Ian_C's workbench - P4 and S7 allsorts

[Ian_C]

Thanks for the series of posts - it is much appreciated and very instructive.

The results look fantastic, thanks for the reminder about the stub drills I really should start collecting a few important sizes.

With respect to the fit of the taper pin, how good a surface finish is there on the ones from Tracey tools? I bought mine from Chronos and whilst they work ok I wasn't that impressed with the surface finish so I'm not entirely convinced that there is full contact of the pin in the tapered hole.

Thanks for the heads up about the pony truck bearings and width. Given how it has turned out do you think it would be worth trying to make the pony truck frames wider for Scale7?

Taper pins. Yes, I've found it very variable. I ended up with some 1/16" pins from two different suppliers. One lot was very tidy, the other was a mixture of OK-ish and rough. The good stuff came from EKP Supplies www.ekpsupplies.com 1/16" x 1/2" Taper Pins Qty 10, about £3.50 I think. I only got the reamer from Tracy Tools, sorry if I didn't make that clear.

Wider pony truck frames? Depends how itchy your hair shirt of authenticity is. You'd have to make quite a few new parts to do that. You could compromise and just put some extra profiled plates on the outside of the frames to space the spring castings out. Honestly, I don't think it's worth the effort.

 

[Ian_C]

Hi Ian,

Very comprehensive set of drawings and an elegant way to solve a problem.

I don't have your patience to make lovely little jigs but use this device to set wheels to back to back and drill for the taper pin.

View attachment 78766

Basically just a piece of bar, I have a stock of suitable sized brass but steel or aluminium would also be suitable, is turned and faced to 31.25 for S7 bb and drilled and reamed axle size. These ones are 3/16". The wheels are inserted with a toolmakers clamp holding them tight against the ends and a drill put through one of the holes, to suit gearbox or insulation, and drilled right through. Once removed the hole in the axles is reamed with a taper reamer. For driving wheels I put a pin through the crank hole into the end of the bar at the correct quartering position, see the holes on the one on the left. Different throws catered for by extra holes.

Ian

Yeah, I like that approach. Thanks, I've learned something this evening! Funny how people find different solutions to the same problem isn't it? I wanted the freedom to choose an axle diameter that suited each job and wanted one tool to do them all, hence the V groove. Your design has the merit of being easier to get geometrically correct in the lathe than all the careful setting up in the milling machine to get the same result. Also provides more support for the wheel rim.

I'd thought of quartering differently too. May post my solution here if it works out.

 

[Lyndhurstman]

And the end result is a pair of passable (but not perfect) links that just need the fork ends cleaning out a little to fit the mating motion parts.
View attachment 78142

Good Grief. That's beautiful. Marvellous. Cap suitably doffed.

Cheers

Jan

 

[Ian_C]

Here's the quartering tool. It follows the well known principle of having two surfaces set relative to the axle centre that contact the crankpins such that they end up 90 degrees apart. The wheel gauging and axle pinning block shown in a previous posting is used to hold the axle. The block can be used independently, as previously described, or installed in this quartering tool.


The quartering tool is designed around a 3/16" diameter axle and 3.0mm crankpins. Of course, once they're set 90 degrees apart you can use any diameter crankpin you like; they'll still be 90 degrees apart. I've made a pair of dummy crankpins specifically for this tool and they're stored in a couple of 10BA holes in the base plate when not in use. The horizontal reference block extends far enough each side of axle centre line to allow the crankpin to be set forwards or backwards for RH or LH lead.


If you use an axle diameter other than 3/16" then the axle centre height in the V groove changes, and that in turn alters the angular relationship of the crankpins dictated by the horizontal and vertical reference faces. Not by much, and theoretically you can get away with a couple of degrees either side as long as all axles are the same. The vertical reference block is fixed through slotted holes in the base plate so it can be adjusted by 1.5mm in either direction to restore the 90 degree relationship for different axle diameters or different crankpin diameters if you wish. The degree of movement and the resulting position on the base plate can quickly be plotted in CAD for any combination.



The accumulated errors from making several parts on a milling machine that isn't to toolroom standard mean that I won't get exactly 90 degrees. But it'll be very close to 90 degrees and, more importantly, all axles will be the same. Once I've done all four axles and checked running with the coupling rods on then I'll find out whether all the theory is borne out in practice!

If anybody wants to see the drawings then let me know and I'll post them.

I'm getting bit ahead of things here because I haven't posted the approach to modifying the Slaters driving wheels and making new axles. I modified a pair, seen here unfinished, as a trial. It worked out mostly as planned. I'll do the rest of them when I get the time and post the learnings.

 

[Ian_C]

The confident assertion I made in an earlier post about being able to remove and replace the lathe chuck and wheel holder without introducing any out of true error turned out to be slightly wrong. For a reason I don’t understand the wheel holding tool did not run quite true when the chuck was replaced on the spindle. The wheel holding tool had not been removed from the chuck meantime. It was only a little bit out of true but it should have been near perfect. Not a big problem because it was easy to reface the part of the tool where the wheel sits.

The issue where, in S7, the Slaters wheel and crankpin boss projects far enough from the face of the wheel to cause clearance problems behind the slide bars was flagged up in a DavidinAus post some time ago. David opted to take 0.4mm off the face and it seemed to work for him. Taking a close look at the prototype drawings in the Wild Swan book revealed that…

• the driving wheels measured 6-13/16” overall from front of axle and crankpin boss to inside face of rear boss
• the rear boss on the prototype wheels measured 15/16” from rear face of tyres to inside face of boss (there's no rear boss on the Slaters wheels, we'd use a washer or two on the model)
• the tyre was 5-1/2” in width

…and converting these dimensions to 7mm and doing the arithmetic I conclude that the model wheels ought to measure 3.42mm from inside face of tyre to outside face of axle and crankpin boss. The Slaters wheels measure 4.23mm. So there’s the missing clearance of 0.81mm each side. The prototype ‘as drawn’ clearance between inside of slide bar and leading coupling rod pin was a mere 11/16” , or 0.4mm in 7mm world. If the MOK kit has the slide bars the correct position (and it should have because there are parts on the S7 conversion etch specifically for this) then half a revolution and CLANG is the guaranteed outcome.

As it turns out you can’t sensibly face the axle and crankpin boss down by 0.81mm on the Slaters wheels. The inside ends of the spokes flare outwards to meet the moulded boss on the Slaters wheels to a greater extent than on the prototype. I suppose it makes the over thick Slaters wheel centres look in proportion. I’d never have noticed if I hadn’t checked, and in 0F it may not matter. It is possible to take 0.55mm off the thickness before you start to machine into the end of the spokes and the face of the boss starts to look like a starfish. If DavidinAus got by with 0.4mm and I can manage 0.55mm then I figure I’m in with a chance provided that I have appropriate coupling rod and pin projection on the leading axle.

Mount a wheel in the holder and check that the tyre runs true. On some of the wheels you could see by eye that the axle insert was a little off true when the lathe was spinning. There's the root cause of the 'Slaters shimmy', as I've heard it called.



The first part of the job is to face off the crankpin and axle boss by 0.55mm using a sharp, tiny, pointy tool. This is the same tool described in the pony truck wheel thread somewhere above. The small point combined with a small depth of cut (0.15 - 0.15 - 0.15 - 0.1 as it happens) gives rise to small cutting forces which can be handled by the plastic spokes and which won’t upset the steel crankpin and axle inserts. A collateral benefit of this is that the moulding sink marks in the original surface of the moulding are removed and we have a nice flat boss like the prototype.



Next operation is to clean out the countersink and square axle hole with a sharp 4mm slot drill.


The 4mm bore is opened out to about 5.0mm with the tiny boring bar. The rationale here is that a boring bar will cut true to centre where a 5.0mm drill might wander a bit depending on how accurately it’s been sharpened.


The last operation differs slightly from the conversion of the pony truck wheels previously described. Scaling from the drawing, the prototype driving axles are about 9” diameter where they project from the driving wheel boss. That’s 5.25mm in 7mm scale, or 5.2mm for convenience. So the outer end of the axles must be 5.2mm in diameter and the bore in the wheel insert must be a gentle push fit onto the axle. For the pony truck wheels I’d made the axles to the required diameter and bored out the wheels to fit. That wasn’t straightforward as I couldn’t measure the bore accurately and had to take tiny cuts with the boring bar and keep trying the axle fit. I did it the other way round on the driving wheels. The wheel inserts are all reamed out to 5.2mm (I have a 5.2mm machine reamer) and the axle will be machined to fit the wheel. It is easier to measure the axle diameter accurately than the wheel bores and we'll get to the finished size faster and with more confidence, and since there are 8 axle ends to do so that’s a worthwhile time saving. The 5.2mm reamer works nicely through a 5.0mm bore.


With a bit of organisation it took me about 15 mins to do a wheel, so in about 2 hours one evening all the wheels were done.

Before and after...


..and all done...


Suppose I'd better make the axles next. This also makes me think about balance weights, which in turn means I need to decide which locomotive I'm actually modelling, which in turn might have consquences further downstream. I fancy a late inhabitant of the mighty 18A Toton, mid sixties, last knockings of steam on the Midland main line and I was a kid in short trousers growing up nearby. My brother reckons he remembers seeing 8Fs on the low level approach through the old Long Eaton station behind the Co-op car park. Must have been' 64 or '65 or at a push '66.

 

[adrian]

The issue where, in S7, the Slaters wheel and crankpin boss projects far enough from the face of the wheel to cause clearance problems behind the slide bars was flagged up in a DavidinAus post some time ago. David opted to take 0.4mm off the face and it seemed to work for him. Taking a close look at the prototype drawings in the Wild Swan book revealed that…

• the driving wheels measured 6-13/16” overall from front of axle and crankpin boss to inside face of rear boss
• the rear boss on the prototype wheels measured 15/16” from rear face of tyres to inside face of boss (there's no rear boss on the Slaters wheels, we'd use a washer or two on the model)
• the tyre was 5-1/2” in width

…and converting these dimensions to 7mm and doing the arithmetic I conclude that the model wheels ought to measure 3.42mm from inside face of tyre to outside face of axle and crankpin boss. The Slaters wheels measure 4.23mm. So there’s the missing clearance of 0.81mm each side. The prototype ‘as drawn’ clearance between inside of slide bar and leading coupling rod pin was a mere 11/16” , or 0.4mm in 7mm world. If the MOK kit has the slide bars the correct position (and it should have because there are parts on the S7 conversion etch specifically for this) then half a revolution and CLANG is the guaranteed outcome.

Thanks for posting that analysis. I admire what you have done with the wheels very impressive - although in some way I'm slightly relieved that I decided to go for Mark Wood wheel castings as I reckon I should be able to turn them to the appropriate dimensions, for which I'll use this post to refer to.

However having looked at the Wild Swan drawings it ill behoves me to point out that it appears that the crank pin boss on the leading driver is recessed lower than not only the axle boss but the tyre as well.

This is the leading driver and the coupling rod boss is offset inwards compared to the centre line of the coupling rod and the fluting of the coupling rod is deeper on the inside surface compared to the outside to clear the axle boss.



Compare this against second driver



If we apply the crankpin boss recess on the leading driver then it could give us a little more breathing space to the rear of the slide bars, although it will depend on how the coupling rods are built up in the kit.

 

[richard carr]

Ian

I use soft jaws that have steps machined into them to hold the wheels in the chuck about 2mm deep. As the steps are cut in on the lathe itself they must be true to the centre of the lathe. Your little boring bar is a perfect tool to do that with.
Your method relies on all the wheels being exactly the same size, which I doubt is the case, as the manufacturing tolerances are not that accurate.

Having said that from my experience Slaters wheels run fine even with what appears to be a fairly large run out error.


Richard

 

[Ian_C]

However having looked at the Wild Swan drawings it ill behoves me to point out that it appears that the crank pin boss on the leading driver is recessed lower than not only the axle boss but the tyre as well.

This is the leading driver and the coupling rod boss is offset inwards compared to the centre line of the coupling rod and the fluting of the coupling rod is deeper on the inside surface compared to the outside to clear the axle boss.

Adrian, that's a very good spot indeed. I confess I hadn't noticed that. I can only assume that some of the chaps in Tommy Colemans's drawing office had experience of working in S7 (..s'obvious Mr Coleman sir, once you've got your model to work properly in S7 then you just scale it up and you have a viable prototype...). I built up the rods as per the kit, so they all have the same offset. We'll get to the messy truth when I finally get my act together and make the axles and put the rods on and fit the cylinders. The other thing to think about here is the balance weights. They do project out beyond the face of the tyre and that's quite a distinctive feature. The built up balance weights appear to project out even by the plate thickness beyond the wheel boss so they must pass close to the inside of the rods. Some photos of WDs show the muck on the balance weights being scraped off by the back of the rods - but there was plenty of muck on a typical WD. By the time I get all this together and make it work I'll be able to work out what I should have done.

 

[Ian_C]

Ian

I use soft jaws that have steps machined into them to hold the wheels in the chuck about 2mm deep. As the steps are cut in on the lathe itself they must be true to the centre of the lathe. Your little boring bar is a perfect tool to do that with.
Your method relies on all the wheels being exactly the same size, which I doubt is the case, as the manufacturing tolerances are not that accurate.

Having said that from my experience Slaters wheels run fine even with what appears to be a fairly large run out error.


Richard

Well, yes, manufacturing tolerances. I wondered about that and I have to say that they all were about the same gentle push fit into the recess. The outer diameter of the tyre must in practice have a very small tolerance. But if they were produced on a CNC machine you'd expect very little scatter on a single batch.

 

[Ian_C]

After a bit of research I found that the choice of late Toton 8Fs wasn't that big. I also discovered that Toton stopped being 18A and changed to 16A in September '63. Good job I haven't acquired an 18A shed plate already! By the end of 1965 it was almost all over for steam at Toton, and those that were resident in '63 and '64 were mostly transfers passing through after a few months to make a last stand elsewhere, or withdrawn to the scrap line. Check out brdatabase.info for this kind of detective work, very interesting. I eventually settled on 48142 as the most promising subject. Having decided that, the next challenge was to find some decent photos of 48142 in the 60's and work out what state it was in. I figured the chances of finding a good photo from the right period in a class this large would be a bit needle and haystack. As it turns out there's an excellent photo of 48142 in the Wild Swan book (and it can be found online too), and, serendipity being what it is, the photo was taken in 1963 at Uttoxeter station, which is now my local station and about 3 miles from where I sit typing this. The loco is in very clean condition and looks like it was recently ex-works. That being the case, I'm assuming that this was its final condition and was unchanged between 1963 (when it was based at 16D) and it's stay at Toton from August to September 1965. The Appendix B in the Wild Swan book 'Variations as built' was a very good starting point for the detail picking. There were a lot of variations that won't show up on a model, such as bronze coating on the regulator rod, but for a class you tend to think of as uniform there are a lot of visible and modellable differences, and since I'm doing a portrait model I'll have to swallow them whole. This is what I've learned so far...

• 8142 - Built at Crewe - Lot 154 - Order E424 - February 1942. Withdrawn in November 1966.
• Was at Toton (16A by then) from August 1965 to December 1965.
• Original tender 9869, should be Mk2 welded type, and still was a Mk2 welded in 1963.
• AWS was fitted in June 1961.
• Short connecting rods, longer slide bars, union link and piston rod (8126 onwards) - so I got the union link length correct then!
• Was one of the few fitted with ball bearing and cover on the eccentric rod big end (and still had it in 1963). Goddam - that needs changing.
• It was built with flush rivets on the front buffer beam, but by 1963 it had snap head rivets.
• Cab commode handrail fixed to the wing plate top and bottom with pillars.
• It was built with hollow coupled axles, but the 1963 photo appears (can't be 100% as most of the axle ends are covered by motion in the photo, apart from a glimpse of the rear axle) to show solid axles on coupled and pony truck. They did mix them up somewhat, but most of those built with hollow coupled axles seemed to keep them into BR days. 48142 appears to be an exception.
• Atomiser steam cock in the higher position on the smoke box.
• Double row of rivets on side of smoke box indicating hinged smoke box cross bar.
• Rivets on lower arc of smoke box front ring indicating liner plates fitted.
• Single cone ejector, with single pipe from cab front. And the single cone ejector body differs from the more common double cone type. Must check the casting in the kit - bet it's a double cone!
• Footsteps attached with flush rivets.
• Rectangular access panels in upper shoulder of cylinder clothing. Got that right pre-emptively as well!
• Larger circular access covers in side of cylinder clothing - I already guessed wrong on that one but I'm not inclined to change it and I'll bet that nobody notices.
• Curved reversing reach rod and tall steady bracket (just missed the straight ones that cut in with 8146 and all the NBL built ones as well).
• Built with built up balance weights, but appears to have all wheels with cast balance weights by 1963 - which may be related to the solid axles noted above. The cast weights covered a different spoke pattern and they have a noticeably different edge profile at the tyre, much sharper. That'll take some working out. Again, they did mix them up in BR days and some locos had a mixture of built up and cast balance weights (and solid and hollow axles too).
• 40% balance presumably, and no star on cab side in 1963.
• Sloping throat plate, domed boiler.
• Top feed pipes semi recessed into boiler clothing.
• Was built with higher mounted tube cleaner cock but by 1963 had the lower mounted tube cleaner cock with external feed pipe from higher up smoke box.
• Access plate in smoke box saddle front.
• By 1963 it had the later pattern top feed cover with ‘top hat’.
• Steam sanding.
• Straight fluted combination lever (and union link forked both ends, mercifully)
• Cross head drop links with 3 stud fixing.
• Pony truck oil boxes on outside of front frames.
• Extra stops and guides on cab gangway doors (not sure what that entails - more photo picking required).
• Stiffening brackets on cab wing plates.
• Separate blower and sanding valves in cab.
• Access doors in platform for steam chest covers (no idea what this means - more research).
• Split cast iron valve spindle crosshead guides.
• Altered brake hanger top bracket pins (but I haven't spotted the difference yet)
• One of the batch fitted with hopper ash pan and drop grate. Operating spindle behind LH trailing wheel. There are some useful photos of other locos with this detail.
• Cab window beading half round section with curved lower window corners.
• Smokebox door locking handle probably plain when built but had a collared end by 1963. Who knew?

That's what I think I've established so far. A surprising (to me at least) number of visible differences to model. And I haven't really taken a close look at the tender yet - I know there were some differences.

Sorry - no photos this time. Normal service will be resumed...when I get my act together and make something. Balance weights probably.

 

[adrian]

That's what I think I've established so far.

That's an impressive level of detailed understanding. I'm going to have to up my game - all I have is a wheel arrangement and number! Oh and a couple of photos so I'll have to go through your list and see what I can figure out for my chosen prototype.

 

[Ian_C]

That's an impressive level of detailed understanding. I'm going to have to up my game - all I have is a wheel arrangement and number! Oh and a couple of photos so I'll have to go through your list and see what I can figure out for my chosen prototype.

All I can claim is that I've learned a massive amount from the Wild Swan books. If I'm honest they're a better source of information and inspiration than the 'structions. All I need to make my life complete (apart from a new lathe with DRO, set of ER25 collets, one of those Noga type DTI stands,......) is The Book of the 8Fs from Irwell Press.

 

[Ian_C]

Following the discovery that 48142 was fitted with ball bearing eccentric rod big ends with the distinctive brass cover I set about modifying the previously made eccentric rods. The Wild Swan 8F book does not have a drawing of the ball bearing rod end but there is a drawing in the Wild Swan LMS Locomotive Profiles N0.6 - The Mixed Traffic Class 5's (page 38). Some Black Fives were so fitted and I'm assuming that the LMS had the wits to use the same details on the 8F. Scaling from the drawing showed that the ball bearing ends were quite large compared with the the more common pin joint, about 9 inches in diameter. Surprising. I had to check my numbers again and stare at a few photos before deciding that was correct. Here's the 'story board', commentary below.

1. The original rod and a couple of lengths of 1/4" brass rod.
2. Some scraps of N/S from the etch fret the same thickness as the rod laminates, flattened and soldered to the ends of the brass rods.
3. Brass rods with N/S ends turned down to the diameter of the rod ends and bearing covers, 5.3mm.
4. Hole drilled through N/S disc and no deeper.
5. N/S discs unsoldered from end of brass rods.
6. The existing big end has the oil box filed off and half the thickness filed away where the first disc will sit.
7. N/S disc soldered to rod located by a drill shank into a piece of Tufnol.
8. Second disc sawn and filed to fit around remaining big end on other face of rod. Lined up and soldered. Plenty of solder added to file back and form the fillets.
9. Cleaned up. Rod complete and looking like a lollipop. Looks a bit goofy, but they really were that size!
10. Brass rods back in the lathe and faced off to remove solder and drill dimple. Set up vertically in a vice in the mill, centred, and three 0.5mm holes drilled down the rod a little deeper than the thickness of the bearing end cap. Back in the lathe to turn the end cap profile and parted off.
11. Wire soldered into the three holes and filed to length to represent the nuts holding the brass cover over the bearing. Sweated into place on the end of the rod.

What I neglected to photograph was the short length of 12 B.A. thread projecting from the back of the big end. This was cut off a brass screw and soldered into the big end hole before the cap was sweated on. It will pass through the hole in the crank and be secured with a 12 B.A. nut behind the crank where it is not visible. Well that's the theory. Assembling the motion will require the patience of a saint...

One feature I didn't reproduce (before anybody points it out!) is the little bump on the cover where the oiling/greasing point was. Couldn't see an easy way to do this and I felt that I'd be better off with clean detail on a simplified part. It could be cast in brass I suppose, but I think the smooth machined surface captures the essential character of the prototype better than the surface texture you'll get on even the best casting. I am my own harshest critic and I'll have nightmares about the missing oiling point. I'll live through it, I'm sure there will be worse compromises to come...

 

[David Taylor]

Looks great, oiling point or no It is surprising how big the rod ends are with roller bearings - the US locos with them on the coupling rods really stand out.

 

[Ian_C]

Here's the detail of the assembly that I failed to cover in the previous post.

There's the 12BA stud in the back of the eccentric big end, a small spacer collar to allow the nut to be tightened without gripping the crank, and the crankpin. I think there's enough clearance for the nut but it could be filed down if required.

And here it is assembled on a wheel (crank not phased properly yet). Hmmm....that crank could be improved, those 4 studs really ought to be sitting in counterbored holes. Job for another day.

 

[adrian]

And here it is assembled on a wheel (crank not phased properly yet). Hmmm....that crank could be improved, those 4 studs really ought to be sitting in counterbored holes. Job for another day.

Previous efforts by @Dikitriki
7mm - Dikitriki's Dark side: L&Y Crab....temporarily

and myself

Tales from a sporadic modeller.

might help

There's the 12BA stud in the back of the eccentric big end, a small spacer collar to allow the nut to be tightened without gripping the crank, and the crankpin. I think there's enough clearance for the nut but it could be filed down if required.

I suspect that it'll be extremely tight on clearance between the back of the return crank and the connecting rod for the nut to fit. I've tried it with a countersunk screw to get the clearance if it helps.

Tales from a sporadic modeller.

 

[Ian_C]

48142 was originally built with built up balance weights and hollow axles but by 1963 it appears to have had a wheel set with cast balance weights and solid axles.

The MOK kit has etched parts for both types of balance weight. If you're looking at the MOK instructions page 15 and wondering what's what, the upper diagram shows the cast and the lower the built up types. The parts on the etch for the cast weights have the 'B' suffix. The plan is to laminate two etched weights together and fix them to the wheels.

As I've come to expect there's a bit more to it than that. Firstly the etched weights don't actually match the Slaters wheels. They're a bit small on diameter and don't extend as close to the rim as on the prototype. Also the weights on the prototype are not all of the same thickness; the weights on axle 3 (the driving axle) are noticeably chunkier than the others and project further beyond the rim. On the wheels with integral cast balance weights you can see that the weights extend the full depth of the spokes, which isn't the case with the built up type where you usually just see the plate edges. New balance weights were made from styrene sheet.

1. Blanks were cut from plasticard. 30 thou (0.75mm) seemed about right for axles 1,2,4 and 40 thou (1.0mm) for the fatter weights on axle 3.
2. Damned if I was going to carefully file a load of round discs. Blanks were clamped on a length of M6 studding and mounted in the lathe.
3. A couple of minutes and a load of plastic fluff later they're all perfectly round and 28mm diameter which matches the Slaters wheels nicely .
4. All the blanks I need and load of spares besides.
5. The shape of the weights was scribed on the blanks using the etched weights as a template. You can see the diameter difference here between the etched weights and the plastic blanks.
6. The spokes covered by the weight had to have the flare of the spokes near the centre boss carefully removed with a sharp scalpel to allow the weights to sit flat on the wheel. The weights were attached using rapid epoxy generously applied to the back and between the spokes.
7. They start to get a bit of character when the weights are attached. Each axle is different.
8. The thickness of the cast weight between the spokes is added using epoxy putty (Milliput Silver Grey). The putty is squashed into the gaps between the spokes behind the weight until it bulges out beyond the edge of the weight, followed by lots of sculpting and fiddling with a wet cocktail stick to blend it with the spokes. The Milliput adheres very well to the wheels and sets hard enough to file and sand to a final shape. The better you can finish it with the cocktail stick the less cleaning up you have to do. The first wheel takes an eternity, but it gets quicker with practice.
9. Once the front side is tidy it's easier just to leave the back to set as it is. A bit messy but once the front is tidy it's better to leave alone.
10. When the putty had set rock hard the back was cleaned up down to the spokes on the mill with the rotary table (a splendid bargain some time ago and I've finally found a use for it). Overkill of course, it could be just as well done with a file and a scraper and some sanding.
11. A bit of tidying up with scalpel and wet & dry. Cleaned with IPA and a coat of grey primer applied to see how it all looks.

There's still the permanent fixing of wheels to axle ends, quartering, gauging and pinning to complete but the end is in sight. The wheels have been a bit of an epic but they run nice and true and they actually look like 8F wheels now, so I think it's been worth the effort.

And please don't think I'm knocking Slaters. I had to start from somewhere unless I was going to make them all from scratch (yes, it did cross my mind but that's a project for another day).

I have a load of circular blanks left over, enough for another set. If anybody wants them just message me.

 

[Ian_C]

Previous efforts by @Dikitriki
7mm - Dikitriki's Dark side: L&Y Crab....temporarily

and myself

Tales from a sporadic modeller.

might help


I suspect that it'll be extremely tight on clearance between the back of the return crank and the connecting rod for the nut to fit. I've tried it with a countersunk screw to get the clearance if it helps.

Tales from a sporadic modeller.

Shucks! You're probably right. I'll see how it ends up when I get the motion together.

 

[Steph Dale]

Ian,
Nice summary. The only other trick I've got in my armoury is to thin the spokes from the rear which is of course unnecessary with the wheels you're using.

Steph

 

[Ian_C]

Couldn't resist posting this...

The driving wheels have had the tyres chemically blackened (Birchwood Casey Gun Blue) and a coat of epoxy etch primer all over. Set them aside to harden off and got on with some actual kit building. The front chassis and footplate sub-assembly and the rear chassis and steps sub-assembly went together with no drama, and the MOK tab/slot/twist assembly aid really makes it easy.

Tackled the smokebox core and the boiler today too. Parts starting to come off the bodywork etches, feels like progress is being made. I don't have any rollers for the smokebox and boiler so other methods were tried. Rolling with a bar on a soft surface made little impression. The material is quite thick compared with what I'm used to in 4mm, and quite springy. Bars from 1" to 1/2" on a cutting mat made no difference at all. Bars on a thick and squishy 2011 plumbing supplies catalogue (now in recycling!) made hardly a curl. Bars on a stack of Scalefour News (heresy, probably) no good. 1/2" bar plus bodyweight on one copy of Scalefour News on top of a a kitchen towel made some impression (cut to thumb on corner of etch and plenty of blood on the kitchen towel - I'll hear more about this I'm sure). In the end I went out to the workshop, put a length of 1" bar in the big bench vice and wrapped the etched parts around that. Worked out OK in the end. The smokebox is a bit tricky on account of the big holes in the etch for the chimney and the steam pipes. The bend radius tends to go a bit wonky near the big holes. Those areas were evened out with a nylon mallet over the bar. Utter blacksmithery, but effective if done with a bit of care. Having soldered them up, I couldn't resist just arranging some of the bits and bobs into a loco shape. Yes, it's progress.

The basic shape of the firebox and boiler does have a whiff of Churchward about it don't you think? Stanier out of Churchward. 28xx and 8F, like mother and daughter. A S7 28xx might be a nice project, and I wonder if Finney 7 will re-introduce the 28xx kit? A late model 28xx (or 38-something I suppose) with a proper cab with side windows as opposed to Mr Churchward's engineman's shelter. Shame they only ever had that dinky Edwardian tender behind them though .