1/32 Promoting Better Wheels and Track

Discussion in 'G1/32' started by David Halfpenny, 20 December 2012.

  1. JimG

    JimG Western Thunderer

    Just found the reference to Ian's article in the MRJ

    Resin-Cast Track Parts for 7mm

    Ian Pusey


    Issue 37 (1990)


    p.394


    7mm


    Ian Pusey is a long standing devotee of 'S' scale. Knowing that he had experience of resin-cast track components , we asked him to review a new permanent way system for 7mm.

    Jim.
     
  2. David Halfpenny

    David Halfpenny Western Thunderer

    Here's a rather crude insulated spoked wheel in our sort of size, made on a bit of kitchen worktop:
    - Slaters batch-produced steel tyre
    - laser-cut spoke Plug
    - poured soft silicone female mould
    - fresh tyre placed in mould
    - poured polyurethane casting resin
    - tyre centred on lathe to drill axle hole true (could use bell chuck)

    Resin Casting - Association of Shrewsbury Railway Modellers

    Southwold spoked wheel for 45mm gauge.jpg

    Wheels like this can include a locking groove inside the tyre.

    I'm wary myself, even though the process could be refined in places, but it does provide a number of different wagon wheels from a single batch of tyres, as suggested by Cynric, end of 2012.

    I particularly like drilling the axle hole after assembly (as opposed to trying to make a super-concentric plastic component in a soft mould). For example one could buy-in high-resolution 3D prints for the centres, inject a resin or adhesive to fix it into the tyre, then drill and ream, cancelling any slight dimensional anisotropy in the prints. (That's important because prints aren't always made the same way up in the machine.)

    Naturally, not everyone wants a wheel factory in the kitchen, and complete tubs of silicone and resin are overkill for a guy who only wants four wheels to start with. David
     
    Last edited: 2 May 2017
    simond likes this.
  3. David Halfpenny

    David Halfpenny Western Thunderer

    If anyone's at The Fosse today, buttonhole me for a natter. David 1/2d
     
  4. David Halfpenny

    David Halfpenny Western Thunderer

    Here's the Shapeways Shop of one of my New Zealand internet chums, showing how he designs his narrow-gauge wheels, and giving digital-image impressions of detail.
    7/8thsNarrowGauge by Vailala - Shapeways Shops
    If you click on a product, then click on the 3D icon, you can spin the 3D image around with your mouse or trackpad.
    Note that the price is for rather more material than we would need for Inserts, and includes his modest margin though not shipping (from Holland).

    He's specified laser-sintered materials - different choices for each of his products. These are far removed from the crude, hollow 'demented glue-gun' prints familiar from hobby machines. Shapeways has additional materials and processes, for example their recent Black Acrylic is smooth, rigid and shows no pixellation even close up. (Trick is to request it without de-sprueing cos they don't always do that the way we would.)
    Among recent additions is a strong Aluminium, which is fine-grained, workable, and perfect for cheap, relatively short-run injection moulds.

    Of course, each 3D process has separate Rules about the minimum sizes of parts, surface detail, gaps, cavities etc. If you draw a part in 3D (using simple and/or free software, some of which works on a smartphone) Shapeways website will auto-check your design for technical issues in a wide range of materials, including solid gold.

    David
     
  5. David Halfpenny

    David Halfpenny Western Thunderer

    While at The Fosse earlier, I took the opportunity to measure the wheels on both G1MRC/Accucraft (3' 4" diameter) and Bowande/Wuhu Brand (3' 7") Mark 1 coaches, and to compare each with Roxey 3' 7" wheels.

    Yes, the roughly 3" difference in diameter looks ENORMOUS - after all it's about 15% difference in area.

    Retro-fitting 3' 7" wheels to the G1MRCo coaches may well be possible - I didn't like to press the point since as soon I unsheathed my Dial Caliper Gauge poor Graham Langer had said, "You frighten me!".
    . . . Yes, it would need a correction to ride height and yes, it would limit curve radius . . . yet Bowande have done it . . .
    . . . . . . And having seen the difference, it's very hard to ignore it.

    As Simon says, you couldn't make it up ( even if Gauge 0 is actually worse, counting all the scale-gauge combinations.)

    Now here's a thought:
    When I put Roxey G1MRA Standard wheels beside the hapless AccuG1M, they looked massively over-scale, but when I substituted the Roxey Dead-Scale wheels, they looked Just Right (if one imagined them in black, of course).

    David
     
  6. David Halfpenny

    David Halfpenny Western Thunderer

    . . . to play with a self-steering bogie on the Switch and Crossing Work, after all the steam engines had gone to bed.

    Most interesting results, that I'll put in a separate thread so as not to muddle this one, because although Better Wheels are involved, Promoting is not.
    Thanks to those who did, and thanks for your helpful contributions. David
     
  7. Simon

    Simon Flying Squad

    The larger wheels will easily fit into the G1MRCo coach without any clearance issues. In fact, if you look at the brake blocks that G1MRCo have fitted, the whole thing looks to have been designed for the correct sized wheels. The immediate "problem" is that you need new bearings of course. Ride height wise, I have a feeling they sit too low as they are, of course they'll look that bit better sat next to 10mm stock with an increased ride height:p

    It would be lovely if G1MRCo corrected this in new batches. It would be even lovelier if they produced the very distinctive and numerous composite coach, I'm guessing they won't though.

    Going back to your resin centres, a friend and I tried this and it works well, but as you observed trying to cast the axle hole at the same time is problematic. We found that you needed to bore them out in a separate operation, which makes it even more of a craft project. What stopped us (back then) was a lack of turned tyres to play with, producing those manually was even more of a craft process!

    I did actually ask Peartree to go ahead and produce some ScaleOne32 wagon wheel sets, but I think he's one of those chaps you have to keep gently prodding before anything happens.

    Different subject, but I think I have got the talented Justin Newitt currently looking at producing some sensibly sprung, easy to use and correctly detailed 1/32 wagon underframe and brake etch sets.

    Simon
     
  8. David Halfpenny

    David Halfpenny Western Thunderer

    My Mark Wood form tools have arrived.
    Here's Mark's description:
    and photo: upload_2017-4-27_14-39-36.png

    The blank is PRESTO MOLY, which I think is M2 HSS, and would be at least a tenner in a shop.
    The 'Scale32' profile is slightly finer than Roxey Mouldings "Dead Scale" wheels, but matches the flange depth. It's wire-cut, making it a completely parallel groove down the front-rake of the tool. This means the tool can be re-sharpened many, many times, unlike one with side-rake too. It also means that even a used one can be used as a Profile Gauge, and also to mark out and check its own replacement (if you need one after Mark retires, and fancy grinding something that small at home).
    I've no intention of trying to shove it straight into a steel wheel blank on any of my (mostly small) lathes - that's for Experiment. The ideal would be to develop a way of using it on a really cheap lathe, but we may have to settle for just a fairly cheap one :) Mark's proven method is at: Turning castings

    I suspect a lot of us will be starting with a commercial wheelset, rather than a bar of inch and a quarter EN1A BDMS :)
    David
     
    Last edited: 27 April 2017
  9. adrian

    adrian Flying Squad



    I've just been turning up some wheel castings using Mark's method - it worked really well. These wheel are slightly smaller being 7mm scale but done in a cheap mini lathe.

    Very Little Gravitas Indeed*

    If you are using his method you'll need some aluminium blanks to make the various mandrels. I found a useful supplier Forward Metals that allowed me to specify custom cuts, I've not got a power saw and didn't fancy chopping 1 1/2 bar by hand. so they did all the cutting for me.
    Free Cutting
    Although if you have a power saw then it won't be a problem.
     
  10. David Halfpenny

    David Halfpenny Western Thunderer

    Here are my first two Scaleone32 wheels, made using a Mark Wood form tool, along with the Standard wheels that I turned them down from:

    20170904_232636.jpg

    The disk wheel is from Accucraft - as it happens, the cheapest commercial wheels I can get.
    It's diecast from some kind of free-cutting buttermetal, with a central insulating bush.
    (Be aware that Accucraft use more than one kind of bush and axle.)
    I've turned all the chrome off the tyre, and reduced the thickness to 4.5mm, a process which produced a en entire matchbox-full of fine, curly swarf.
    I shall fill the stark hollowed face with some kind of resin, then drill through three of the six holes.

    The spoked wheel is from Walsall - the second cheapest I can get. They come without axles and have moulded plastic spoked centres with 1/8" holes.
    The tyre is free-cutting steel that disintegrates into fine chips.
    Because it's difficult to turn the spokes, I stopped reducing the thickness when I got to 4.7mm. I'm surprised that the extra 0.2mm is so visible; room for improvement.

    As each type of wheel needs it's own chucking method, I'll try some further makes (notably Slaters F series) before describing turning. My methods are a throwback to a pre-industrial age: simple, accurate but s l o w, using a cheap wood-turning lathe and little more than chuck, form tool and caliper. I can put the whole wheel-turning outfit in a carrier bag and lift it with one finger.
    Suffice it for now to say that, by starting with a ready-turned wheel made of free-cutting metal, all I had to do was rough off most of the excess metal 'near enough' with hand tools, then finish the flange with the form tool, also held in my hand.​

    While these two wheels aren't perfect to my critical eye, they cost less than £2 each, have a better profile and better finish than they started with, and seem perfectly usable. Time will of course tell - the next steps are to fit them to axles at their new Back to Back, and then find or make a Scaleone32 or Exact Scale turnout.
    Yet another reason for hoping Simon C can come to the G1MRA AGM next month :)

    David
     

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