While the T3 class loco is in the paint shop, this is the next loco project. I chose it partly because there is plenty of information available. I got copies of the LNWR drawings from the NRM and visited the preserved Hardwicke at Shildon to take lots of photos (great cooperation from the staff at both places). From that I was able to do a very detailed solid model. I intend to use commercial laser cutting and 3D printing services, and possibly some CNC machining, partly to speed up the project but also because I'm interested to explore how we can use modern manufacturing methods.
Laser cut steel for the frames and other flat components.
Steel.png
The frames and stretchers were designed with slots and tabs for assembly. The slots were so well cut that I could just put it together for the photo. It will, of course, be soldered up later.
Trial assy.png
I had the driving wheel centres 3D printed in PA-12 nylon some time ago to see if the combination of printed centre and turned steel tyre was viable. There's another thread on this forum about that, but here is the finished product.
Driving wheel.png
Other components 3D printed.
PA12.png
There is also a growing collection of machined parts. These were the ones I judged not feasible or too expensive to have made.
Machined parts.png
And this is the Mark 2 version of my spur gear drivetrain. It comprises a Polulu 60W motor which comes with an integrated gearbox to drop the rotational speed to 500 RPM, then a spur gear to the driving axle. The Mark 1 version went into the T3 loco. The only problem with that was that I underestimated the axial force exerted by the spur gears - they try to push each other out of mesh. Not only was it hard to stop the driving gear sliding along the motor shaft, but I was concerned about durability because, when I dismantled the inline gearbox, I discovered that the thrust bearing was quite crude (but at least it had one).
Powertrain.png
The Mark 2 version has a ball thrust bearing between the spur gear and the motor casing to take the load. There wasn't enough room on the driving axle for anything similar to that, so I added a brass sleeve to fit between the spur gear and the gearbox frame. At least that will be quite accessible for regular oiling. The T3 drivetrain has been retrofitted with similar bearings and so far it works well.
Nick
I think I'm going to enjoy this build!
Mike
Doh! For spur gear, read bevel gear. The curse of old age strikes again.
Nick
Regarding the accuracy of the laser cut parts, this might have had something to do with the accuracy of the drawings.
John
Hi John,
The laser cutter follows the instructions it's given, so for sure the accuracy depends on that. Using 3D CAD makes it easy to ensure that the slot and tab are both exactly the same size and in the right positions. From the CAD model I can generate inputs for both laser cut and 3D printed parts.
Laser cutting like this was new to me, so I was pleased to discover that the process gave sharp corners and edges with no significant roughness or burring.
Nick
Coupling, connecting and eccentric rods made by traditional drilling, sawing and milling.
Rods.png
While making them, it occurred to me that I could have shortened the process.
When I was deciding what to make by laser cutting, I was concentrating on flat parts like frames, and the rods struck me as too 3D. Not so! The traditional way of making them is to start by cutting the outline and then machining the width as necessary. Since laser cutting can be done in a wide range of material thicknesses, I could have had the outlines (side or top, depending on the complexity of the part) done that way, leaving me with the 3D shaping to do on my mill. That would have been a significant saving in time. Oh well, I'll remember that for the next project.
Next up, the remainder of the valve gear parts, then assembly can start.
Nick
Excellent work Nick.
On the coupling rods do you fit them to the wheel centres to check fit before opening out for the bearings?
Mike
Hello Mike,
It's all done by direct measurement. I checked the laser cut frames and they are as accurate as I can measure. The coupling rod centres are drilled directly (my mill has a quill and a DRO - the latter means I hardly have to mark out anything), and I set the quartering of the driving wheels using a jig. They may not be exactly 90° but it's an electrically powered model so that doesn't matter, but they are all the same, which does matter.
Of course nothing is perfect and I often have to open up one or more of the coupling rod bushes to give free running, but not usually by more than 0.1 or 0.2 mm.
Nick
Here are the slidebars, crossheads and all the remaining valve gear parts, all made by traditional methods. As previously mentioned, I'll consider making more use of laser cutting next time around, but sadly not 3D printing, which in metal is way outside my budget.
IMG_20221116_142709635.jpg
When assembled, it should look like this. The valve gear is a form of Stephenson's, but straight link and balanced, so the valve rod goes up when the link goes down (and vice versa). From the modelling point of view, it just means more components and pivots (groan).
Loco v104.png
That's everything done for the chassis, bar a few little bits and pieces. Ready to start building!
Nick
Wow, Thats really impressive!
The crank axle.
Crank axle.png
In case anyone is in doubt, it is built up, not machined from solid - I'm not clever enough to do that. All the joints were glued and pinned, then the axle was cut away between the cranks and cleaned up. The eccentrics are secured with grub screws so as to get the valve timing right. I know it's an electric drive, but I might as well get it right.
When I checked my photos of the preserved Hardwicke, I was surprised to discover that the left crank was leading. On delving further, I discovered that this was common practice for the LNWR, unlike many other British railways and builders where the right crank led. That meant I've built several locos in smaller scales the wrong way round. Whew, nobody noticed (unless they were too polite to mention it).
Nick
"There's this crazy guy in G3 who assembles his model locos the same way as the real ones were ..."
Cylinder front 1.png
Let me explain. Usually I'd do features like this using simulated studs and nuts, but my usual suppliers could not provide them in the right size. Why not, I thought, use scale nuts and bolts? M1.0 was exactly right, and I bought enough of them from Prime Miniatures (https://www.prime-miniatures.co.uk/) for less than I would have paid for the simulated fittings. Win, win! Okay, they were a little more fiddly, but the result was worth it.
Cylinder front 2.png
Nick
Impressive work Nick, the more crazy the better.
Mike
This project was always an experiment into how far I could take new technologies, and of course you don't know the limits until you try to push too far. Herewith, the story of the motion plate. The real thing wasn't a plate, it was a cast component with flanges, strengthening ribs, and of course brackets to hold the slidebars. An obvious candidate for 3DP.
Motion plate 3DP.png
Unfortunately the print in nylon wasn't up to the job. It was just too flexible. Mike Palmer very kindly offered to make one in brass on his CNC mill, but the many narrow corners and pathways would have been a serious struggle. Miniature CNC machines do exist, but they come with anything but miniature price tags. So it was back to the old ways, starting with a steel plate (done by laser cutting, FWIW). To this I silver soldered the brackets for the slidebars.
Motion plate steel.png
The tedious bit was cutting out the ribs along the top and round the openings from brass with a piercing saw, then soft soldering them into position. You will see I have simplified the detail somewhat, but I don't think it will be too obvious. The plate will be attached to the frames using tabs and slots instead of rivetted flanges. The flanges on the original will be dummies, riveted to the frames.
Motion plate overlaid.png
How else could I do it? 3DP in metal would be nice, but brass has become very expensive and for various reasons mild steel still isn't very printable. Stainless steel is probably the best option at present (as long as you can be sure you will never need to solder anything to it), but for this component it is still about £40 for a one-off. No, until metal printing becomes a lot cheaper and better, for some things the old methods will still be used.
Nick
Nick,
A pity about the nylon motion plate since it looks to have a very nice "finish"/patina and would have saved a lot of time. I have resevations about using non-metallic 3D printing for mechanical/stressed parts and your testing the limits has been a useful exercise in that respect.
The intricate work involved in fabrication of the replacement part has certainly produced a worthy replacement.
I am working with PETG to produce coach bogies and it is extremely strong in thicker sections but is still at the proving stage.
Who would you use for printing in brass or steel?
Regards,
John.
What about carbon fibre?
Regards
Ralph
Nick
Looking at the motion plate again, we could have cut the plate with side ribs and mounting lugs from say 5/16in brass then cut two surrounding ribs from 1/16in brass as one piece and solder on both sides. Not a problem if you wish.
Mike
Thank you everyone for your comments.
John,
I like the finish too! It looks rougher than it actually is, but as received, under a coat of paint I think that it looks like an iron casting straight from a sand mould, which is just right for many components. It's also easily smoothed if necessary. At present I don't know who I would use to print brass or steel, but at some point I will need some boiler and cab fittings in brass (for the sake of appearance) so I must come back to it. Steel is a bit of a hopeless case at present. The only print companies I can find that do it use a bronze/iron alloy that is strong and can be soldered, but looks more like bronze than iron so won't do for unpainted parts like rods and valve gear. Stainless steel is more feasible, but again, the appearance is wrong.
Ralph,
Interesting thought. Its strength and rigidity properties are encouraging. The web says it is printable on desktop machines using a hardened steel nozzle (the filament is abrasive). Anyone tried it, or care to try it? A quick search did not throw up anyone offering it commercially to our market, but I'll have a deeper dive. It is not for unpainted parts, of course.
Mike,
Ah, there's always a solution. Well, it's done now, but maybe we can try that next time.
Nick
The handmade final version looks superb. For the next one ;) what about printing a wax and then casting it in brass?
Mike
I have a kilo of Sunlu black PLA+ filament with added Carbon Fibre that I've not used (still sealed). I also purchased a triple pack of E3D hardened steel nozzles for use with it.
I had something in mind for it at the time but in the end decided to reinforce ordinary PLA+ with a steel piece instead. I beleive it's a good bit stronger than PLA+ but haven't needed anything special for my prints since. If anyone would like to try it - you can have both for £30 plus postage - that's about half current list price I think (approx £30 apiece).
Regards,
IanT
Mike,
Interestingly, that is the process that is now offered by printing shops. When I first started looking into metal printing, brass was directly printed using a laser sintering process. Now they have switched to a hybrid wax printing/investment casting process. I guess that the industrial market for brass printing is so small that there isn't much incentive to develop the sintering process. But it's not completely dead, sintering machines are still on the market. So we shall see how it develops.
Back in the here-and-now, I was quoted ~£80 for the motion plate in brass using the hybrid process. Err ... no thanks.
Nick
There is also the process called "lost PLA". This is analogous to "lost wax". This would give you a more robust investment for the sand to be packed around.
Regards
Ralph
Nick,
Who supplied the quote for the brass casting?
I shall need a SV (with top feed) casting for my GWR "Saint" (the Walsall M I version is the shorter more modern replacement type).
Regards,
John.
Ralph,
I suspect some of the vendors may be using "lost PLA" instead of wax - they are usually not very explicit about it. My personal interest is in "one stop shops" who produce a component from a CAD file. If one were looking to print masters and have someone cast from them, then obviously a conversation with the caster would be the starting point to choose the right material. If you are wanting to do the whole thing, printing and casting, yourself, well, you probably aren't reading this forum anyway!
John,
Shapeways. Be aware that they manufacture in the EU so you will pay import duty on top of the quoted prices.
Nick
More experiences of using 3DP components. I drew and had printed driving wheel hornguides pretty much to scale with very little compromise, and they looked good.
3DP hornguide.png
The problem was the narrow crossbeam at the top. On the prototype it doesn't matter because it doesn't take any significant load, but it's a different matter for the model. The prototype axleboxes have underhung springs that transmit the weight of the engine directly to the frames. I could not use that on the model (now someone is going to tell me how to make working leaf springs of exactly the right strength) but chose the usual modeller's arrangement of coil springs above the axleboxes bearing on that there crossbeam. The crossbeams would be taking most of the weight of the loco, they would flex too much and ultimately fail.
My first attempt was a little piece of angle above the crossbeam to strengthen it.
3DP hornguide strengthener.png
It wasn't terribly successful and I didn't like it because it looked like the bodge it was. The photo also shows another problem that arose in rivetting the hornguide to the frame. I didn't want to rely on epoxy alone considering the shear load there would be and anyway, rivets are prototypical. The softness of the plastic meant that it was difficult to set the rivets well, and if you look carefully you can see some of them bent this way and that.
So I gave up on the printed components and my friend Mike Palmer very kindly made me a set in brass on his CNC mill. In doing so we had to loose some of the detail but the result is much more robust and could be soldered in place. The rivets are now cosmetic.
CNC hornblock.png
The photo also shows the new motion plate and the rear covers of the cylinders which I had to redesign and replace because it proved impossible to attach the slidebars to the original one without a 1:22.6 scale spanner and 1:22.6 scale fingers to hold it. F360 does a lot of clever things but fails to warn you about that.
The bottom line: 3DP technology (as we amateurs know it) isn't ready for components that take any sort of load.
Thanks to Mike Williams' good offices, I have recently acquired a copy of the Bill Finch Portfolio of these locos. What a wonderful resource - full of detail sketches of all the fittings which clarify the works drawings immensely. Oh, but all those extra fittings to model. When did I say this would be finished?
Nick
Slidebars in place, and checking clearances with crossheads:
Slidebars.png
Just like the prototype, the slidebars are held in place with bolts, except that mine are M1.0. I was nervous about cutting a dozen tiny threads in 2mm thick steel (visions of a bin full of broken taps), but using a brand new tap, cutting oil and taking it slowly and carefully, all went well. I can pull the bolts up suprisingly tight, but if they do come loose in service I'll use a drop of threadlock.
Then disaster, or so it seemed. On one driving wheel the tyre had come detached from the centre over a segment of the circumference.
Tyre separation.png
The rest of it was still secure and I could not see how to get the tyre off completely without a high risk of damage. Close inspection showed epoxy still attached to both surfaces, so most likely the failure was due to poor mixing of the glue and hardener (another lesson learned). I used a few drops of the thinnest Loctite readily available in the hope that it would penetrate into the gap before going off, and it seems to have done. Phew.
Nick
Next the assembly of the wheelsets. The wheel centres were 3D printed so the bore was "dead-on", but nylon is an elastomer and in practice they grabbed the axle a bit more than was convenient for final adjustments, so I very carefully eased them out with wet and dry wrapped around a mandrel of suitable diameter. These are the tools to set the wheels in place and hold them while the adhesive takes.
Quartering jig.png
The H-shaped part carries the axle and the two cutouts are sized to hold the axleboxes. Quartering is done by resting the crankpins on the two pillars.
Quartering setup.png
Once you know the height of the axle from the baseplate, the size to make the pillars is a matter of geometry (or if the thought of square roots makes you weak at the knees, draw it in CAD). The remaining parts are to check the back to back dimension, but I leave them in place during hardening just in case anything tries to move.
BB dimension check.png
And there's the finished wheelset. This is the driven axle so it has the motor-gearbox unit attached, but the crank axle is similar.
Driving axle assy.png
Nick
Here's the valve gear assembled. You can't really say it works for an electrically powered model, but it goes round as it should. Still some temporary fittings to be replaced with the permanent ones, but it feels like a milestone reached.
As always, the assembly was fiddly and frustrating, with the usual problems of building order: can't fit A before B, but need A in place in order to fit B. 1:22.6 scale fingers would have helped a lot. Or a third hand. Or both.
Valve gear 1.png
Valve gear 2.png
Nick
Lovely work Nick - very well done.
Regards,
IanT
Nick
An excellent piece of workmanship, it is encouraging to see a member appreciating railway engineering by recreating it in such detail, a rare event in G3.
I hope it will inspire others.
Mike
The brakes are between the driving wheels, with a single actuating lever. This appears to be common for 4-coupled LNWR locos of this era, and it is a characteristic feature. The parts are the usual mixture of laser cut, 3D printed and fabricated.
Brake parts.png
Of course the assembly hides much of it. At least I didn't have to model all the linkage behind that cover.
Brake assembly.png
This is the brake cylinder located beneath the cab and the various actuating bits and bobs. Notice the pull rod - as an experiment I had it 3D printed.
Brake actuator parts.png
The eyes are fine, but the rod itself looks rather coarse and is not straight. The material is sufficiently elastic that it won't straighten of itself so I might have to tension it when I assemble it enough to pull it straight. If that doesn't work I will replace it with a metal rod and reuse the ends if possible.
Nick
Brake actuator assembly.png
I didn't like the pull rod, but I did manage to cut off the forked ends and drill them for a steel rod so it was not wasted. This is a trial assembly. Hats off to Crewe, it is an ingenious mechanism that pulls the engine and tender brakes all from the one cylinder. I won't try to replicate that completely, even in a non-working form.
Nick
Thinking ahead, I shall need a number of brass fittings in the cab. For the T3 I had similar fittings 3D printed in brass and was very pleased with the results (http://g3forum.org.uk/index.php?topic=2436.45). However, this process has become a lot more expensive and that's made me think about alternatives. Mike Williams suggested I have several sets cast and take advantage of the economies of scale, because the same fittings were used in different classes of loco. But at my rate of building I doubt that I will last long enough to make it worth doing.
I wondered about metallic paint on 3D print in a plastic material. It is a long time since I last used such paint and maybe it was worth another try. The motion plate printed in PA-11 MJF that I had rejected as too flexible was now spare and served as a test piece. The paint is Humbrol #54.
The left hand half of the plate in the photo is out of the tin. For comparison and because your screen will probably render colours differently from mine, I included a couple of scrap pieces of brass, one newly polished and the other somewhat tarnished. The paint colour is much too red, more like bronze than brass. The right hand half is the brass paint with a bit of yellow added. That brings the shade closer to the tarnished piece but also loses some of the metallic lustre. I think that's because the brass paint is actually tiny flakes of brass in a clear paint medium, and adding a non-metallic colour has the effect of diluting them.
So I'm really not sure at present. Fine-tuning the mix will probably get the shade more accurate but I'm not hopeful about getting that lovely polished brass finish this way.
Nick
Brass painting.png
The ash hopper under the smokebox is fairly unique to LNWR locos as far as I know. Photos don't make it clear, but by peering underneath the preserved Hardwicke I managed to make out what it looked like, and I think this is a fair representation. The cylinder drain cocks were based on commercial handrail knobs, since they were a spherical shape and about the right size. It saved me a tricky machining job.
Chassis 1.png
The last details are the drain cock linkage, the pipe to the crosshead pump, and the oilers to the leading wheel axleboxes. And that completes the model below the footplate (I think). Next up will be the smokebox.
Chassis 2.png
Nick
Stunning attention to detail Nick, it really shows what is possible in Gauge '3'.
Thank you for sharing this.
Regards,
IanT
Model engineering at it's finest, a joy to behold.
Mike
Some more experiments with colour. I realised that the base colour might make a difference, so on the LHS of this test piece I first painted an opaque layer of yellow then covered it with out-of-the-tin "brass" paint. It's about the same shade as the sample of brass and yellow mixed, but with a bit more metallic lustre.
It was also suggested to me that I try gold paint, and that is what you can see on the RHS. It's not very brassy, and not very gold either for that matter. I also tried a sample on a plain white background to see if it made a difference, but not really.
So I still haven't found a way to make plastic look like brass.
Nick
Brass painting 2.png
Back to the loco. Most electrically powered locos, as far as I know, are built using a separate chassis and body, the body removing to get at the works. That's not going to work here because of the way the leading wheel spring is attached. The hangers are bolted to the frames to take the load, but the front hanger has to pierce the smokebox wrapper.
Smokebox assembly problem.png
That means if you bolt the hangers to the frames, you can't get the smokebox off, but with the smokebox and boiler in place it is all but impossible to remove the spring. Incidentaly, on the real thing lead sheet was forced into the space between the hanger and the wrapper to preserve the smokebox vacuum. It all sounds like a bit of a bodge. Couldn't they come up with a better idea? Clearly, DFMA (Design for Manufacture and Assembly) hadn't been invented in Victorian times.
My answer is to attach the smokebox permanently to the frames. The boiler is part of the body assembly, and bayonets into the back of the smokebox. To remove the body, release the screws which will be under the cab, slide the body backwards about a millimetre, and lift it off vertically. It will work because there are only two external pipes connecting the boiler and the smokebox and it's easy enough to release them for dismantling.
The smokebox skeleton is a straight forward bit of sawing, filing, and turning.
Smokebox skeleton.png
Thw wrapper has two rows of rivets at front and rear. I decided to press them rather than add them separately and solder them, partly because I couldn't find any rivets of the right size, but mainly because I didn't fancy drilling so many tiny holes.
When I made my rivetting tool, many years ago, I designed it so that it could be clamped to the bed of my Sherline lathe. The work is clamped to the cross slide and moving the saddle and cross slide gives nice uniform rows of rivets in both directions. Here is the first row
Smokebox riveting 1.png
and here is the second row, positioned by cranking the x-axis the correct amount and maintaining the same spacing on the cross slide.
Smokebox riveting 2.png
I prefer doing it that way than relying on the anvil diameter to space the rivets. It works better for me but I know that the late, great Beeson and Reynalds both used the anvil edges, and who am I to argue?
Nick
I hope no-one is expecting an easy way to form the reverse curves in the wrapper so that it fits the skeleton, because I'm going to disappoint you. I used rolling bars and bending bars, did it a bit at a time, kept trying it against the skeleton - and it still didn't fit perfectly. But I managed to persuade it into place by holding it on the skeleton with a collection of clamps before soldering it up. It was not perfect but the solder fills up any remaining gaps.
But before that, it was necessary to add the dummy boltheads at the lower edge of the wrapper. The missing one is where the spring hanger will go.
Smokebox wrapper.png
I cut the wrapper slightly over width so that I had an edge on the outside to solder to (much easier than soldering inside), then filed it back flush to give nice sharp corners.
Smokebox front.png
Smokebox rear.png
The black bits are 3D prints of the chimney, door, and the blower pipe elbow in SLS nylon. I had them done in black rather than the default white so that if anything got scratched it would not show badly. Unfortunately it makes it difficult to photograph to show the detail to advantage, but take my word for it that the surface finish and the detail are excellent. I was particularly impressed by the consistently thin base of the chimney (it used to take me several hours to file these up in brass and I never got it that consistent) and the detail of the door wheel and handle.
These prints are a step up from the last set of comparable prints that I had done a couple of years ago. It just shows how quickly 3D printing technology continues to evolve.
Nick
Quite superb Nick, as ever. You might want to check the bolts on that excellent chimney base because I THINK the centre bolt on Jumbos also held the petticoat pipe in place and had a lock nut.
Mike
Mike,
The preserved Hardwcke has a locknut on the LHS only. But there is also a photo of that same loco in LMS days with a locknut on the RHS - whether in addition to or instead of the LHS isn't clear. Photos of other members of the class show both with and without but of course show only one side.
But your point is well made. I'll have to decide whether to get a new print done, or add a tiny nut with a drop of adhesive. To which side depends on the name and number I finally choose.
Nick
Next up, the footplates. Yes, there are two of them, LH and RH. Oh dear, more curves to form where the tops go up and over the coupling rods. After an abortive attempt to make them in one piece, I decided to make them in three pieces and join them. Here is a reverse curve being formed around suitable blocks (diameter chosen by experiment on pieces of scrap).
Footplate_1.jpg
Then soldered to the footplate side.
Footplate_2.jpg
You can never have too many clamps.
Footplate_3.jpg
All done and cleaned up. Unlike Ernie Wise's hairpiece, you can see the joins (just) but they will disappear under a coat of paint.
Footplate_4.jpg
When I encounter things like this I always wonder how it was done on the prototype. Did they somehow shape it all in one piece, or make it in sections? There is no evidence of joins in any of the photos that I have. I'll have to examine Hardwicke again next time I get the chance of a visit to Shildon.
Nick
Lovely work Nick!
Regards,
IanT
I see you have the rear corner of the footplates just right. The curves there are very important, which many people don't realise until they come to do the lining! But you clearly know that because it is superb.
Mike
Thanks Ian and Mike. I always try to collect as many photos of the prototype as I can, so that I can understand and get right details like the rear corners. Glad you spotted it!
The firebox is the usual wrapper around a skeleton, and the boiler is simply a rolled cylinder.
Firebox skeleton.png
Then I did a trial assembly to make sure everything fits. The dome, safety valves and backhead are 3D prints.
Boiler and firebox.png
Here's the backhead in detail. It took quite a long time to draw because of the complexity, but it was worth the effort. I'm sure I saved myself a lot of time. Actually I had to carve bits off the bottom to get it to fit. It was just a bit too tight due to the stackup of tolerances (a posh way of saying that I got the boiler just slightly too long). In future I will try to allow for things like that when drawing them. Incidentally, there is some wierd camera lens distortion in that photo - the boiler fittings are actually in a line.
Backhead.png
Another interference point is that the boiler makes contact with the leading drivers because the G3 back to back dimension is smaller than scale. I'll have to cut out a clearance for that, which won't be visible behind the splashers.
Nick
Specially for Mike Williams (post #39) :)
Lock nut.png
Thank you Nick, I will sleep easier tonight knowing you have done that!
Now be honest, having mentioned it (my big mouth!), had you not done that, then it would have bugged you every time you looked at the engine? A bit like Geoff Pember's 7mm version 40 years ago. He found that he had the wrong crank leading. Nobody else knew or could see it, but he knew and couldn't live with it until he'd made a new axle!
Mike
Mike,
You're quite right (of course). When you first mentioned it, it went on the To Do list. I'm very grateful to people who point out to me things like that, because I find that it's very easy to overlook details.
Nick
Not much time in the workshop recently, what with other things (not just the G3S Newsletter) getting in the way. However, I've recently been continuing the bodywork with the rear splashers, which have a curved corner and then merge with the firebox.
Rear splasher.png
The tape is holding it temporarily in position. I'm not ready to solder it up, but I have to check the fit to the firebox and the fit of other cab parts to it. If you are hoping I can reveal some clever CAD-based method to make the curve where it meets the firebox, I'm going to disappoint you. The trouble is that anything I make that is folded or curved never comes out exactly to the drawing, and that applies here to both the splasher and the firebox. In CAD I can define the curved end of the splasher to the n'th decimal place, but in metal it never quite fits. Instead it required patient cutting and filing by hand until the gap is small enough to be able to solder it up – in fact, the traditional way.
The other problem was the arm rest on the top of the splasher. For some unaccountable reason I persuaded myself to solder the splasher side to an oversize piece of material and cut it to the correct profile. Not clever. It is really difficult to get the saw in close and still control it, so it goes wandering. After messing up the first two attempts, I did the sensible thing which was to cut it out first then solder it. The cutting was done on the milling machine with a rotary table to make the round end where the handrail fits, and after that it just needed the top edges rounding and polishing.
Arm rest.png
Nick
Nick
One way I have found to tackle boilers and firebox to fit over splashers is to make dummies. Draw out the development in CAD print it and use the print as a template to cut out the shape in styrene, then offer up to the splashers and note where adjustments may be needed, and repeat the exercise until you have a good fit.
However, there is always a bit of fettling needed.
Mike
P1030203.JPG
Splashers.png
I was peering under the footplate for some reason or other, and realised that the low angle could give an unusual and striking photograph. Since the sun was shining I took it out into the garden to make best use of the natural light. I don't have a garden railway, it is just perched on a suitable timber.
Both sets of splashers are done. A few details to add to the footplate then on with the cab.
Nick
The cab structure is mostly complete. The roof is the only outstanding part and that will be removable in order to access the interior and backhead. Like all platework, it is sawing, filing and soldering and there isn't much more to be said about it. People have asked about the sharp corners. The trick is to make one side very slightly (fraction of a millimetre) over-length, run a fillet of solder into the inside corner so formed, and file the excess away.
Cab exterior.jpg
Cab interior.jpg
Now that the nights are drawing in I'm less enthusiatic about heading to the workshop in the evening, so I've been drawing the backhead fittings. I haven't drawn all the pipework because that will be done using copper or brass wire, bent and cut to fit. The fittings will mostly be 3D printed in nylon or, where the finish is brass, cast from 3D printed masters. The casting is a lot more expensive, but fortunately the LNWR didn't go in for "bling" as much as some railways and were happy to paint rather than polish a lot of parts.
Cab fittings drawing.jpg
Nick
Santa (cleverly disguised as a delivery driver) came early this year. Let's see what is in the stocking ...
First up, brass castings of several backhead fittings.
Brass castings 1.png
Brass castings 2.png
These were done by the hybrid process: a wax pattern was made by 3D printing from my solid model, and that was used to make an investment casting in brass. It saves me having to make a pattern, and the casting quality is quite good enough and needs little in the way of finishing from me. I put all the parts on a sprue. Because of the nature of the casting process, that made a big difference to the cost over casting each part separately. However, the per-unit cost of casting is quite high for one-offs and to take advantage of the price breaks I had four sets made. That's one for this project, one for a future project still in the thinking about stage, and, er, two extra. Maybe there is someone out there also building an LNWR prototype?
Next a collection of parts 3D printed in SLS nylon.
PA12 fittings.png
Hmm, a bit of a mixed bag here. The little fittings - fixing brackets, elbows, tees - are nice. The reverser is okay but missing the handle on the outer rim of the handwheel (a bit of wire will fix that). Close up, the finish is a bit rough but I can smooth that down.
Reverser.png
The steam turret is supposed to have three handwheels.
Steam turret.png
The centre one is broken and the smaller outer wheels just haven't come out. Clearly the spokes are too thin for the printing process. In the past suppliers have warned about this sort of thing when I submit the file, but I guess they didn't do that check this time. I will take it up with them, but most likely I won't get anything more than a refund on these parts. Apart from the handwheels they are okay, so either I'll get the handwheels cast in brass and end up with a lot of extra ones, or I'll have to machine up the few I need. I will think about that over the turkey and pud.
The injector controls also have handwheels. In one case here one wheel is broken, but the other is okay and there are enough spare for what I want. When ordering 3D prints of small components, I often get considerably more than I have asked for at no extra charge. Mavbe that's how their automated process works. Whatever, more and more surplus fittings are accumulating in my workshop drawers.
Injector control.png
In the meantime I have also been machining some fittings that for various reasons weren't feasible or economic to print, or I just fancied making them the traditional ways. Here are the spectacle frames, gauges, whistles and safety loops. And there are more to come.
Machined fittings.png
In the detailing phase, I spend some time going over the drawings and photos, making a list of all the parts to do. That way things don't get forgotten, but it also gives me a sense of achievement as I tick each one off the list as I do it.
Nick
Just magnificent. Reminds me of when a company "Hobbyhorse Developments" started out in 7mm many years ago.
"Maybe there is someone out there also building an LNWR prototype?" I don't know of one (seriously!), but hope the parts will be available not just to current builders but well into the future, somehow.
Mike
NOTE : A discussion revolving around availability of parts is continued at
http://g3forum.org.uk/index.php?topic=3122.msg19622;topicseen#msg19622
John Candy
I've started adding parts to the backhead.
Backhead assembly.png
This is where the photos of the cab interior of the preserved loco are really helpful because with all the pipework it becomes a 3D jigsaw so I am starting at the back and working forward. Once I've populated the backhead as far as possible, it goes into the cab and then the fun really starts.
Nick
I blame Bill Finch. If he hadn't published a book full of dimensioned sketches of the preserved loco, there are details I would never know existed, let alone model. And if I didn't get so distracted, it would be nearer finished. So, on the side of the cab we now have the staff carrier and the boiler certificate holder. Who knew?
Cab details.png
Nick
I wasn't happy with the print of the steam turret and I was prepared to replace the handwheels, but discovered that I'd made a mistake in the solid model so decided to do the whole thing again. This time I thickened up the spokes and lever arms in the hope of makng the print more reliable, and I got the print made elsewhere by an individual recommended to me by Mike Palmer (thanks, Mike).
Steam turret v2.png
It's done in a softer plastic but it carries no load so that should not matter. The quality is pretty good, though the spokes, particularly on the smaller wheels, now look a bit heavy. I will try to improve the appearance with a bit of gentle scraping with a sharp knife.
Nick
First it was freezing cold, and now half an alphabet of storms have blown over, so I've left the workshop for the time being and have been working in my warm office on the solid model of the tender. It isn't and won't be a complete model. I have concentrated on those parts that I plan to get made and omitted a lot that I know I'll be making myself.
Screenshot 2024-01-19 123859.png
Most of the work has gone into the chassis. Almost everything you can see here will be made by laser cutting (the flat parts) or 3D printing (springs and axleboxes).
Screenshot 2024-01-19 123017.png
Another concern was fitting everything together, particularly around the water scoop where it and its actuator, the brake rods and their actuator, and the axlebox keepers all get a bit close. At the same time, I've tried to work out how it can all be assembled and disassembled. I had to leave off a couple of minor details, which I hope are inconspicuous, because it was just too difficult to fit them in. I'll leave it to the LNWR experts to see if they can spot what they are.
Screenshot 2024-01-19 124101.png
Nick
Yay! The cab and backhead are finished at last. There were so many details to do, everything had to be done in the right order and painted as we go because there is no hope of painting them afterwards. (There's still some painting of the more accessible parts to be done). The pipework is a real cat's cradle and I bet it drove the Crewe fitters as nuts as it did me. Most of the pipes had to be made two or three times before I got them right. They are mostly copper but some are brass where I didn't have copper wire of the right diameter.
Cab interior 1.png
Cab interior 2.png
I'm still not entirely pleased with the steam fountain. The handwheels and levers look somewhat coarse. As previously discussed, that is because I was pushing the limits of the printing process. In the end I decided to put up with it because, when I put the cab roof on I realised that it wasn't as obvious as it is in the photos. But if I were doing it again, I would get a casting made. Not only for the sake of appearance, but also because I could then solder all the pipes to it. As it is, they had to be glued, and plastic doesn't take well to being glued to metal. When I made the solid model I included holes for the various pipes sized so that the pipes were a good push fit. The inherent elasticity of the plastic allows that and it is probably that more than the adhesive that is holding them in place. Some of them are so wedged in place between other bits that they won't move anyway.
Nick
Just fabulous. Faultless. What an incredible advert for our scale.
Mike
Nick I thought I recognized this loco from another place. Wow wonderful work.
Michael
The loco has now gone to the paint shop, where it will be for some time because painting isn't my favourite task and I'll happily take any excuse to do something else. The present excuse is that bits for the tender have arrived and are just asking to be worked on.
The wheels, as before, have 3D printed nylon centres. Previously, I made the tyres for the loco wheels from some large diameter steel bar. This time I got blanks laser cut in steel. It actually worked out roughly the same price (large diameter bar isn't cheap) and should be quicker to cut because there is much less material to bore out from the centre.
Carrying wheels.png
So why so many wheels? Well, I decided to get enough parts for two tenders. The LNWR must have built lots of these tenders because I've seen photos of them trundling around behind many different classes - so I have options for future (undefined) projects. I might even build two because it's usually quicker to build together rather than one after another. I also needed a new wheelset for the loco to replace the existing one that has the wrong number of spokes (oops), and I added a few more just because. Actually I think I got a price break on either the centres or the blanks. It's worth seeing where this cuts in when placing an order.
Along with the tyres, I ordered the steel parts for the tender frames. Again there's enough for two tenders. When I get bored of turning tyres I can start assembling this lot.
Tender frames.png
Nick
Two tenders! I can't wait to see what the second engine might be. If its a goods engine you'll be wanting plenty of LNWR wagons ;)
Mike
Haha! Actually I do quite like the Crewe 0-8-0s, particularly the ones that had to have a kink in the valve rod to avoid the front axle, but I might want to negotiate a discount for quantity on wagons.
Now, where were we? Oh yes, tyres. Warning: this post is about turning tyres, so if you have no interest at all in lathe work, you may decide it is not for you. Feel free to move on.
And if you're one of those annoying people with a toolroom quality lathe and a zillion years' experience, this post certainly isn't for you. I'm not in your league. I'm one of those people who thought it would be fun to have a lathe and went on from there.
The first task is to reduce the blank to thickness and bore out the ID to the correct size. My chuck was only just big enough, but it did hold them securely. I used a headstock backstop so that each blank goes in the same position, and a carriage stop to avoid running into it with the boring bar. All the tyres were done using this setup before moving on.
The lesson here was the layer of hardened material that is formed by the heat of the laser at the cut edges. Reminiscent of the skin on the sand casting beloved by model engineers of a certain generation. Not tool steel hard, it does cut, but takes it out on the tool.
I was expecting that, but I was surprised how deep it was - up to 0.8mm in my case. It dulled the edge of an HSS tool very quickly. Yes, I'm still in the 20th century for lathe tools but I mostly use HSS tools because so much of the turning that I do requires a special tool form to be ground and it's a lot easier in HSS.
That was certainly true until I discovered that the awkward bits could be 3D printed.
Anyway, I switched to a carbide insert boring bar which did a much better job of cutting. The only tool I had available is much longer than I needed so it vibrates a bit and the quality of the finish is not great. But I will be gluing the centre in place, and a slightly rough finish (this isn't an argument for a ploughed field finish) means a greater surface area in contact with the glue which is all to the good.
Tyre_1.png
Once the ID is correct the tyres go on this fixture. Where the tyre is mounted it is turned in situ to a good running fit on the tyre ID. Then it never leaves the chuck until the whole batch is done to ensure that the tyres are concentric.
Tyre_2.png
Each tyre is clamped in position, and the first task is to reduce the OD to the diameter over the flange. Again there is a layer of hardened material to get rid of and I used a carbide insert tool for this. Incidentally, when I ordered the tyre blanks from the cutting firm, I did add enough margin on both ID and OD - just. Phew.
Tyre_3.png
Now to form the profile. Lock the saddle and set the top slide over at 3 deg to give the correct taper on the tyre. The tool is moved exclusively by the top and cross slides in this operation. The leading edge of the tool is set at the correct angle for the flange. Then cut to final diameter plus a very small margin (say, 0.05 mm or a couple of thou in old money).
Tyre_4.png
Now for the controversial bit! I get the final shape using a form tool (from Mark Wood (http://www.markwoodwheels.co.uk/)). I like it because the final profile is entirely consistent. Lock everything that can be locked on the lathe, use a very slow speed and feed the tool in slowly. If you do it right and keep the final cut very fine, it doesn't chatter.
People have told me they can get just as good a finish with conventional tooling and the form tool isn't worth the cost. I just checked and I see that the cost is almost double what I paid about eight years ago, so you might think twice about it. Anyway, I've done about 40 tyres in G3 so far so it's beginning to pay for itself.
Tyre_5.png
We're still not quite finished. The surface needs some attention with a fine file (I know, sacrilege) and wet-and-dry paper. Then it is finally done.
Tyre_6.png
Rinse and repeat twenty times. A pile of finished tyres is gradually building.
Tyre_7.png
That's it. There are lots of instructions on the web about how to turn wheels from castings, but I decided to set out how I did it from laser cut blanks, which isn't quite the same. If you stayed the course, thanks for your company.
Nick
Stepping back to the engine for a moment, I've finished painting the chassis. Quite easy due to the monchrome tendencies of the LNWR. The eagle-eyed will notice that the front wheels now have the correct number of spokes.
Chassis painted_1.png
Back to the tender, I now have enough wheelsets for two six-wheel tenders. And a few spare wheels in the drawer just in case.
Tender wheelsets.png
This is a trial assembly of the frames, all set up ready for soldering.
Tender frame assy.png
Nick
The next job is the hornguides. I need a couple of dozen of them, so some organisation is called for, because I'd drive myself nuts if I had to mark out and cut each one individually. What we need is a jig, or several jigs. Spoiler alert! This is the end product.
Hornguides_1.png
The first question is, what are the important dimensions and features? The holes here have to align with the holes in the frame to pass the rivets through, and the hornguide must be a right angle for the axlebox to move as it should. Sounds obvious, but the answer tells us how to proceed. Get those things right and the parts will fit and do what they have to do. I can allow a bit of leeway elsewhere. Not so much as to be screaming obvious, just not to be quite so careful about.
The right angle is ensured by starting with some milled (not rolled) angle of the correct dimension. The photos below shows one such clamped in a jig for drilling the holes. That way I have only to set out the holes once. The jig is also the exact width so that after drilling I can use it to cut and file the angle to length without having to measure.
The angles are LH and RH, so the jig is reversible - do one half the angles, turn it over and do the other half.
Hornguides_2.png
Hornguides_3.png
And here are the two sets.
Hornguides_4.png
One of the outer corners is radiused. I filed a quarter circle on a scrap of material of the right size, clamped it to each angle in turn and used it as a filing jig. But forgot to take a photograph - sorry.
Next up is the base which is soldered in place. Here is the soldering jig which is just a few pieces of scrap wood. It holds each angle against a strip of material that has the correct width and is much too long in order to make it easy to hold. After soldering, the base is cut and filed to size. The soldering jig has LH and RH sides, too.
Hornguides_5.png
Finally, there is a hole to drill and tap in the base for the stud that will eventually hold the keeper in place. Another drilling jig is called for in which the angle can be clamped for drilling. Tapping is then done by hand.
Hornguides_6.png
Hornguides_7.png
And there they all are, lined up and ready for riveting to the frame. Yes, there are two tenders' worth. It's a lot more time-effective to set up and do them all now, rather than half now and half at some later date.
Hornguides_8.png
Nick
The keepers are assemblies of plates which are bolted to the hornguides and rods between them. This is the drilling jig for the plates, two holes for the hornguide studs, and one hole at one or both ends (depending on whether it is an outside or centre axle).
Keeper_1.png
And here are all the parts for one assembly, ready for soldering.
Keeper_2.png
Once soldered, the ends of the plates had to be filed to a smooth transition to the connecting rods. There's no easy way to do this. Coarse then fine half-round needle files, followed by coarse then file wet and dry, and keep inspecting it from all angles to spot and get rid of the humps and dips.
Keeper_3.png
Nick
Not much progress recently, what with the G3 Society Annual Show and then the Newsletter, and as I write this the sun is shining (at last) which doubtless will mean a summons from the Head Gardener. In between whiles, here are the tender buffers.
The heads and stocks are fairly straight forward turnings. Here are the stocks rough turned:
Tender buffer stocks.png
and fine turned and polished.
Tender buffer 1.png
Drilling holes for the rivets, using the rotary table to get an even pattern. That drill is 0.8mm diameter and I decided that the hole is far too deep, so I drilled most of the way using a larger drill and left a couple of millimetres to break through. The rivets turned out to be a good push fit and would probably have held themselves in place, but I added some epoxy to make sure.
Tender buffer 2.png
Here is the assembly. The stock is drilled deep enough to accommodate the head and the spring compressed, and then continued at a clearance diameter for the screw. The back face is counterbored quite deeply so that the head of the screw remains in the hole when the spring is fully compressed. That way the buffer is fully self-contained.
Tender buffer 3.png
Nick