Ian_C's workbench - P4 and S7 allsorts

[Ian_C]

The cab roof is another job that's been continuously pushed down the to-do list in favour of easier stuff. Can't put it off any longer I'm afraid, and it did turn out to be a bit of a performance.

I wanted the roof to be removable to make assembly of the cab interior detail and painting of the cab easier. The design intent of the kit is to solder the roof to the cab front and sides, so some modification was necessary.

The kit provides an etched roof (flat), a sliding ventilator part and a half etched plate for the rear of the roof to represent the section that can be unbolted to enable lifting gear to get to the rear of the drag beam. The cab profile is not an easy shape to form, consisting of a sequence of curves and straight sections. After a lot of careful bending and tweaking I got a reasonable fit onto the cab but it was clear that I'd never get it to sit down perfectly. For fixing I'd considered small screws inside the cab, springy wire clips, micro magnets, but none of them seemed straightforward. The solution I adopted was to avoid fighting the springiness of the formed roof and make it a rigid lid that dropped into place and was retained by gravity and friction.

First step was to make some stiffening ribs to hold the cab roof to the required profile. The etched cab roof rib that was already part of the cab assembly was unsoldered, tacked to a scrap of N/S sheet (0.7mm ish) and scribed around, and repeat. Piercing saw and files get you two very stiff ribs of the correct profile that can be soldered inside the roof. The etched rib is the uppermost in the photo below. I included some prongs at the ends of the rib, and they will locate in some slots cut in the cab side flange.


One rib was soldered in place just far enough back from the front edge to to be clear of the inside of the cab front sheet. The other sits just in front of the etched cab frame rib. This means that the longitudinal ribs provided in the kit that fit between the cab front sheet and the etched rib can't be used. They don't serve a purpose any more so bye bye. The kit intends the cab roof to be located by tab and slot. The tabs on the etched rib can be filed off and the slots near the front of the cab roof can be soldered up (the two small scraps of brass in the photo below). Now the roof is fixed to the exact profile, there's no springiness and it's become a rigid unit. The other bonus is that it can be held by the rather substantial ribs for the work that follows.


With the ribs fixed, their positions on the cab roof flange can be marked. Well, almost. The etched cab sides have a flange above the windows to stiffen the top edge of the side sheets (I guess) and to provide something to solder the edges of the roof to. To prevent distortion of the window frames when the flange is bent there's a long relieving slot etched along the bend line. It certainly prevents the top of the window frames from being distorted but it all but negates any stiffening effect. Also the only areas where the flange is attached happen to be where the roof ribs are, so cutting a locating slot there makes the stiffening flange minimally attached. The remedy is to solder a length of 0.5mm wire inside the bend and fill the slot with solder (dotted line in the photo below). That makes the whole thing far more solid and we can cut locating slots without a problem. The locating slots are circled red in the photo below. If the slots and prongs are matched very carefully the roof can be a gentle press fit into position and be accurately located on the cab. A lot of words, but I hope it's clear from the photos.


With that problem solved we can look at the cab roof detail. The Stanier roof is quite a dog's dinner of plates, angles, rivets, rain strips and beading and of course the ventilator hatch. The simple etched parts look a bit 2D and don't do it justice. More hairshirted tomfoolery follows of course.

The rear edge of the roof (1/8" plate on the prototype) is finished with an angle section to stiffen it and stop rain dripping on the fireman. The angle is 1-1/2" on the prototype, and that's about 0.9mm in 7mm scale. I represented this with a strip of brass soldered to the edge and filed to shape. Rather than try and position a tiny strip accurately it's easier to solder on a wider strip in roughly the right place and file it back to size. It helps to anneal the brass first to make it easier to bend. Here it is soldered in place.


File the lower edge of the strip flush with the inside surface of the cab roof first. Then mark 0.9mm offset from that edge and file the top edge of the strip back to that line. Finally cut the ends off the strip to match the edges of the half etched overlay plate.


There's worse to come. The cabs had a beading section running from above the cab side wing plates (to which the cab doors are attached) up the rear edge of the side plate and following the roof edge curves around to butt up to the end of the aforementioned angle section at the rear of the roof. It's a surprisingly chunky section, measuring 2-1/4" x 3/4" with a sort of shallow 'D' profile. That's 1.3mm x 0.45mm in our world. That was made by making some 1.3mm wide strips about 60mm long from a sheet of 0.45mm N/S.


There's a lot of bending in both planes and the strips need to be annealed to make that possible. Heat them to a gentle red with the mini torch, pick them up with tweezers and wave them around in the air for few seconds. That cools them fast enough to anneal them fully, and they're very pliable to begin with. I started at the top and worked my way around the cab curves and down to the wing plates. This time the strip has to be accurately positioned so that it's centred on the edge of the roof. No bodgery and filing to shape permitted here. I pre-formed the initial curve along the rear edge of the roof and tack soldered that in position first. Then it was a case of working along pressing the strip into position and tacking. Note that the more you bend and re-bend the strip the more it work hardens and may eventually fatigue through and break. It's easy enough until you get to the last bend where it runs down the rear of the side sheet. The roof has to be placed on the cab to form that bend and because it's quite a tight bend across the flat of the strip it's an a*s*.


Because the roof is to be removable the bead strip has to be cut near the junction of roof and side sheet. I chose to make the cut where the bend straightens out. It means there's a little bit of beading projecting from the cab roof corner and the roof has to be handled carefully thereafter to avoid bending it out of shape. The final short straight section of beading on the rear of the cab sheet is positioned to match. When it's all tacked in place it can be carefully soldered along its length. The final task is to create the D section by rounding the edges with files and wet & dry. You can see the break in the beading here, and I'm hoping it'll be less obvious when painted.


The roof edges on the prototype were formed up into a semi-circular rain gutter about 5/16" outside radius. Can't really replicate that at this scale, but a flat edge doesn't look right, so a length of 0.3mm brass wire was soldered along the edge and blended in. Of course it's not the U shape of the prototype but it looks the part at a normal viewing distance.


The etched part for the roof vent was a bit clumsy so a replacement was made from a scrap of N/S closer to scale thickness. It took a bit of research to figure out whether there was any detail on the ventilator. The cab drawings in the Wild Swan book show that the whole ventilator hatch was riveted together. Eventually I found a good photo looking down onto the roof of a Black Five which had an almost identical cab. Looks like the small rivets were flush with the surface and don't show at all. There were four bolt heads along the rear edge and they were made from 0.5mm wire soldered through holes and filed down. Here's the finished roof in position. A lot more work that I'd imagined, and I hope the Modelu crew appreciate it when the scaleseven Toton drizzle doesn't run down their little resin necks.

 

[Dan Randall]

I hope the Modelu crew appreciate it when the scaleseven Toton drizzle doesn't run down their little resin necks.

That did make me chuckle!


Regards

Dan

 

[Ian_C]

Just for fun* , the water valve control for the live steam injector. The handle's about 3mm long. A bracket from NS scrap, a tiny turning, some 0.6mm wire and a little 0.5mm wire, all silver soldered together.


* - legal definition of 'fun' that you were previously unaware of.

 

[Ian_C]

When I made the oil boxes for the framing I forgot to make some for the cab. Two varieties; 2 x larger oil boxes with two outlets each, for the rear axleboxes I think, and 1x smaller oil box with three outlets, which I assume is there to lubricate the damper control linkage beneath the cab.

A bit of 'how to ' for those wot's interested. The basic section (1.5mm x 1.8mm) was milled from some 1/8" brass strip. The angle on the top for the lid was filed on and the section cut into oil box lengths (2.7mm) and cleaned up. The outlet positions were marked on the bottom of the boxes by eye using a sharp scriber to make an indent. That's usually just enough of an impression to start a small drill. The holes were drilled using a pin vice, 0.5mm for the small box and 0.8mm for the larger. Short lengths of micro bore brass tube were pushed into the holes and snipped off over long. Some pieces of scrap etch were cut well over sized for the lids. The whole lot was cleaned and silver soldered together (Linbraze TOS155-HA30-W1 silver solder paste with flux , 630C, in 10g syringe applied with the tip of a cocktail stick - makes it easy). Various stages of finishing and cleaning up shown below. I have to say that taking photos of your work like this does show up all the carbuncles and provides some motivation to improve.


That's definitely the last of the oil boxes. Unless there are some on the tender - I'm not going to check.

 

[Ian_C]

Here's where I've got to with the cab interior.





Still a few things left to do. I see that the oil box on the reverser pedestal is a little wonky, needs adjusting. The cab windows need to be fabricated. I'll be trying to use microscope cover slides for the glass so they might be thin enough to make the sliding window actually slide. Slaking pipe and valve on the fireman's side. I think there was a section of steel tread plate beneath the firehole. Cab doors. Fall plate. Now I think about it there are quite a lot of things left to do!

There's one minor mystery though, and something I overlooked when I was detailing the backhead. The official LMS cab photo shows (if you look carefully) a heat guard to the left of the firehole to save the driver's legs from intermittent roasting when the fire doors are open. I doesn't seem to be present on any of the preserved 8Fs so far as I can tell. Was it a 'great idea' that was quickly discarded? Something that's not favoured in preservation? Would it be present in BR day's (and I can't find a cab interior photo from the BR period)? Anybody know?

 

[Dave Holt]

I've searched through all the likely books I have and also cannot find any photos of the cab interior in BR days. All Stanier classes had these heat shields when built. They had a tendency to work loose and there were official modifications to the fixing arrangements. However, I can't find any thing to suggest there was a modification to remove them. Perhaps if they became too loose, they would be removed from individual locos by the shed fitters?
In preservation, I suspect that, like our (not Stanier) loco, people just haven't got round to making and fitting the guard. Also, in our case, the railway isn't keen because the guard makes it hard to fire from the wrong side and perhaps amateur firemen don't all master firing left handed, as required to fire from the right hand side. In addition, the guard can make fire cleaning more difficult, Again another disincentive to fit one in preserved locos.
Not conclusive I'm afraid, but on balance, if it were my model, I'd fit the heat shield.

Dave.

 

[paulc]

Hi Ian , my microscope slides tend to fall to pieces if i look at them the wrong way , i wish you luck with a sliding window .

 

[Ian_C]

How to fix the backhead into the cab and still have it easily removable? A magnet glued to the inside of the backhead, and a piece of steel fixed to the cab front sheet spaced off so that they just make contact when the backhead is in place. The magnet was from Eileen's Emporium. Hopefully the pics make it clear.



In other news... there's a small valve or tap that controls the supply of water to the slaking pipe/coal watering pipe/fizzle pipe/whatever. No castings that look anything like or can be butchered, so have to make from scratch. Some tiny turned parts, scrap etch and bits of wire. Silver soldered together.

 

[P A D]

Hi Ian,
Nifty idea using the magnet to fix the backhead. I usually go for a screw through footplate into a tapped hole in the base of the backhead, but that is simpler, so I'll file it away for future plagiarising. Lovely work on the slaking pipe valve.
Cheers,
Peter

 

[Ian_C]

Hi Ian , my microscope slides tend to fall to pieces if i look at them the wrong way , i wish you luck with a sliding window .

Here's one way of cutting microscope cover slides to size. Daresay there are other methods, but this seems to work most of the time for me. You can get cover slides in various thicknesses, look on Ebay or Amazon. The ones I have are by Amscope and between 0.12mm and 0.16mm thick. You get a box of 100 for £peanuts. That's pretty thin, and they're correspondingly fragile, but they're close to scale thickness (about 1/4") so window frames don't have to be over thick and the glass edges are not obtrusive where they're visible.

This is how I cut them...


You need something to scribe the glass. I use a tungsten carbide tipped scriber sharpened to a dead sharp point with a fine diamond abrasive hone. Some folk use a diamond record player stylus in a pin chuck, but I've never tried that. You need to work on a rigid surface. Any bending of the glass as you scribe causes it to break in uncontrolled directions. I draw the shape I'm cutting in fine pencil on a scrap of printer paper (90g/m2, but I don't think it's critical as long as it's not too thick and squishy). The paper is placed on something solid and flat, in this case a turned steel blank I use as a an anvil and mini surface plate. I use a lollipop stick as the straight edge to guide the scriber. It's kinder on the glass than a steel rule. Position the cover slide over the pencil marks. Hold the non-waste side under the stick, firmly enough to stop it sliding around but not so hard that it breaks the glass. I've found that the section of glass held under the stick is less inclined to break. Draw the scriber gently over the glass. You don't need to press down at all if the point's really sharp. It creates an almost invisible line on the surface of the glass. Often it'll break as soon as the line's scribed. If not, then pick it up and place the line over the edge of the stick with the waste section overhanging and gently bend the glass. It'll snap along the line. I use a lump of BluTack to pick up and move the glass pieces around. The diamond abrasive honing stick is also good for smoothing or shaping the edges of the glass, radiused corners etc. Light touch required and work along the edge of the glass rather than across it. You break a few to begin with, but once you get a feel for it it's surprisingly easy. I find the reject rate is about one in three. Make a few spares as you go! Better wear safety glasses as well, sometimes bits ping around when you break them.

The sliding window frame's a bit of a head scratcher at the moment. You're only defeated once you've given up, and I've not given up yet. Next post probably!

 

[paulc]

Here's one way of cutting microscope cover slides to size. Daresay there are other methods, but this seems to work most of the time for me. You can get cover slides in various thicknesses, look on Ebay or Amazon. The ones I have are by Amscope and between 0.12mm and 0.16mm thick. You get a box of 100 for £peanuts. That's pretty thin, and they're correspondingly fragile, but they're close to scale thickness (about 1/4") so window frames don't have to be over thick and the glass edges are not obtrusive where they're visible.

This is how I cut them...
View attachment 112267

You need something to scribe the glass. I use a tungsten carbide tipped scriber sharpened to a dead sharp point with a fine diamond abrasive hone. Some folk use a diamond record player stylus in a pin chuck, but I've never tried that. You need to work on a rigid surface. Any bending of the glass as you scribe causes it to break in uncontrolled directions. I draw the shape I'm cutting in fine pencil on a scrap of printer paper (90g/m2, but I don't think it's critical as long as it's not too thick and squishy). The paper is placed on something solid and flat, in this case a turned steel blank I use as a an anvil and mini surface plate. I use a lollipop stick as the straight edge to guide the scriber. It's kinder on the glass than a steel rule. Position the cover slide over the pencil marks. Hold the non-waste side under the stick, firmly enough to stop it sliding around but not so hard that it breaks the glass. I've found that the section of glass held under the stick is less inclined to break. Draw the scriber gently over the glass. You don't need to press down at all if the point's really sharp. It creates an almost invisible line on the surface of the glass. Often it'll break as soon as the line's scribed. If not, then pick it up and place the line over the edge of the stick with the waste section overhanging and gently bend the glass. It'll snap along the line. I use a lump of BluTack to pick up and move the glass pieces around. The diamond abrasive honing stick is also good for smoothing or shaping the edges of the glass, radiused corners etc. Light touch required and work along the edge of the glass rather than across it. You break a few to begin with, but once you get a feel for it it's surprisingly easy. I find the reject rate is about one in three. Make a few spares as you go! Better wear safety glasses as well, sometimes bits ping around when you break them.

The sliding window frame's a bit of a head scratcher at the moment. You're only defeated once you've given up, and I've not given up yet. Next post probably!

I don't have any problems cutting standard windows , it was the fact that you wanted to make a sliding window with all its flexing that got my attention . Any luck yet ?

 

[Jim pairman]

The finer the “scratch” on the glass the better the break as the former concentrates the stresses better.
Jim P

 

[Ian_C]

Paul C - I don't have any problems cutting standard windows , it was the fact that you wanted to make a sliding window with all its flexing that got my attention . Any luck yet ?

After epic diversion (design & make projects for non-modelling purposes) and distraction (making a tool & cutter grinder), here's where I've got to with the sliding windows.

Attempting to follow the prototype is usually the right thing to do, and the windows on the prototype slide in cast brass channels, so we need to make some tiny channel sections. Opted in the end to machine them from brass. The best way of doing that seemed to be by cutting them with a slitting saw. Except...I didn't have a slitting saw. Well, not a proper one. I did buy a cheapo slitting saw arbor and some saw blades ages ago, but they seem to have have been designed and made by somebody with no understanding of engineering principles and didn't look like they'd be able to cut anything. (Lesson continually re-learned: bargain engineering equipment from the hobby engineering trade is usually pants. Save up for proper stuff, it actually does the job it's intended for!) Besides I needed something much smaller for this job. The channels scale to about 0.5mm wide in 7mm, and small saw blades of that thickness are readily available. Though I'd have a go at making my own slitting saw arbor.


For maximum rigidity the arbor is machined directly from a 3MT blank arbor. I've sacrificed depth of cut for a bigger clamping disc and a bigger friction radius. The blade location spigot was machined directly onto the arbor with the 3MT in the lathe spindle, so a minimum of run out on these small blades. That was easy enough to make. Of course I don't learn the lesson do I? I bought some 'reasonably priced' blades (0.5mm and 1.0 mm thick) and whaddaya know? The hole isn't exactly in the centre of the blade, so I have some runout after all. Having purchased 30 odd teeth, only one or two are actually doing the cutting. At least there's no wobble so they cut the correct width - count yer blessings.


1 - You can probably make out the dimensions and method from the sketch.

2 - A piece of 3mm brass was cut over sized and soft soldered to a sacrificial length of 3mm strip. Needs to be big enough to hold the channels far enough above the vice to give the slitting saw enough room.

3 - Trammed up to perfection in the milling vice and reduced to 1.3mm thick.

4 - Making the first cut at the top and working down from there with cuts at various depths using fine feed on the quill and table Y.

5 - Unsoldered carefully from the base strip and cleaned up. Worked out better than expected. Need two more for the other side of the cab...

Some modelling might actually happen next.

 

[paulc]

Thanks for that Ian , i wait with interest to see how it all goes together.
Cheers Paul

 

[Ian_C]

Things didn't quite work out the way I'd planned. 'Planned' is a strong work in this context. Superficial thinking is closer to it. There's a lot of fudgery in scaling down the cab sides and window components: etch thicknesses, overlays, accumulated assembly tolerances etc. The channels I'd made were almost exactly to scale, but because of fudge they held the rear, inner window frame too far inset from the front outer frame. The channels were soldered to a piece of NS scrap and filed down from 1.3mm wide to around 1.0mm. Next problem: I'd soldered a piece of brass wire into the angle of the folded flange along the top of the cab sides to reinforce them. Seemed like a sensible thing to do at the time, but it got in the way of the upper channel, so had to be removed.

I've looked at a lot of 8F photos, and the only ones I've seen with the rear window closed in the rear position are on locos being delivered new into service, glossy black and shiny buffers. Every loco in service seems to have the rear window slid forward to the fully open position, although I bet they'd be closed heading north from Settle Junction in the winter! Similarly I've never seen an 8F with the front window slid back to open it. Therefore I've no qualms about soldering the front window frame directly in position. I should mention in passing that the MOK kit provides the two inner window frames etched as one part, so they need to be cut apart to do this.

With that done, the channels were trimmed to length and tacked in position. Working inside the partly assembled cab was a pain. Access for soldering irons and assorted prodders and holders is limited. At which point the next problem became apparent. With both channels in position it wasn't possible to fit or remove the sliding window frame. Doh! The answer was the shorten the upper channel so that when the window is slid fully forward beyond its normal fully open position it can be disengaged from the upper channel and removed. Some cruel close up photos show how it worked out.

Here the rear window is slid fully to the rear in the closed position.


Some explanation on this photo showing that whereas the lower channel runs the full length of the cab side, the upper is shortened.


Here it is with the rear window frame slid forward almost to the point where it disengages from the top channel, at which point it can be tilted inboard slightly and lifted out of the lower channel.


The glass made from microscope cover slides (previous post) will sit neatly in the half etched recess on the inside of the frames.

Just got to do the driver's side now. Since the front windows will always be closed, and the rear windows always open I have to wonder if it was worth the trouble!

The next challenge is to make the tiny wind deflector screens that project from the cab side between the side windows.

 

[paulc]

Great job Ian , i thought when you first mentioned doing this that you were pushing the boat a bit far , I will go and eat my humble pie now .
Cheers Paul

 

[P A D]

Very nice Ian,
I like the slacking pipe. You've made the reinforcement differently to mine that I did on the Stanier 2 6 4. On mine, I held the wire in a pin vice and then rotated it on the edge of the bench with a Stanley knife held at about 45 degrees. It scores a spiral groove along the wire but I think your method is more realistic. Mine looks better when used to represent lagged pipework. Keep pushing the boat out.
Cheers,
Peter

 

[Ian_C]

8Fs carried a works plate, or builders plate, usually on the front frames. LMS built 1942 Crewe, etc. What I can't figure out is whether there was one each side or one plate on one side. If one plate, then which side? You'd think it would be easy to figure out from photos, but it isn't. You only ever get to see one side on a photo, and finding decent LH and RH photos of the same loco at about the same time is difficult. I think I can find evidence for all of the above on some locos at some times. Some locos seem to have changed sides at some point, plus later in the 60's it looks like some didn't carry plates, or at least there's an oval patch in the frame crud where a plate used to be. Any logic or system to this?

After a long pause I'm back to thinking about getting some sets of plates etched. Any recommendation for a photo etch company that'll look after a first time etcher?

 

[daifly]

FWIW, the 8F at Highley has one each side. I can't imagine that this is a preservation mod!
Dave

 

[Ian_C]

Wind deflectors were fitted to the cab sides between the front and rear windows. They seem mostly to have been left sticking sticking out at 90 degrees to the cab side. Roughly they're a hinged frame, a bracket top and bottom and a sliver of glass. They're bigger than you'd think, so can't really be left off. I can't find any parts for them on the etch, so they'll have to be made from scratch.

I started by modelling the brackets approximately in CAD to get the sense of them. They're small parts at only 0.9mm top to bottom, and 2.0mm wide.


I milled the bracket section into a length of brass, and just marked the hole positions with a the tip of a small centre drill. Easy enough to do on the milling machine by DRO. Set out a few spares as well! Once off the mill, the holes were drilled through 0.35mm as nearest match for 0.33mm brass wire. Each bracket was cut off the length with a piercing saw and cleaned up. The pivot holes were centre marked by eye with a sharp scriber and drilled through 0.35mm again. This is about the limit of what I can handle at the moment. Holding the parts and seeing what you're doing at this size is just about possible. As the photos show, the usual tools and techniques don't give a crisp shape and finish working at this scale - at least when I'm using them! Watchmakers do remarkable work on parts this small and sometimes smaller, so it is possible.


The assembly was designed to be pinned together with wire for silver soldering. It was set up carefully on a soldering block, the wire being pushed into holes drilled in the block. Used tiny amounts the 630 C paste applied by the end of a cocktail stick.


Gentle heating was necessary to avoid melting the small parts, particularly the wire. Watch very closely and when all the joints just flash silver then stop. When it's cooled, carefully tease it out of the block. Looks a bit goofy at this stage.


Snip off the excess wire and clean it up. I did manage to make the piece of glass from microscope cover slide, that's what you see in the photo. I found it impossible to clean up the edges neatly. Even with the finest diamond abrasive I couldn't avoid edge chipping. In the end I made the 'glass' from a scrap of Cobex. Much easier to handle at this size.


Here's one installed, with Cobex glass. Slight disappointment that I ended up with the brackets slightly too close together, so they don't site quite right on the beading around the windows. The lower bracket is in the correct position, the upper slightly low and just resting on the beading. I'm hoping it's not too noticeable on the finished model. The glass tapers in at the top, presumably a loading gauge consideration. The taper on the glass looks a bit shallow in the photo. I ought to make a better one!


That's another nadgery little job done. Cab wing plate handrails and cab doors next on the list.