a picture so hopefully I can make some sense of proceedings.


I think I'll start here. The sliders themselves are made up from a number of laminations from the nickel silver valve gear and motion etch. There are dimples etched in the parts that are to be drilled through 0.45mm so that wire pins can be used to align the parts. It's a good idea and it does make things easier. As you can see there are a several sub-assemblies that need to be soldered together to make up the crosshead /piston rod and slider assemblies. The challenge is to solder it all together without unsoldering the sub-assemblies. If you ever bought a step soldering kit or a temperature controlled soldering iron, now would be the time to use it. I managed the job with silver solder (about 630), 224, 179 and 145 degree solders.

I spent some time looking through the kit contents for the crosshead castings. Without success naturally, because there are no crosshead castings! The crosshead is fabricated from etched parts, a casting (except not really, discussed later) and some rod. Start the whole job by folding up the crosshead etch. In spite of the target dimensions given in the instructions, the etch will fold up how it jolly well likes and the gap between the crosshead cheeks is what ever you end up with. It's easier to fettle the slidebars to fit the crosshead than vice versa. The etch parts for the cross head were put together with 179 solder.

I opted to silver solder the slidebar laminations together so that they're solder proof later in the game, and so they can be polished up to a higher level than soft solder. You can see the assembly of slidebar laminations being pinned together top right of photo. An excess of silver solder was built up on the laminated edges to fill any gaps. It all gets filed and polished off later. Silver slidebars eh? A bit flash for a WD.

The lower slidebar is supposed to be 1.6mm wide, but for me, to match the crosshead, it came down to 1.5mm for a comfortable sliding fit. There's bit of careful filing to create the tapers. Files, wet & dry and down through the grades of micro abrasive pads to end up with a final polish with 12,000 grit (well, dust).

The connecting rod is a simple lamination. It's necessary to reduce the radius around the end of the little end to make sure it clears the back of the piston road socket in the crosshead.



The piston rods are 3 -1/4" in real life, near enough to 1.0mm in 4mm scale. The instructions don't specify what's to be used for the piston rod, but there's some 1.0mm N/S rod in the box so I'm assuming that's it. There are some tiny brass castings (centre of photo above) for the socket in the crosshead where the piston rod end is secured. The problem with these is that they're really difficult to clean up neatly, and you have to drill them out to fit the rod (better than hole too big I guess). I managed to drill through not quite along the centre so they sat a little squiffy on the rod. Hmmm....would anybody notice? Nah...not right is it? So replacement sockets were turned from brass, and the hole goes true through the centre. Tiny flats were milled on the end to fit inside the crosshead cheeks. The rods were silver soldered to the sockets and the rear ends cleaned up to make sure they clear the little end of the connecting rod.


The slidebars were partly assembled by soldering the tiny spacer laminations at the rear end. To do that the slide bars were clamped together with a spacer between them, carefully aligned, the spacer laminations fiddled into position, and the end soldered up with 224 solder. Worth noting here that Mr Bradwell reckons the gap between slidebars should be 0.75mm. With the little spacer blocks in place the gap practically ends up after soldering at about 0.9mm. That matches the top slider of the crosshead very well with sufficient clearance to slide nicely. In any event you can tweak the clearances with a fine file if necessary. You can also just make out the little end pins in the photo. They are made from a length of 0.8mm brass wire, a tiny turned washer (see upper left of first photo) and a 16BA brass nut drilled through 0.8mm. The five nuts holding the cross head together are made from short lengths of 0.45mm brass wire soldered in the holes (145 solder, and be quick about it!) and filed down to about 1xD in height.


Once loosely assembled to the cylinder frames like this, the alignment of the piston rod and slidebars can be established and the turned brass sockets and rods can be soldered to the crosshead in situ with 145 solder, being very careful not to let any solder stray onto the slidebars themselves. Here it is with the connecting rods in place and retained by the little end pins. What I've not dared to do yet is fit the spacers between the front of the slidebars. When they're in place the crosshead is trapped and it would be difficult to get them out again (the slidebars are silver soldered, so maybe it wouldn't be a disaster). I'll get the slidebar supports fitted to the chassis and all aligned with cylinders etc before I do that.


As it happens it was my partner's birthday this weekend. She's a keen gardener, so I thought I'd make her a pair of gardening themed earrings. Small pieces of sterling silver are really quite cheap (but don't let on please). Same tools, same skills, similar materials, different result. Not sure I'd like to scratch build in annealed jewellery silver though, soft and gummy stuff.

In other news, I had my first covid vaccination today. Had to drive a little way to get to the place. Probably the furthest I've been from home in the best part of a year. Driving home along empty roads in the spring sunshine, indestructible with 0.5ml of Astra Zeneca in my arm, was quite ... uplifting. Maybe there's light at the end of the tunnel (or it's a class 8 head lamp coming straight at me).

 

[Ian_C]

To get the slidebars installed you really need the motion bracket in place, since it supports the rear end of the slidebars and sets them at the correct angle. The whole episode took all weekend and was far from straightforward.


1 - The instructions say that you may need to cut away some of the motion base plate to enable access to the spring adjusting screws on the front two axles. I can confirm that there's no doubt about it! You have to make cut outs to clear them.

2 - The motion brackets themselves were faffy little assemblies, and the instructions were not abundantly clear on a few points. There are some small tabs that are etched to make a double fold, but it's not clear what purpose they serve or which way they fold, etch line inside or out. When you try and assemble the motion brackets the penny drops, and naturally I'd guessed wrong, so the tabs had to be re-bent the other way. Fortunately I managed that without snapping them off at the etch line. The pivot centres for the expansion link are located by passing a length of (straight!) 0.8mm wire through the brackets and straight through etched holes in the chassis side plates. Clever! Once that's done the cylinder base plate can be screwed to the chassis, the motion bracket assembly slotted into the chassis, and the two soldered together. Then the relationship between cylinders and motion bracket is set and the slidebars can be fitted.

3 - It was at this point I decided to look ahead and check that the cylinder wrappers were the same width as the front and rear cylinder ends. Well, not quite. I found that the cylinder ends were not quite parallel, slightly closer together at the bottom than the top., an error I'd made when I originally made the cylinders up in...errr...1998. It was possible to tweak them to the correct dimension, and to keep them there I elected to pass a length of 1.0mm wire right through for the cylinder relief valves and use it as a soldered in spacer. I kind of expected there to be relief valve castings in brass, but apparently not. Bradwell suggests wire, and I didn't fancy making cylinder relief valves from scratch, so wire it was.

4 - The covers were added to the front of the cylinders. Again a bit of a fiddle making them from two laminated etched parts, getting them round and with etch cusps filled and filed smooth, and getting them soldered to the cylinders with out them becoming misaligned. The cylinder relief valve wire helps keep them in position.

5 and 6 - Finally the fitting of the slidebars. I should add that there was a tricky, sweary little interlude where I fitted the spacers to the front of the slidebars, and with that the crossheads were trapped for good. You need to make sure there's no twist between the motion brackets and the cylinders, otherwise the rear ends of the slidebars are at the wrong height and they look wonky relative to the cylinders. After a lot of fettling and squinting they're correctly positioned and can be soldered to motion bracket and front of cylinder.

There's a potential problem though. The fit of crossheads in slidebars was very good and allowed an easy sliding fit - until...you solder them in position! It seems to be a quirk of geometry and friction that makes the crossheads prone to lock solid if they're not pushed in exactly the right direction. Any off-axis force locks them solid on the slide bar, even though there's a slight clearance at all points. Lubrication helps, a little. I'll need to fit the connecting rods to the cross heads and the driving axle and see if the connecting rod motion causes them to lock. Not sure what I'll do if that's a problem.

Here's something that I've discovered. If I connect the instrument maker's vice device to the RSU ground I can use it to hold things in the right place to apply the RSU probe. It's more versatile then soldering everything on the clomping great RSU steel baseplate. You can see the RSU ground lug trapped between the bench and the vice base casting. I might tap an extra hole in the casting so I can screw the ground lug on when I need it. In this photo it's being used to zap on the cylinder front covers.


If you have 15 minutes, this is worth a watch... Zen and the Art of Model Making
Not much to do with Tang dynasty Mahayana Bhuddism, but about Philip Reed, a most remarkable model ship maker. The ship counterpart of Beeson, Miller or Reynalds. Once you're hooked, he also has a few commentaries on specific ship models on You Tube. There's something to aspire to; to achieve the model railway equivalent of Philip Reed's ships.

 

[Ian_C]

The pony truck was reasonably straightforward. The etched parts, although fiddly, went together well. I did make a few small changes as I built it up and worked out the installation.


As designed, the axle passes through slots in the etched frame, and you'd have to assemble the wheels to the axle and get them to gauge in situ. Also they'd be there for clean up and paint, which isn't ideal. I slotted the frames to the bottom edge so the axle can be removed when required. I'll solder or cyano a small keeper wire across the open end of the slot when I'm closer to completion.

Once the etched parts are soldered together , there are white metal castings to apply to the sides, although you'll not see much of them behind the solid wheels. If nothing else, they add a bit of mass to the truck.

The wheels are Gibson. They're sort of correct in so far as they're disc wheels and of the correct diameter. The prototype pony truck wheels were actually iron castings. Even the tyre was cast integrally in iron. For that reason there's no separate tyre shrunk onto the wheel and the rim looks finer in reality than these it does on these wheels. I can't see an easy way to fix that without risking damage to the wheels, so I'll stick with what I have. Also the cast boss was quite thick, presumably to resist cracking as the axle was pressed in. On the Gibson wheels there's almost no boss. I might turn up some small collars and see if I can blend them in with the moulded wheel centres. Bit of a signature item on the WD I think. May get away with this in 4mm, but you'd have too get its right in 7mm (which means the Roxey/Snowhill kit is prodding at the frontal lobe again).


With the castings epoxied on, the spacer washers to control the wheel side play can be calculated and turned from brass. They're 0.5mm thick on this model. The wheels were assembled on the milling machine, similar to the tender wheels on an earlier post. Incidentally, the axle works out about 0.3mm too long when the wheels are to P4 gauge, so it was filed back flush with tyres. The pony truck frame pivot is a 14BA screw. I opened out the hole in the frame to 1.5mm and made a small bush to solder to the screw to provide a tightening stop and retain the frame.


The Bradwell ethos is to have all axles sprung, and the pony truck's no exception. That's done by some springs made from phosphor bronze wire. They pass through a slot in the rear frame crossmember and bear on the top of the axle. One of the springs is traced in red in the photo above. Needless to say, a right faff to get all the bends in the right place and two springs approximately the same. But they do work rather well.



With the wheels dropped in and the axle resting on the springs. You can see the springs a little more clearly in this photo.


Pony truck fitted to the chassis. So far as I can tell the idea is that the pedestal thingy on the front of the chassis rests in contact with the top of the pony truck frame and the pony truck springs effectively push the truck frame up into contact. That means the pony truck should carry some weight. I'll have to see how it all works out when it's properly wheeled and the ride height adjusted. The stiffness of the springs could be changed by changing the free length of the wire. Bradwell suggests 15mm is about right, so that's where I've started. There is a suggestion for side control springs, also from phosphor bronze wire, but I can't make sense of the instructions, so I'll step past that complication for now. I'll bend the guard irons out to the right position when I get the rolling chassis back on rails. Altogether the pony truck's taken an inefficient day's work to get to this point.

There's very little on line about this kit. I guess it's a bit vintage, so most of the ones that were built pre-dated posting on the web. I'm finding that it's quite a challenge to build, and I'd love to know how many actually got finished before the Bachmann WD came along. If any WT'ers have one, and are willing to post a photo, I'd be happy to see them.

 

[Ian_C]

The cylinder wrappers were a challenge. It was really hard to get them aligned all the way round the cylinder formers. The front and rear formers being not entirely parallel was the cause. Next time I do something like this I'll machine some spacers to assemble the cylinder formers to guarantee parallel. A small amount of fettling was necessary in the end. It doesn't show really, so I got away with that. The drain cocks are beautiful little brass castings. Roughly put together, and it feels like progress. Completing the valve gear is the next step I guess.

 

[john lewsey]

That looks really good Ian
John

 

[Ian_C]

Back in the day I vaguely remember test running the rolling chassis with the coupling rods on. Even more vaguely I seem to remember that it ran OK. Older me has little faith in the ability of younger me, and back then I don't think I had any measuring device more sophisticated than a 6 inch steel ruler. Just out of curiosity I thought I'd measure how accurate the axle and rods centres are. I think I set the axle centres from the rod centres using those dummy axles with a spigot on the end over which the rods are dropped. I think there were springs involved to stop the axle bearing guides from flopping about, and probably a flint axe.

How to measure something like this? I have the usual selection of edge finders and a Haimer for the milling machine, but they're not much use on features this size. I'm sure I read somewhere that Swindon was using optical methods for cylinder alignment when the rest were using bits of wood and string. Hate to admit it, but I'll follow Mr Churcward's lead on this. A couple of years ago I made an optical centring microscope for the mill. It was from a Hemingway kit. Took some time and head scratching, and in the end I had to modify the optics before I was happy with it. Not sure what magnification I ended up with, something like 40x or 50x. Having got it set up and centred properly, I've not found much use for it...until now!


The chassis was set on a parallel in the milling vice and just nudged up to put the straight top edge against the rear jaw of the vice. The focus was set using the fine feed on the quill. The depth of field is tiny, so it's a really useful way of adjusting focus. It's OK in workshop ambient light, but an extra light source from one side helps to see the edges clearly. Using the DRO turns it into a low rent co-ordinate measuring machine.


I set the X zero as the rear edge of the chassis side plate, and Y zero as halfway up the horn guide gap, roughly where the axle centre should be. Then, working from rear to front, I found and recorded the inside edge of the horn guide bearing faces. At this magnification the brass looks like the surface of the moon, and your tidiest work looks like a ploughed field. I'd rounded the edges of the plates making up the bearing faces to prevent the bearing blocks binding, so some fiddling with focus was needed to find the actual faces. Flipped the chassis over and did the other side.


I did the coupling rods in a similar way. This time I just laid them on the vice jaws, roughly lined up with the edge of a parallel. Because they're articulated I centred on the crankpin holes (the graticule has crosshairs and concentric rings so that's easy). I took the leading crankpin hole as zero datum and took X and Y measurements for the other holes. The distance between centres can be calculated from the X and Y differences between adjacent holes. Yes, those nice neat holes look like shell holes at his magnification - ugly!

The measurements were dropped into a spreadsheet to find the results. Axle centres from the chassis first...

The horn guide gaps I guess are meant to be nominally 4mm. They vary between a slightly tight 3.89mm to a clearance of 4.10mm. Not bad for etch fold ups and manual soldered assembly.

The effective axle centres calculated from this vary from the exact scales dimension by no more than 0.07mm (and that's about 5mm on the prototype!), and most are closer than that. And the difference between axles centres between the LH and RH sides is no greater than 0.13mm.

I have to say I was surprised that it was so accurate. Just shows what you can achieve using basic tools and techniques if you're careful and follow a logical process.

The coupling rods next, and if I set the axles from the coupling rods you'd not expect them to be much different.


Once again the centres don't deviate from nominal by more than 0.07mm. The interesting thing about this is that the rod centres are really set by the etching artwork and process, and you have to conclude that Mr Bradwell and his etcher did a good job here.

Comparing rod centres with the corresponding axles centres shows a maximum deviation of o.13mm, and mostly a lot less.

The DRO measures to 0.005mm allegedly. There will be small errors in finding the hornguide edge positions. I've rounded to the nearest 0.01mm which is probably appropriate.

What I've not attempted to do is measure how perpendicular the axles are to the chassis centre line. The chassis could be slightly trapezoidal in plan and still give good centre distances. It probably has less impact on smooth running than matching axle and rod centre distances. Also what's not taken into account here are mechanical clearances; between bearing blocks and horn guides, and between axles and bearing blocks. I do have the bearings and axles marked so they always go back in the same position. Other variables are the crank throw of the wheels and the crankpin to rod clearances and the quartering.

Overall I'm surprised how accurate everything is. I'd expected much worse. Bit of an eye opener. Could I actually do much better now I have better tools and measuring equipment? Probably not, but I was younger then with better eyesight and a steadier hand!

When you start to add up tolerances like this it seems like a miracle that eight coupled models of this size actually manage to run at all. Then again the WDs were notoriously slack mechanically, hence the clanking. I recall an anecdote, maybe Keith Miles in BRILL back in the day, about getting a set of WD rod bearings machined to the 'correct' size to demonstrate to the shed fitters than there was no need for the clank. Naturally , when they were offered up they wouldn't fit. Eyes were rolled and toldyousos muttered from under cloth caps, and back they went to the machine shop to be bored out to a size that allowed them to be 'thrown' onto the crankpins.

 

[Deano747]

Hi Ian

Very interesting approach.
I do like the mini lamp/torch and magnetic base, any info please.
Thanks.

Regards, Rob.

 

[simond]

Much impressed with the optical shenanigans!

 

[Ian_C]

I guess, like many of us, I tend to be UK centred when it comes to railway modelling. While searching for something else, I came across this French fellow producing models and components in 1/43.5ème , Benoit Semblat. Something to aspire to, hein?

 

[Ian_C]

Hi Ian

Very interesting approach.
I do like the mini lamp/torch and magnetic base, any info please.
Thanks.

Regards, Rob.

Sorry Rob, I've no idea! Was from Santa Claus years ago. Thought it was from Chronos, but no longer listed. It's no more sophisticated than a cheapo LED torch or bike light, mounted in a Terry clip on a length of flexy stalk, screwed to a round magnet base. You could probably make something similar for a few quid. Just handy on small work in the mill, where the machine head is low enough to block out the workshop lighting.

 

[Deano747]

Thanks, Ian.

Looks very useful for getting under the head, as you said. I have a torch similar, and a magnetic DTI base so should be able to cobble something up when I've got some spare time.

Regards, Rob.

 

[daifly]

Looks a bit like one of these.
Dave

 

[Deano747]

Perfect, thanks Dave.

Regards, Rob.