A small G3 loco

Discussion in 'G3' started by jamiepage, 9 April 2015.

  1. jamiepage

    jamiepage Western Thunderer

    Over the winter I sketched out the idea of a small live steam G3 loco specifically designed for R/C shunting rather than high speed express running; and also to use as many off the shelf components as possible in its construction without compromising overall accuracy too much.
    The prototype selected was one I had wanted to build for a long time, one of a batch of three 0-6-T locos supplied byDubs to the SM&AR in 1881 which satisfied the requirement of being small and hopefully fairly straightforward.
    Wheels were available either as castings from Mark Wood or as complete wheelsets from Slaters, and a standard Roundhouse Engineering boiler plus gas tank, burner, regulator and lubricator would all fit the scale outline.
    Off the shelf R/C gear would hopefully fit in, especially if the side tanks are used.
    A Paul Forsyth G1 cylinder design (for larger prototypes) would fit well and castings were available although I may well chew them out of stock material.
    Shunting will require fully reversible valve gear rather than the simpler slip eccentric, and although Roundhouse do supply a simplified Walschaerts set, the original used inside Stephenson's.
    There is a published G1 design by Martin Evans for a Brighton Atlantic which incorporated Stephenson's, and a quick look suggests it should fit, just. The design seems well proven so presumably the geometry is ok.
    Finally, and with the shunting brief in mind, there is now an off the shelf 'Slomo' flywheel-type device available which can flatter the slow speed characteristics of 16mm locos for which it was designed, and with the help of the Australian manufacturer a slim version may be available to fit within G3 frames.
    No official drawings exist for these locos, so far as I know, but Mike Barnsley's excellent book on M&SWJR (which grew from the SM&AR) stock has some elevations so with those plus a selection of photos a working drawing was produced.
    From that, mainframes were cut, actually milled, from mild steel and buffer beams from brass which happened to be at hand.
    The distinctive diamond- shaped coupling pocket plates were sweated on, as were rivets into drilled holes. Springing may be proven necessary, or even just desirable, but for the moment simple unsprung axleboxes suffice.
    Photos just about show progress to date although the frames have since been disassembled again, mounted on the mill at an angle and registers (holes) for the cylinders have been machined in.
    IMG_0001.JPG IMG_0001.JPG
    Jon Nazareth, Simon, Mike W and 13 others like this.
  2. Dikitriki

    Dikitriki Flying Squad

    What a fantastic project! I particularly like the idea of a controllable live steam shunter.

    It seems that most videos I see of live steam locos show locos going far faster than I would want, and frankly it's a bit off-putting. So I am very interested to see whether you can accomplish all your aims and get the slow controllable running you want.

  3. Steve Cook

    Steve Cook Flying Squad

    Brilliant stuff Jamie, I hadn't realised you were already cutting metal :)

    Like Richard I'll be looking forward to seeing how you get on, especially with a Slomo (videos and details here) in place. If you need any measurements of the latter just shout - its my guess the height isn't going to change in order to squeeze the flywheel and gears in.

    Thanks for giving me and Simon chance to catch up on the PMV :D

  4. jamiepage

    jamiepage Western Thunderer

    Richard, thank you. I really don't know whether I can do it, but others have. Use Steve's link, select 'videos' then 'scratchbuild and custom videos' to see some shunting on the kitchen table. It's this sort of thing in a standard gauge context that appeals.

    Steve, thank you. I have corresponded with Terry from SSP, who has been extremely helpful. Certainly the width needs attention because his Slomo's have so far been designed to fit within outside framed 16mm locos, but hopefully he will be able to re-engineer it. Height should be ok, length..not sure, actually. Clear space between the relevant axles is 71mm on this model (78mm centres), how does that compare with the standard Slomo?
    As an aside, I hope to get the transfers on the PMV later, after which the rest of Cambridge Custom transfer sheet BL97 (10mm) will be surplus. Very happy to pass it around the other WT G1 PMV's (three I believe at the moment?) as they become ready. Otherwise it will just get wasted so very happy to see it used. Isn't there a blue one painted?
    Steve Cook likes this.
  5. Steve Cook

    Steve Cook Flying Squad

    Hi Jamie
    It should fit lengthwise then :) Dimensions for the Katie and Billy chassis (which the Slomo was designed for) are on the Roundhouse website click on Kits on the LH menu and scroll about halfway down. The axle centres are 76mm and I've just run a set of verniers between the axles on my mock up - it measures out at 69.68mm and a Slomo fits OK.


    The Slomo frame fits between the wheel running surfaces as it runs the full width of the engines chassis.


    Looking at that photo though (ignore incorrect alignments etc, I was just playing around to check sizes), you can get rid of a lot of the width on the LHS which isn't used, the Slomo could then just squeeze down to 38.8mm across frames which should fit between frames of a G3 loco OK too.

    Good luck with the transfers and thank you for the offer of some of the remainder, that would be brilliant :) It makes sense to use as much of one sheet as possible and share the cost between us all.

    ceejaydee and D816Foxhound like this.
  6. Dikitriki

    Dikitriki Flying Squad

    Hi Jamie, Steve,

    I've been through the videos and fitting instructions on the SSP site. What a wonderful piece of kit. The difference in the running is astounding.....and everything I would want in a live steam loco. Brilliant:).

    If it can be redesigned to a 38.8mm width, does that mean it could fit in a G1 live steam loco?

  7. Steve Cook

    Steve Cook Flying Squad

    Hi Richard
    I'd say probably not, even depending on track / wheel standards. If the engine was built to the Standard wheels standard, the width between frame rails is about 33.5mm. Even at ScaleOne standards with a B2B pushed right out at 42.25mm, that would leave only 3.75mm for frame width (x2) and clearance, thats getting pretty tight, bordering on the not feasible side.
    Makes me want to see if there are any standard gauge outside framed locos though...
    Apologies for the slight derailment Jamie :oops:
  8. David Taylor

    David Taylor Western Thunderer

    That already looks great! Looking forward to watching this come together.
  9. jamiepage

    jamiepage Western Thunderer

    That's very helpful indeed, thank you. No charge for the transfers, happy to pass them round to yourself, Simon and Roger- indeed any other WT PMV project.
    Thank you. By the way, I think I will be scanning the 2-6-0 drawing soon. If so, I will send a copy.

    Steve Cook likes this.
  10. AJC

    AJC Western Thunderer

    A really interesting project this, and the mechanics are fascinating.

    From my perspective, much of the interest is a forthcoming 4mm model. No, not of the SM&AR loco, but a slightly smaller Dübs - based on the Branchlines kit for the Manx Northern Railway's 'Caledonia' - converted (in my case) to EM. Quite why I decided to do this is a moot point and, to be honest, I can't remember... There's a good chance yours will steam before mine runs!

  11. jamiepage

    jamiepage Western Thunderer

    Yes, Caledonia does enjoy the same house style and is likewise an attractive prototype.
    For completeness, herewith a photo of a photo of the original.

    Mainframes progressed as far as desirable before fitting cylinders so they are the next proper job. The frames were registered together using three axleboxes and had to be reset on the milling bed at 6 degrees as a pair. This was achieved using an insert through driving axlebox and a predrilled sighting hole on cylinder centre, the frames then fiddled until both aligned with the mill's long axis.
    The cutout was established with holes drilled in each corner then a slot drill to cut to size. Using oversized holes in each corner was a cop out to short cut the need to file square corners, but which will not be visible eventually.
    The cylinder centreline by the way, runs along the top of the cutout because only a half- height steam chest goes through into the between- frames area.
    The opportunity was also taken to drill a few holes with the frames registered together before removal.
    IMG_0001.JPG IMG_0002.JPG IMG_0002.JPG
  12. JimG

    JimG Western Thunderer


    I think a lot of the North British Loco Works material is now held by Glasgow University and this NRM document would seem to confirm it - certainly for the Dubs locos.

    http://www.nrm.org.uk/~/media/Files...ntroduction to North British drawing list.pdf

    ...so there might be an official drawing. :)

    And here's a bit of info about the Glasgow University Archive service for the North British and the Andrew Barclay material.


    The NB material came to the university from Andrew Barclay in Kilmarnock. When NB Loco shut down in the early 1960s, Andrew Barclay took over the maintenance of their existing locomotives and all the records were transferred from Springburn to Kilmarnock. The story is here


    Back to the present. :) I shall watch this loco building with interest. Do you think that a Gauge 3 loco will need a Slomo? I would have thought that the larger driving wheels - probably larger diameter than those on the large scale narrow gauge models the Slomo was designed for - might reduce torque at the rail and minimise jack rabbit speed responses.

  13. jamiepage

    jamiepage Western Thunderer

    Thank you very much indeed for the links.
    As to the need for a Slomo, I guess the answer is that I don't know. I would like this loco to be optimised for slow speed, shunting type operations and am happy to try anything that may help. Certainly, a G3 loco should enjoy more mass than G1 etc, (although this is a small loco by any standards) but with luck the Slomo will enhance any intrinsic characteristics I can build into it. I will work on the principle that it won't hurt, because I'm not interested in this loco haring around the mainline.

  14. AJC

    AJC Western Thunderer

    Thanks for sharing that work's shot of the SM&AR loco, which should prove extremely useful. There are plenty of characteristic Dübs features there - the footsteps attached to the slidebars (now those will be fun to do in 4mm) wheels that look slightly too big and the distinctive shape to the cab. I'll post where I've got to in a bit, probably after the weekend.

  15. jamiepage

    jamiepage Western Thunderer

    I had a set of Mark Wood castings for a Terrier, and like all of Mark's wheels they were absolutely spot on for prototype. This Dubs loco similarly had 4ft, 12 spoke wheels but unfortunately with pin between rather than in line as the Terrier. The chances of another more correct G3 casting becoming available is pretty remote so I will live with the compromise in the interests of making progress. Hopefully, that will be the biggest compromise necessary, and the large marine- type coupling/ connecting rod bearings should camouflage the error to some extent. Slightly different balance weights will be modified to suit.
    The ability to remove wheels from their axles was tempting, if only to remove the need to drop complete wheelsets later (although the front axle will probably need to be released from below). The castings were therefore sent to Walsall Model Industries who machined them to fit their square ended axles. Superb service, very reasonable price and they re-arrived back here 48 hours later. Can't rate them highly enough.
    Couldn't resist the temptation to assemble the frame for a push up and down a piece of track. The flanges look rather coarse but they are turned to the coarser of two G3 standards to compensate for outside tracks and lack of springing.
    AJC, JimG and Steve Cook like this.
  16. mickoo

    mickoo Western Thunderer

    Now just you look here young man!, you must stop posting all this G3 stuff, I'm finding it very hard not to have a whimsey at something larger than S7 :cool:

    Seriously....very nice work :thumbs:
    Scale7JB likes this.
  17. jamiepage

    jamiepage Western Thunderer

    Thank you very much.
    Have a whimsy? Do. Do. I suspect it has never been easier than it is now, what with good quality kits and components from Mike Williams Models, Walsall Model industries, Slaters and no doubt others. A quick wagon kit needn't lead to anything else of course.
  18. mickoo

    mickoo Western Thunderer

    You don't know me very well then LOL, a whimsey for me would not be a 'wagon' more like a SAR 25NC, C&O H7 or UP Challenger :eek: I like 'big' engines.

    But, I have to confess these photos took me by surprise.

    Firstly this which I have coveted for a long time.

    And recently I happanced across this scene.

    I also have a massive soft spot for Welsh Slate mine Saddle tanks
  19. jamiepage

    jamiepage Western Thunderer

    Then this may do? A beautiful 1/24 line drawing of The Penn GG1
  20. mickoo

    mickoo Western Thunderer

    You know me better than I thought!!!

    PRR GG1's are the dogs danglies, their T1 and J1 are no slouches either!....must resist the dark side :headbang:.

    All are massive in 7mm but G3, they'd be something special, even as mantelpiece queens :thumbs:

    That's a very nice drawing, where did you source it from please?