Ian_C's workbench - P4 and S7 allsorts

Discussion in 'Workbenches, including workshop techniques.' started by Ian_C, 21 May 2017.

  1. Threadmark: More boiler fittings and modeller's block?
    Ian_C

    Ian_C Western Thunderer

    I do sometimes reach stages in a project where I get stuck, can't see a way forward and lose interest for a while. The dome and top feed cover has been such an episode on the 8F.

    As previously posted the parts were modelled on CAD and sent for 3D printing. It tool a while for the parts to arrive. Here's what I ended up with.
    3 d print dome.jpg
    The dome came out OK. There is the inevitable 'grain' from the layering of the printing process but the dome isn't too difficult a shape to rub smooth with wet dry. The tiny holes to mark the fixing screw positions can just be seen. The edge of the dome is nice and thin. It's about as thin as I think you can get away with using this process and I have to confess that I managed to chip the edge on a couple of prints when I was smoothing them down. And fortunately it sits nicely on the tapered boiler with out any fettling.

    top feed 3d print.jpg
    The top feed cover didn't work so well. I misjudged the thinness of the edge I could get away with on the 'top hat' cover ,and you can just see in the photo that the layering has broken the edge into a number of strands. That had to be filed off and replaced with a tiny brass shim part. The other problem, that I'd kind of anticipated but thought I'd see how things turned out, was that it's a relatively small part with some tight features and curvature and it's not very easy to clean up. I did model the fixing screw heads but they don't show up well in the photo, and anyway, they all were sanded off in trying to clean up the surface of the part.

    3d prints fitted 1.jpg
    I thought I 'd have a go at fitting them to the boiler to see how they looked. I found it difficult to get a feel for them in the native whitish print material so sprayed them over grey temporarily. OK, the paint job's pants. I didn't clean up thoroughly, hence the horrid little hairy, gritty bits. Not to worry, it'll all be cleaned off before proper painting. The dome doesn't look bad. You can still see some traces of layering but I think another gentle sanding down with fine wet & dry will make them disappear under the final primer. The screw heads were made by drilling through the guide holes 0.5mm, inserting short lengths of wire and filing them back to just proud of the surface. They're appropriately subtle. You can see that the top feed cover ended up quite a mess and it'll have to come off. 3D printing isn't the way to go with parts like the top feed cover in my opinion.

    So I'm still stuck for a top feed cover. There's the option to use the casting supplied with the kit but that's not great either, and in using the drawings in the Wild Swan book to produce the CAD I did confirm that it's actually too small in most dimensions. The only option left now is to scratchbuild one, and that doesn't look straightforward to me. Much head scratching before scratchbuilding.
     
  2. thruxton

    thruxton Western Thunderer

    Ian

    Having started to use 3D prints quite a bit, I have found the newer 'self levelling' acrylic primers to be a boon (eg Badger Ultimate Primer). Rather than sound the material to shape, the stratas can be easily filled and the primer sanded smooth, which is often not even required on flattish surfaces.

    These newer acrylic primers fill and sand very well, and also come in black to help with metallic finishes.
     
    Rob Pulham and simond like this.
  3. Threadmark: Top feed cover from scratch - part 1
    Ian_C

    Ian_C Western Thunderer

    I'm not great at sculpture, so the prospect of taking a lump of brass and filing away all the bits that didn't look like a top feed cover wasn't an option. It did seem possible to make the basic shape on the milling machine and finish the radii by hand. Something like this...

    basic shape 1.jpg
    Lump of brass squared up and set in the vice. The hole is on the centre of the boiler section at the top feed position. Since this has already been modelled up in CAD all the dimensions required are to hand.

    basic shape 3.jpg
    Here's the blank with the thicknesses and widths of the central cover and the flanking clack valve covers cut to the final size. You can see where this is heading...

    milling curve 1.jpg
    The blank is mounted on the rotary table using an arbor made from an offcut of steel bar. Having previously positioned the rotary centre in line with the spindle, the table is moved to position the milling cutter to cut exactly the radius of the boiler beneath the top feed. Much tedium ensues as many passes of the cutter nibble away through the blank. There's some approximation here though. The boiler (or more correctly the boiler cladding on which the top feed cover sits) is tapered, and theoretically the section at this point isn't quite circular, it's a slight ellipse, conic sections and wot not. A small amount of fettling with a file will be needed to accommodate the taper so the top feed sits nicely upright on the boiler.

    milled blank 1.jpg
    Here's the milled blank, and you can see that it's somewhat bigger than the casting supplied with the kit. I suppose I could have milled the angles on the flanks while it was on the rotary table, but didn't think about it until too late.

    milled blank 2.jpg
    Here it is with the angles sawn and filed and the machining marks cleaned off.

    marking blank 1.jpg
    Next job is to mark on the centre section the lines that will be the guides to file the radius. The first pair of lines away from the corner mark the 45 degree tangent surface to the radius. The second pair of lines from the corner mark the tangent where the radius runs out. By filing the 45 degree first it's relatively easy then to blend the resulting chamfer to the tangent lines. There's an earlier post about the firebox back head that covers this approach in more detail.

    filing blank 1.jpg
    A bit of careful filing up to the lines with a big file produces the first 45 degree chamfer (and quite a lot of gold dust).

    marking blank 2.jpg
    Following the same approach the filing lines for the clack covers are marked next.

    filing blank 2.jpg
    And a bit more filing produces this with all the 45 degree chamfers made. Had Stanier been an adherent of the Cubist movement I could probably have left it at that. Unfortunately the Crewe tinsmiths were less progressive in outlook and their aesthetic demanded radiused edges all round.

    on base 1.jpg
    The base plate cum mounting flange shape, when made a flat pattern by CAD, is a damned funny shape given that it wraps to a slightly conical surface. I didn't fancy trying to mark that out. Instead I cut a rectangle of brass shim somewhat larger than the top feed cover, curved it to sit tightly on the boiler, lightly tacked it in place, positioned one of the 3D printed top feeds on it and marked round the edge carefully with a very sharp scriber (so the 3D printed top feeds were useful for something in the end!). Voila, the outline of the damned funny shape! The flange was cut by snips, piercing saw and filed to the final shape. It was fairly flattened in the process but it was easy enough to form again to match the boiler. The fixing holes were marked and drilled 0.5mm. Here's the blank with all the radii filed and cleaned up and tacked to the mounting flange.

    Take a break here. Part two follows...
     
  4. Threadmark: Top feed cover from scratch - part 2
    Ian_C

    Ian_C Western Thunderer

    We're back to worrying about the differences between Stanier and some Ivatt top feed covers again. I know that 48142 had an Ivatt type cover with the little raised cover on top at this late stage in it's life (1965-66). The hair shirt of authenticity itches mightily so I have to make the top cover. Here's the bit I can't be certain of. Originally all the 8Fs (apart from 8000 - 8011 with domeless boilers) would have been fitted with the typical Stanier type top feed and clack valves, and would have had the matching sheet metal covers with a hole in the top of each of the clack covers through which the valve setting screws projected. That's clearly seen on most photos of 8Fs. Later on there came an improved top feed and clack arrangement from Ivatt that was fitted to some later class 5s. This arrangement moved the clack valves to a more central position beneath the central part of the cover, and there was no need to have holes in the flanking covers since they only covered the feed pipe joint. The little Ivatt 'top hat' covers (not shown on the following drawing) allowed access to the clack valve screws in their new location.
    clack valve compare.jpg
    The clack valve positions are marked in orange on these scans (from the Wild Swan Locomotive Profiles for 8F and later Class 5s).

    Some 8Fs clearly had the later type of top feed cover, witness the 1965 photo of 48142, but it doesn't necessarily mean that it had the later type of top feed arrangement because the original arrangement would fit equally well under the later cover. As boilers were exchanged at overhaul it's possible that some Ivatt style top feeds found their way onto 8F boilers and it's entirely possible that the metal work for covers got mixed up as well. What I'm not sure about is whether 48142 had the original clack covers with the now redundant holes in, or a later set of covers without any holes. I've looked at lots of 8F and Black 5 photos and I've not been able to clearly identify any covers with the Ivatt 'top hat' that had holes in the flanking covers. Therefore my supposition is that 48142 had no holes in the top of the flanking covers. And I'm waiting for the Irwell 'Book of the 8Fs - part 2', which will cover 48142, to come along and prove that I guessed wrong!

    Still have to make the 'top hat' though since I was unable to remove the one from the top of the 3D printed top feed without damaging it. That thing was a swine to make last time so I made a little press tool to simplify things this time around.

    press tool 1.jpg
    A slot of the correct width and depth was milled in an aluminium offcut and the mating part was machined on another, making allowance for the thickness of material (0.08mm brass shim as it happens). A strip of brass shim the right width was placed in the tool and the whole squeezed in the vice.

    pressing 1.jpg
    You end up with this. Rivets are pressed in to represent the fixing screws and the cover is cut from the strip and tidied up. At this size it's not possible (for me at least) to get the rivets in the right place by eyeball every time, but now it's a moment's work to press another one I made three and used the one with the least wonky rivet pattern.

    finished top feed 1.jpg
    The solid cover is soldered to the mounting flange, checking that it all still sits on the boiler neatly. The joint between the cover and the flange is in reality a continuously curved piece of sheet metal. I built up as big fillet of solder as I could and filed it back to neat join. I'd have preferred a bigger fillet but the solder just wasn't having it. We'll see how it looks when it has a coat of primer. The fixing screw heads are represented by 0.5mm brass wire soldered into the holes and filed down. Mr Ivatt's top hat was zapped on with the RSU. I've omitted the screws that fixed the flanking covers to the central cover; difficult to do and with a high probability of messing up. If you were going to point that out I've just saved you the trouble!

    Finally I have a top feed cover, but the boiler fittings aren't defeated yet. Oh no! There's still the matter of the single cone ejector...
     
  5. Rob Pulham

    Rob Pulham Western Thunderer

    Superb Ian!
     
  6. Threadmark: Some more boiler fittings - the single cone ejector
    Ian_C

    Ian_C Western Thunderer

    Some of the earlier 8Fs , of which 8142 was one, were built with single cone ejector instead of the much more common double cone ejector that came later. It appears that some of the locos had the single cone ejector replaced by the double cone ejector later in their lives. The only photo of 48142 that I can find was taken from the wrong side so I can't be sure which ejector was fitted in the mid sixties. Studying lots of other photos of 8Fs suggests that most 8Fs fitted built with a single cone ejector retained them into the BR era. Therefore I'm assuming the 48142 would still have had the single cone ejector in 1965. Again, can't wait for the next Irwell book to prove me wrong!

    So far as I can tell nobody offers a casting for a single cone ejector of this type so it'll have to be made from scratch. There are some decent photos showing the critter and it is shown on the pipe arrangement drawing on page 85 of the Wild Swan book. There's enough information to have a go.

    As usual it was scaled from the drawing and referring to photos to sense check the thing it was possible to model it roughly in CAD.
    ejector CAD.JPG
    Helps me get a sense of the thing and I can then break it down into simpler parts that I can actually make.

    ejector parts.jpg
    That's one problem with CAD, everything's the size of the screen. It's not until you sketch up the individual parts and start making them that you realise just how small this thing is. Here are the components, including the mounting bracket to the firebox. Most of the parts are designed so that they're positively located for soldering. That way you don't have to hold them in position as you solder them, and early parts don't come off when you solder on later parts (most of the time!). Here are the bits, including the mounting bracket to the firebox. I was encouraged to have a go at this by reading about a chap called David Smith making injectors and similar parts for 7mm models, worth a look at his website ...
    LMS 5F5P Class Mixed Traffic No. 5108 and 5XP Class No. 5663 Express Passanger Locomotives


    single ejector finished 1.jpg
    Here it is soldered together and cleaned up. The main body was a casting in real life so I've left some solder fillets in corners and rounded off the outer edges a little. I'll admit to some approximation; the two round thingies projecting from the top of the body should have hexagon tops. I'd probably make more of a mess by trying to file them to a hex so I'm better leaving them alone. The photo is a cruel enlargement so it'll not be very noticeable on the model.

    single and double ejectors.jpg
    Here's a comparison of the double cone ejector casting supplied with the kit (and correct for the majority of 8Fs) and the single cone ejector. You can see there's quite a difference.

    Somewhat of a diversion, but if you fancy reading about some of the more unusual attempts at steam powered railway locomotives check this out...
    Loco Locomotives.
    ...including a locomotive with non-circular wheels.

    Blimey, it's 2019 already. I wish you a peaceful and successful New Year.
     
  7. Threadmark: Some more scratchbuilding - the live steam injector
    Ian_C

    Ian_C Western Thunderer

    The casting for the live steam injector supplied with the kit wasn't correct for an 8F, some of the inlets and outlets were pointing in the wrong directions. Ragstone do have a casting that appears to match, however Mr Ragstone says that the tool needs renewing so it'a a long wait for one of those. Having had reasonable success making the ejector from scratch, and inspired by David Smith LMS 5F5P Class Mixed Traffic No. 5108 and 5XP Class No. 5663 Express Passanger Locomotives, I thought I have a go at making one from scratch. It's a Gresham & Craven No 11 live steam injector and there's little information to be found on the web. Also beware preserved locos, seems like one of the preserved 8Fs at least has had a different type of live steam injector fitted, probably a more reliable one! It was possible to puzzle it out from some of the drawings in the Wild Swan book and a few photos that show glimpses of the critter. Usual approach: scale from drawings, sketch (scruffy), CAD and then break it down into simple parts to make.
    live injector sketch.jpg

    Modelled in CAD with connections labelled...
    live injector CAD 2.JPG

    ...and the other side...
    live injector CAD 3.JPG

    ...and just for fun, a screenshot of the CAD with just datum planes and some section curves showing. Stuck me as being a bit arty, what you'd end up with if Gresham & Craven had commissioned Mondrian to design the cover of their 1932 injector catalogue...
    live injector CAD arty.JPG
    ...maybe.

    Quite a long time in the workshop listening to rain hammering on the roof and a handful of small parts results.
    live injector parts.jpg

    The parts were designed to be pinned together with 0.8mm brass wire to help keep things together as the assembly was soldered up. Wire soldered in hole and parts threaded on.
    live injector assy 1.jpg

    A fillet of solder was left round the joints and cleaned up to make it look a bit more like a casting.
    live injector assy 2.jpg

    Working from one end to the other and being very careful not to melt the solder on the preceding joints gets the thing together. Unusually I used a higher melting point solder (Carrs 224) for this to improve my odds of fixing the pipework in situ later without unsoldering the whole show. live injector finished 3.jpg
    live injector finished 1.jpg live injector finished 2.jpg
    The two wire stubs sticking out of the mounting bosses will be used to pin the injector to the rear steps to provide a positive location.

    Surprisingly no swearing on this job, but the whole week's quota of gumption was used up in one go. The photos are cruel and show up lots of minor messiness. It really is a little thing, about 11mm top to bottom, and partly hidden under the cab behind the steps, so it'll look OK. Should I dare to add bolts to the pipe flanges?
     

    Attached Files:

  8. adrian

    adrian Flying Squad

    Superb research - I've bookmarked this for when I get round to my build.
    Love it.
    As a suggestion - as you've taken the trouble to design it with pinning together I'd seriously recommend silver soldering the components together. This pinning together of items is exactly what I'd do when silver soldering together items for pattern making. Because of the way you heat the whole component when silver soldering the way that the silver solder flows into the joint is extremely satisfying and it flows very evenly and will make it look like a casting.

    The other thing is with silver soldering is that you can see very clearly when the solder flashes across the joint, the valuable point to note is that when you make a silver soldered joint you then need a slightly higher temperature to remelt the joint. Unfortunately I can't find a reference to back up my claim, however from my experience with a little care when heating the joints it is possible to use the same silver solder on a new joint without melting a previously made joint. You can get silver solders that melt at different temperatures usually about 4 different grades although I have found that the higher temperature silver-flo solders don't seem to flow into the joints as cleanly as the easy-flow solders.

    If you silver soldered the injectors together then you wouldn't have any concerns about it falling apart when soft soldering in the copper pipework.
     
    Len Cattley and Dog Star like this.
  9. Brian McKenzie

    Brian McKenzie Western Thunderer

    At one time I was making a lot of patterns for investment casting. These were assembled by press fits or with pins as Adrian suggests. All were silver-soldered (to withstand the pressure and temperature when vulcanising the chunks of rubber - stacked all around and poked inside the pattern - to eventually compress down into a solid rubber, before splitting it open as a mould).

    Easy-flo No.1 rod (50% silver) was used, by hammering the end of whatever diameter rod I could purchase into a thin foil wafer*, then slicing tiny slivers off that - to apply to the joint. Powder flux was dropped from the fingers onto the joint as it heated up. The silver-solder alloys with the base metal surface to form a new metal that obtains a slightly higher re-melt temperature. This has been enough to stop any earlier joints re-melting.

    The occasions when any re-melting of a LARGE joint has been necessary is when I can get into trouble, as the higher heat required can sometimes round off the edges of thin components if not careful. Mild steel has more recently been used in patterns to best retain sharp edges and detail crispness.

    Ian would have no trouble doing any of the above, it's easily learnt and the use of silver-solder in some joints would ease assembly. I delight that Giles Favell is such a good proponent of this process.

    *buy silver-solder in foil form if you can.

    -Brian McK.