1/32 Coaches for the Garden

Discussion in 'Techniques' started by JimG, 7 July 2016.

  1. JimG

    JimG Western Thunderer

    One of these days I could have an operating layout in the garden and I'll need some coaches. For me, building coaches is a lengthy process so I thought I might make a start now so that there was a possible chance that something might be ready in time. :) I actually made a start last year but I had just doubled the sizes I had used for S scale coaches a year or two ago and I wasn't too happy with some of the compromises I had made in S scale since they were amplified by the up-scaling.

    The one thing that did worry me was the depth of the inset of quarterlight glazing. In the S scale coaches I had taken the easy way out and made the glazing insets for droplight and quarterlights the same to eaase the construction of the body sides. However, the more I looked at pictures of Caledonian coaches, the more it became obvious that quarter light glazing was actually getting close to being flusher. One of my drawings of a MacIntosh caledonian coach had quite a clear cross section of a window

    CalDoorDetails.jpg

    ...and I used this to trace a drawing in Draftsight and work out dimensions in 1:32 scale. It worked out that the quarterlight glazing was inset by 0.9mm from the outer surface and the droplight frame was inset by 1.25mm.

    So I opted to try something I haven't done before on the CNC mill and to mill both sides of a piece of material. It means you have to flip the material in register so that the machining of both sides lines up.

    32Coaches001.jpg

    I started on the rear of the coach side and machined the recesses for the droplight glazing - 0.35mm deep, the difference between the droplight and the quarterlight glazing insets. I have only machined the areas necessary to save time - the unmachined parts will disappear when the quarterlight apertures are cut out. The part was also machined to be 3mm oversize all round.

    32Coaches002.jpg

    Then the sheet was flipped over on the horizontal plane and the alloy guides are set to -3mm on X and Y axes to match the 3mm oversize of the sheet. The alloy strips are aligned with my cheap and cheerful toolmakers buttons - thick brass rings with oversize holes for the roundhead woodscrews. I use a 6mm diameter rod in the mill spindle, slacken off the woodscrews holding the buttons, place the spindle in approximate position for the X axis and move the button until the alloy strip bears against the 6mm rod, then tighten the woodscrew. Repeat this for the other button on the X axis and set the X axis value to zero. This sets the face of the alloy strip at Y = -3. Do the same for the Y axis and that strip's face is at X = -3. The material is held by double sided tape.

    32Coaches003.jpg

    The first big cut is to surface the material to set the correct overall thickness. The raised parts are the material for the bolections - similar to David Jenkinson's bolection method where he stuck rectangles of styrene over quarterlight apertures to form the bolections by cutting out the window aperture and shaping the inner sides. The lower panel has also been cut.

    32Coaches004.jpg

    The next operation cuts all the upper panelling and also cuts out the droplights and quarterlights with the waste material being left in situ. The material to form the bolections is also apparent.

    32Coaches005.jpg

    This is a closeup showing the bolection material round the quarterlights.

    32Coaches006.jpg

    The bolections have now been formed into their final shape. The bolection on the left was a cock-up. I used the code I had generated a year ago but forgot that I had altered the window shape to be more accurate, so the cut was made out of alignment. I re-wrote the code and the other bolections were the result.

    32Coaches007.jpg

    The final operation was to drill pilot holes for door stops, handles, grab irons, locks and hinges, and to engrave the door lines. Then the piece was machined to size, getting rid of the 3mm margin all round. It was then removed from the machine table.

    32Coaches008.jpg

    ...and the acid test was to turn the piece over and see if the rear apertures lined up - and they did. :) The shadows give the impression that they are a bit off, but they are actually pretty well spot on. Absolute accuracy is not really require for the glazing slots, but it's nice to get them where you want them. :)

    32Coaches009.jpg

    I gave the part a quick scoosh of grey primer to make things look a bit better to the camera.

    This is the centre section of a 48 foot coach side. The coach will finish up 18" long and my CNC mill cannot cope with that length, so the side has been cut into three sections about 6" long to coincide with door lines to disguise the joins. The support parts for the sides will be in two parts, 9" long, which my CNC machine can just accommodate.

    I'm waiting on some glazing material coming so I'll post a picture when the glazing is fitted to show the effect properly.

    This part will be treated as a test piece because of the problem with the left hand bolection, but the only way I could check my bolection code was to try it and by the time I had found out it was wrong it was too late. :)

    Jim.
     
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  2. Simon

    Simon Flying Squad

    Beautiful work as ever Jim, I look forward to Caledonian excursions running through Launceston Road:)

    I'll try and bring 28A back into my "doing pile" to provide a suitably period companion locomotive...

    Simon
     
  3. Heather Kay

    Heather Kay Western Thunderer

    I presume the coach side will have a turnunder, so I wonder how you will approach that when the time comes, Jim?
     
  4. JimG

    JimG Western Thunderer

    Heather,

    The oven at 100C for about 20 minutes. :) I've machined a former out of MDF to hold the sides with the scale 2" of turn under required. I used this method with my S scale coaches and it worked very well.

    32Coaches010.jpg

    This is the MDF former with the machined profile of the side. The side part is clipped under a lip on the alloy strip at the bottom of the tumblehome...

    32Coaches011.jpg

    ...then the "U" section alloy girders are put in place to hold down the upper section of the part . The whole lot is then put in the oven to get heat formed.

    I had a trial run with this setup last year but ran into a problem with the alloy clamping parts. They were tending to bow when screwed down and when the styrene softened in the forming process, the ends of the coach side were being squeezed and slightly deformed. I'm going to try fitting lands of the same thickness as the sides around the screws so that the alloy lengths can't be over-tightened to see if this avoids the problem.

    Jim.
     
  5. Heather Kay

    Heather Kay Western Thunderer

    I figured you would probably have a well thought out solution. Thanks for sharing! :thumbs:
     
  6. JimG

    JimG Western Thunderer

    That would be an excellent visit. :)

    I should try and bring an appropriate locomotive, maybe a Dunalistair. Oh Lord, there's another long term project. :)

    Jim.
     
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  7. JimG

    JimG Western Thunderer

    Having a break from digging holes, I progressed a bit with the coach sides. A couple of weeks ago when the weather wasn't so good I spent a couple of days machining up the bits for a side to make sure the procedure worked.

    32Coaches012.jpg
    The three exterior parts are at the top with the two interior supporting parts underneath.

    32Coaches013.jpg
    Here's a closer shot of the supporting inner side which is similar to David Jenkinson's method with the two levels to support the outer sides with tumblehome. Recesses are also machined to accept the glazing material, the central, droplight ones to hold the glazing plus the droplight frame and the quarterlight recesses, when added to the recesses on the back of the outer sides, will hold the quarterlight glazing.

    32Coaches014.jpg
    The outer sides were "cooked" in the oven for twenty minutes at 100C on the former shown in a previous message. here one of the outer sides is held in position on the inner side to show the forming of the side.

    32Coaches015.jpg
    The two inner side parts were joined together with a short strip of 40thou Plastikard...

    32Coaches016.jpg
    ...then the outer sides were added. The outer sides were lined up longitudinally using the windows as a reference. the width of the window openings is the same on the inner and outer sides so its quite easy to align them by putting the blade of the small square in the opening and twisting it until it aligns both parts. I also just tack welded with the Mekpak until I know that parts were square and aligned.

    32Coaches017.jpg
    The finished side with all parts in place. At the moment they are glued top and bottom but I still have to go round every window opening and apply MekPak to fully glue back and front together.

    I did throw up one problem which I thought I might have, and I did. :)

    32Coaches018.jpg

    32Coaches019.jpg

    The forming of the tumblehomes is not quite an exact science and I thought I would be lucky to get the curves on mating parts to match exactly and that proved to be the case as shown above. The mismatches actually look worse in the pictures than they do in real life, and I note the slight vertical mismatches as well. :) I'm considering machining a piece of styrene to the same shape as the former used to shape the tumblehome and placing this behind the join of the sides so that there is something behind the sides to persuade them into an accurate match. I'm also thinking about machinign a small chamfer on the mating ends of the outer sides to help disguise and slight imperfections. The other door lines on the coach side will be milled with a "V" shaped cutter and I could use the same cutter on the edges to produce the chamfer.

    I'll go on and fit the glazing to see how it looks. Adrian kindly sent me some 0.5mm PETG and I'm going to see how that looks. Otherwise this side is a guinea pig and won't ever finish up on a complete coach. I also have to include openings for a third hinge at the bottom of the doors. I didn't read them off the GA drawing but noted them on photos in the Caledonian Coaches book after I had machined the sides. So I'll use it as a practice side for painting. :)

    Jim.
     
  8. jamiepage

    jamiepage Western Thunderer

    Jim,
    Splendid stuff.
    Could I venture that the minute mismatches add to the overall character? I guess if a mismatch shows itself as a single vertical joint along the full depth of a coach side them it may draw attention to itself, but minute lack of registers, panel to door, say, are part and parcel of a wooden coach body.
    Irrespective of that, really interesting stuff, thank you.
    Jamie
     
  9. JimG

    JimG Western Thunderer

    Jamie,

    I would agree that modelling the imperfections of the prototype can add a lot to a model - good weathering is one such instance. But I have worries about these panel edges possibly moving later on in the life of a model. The panel styrene is 0.9mm thick at the edges so there's not much of a surface area for an end on contact. Support for both sides of these edges should give a stronger joint and it won't take too much effort to knock out - I'll let the CNC mill take the strain. :)

    Are you making any more coaches?

    Jim.
     
  10. jamiepage

    jamiepage Western Thunderer

    Jim,
    They do look excellent.
    Yours
    Jamie
    ps No, but I still have a box full of panels and doors though!
     
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  11. JimG

    JimG Western Thunderer

    Almost a year later, I'm back on the 1:32 scale coaches again. It dawned on me that building these coaches would not be a quick job and if I wanted finished stock to coincide with the layout in a working state, then I had better start making a move now. Please note that I'm thinking in years here, not months. :):)

    So I set up the mill about three weeks ago to start producing sides. I made one change from the test side shown above. I had left slots for 0.5mm glazing but I decided to go with 1mm thick PETG after Adrian kindly sent me a sample of PETG. So the slots were deepened to allow for this material.

    The outer sides are made in three parts with all panel and bolection details machined in situ and the pilot holes for door handles, grab handles, etc., are drilled and the door lines are engraved.

    32Coaches020.jpg

    ...and here's the result - enough sides for four coaches - a full first at the bottom, a full third just above it and two brake thirds above that. The parts at the very top are the inner support sides for the full first to provide the outer sides of the Jenkinson style inner support box.

    32Coaches021.jpg

    ...and a closer shot of some of the sides showing (as much as white styrene will allow :) ) the panelling, bolections, door lines and hinge sockets. The pilot holes for the door fittings are in there somewhere. :) Machining the three parts for one side took about eight hours at best and could take a good bit longer if I was otherwise engaged when tool changes were required. The prototypes are Caledonian 48ft, 8'6" wide stock.

    I'm also working on how I'll build the underframes. The prototypes had 12" wooden buffer beams with 9" steel channel solebars. I have wood for the buffer beams and I'm working on a way of producing the channel section solebars - maybe having them etched in nickel silver with fold lines. I'm not sure if I can etch the full ~18" length so I might have to look at etching ~9" sections and making an invisible joint in the middle.

    I also have to look at providing Fox 8' wheelbase bogies to go under the coaches so I'm working on making resin cast sides to best represent the pressed steel sides of the prototypes. I'm thinking of providing an etched inner frame with inside bearings and I'm thinking of springing them in a similar style to the Mitchell/Pendleton design in the smaller scales using primary and secondary sprung suspension.

    Jim.
     
  12. lankytank

    lankytank Western Thunderer

    Jim

    You could look at the channel sections supplied by Metalsmith (Leeds) Ltd, in lengths of 1/2 metre & full metre..... :rolleyes: :thumbs: :thumbs:

    Here...... www.metalsmith.co.uk/metals-materials.htm - scroll down into the yellow section, codes start MBC

    Just saying.......
    Barry

    Sorry Guys, blatant advertising, if I need to stay in after school so be it....... :D
     
    Last edited: 19 May 2017
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  13. JimG

    JimG Western Thunderer

    Barry,

    Many thanks for that pointer. That is one source of metal sections that I didn't know about. They do a 7mm x 3mm milled section which is very slightly undersize for a scale 9" by 0.006" so I could maybe put up with that. :):) The half metre length suits the coach lengths with not too much wastage. The section would also do for the 50ft coaches I would like to build when I've finished these ones.

    Jim.
     
  14. lankytank

    lankytank Western Thunderer

    Glad to help. Book mark it.........

    Hmmm, 6 thou.... I'd have to squint....!?!? ;) ;) Maybe a piece of packing between the channel & floor could take care of the discrepancy :rolleyes:

    Barry
     
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  15. JimG

    JimG Western Thunderer

    The standards are ScaleOne32 so Mr. Castens might have something to say about it. :):):)

    The prototype had packing between the bottom of the coach body and the underframe so any differences can be taken up with that, and I can build the coaches such that no one can get a micrometer or a vernier near the solebars. :):)

    Jim.
     
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  16. JimG

    JimG Western Thunderer

    Over the past week or so, with the poor weather, I've pressed on with some work on the coaches.

    To cut a long story short, I got both sides of the seven compartment all first built using the same methods as I had a year ago and shown earlier in the thread.

    32Coaches022.jpg

    I managed to join the three parts of each side successfully this time round by providing support beneath the join in the tumblehome area to stop the edges misaligning.

    32Coaches023.jpg

    I machined up a set of support parts in a long strip to cut off as required.

    32Coaches024.jpg

    ...this shot showing the profile of the parts.

    32Coaches025.jpg
    The next job was to machine the floors out of 3mm styrene. Once again I hit the length restriction of the table size on the CNC mill so the floor is cut in three parts - the top two parts and the one part on the bottom left. the floor parts are also grooved to accept the compartment partitions. The end support are cuts from 2mm styrene and are bottom right.

    32Coaches026.jpg

    The inner joints on the floor parts have rebates cut to allow the insertion of a strip of 40 thou styrene to provide a larger gluing area. The different widths of the rebates is down to a minor c*ck-up in setting up for machining - there's no reason for it. :)

    32Coaches027.jpg

    One side is stuck to the floor...

    32Coaches028.jpg

    ...then the other...

    32Coaches029.jpg

    ...and then the ends are added.

    It is big. :) Thank goodness I'm not building Caledonian 65ft Grampian stock. :):)

    The next job will be to cut the panelled ends and partitions and get them fixed on. Then I will go over the whole coach and make all the glue joins. At the moment the sides are only tack joined to the inner supports until I've double checked that the PETG glazing material will fit nicely in the glazing slots. Then I will go round every quarter and drop light opening with the Mekpak.

    Jim.
     
    Last edited: 2 August 2017
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  17. JimG

    JimG Western Thunderer

    I've been thinking ahead to bogies for the coaches. The Caledonian used Fox bogies for their 48ft stock and there's an excellent GA drawing in the Caledonian Association book on coaching stock so I had no excuse. :) I still haven't decided whether I will be making a master for casting, or making each part required. I'm intending that the bogie sides are cosmetic and that the bogie will have inner frames to locate bearings and suspension. I'll probably do an etch for the inner parts of the bogie.

    The main feature of the Fox bogie was the pressed steel sides with heavy flanging on the top and bottom edges. The radius of this flange was about one inch radius, so is quite noticeable. the depth of the flanges was three inches.

    I opted to cut the side from 3mm styrene on the CNC mill. The styrene was cut down to 2.4mm to get to the scale three inch depth and the outline was cut, and pilot holes for all the river holes drilled. the curved flange edge was then machined using a ball ended bit and a bit of hand coded GCode.

    32Coaches033.jpg

    The various plates to fit on the side were cut from .75mm styrene surfaced down to 0.6mm to get the 3/4" prototype thickness.

    32Coaches034.jpg
    A slightly tighter shot showing the machining of the curved edge. All the pilot holes drilled on the CNC mill have been opened out with a 0.8mm drill to suit the brass rivets I have.

    32Coaches035.jpg
    This is the first plate being placed using the brass rivets through some of the holes to locate it before stickign it down with Mekpak.

    32Coaches036.jpg
    The side with all the platework in place and most the rivets inserted. the holes for the footboard supports - like the two at the left - have been left till the footboards are fitted much later.

    I'm not sure about the 1/32" brass rivets. Their size is about correct but I think that they might be just a bit too prominent. They might look better after getting a scoosh of primer or I might have to look for an alternative. I might try getting some scale 7/8" G scale Archer rivets or I might try George Slater's rivet method, applying heat to the end of plastic rod to get a mushroom head effect. This only works on the old Slaters red/brown rod and I might have enough of it left to do the job. It would need to be the 30 thou size. My only reservation with this method is getting the heads to be the same size since the size can vary depending on the time the heat is applied and the distance from the heat source. I no longer smoke so I can't use George's heat source of choice, but I now make do with a candle flame. :)

    Jim.
     
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  18. Dikitriki

    Dikitriki Flying Squad

    I don't know the prototype, but my initial reaction was that the rivets were oversize - sufficiently oversize to mar the appearance.

    I'd do one perfect side and have the rest cast in resin. You never know who else might want 1/32 Fox bogies;).

    Richard
     
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  19. jamiepage

    jamiepage Western Thunderer

    Jim,
    Excellent stuff. Have you perused the Scale Hardware lists for alternative rivets?

    Small Parts & Hardware

    They may be worth the investment, especially if you go down the route of fettling a master for casting.

    Happy New Year to you,
    Yours,
    Jamie
     
  20. Dog Star

    Dog Star Western Thunderer

    Jim,

    Given that you are using styrene for the solebars, how about the Grandt Line range of rivets? Search the 7mm NGA website and you shall find a range of head shapes and head sizes... might need to order a few packets to find one that suits your application.