7mm US model dabblings

Discussion in 'Area 51' started by Jordan, 8 April 2013.

  1. mickoo

    mickoo Western Thunderer

    A UK replacement in 1:43.5 (approx ;)) scales out at 2'-6" or 30" for US 1:48th 33" wheels.

    Roxey do some steel diesel wheels at 2'-8" with a thread width (code) of 0.145...ish which scale out in 1:48 to 35" wheels (approximately).

    Given the cheapness, local (in a global sense) availability, lack of VAT/customs/postage from the US, then the extra 2" in diameter is something I might just be able to live with. In real terms an extra 1.06 (rounded up) mm in diameter.

    I already have a set of ball races but the I/D is 2.0 mm and Roxey steel wheels (there's five sizes in their range with the screw on wheel) have axle ends at 1.96 mm. May opt to turn them down and sleeve with some thin bore tube.

    The truck frames are fully articulated, too much in all honesty and the sides wobble and cant over, need to find a way to take a lot of the slack out, may even loose the springs (under nourished compared to 1:1) and fit more detailed ones, no need for the full five nest set up, the outer three should suffice visually.

    The side frame twisting may well come from worn axle bearings, won't really know until I pull one apart shortly. The trucks are detailed enough as they stand to add more, they're quite exposed under the tender so some brake gear and rigging is in order, maybe not full rigging (tempting just for the hell of it).

    Replacement truck wheels required are eight 33" wheels, one 36" wheel and one 45" wheel, the drivers I think I'm really stuck with, I don't see any realistic way of slimming them down and not damaging some detail, maybe a bit off the back face but that's your lot I reckon.

    PSC do have some wheels, they do the 33" and 36" with blunt end axles but no idea of diameter, the added bonus is the tapered axle they have in the middle, easily seen on the tender axles as they are quite exposed.

    I've not checked NWSL yet though, PSC was an idle check after looking for tender castings. I'm trying to find some oil (spade handle type) isolation valves.

    The biggest priority now though is a layout, I've a rough idea in my head bouncing between a city type depot, typically LA in style for architecture, love that 30's look to bridges and buildings; or in the wilds, Dunsmuir, Keddie, Thistle with rocks, cliffs, fir trees etc.

    Must have a bridge somewhere and water, hard asks given the small space I have.

    Motive power is simple, SP, UP, DRG (not a big fan of ATSF) in the mid/laye 50's and location is probably fictional somewhere in California where everything is a mandatory oil burner, that simplifies your coal and ash facilities but limits any coal burners I'd like to add, UP nines or Big Boys spring to mind; it does also seriously limit your DRG fleet.

    The turntable is limited to 100', primarily due to domestic space (plus its the only one I have drawings of) but also as a challenge and limit to larger locos, they can always be turned on a wye off scene.

    Having said that I have seen photos of larger engines being turn with the use of track skates/jacks/ramps. Big boys were turned at Denver on their 100' table. I do have a cunning plan to fit something like that to the end of the table, a sort of lifting section right at the rear to tip the end of the tender up to clear the rail head.

    Track plan is simple, depots are not complicated, anywhere from three to five straight lines converging toward the table pit but I want to add at least one crossover and a spur for the bypass line used by diesels. The quest now is what size switch to use #6 is too small for an articulated engine, a #8 or #9 is better but added length makes them hard to fit in confined spaces.

    Right, time to sharpen the pencils :thumbs:
    Last edited: 18 September 2020
  2. Steph Dale

    Steph Dale Western Thunderer


    That's about 1.6thou"" clearance so that, or thatabouts*, is a good clearance for a relatively straightforward fit, or a good one involving retainer. Either way it's in the 'not s*dding about' category and they should work fine.

    My worry would more be working out how to allow the axleboxes to trolley (sideplay) to allow the loco to go round corners.


    *assuming a real-world tolerance on the machining.
  3. mickoo

    mickoo Western Thunderer

    Lateral play is a good.... 'sticking' ...point

    Big as this engine is, massive is more like it ( I passed on the AC-12 BTW and looking at the final price compared to better imported brass models currently floating around....I'm glad I did) but it does break down into much smaller units, the benefits of articulation :thumbs:

    The lead and delta trucks are short wheel base so no lateral play planned, the tender Buckeyes are also reasonably short wheel base and again no side play intended.

    In conjunction with all this I'm planning the layout with 'accommodating' curves and switches and may need to gauge widen, to that end I'll try and keep to 96" radius which in real 1:1 terms is still very tight*.

    Back to the engine, the Challenger has really quite short driver wheel bases, shorter than most BR Pacifics, I'm hoping that given the relaxed curvature and general slop twixt wheel and rail that no side play will be needed on the engines.

    That's all irrelevant if I can't even get roller bearings onto the driven axles, those are the ones that really need it, given the huge weight of the engine. I don't really want to punch the axles out and then fight all that quartering again.

    I've just had a quick look under the engine, took a couple of shots and turned it right way up quickly, they don't make horror movies like that anymore :eek:

    Young viewers and those faint of heart should scroll by the next images swiftly. Those more comfortable with Chucky and Mister Kruger please feel free to follow along.



    Diverting from bearings briefly the images show just how much work is entailed, from the rear, Delta truck = junk, rear frame extension with pseudo ash pan profile = junk, I can't see if the extension is actually a real extension or part of the rear (main) engine. If not I'll have to cut it off and affix a more correctly profiled one in due course....time to get that milling machine I've been promising and putting off in equal measures for years.

    The cab looks like it's retained with a couple of screws, good it needs to come off as the rear wall is incorrect, no detail, no rear windows and cut outs under rear seats all wrong, actually most of the butt end is woefully wrong, time for some more etch work in due course.

    The base of the firebox is wide open and the void visible from even moderately low angles, a new oil burning shield needs putting in there, there's some sort of chuff mechanism on the intermediate axle, off with his head and into the bin chummy boy.

    Up front, lead truck = junk, straight into the bin, there's some large voids in and around the front cylinders so I'll make up some blocks that look more like the real deal in profile and fit in there. You can see where the exhaust pipe fitting needs fixing into, need two of them, one each side and a centre one for the live steam pipes.

    There's a lot of detail on the model but a whole lot more pipework needs adding, there's no drain cocks as such, sand pipes and oil lines etc but most of the larger castings are present and fit for purpose. Probably the biggest hurdle is the running boards, these need lightening holes in them, it's a really obvious feature on these engines. The current ones are I think cast and fixed in several places, experience with cleaning up the tender so far has shown that what ever solder they used, it needs to be really hot before it becomes workable....expect much swearing here then.

    There's no brake gear as such, that all needs adding, other than some milling it's nothing untoward, just larger and more of it than usual :))

    Back to the bearings, the engine bearings are retained with keep plates, the axle box isn't quite big enough I think to bore out for roller bearings, the axles are 5.91 mm....there must be an imperial figure that makes more sense....can't be figged to work it out....which is quite chunky, the axle box guides are 8.9 mm wide, that doesn't leave a lot of meat for roller bearings.

    I'm not keen on milling the main frames to be honest, the only other solution is to fit smaller axles and bush the drivers out accordingly, plenty of time to mull that over before I get there.

    Of course, I could just do nothing, it doesn't need roller bearings and I'm sure with a new modern motor, DCC and higher ratio gear box it'll be nice and smooth as a depot queen, I have no current plans to thrash it at a scale 80 mph...yet muhahahar.

    * the large radius becomes more relevant, as will lateral play when I get to the bigger and longer fixed wheel base engines, the big decapods (UP, SP, DRG) and the UP Union Pacific class (big nines or 4-12-2) are going to sweat some muscles on those curves.
    Last edited: 18 September 2020
    PhilH likes this.
  4. Lancastrian

    Lancastrian Western Thunderer


    Gauge widening ? Just go S7 ;):))

    mickoo likes this.
  5. Steph Dale

    Steph Dale Western Thunderer


    Sorry, you've lost me - I was commenting on the use of 2mm bearings. I had assumed these were in a diesel drive bogie?

    In terms of roller bearings, they'd certainly work, but I've never seen them at size/price I'd want to afford (for a whole loco). Ball races are affordable, but generally a pain because of the need to have the movement in the axleboxes of steam locos. It's a slightly different proposition in an outside-framed diesel bogie - it just needs to be designed in.

    mickoo likes this.
  6. mickoo

    mickoo Western Thunderer

    Well that wasn't hard then :p No, not diesel bogies, not yet anyway, that's another bowl of stringy noodles to unravel another day :thumbs:

    Re-read all of above, substitute ball for roller and bearings for races, I knew what I meant, sadly the rest of the world didn't :))

    No need for lateral axle movement in steam (or anything really) if you don't need it.... explained above for the Challenger....in simple terms, enlarge your radii to suit.

    I have some very big steam engines and rather than mash them up to suit tight curves I am in the enviable position of having a green field site for a layout.

    You have to decide which part is the dog and which part is the tail...which wags which, traditionally the layout wags the tail and places restrictions on motive power and enforces compromise. I'm switching that, because I can, the engines dictate the layout.

    If side play is needed then fit the 'ball race' inside a standard (steam engine) bearing and let that have lateral float in the frames, not so easy on a diesel I will concede, but then if your radii is 96" you'd have to question if lateral play was really needed.
  7. mickoo

    mickoo Western Thunderer

    Oh dear......:p

    It's US 1:48 old sport, P48 in their terms, which is even narrower ;):))
    Lancastrian likes this.
  8. JasonD

    JasonD Western Thunderer

    For a 5.91mm axle 15/64" is a clearance hole! By 0.04mm. Time for the 'factory' to get some new tools?

    Throw-away suggestion: InterMountain code 145 33" nickel-plated brass wheels, but with pointed thicker axle ends. Take up the slack a bit when 2-railing Lionel trucks ... OK not precision stuff, but I probably have 6 axles. I'll check if have any alternatives, NWSL the most likely.

    I have 2 boxed and maybe 2 unboxed Atlas code 148 rail, 7.5 turnouts here.

    You may remember I model the D&H in leafy NYS, but I do remember (not that well it turns out) driving up from Sacramento and having a great Mexican breakfast in Colfax? And later a museum visit WP Museum(?) with 10 minutes at the controls of an Alco S2 (only blow the horn once, otherwise the neighbor up there complains!). Happy days ... O-scale Convention's in Denver, June(?) 2021
    mickoo likes this.
  9. JasonD

    JasonD Western Thunderer

    Laugh of the day (mainly 'cos I thought he must be joking), all this talk of radii ... Dapol Pannier acquired by American 3-railer who'd laid an oval (no turnouts) of O-45 3-rail Atlas track, yes plastic sleepers and 22.5" radius, on ogaugerr.com forum chugging round quite happily hauling tinplate 4-wheelers.
  10. Mudhen

    Mudhen Western Thunderer


    All very interesting reading, I'm looking forward to watching the progress. Given the many compromises in the running gear how dimensionally accurate are loco and tender bodies, boiler etc?

    all the best
    mickoo likes this.
  11. mickoo

    mickoo Western Thunderer

    Can't afford O gauge track?


    Just lay two extra N gauge lines.

    Given the depth of high rail flanges that U boat must be banging those tie plates pretty bad :))

    Code 148 might be a bit heavy weight for a depot? I was looking more at code 125 sort of size. I'm not sure on the 7.5 frog, might be a touch too tight, need to get my head around visuals and clearances, I was figuring #8 would be the minimum I'd need.
    JasonD likes this.
  12. Steph Dale

    Steph Dale Western Thunderer

    It's been a long week. :))

  13. mickoo

    mickoo Western Thunderer

    To be fair Tim, the upper works are pretty close so far to the works drawings I have, it's just below the hem line that things get a bit Neanderthal :D
  14. mickoo

    mickoo Western Thunderer

    You are forgiven :bowdown:

    Fortunately for me, this weeks more pressing engagement has been which pack of biscuits to finish first :thumbs:
    simond likes this.
  15. Jordan

    Jordan Mid-Western Thunderer

    Beat me to it. It does make me smile that going to 'proto' standards in US O means narrowing the gauge, whereas in every British outline case it means widening... :rolleyes: :)
  16. simond

    simond Western Thunderer

    Would have been nice if they’d started with a scale and simply scaled the gauge to suit.

    Toy trains more of an issue..,
  17. JasonD

    JasonD Western Thunderer

    But S-scale is the only one that's right for everyone. So, why is it the least popular?

    Anyway, the O-scale coc... er, compromise means I can run American freights thru' British stations without tearing the platform edges off and demolishing the footbridge.

    Toy trains: in the UK it's 'fine-scale' or 'coarse' (aka the rest). In the US it's O-27, 3-rail and 2-rail. O-27 was/kind of is S-scale bodies on O-gauge trucks. 2-rail is what we call RTR (you decide if it gets the tick in the box). 3-rail is like news-readers where the bit above the desk is nice, but the bit below the desk can be the trousers, etc that go with the nice jackets, or pyjama trousers for ... well, 3-railers. 2-railers may still need to put nice shoes on (the wheelsets) and ... oh, this getting too difficult! Lovely scale length 89ft Autoracks with working end-doors and internal decking ... 3-rail from Lionel?!? Just change his shoe... wheels, wheels!!
    simond likes this.
  18. Overseer

    Overseer Western Thunderer

    @mickoo, I am struggling to understand your resistance to converting steam locos to P48 while you are correcting so much else on the loco. The difference in back to back is less than 0.5mm and no narrowing of the mainframes would be needed to convert to P48. The cylinders may need to be moved inwards but that depends on how much has been fudged in thickness of coupling and connecting rods etc. The driving wheels look like the tires could be pressed off and turned to p48 and the centres reduced in width from the back to achieve scale wheels at no extra cost. If you choose a compromise standard how do you make it compatible with other models? - scale or near scale wheels set to O back to back would be very close to P48 and probably wouldn't run on O track but if you increase the back to back to work on O track there would be problems with check rail clearances and probable derailments through turnouts. P48 looks easier to me. I agree O diesels are a bit of a pain to convert because the truck sideframes are too far apart to suit wide wheels, but the improvement in appearance is significant.

    To show the similarity in back to back dimension these are some Atlas roller bearing caboose trucks I am converting to P48, one part done and the other as supplied.
    Atlas p48a.jpg
    Atlas p48b.jpg
  19. mickoo

    mickoo Western Thunderer

    They look nice.

    I initially wrote a long wordy replay which basically explained why I was doing this and that and justifying my point of view.

    On final review I figured no one would read it, would glaze over after the second sentence, doesn't really care, so I cut all the :shit: out and was left with these few points

    I'm not modelling P48.

    I am exchanging those wheels (that are easy to do) which are code 172 for code 145, the back to back remains the same, aka O fine.

    Those wheels that are too complicated to change stay, I don't have the time, energy, enthusiasm, skill set, tools to change them.

    I admire people who model P48 and S7, go for it, it leaves me stone cold dead but you have my respect.

    I am in a minority of one, I don't mind, I am happy in my own world of soft play toys and pink elephants, I sleep easy with that knowledge.

    I might die in my sleep, it's only a toy train, the worlds going to pot, does anything really matter any more, group hug :thumbs:.
  20. JasonD

    JasonD Western Thunderer

    At the risk of boring everyone again, I've recently moved to Westbury, about 4 miles from the West Wilts Gauge O Group's clubroom in Trowbridge with a nice big test-track setup.

    I can road test my American stuff with long trains and DCC installs and dream on about the forthcoming switching pike in the garage (hole in wall next year to small roundy-roundy outside...?). If I had been tempted by P48 (for diesel-era stuff?) I couldn't do the first bit, so maybe the second bit would have been less satisfying.

    Mick, at the risk of telling you something obvious, people like Dave Brooks at JPL can skim those trailing wheels - well, it's worth a chat. But you knew that. As for your 'own world of soft play toys and pink elephants', it's those folks with modern-day 'elephants in the room' I feel sorry for. And I have the permission of the Good Parrot on my right shoulder to say so.