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A small problem??.now in the paintshop


burgundy

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I have been presented with one of those “interesting challenges” – in the shape of some components for a small 4mm scale tank engine. I should like to motorise it – obviously – but the problem is that there does not seem to be much space for a drive train. With my 4mm scale mindset, I am struggling to see where to fit a motor and gearbox, but I rather hope that someone who models in 2 or 3 mm scale will come back to point out how there is loads of space – if only you know how to use it.

The loco in question looks a bit like the one illustrated here – post-9472-0-45383000-1351714651_thumb.jpg
only a bit smaller. The prototype is a “Sharpie”, a standard product of Sharp Roberts throughout the 1840s, and delivered in increasing sizes as the decade progressed. The illustration shows one of the larger ones, with a 10’ long boiler, whereas earlier ones (like the one I am dealing with) had an 8’ boiler, with an equivalent reduction in the spacing between the driving and trailing axles. This one (and my intended model) had been converted from tender locos into 2-2-2 well tanks.

As far as I can see, there seem to be two possible ways to fit a motor and gearbox. One is to install a motor in the boiler, with the gearbox hanging downwards: the other has the motor standing upright in the firebox, with the gearbox protruding forwards.

The space available in the set of castings is somewhat limited. The boiler has an internal diameter of 11mm (you would need to grease the sides of an 11mm can motor to get it to fit), by 32mm long. The firebox is 12mm front to back, 14mm wide and about 14mm tall (with a curved top). This seems to preclude the normal range of motors to which 4mm scale modellers are accustomed – hence my invitation to those who are used to managing smaller spaces. I am not looking for huge haulage power, but the ability to pull the skin off a lightly cooked rice pudding would be nice.

Additional points will be awarded to those who can figure out how to include a DCC chip and a set of speakers (although I have no intention of doing so!).

Any suggestions would be very welcome.
Best wishes
Eric

post-9472-0-45383000-1351714651_thumb.jpg

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ISTR someone - Ross Pochin? - building a 2-2-2 which cheated prodigiously by powering the leading and trailing axles instead of the drivers, the motor straddling the unpowered driving axle. Such a ploy would probably meet or exceed the rice-pudding requirement.

 

I assume the loco in question is one of the LBSCR pool Sharpies, maybe 42-44?

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Thanks for the comments.

The loco illustrated is one of the batch delivered in early 1849 by Sharp Brothers after the Pooling arrangement was finished and was converted to a tank engine in 1860. The components that I have acquired include a shorter boiler (8 foot long), implying that it is one of the "early Sharps" or "Intermediate Sharps" which, as Ian suggests, were delivered to the Joint Pool in the mid-1840s. If we are really being picky about the pedigree, I guess that it has to be Joint Committee No 88, later Brighton No 50, which, according to Bradley, was the only one of this lot to be converted to a tank engine (in 1851) and was sold to the Colne Valley Railway 9 years later. However, I confess that I was led astray by the availablity of the components and have not looked too closely for the exact historical prototype :secret: .

Reverting to the model, I can also remember the Furness single tank that Ross Pochin built - although I had forgotten that the drive was on the leading and trailing wheels (someone also did a Stroudley Single like that). The significant flaw in this argument is that I am not Ross Pochin and I rather doubt that I could fit all the necessary plumbing into the space available! In fact, I am not sure that there is the space for a 1015 flat can motor, as the rounded bits of the can measure a whopping 12mm, which will be too large for the boiler - although it might just squeeze into the firebox. I had been wondering about some of the products mentioned here, which seemed to offer some even smaller motors - although I should be interested to know whether they would pass the rice pudding test. If anyone has experience of any of these, I should very much like to hear.

Again, many thanks for the suggestions.

Best wishes

Eric

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A 1015 will fit in a 11mm diameter boiler no bother. I'm expecting to power my J79 with one and that's probably slightly under 11mm. A 1015 plus highlevel gearbox is 22mm long by 10mm wide (hence the 1015 ;) ) so it would extend 10mm into your boiler - although you can probably squeeze a bit more length out of the firebox hollowing the backhead.

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Thanks to all for the further comments.

In the light of Katier's data on the dimensions of the combination of a 1015 and a HighLevel gearbox, I had another go at seeing whether this could be squeezed in. The critical dimensions appear to be from the driving axle to the back of the firebox and from the driving axle to the top of the firebox. Both appear to come out at about 19mm. There are none of these new fangled cabs or side tanks for hiding stray bits of motor or gearbox, so there is no alternative to trying to stay within the dimensions of the boiler and firebox. As an aside, I also checked the dimensions of the 1020 flat can that I have for another project and confirmed that the rounded dimension (i.e. not the flat bit of the can) comes out at slightly over 12mm, so, unless there is a 1020 true can motor that I have overlooked, I am not clear how this would fit into an 11mm diameter boiler.

That gets me back to looking for more exotic motors and my thanks to Penlan for pointing out the CLAG website. This in turn led me to Nigel Lawton's site which offers some interesting further options. I will see where this takes me.

Best wishes

Eric

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Oh and regarding the motor/boiler relationship - Good point - only thought it are the splashers standalone or do they touch the boiler. Then certainly appear plenty big enough to hide a slot in the motor.

 

Another thought is to enlarge the boiler by 1mm. Hardly noticeable and gives more room to play with.

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Eric

 

I don't know if this helps, but I have tried to superimpose the data for the Horizontal Micromiser from High Level's excellent planning sheet on the drawing you provided, and it looks as if it might fit, apart from having to hide a cut out in the boiler behind the driving wheels, as I assume that the bottom of the firebox is roughly straight sided to accommodate the grate. The HL drawing seems to use a 1020 motor, so a 1015 Mashima would probably fit into the shorter driver to firebox dimension for the smaller Sharp.

post-189-0-64439700-1351808685_thumb.jpg

As for how to fit a decoder, not that you sound serious about it at the moment, a small one would fit in the smokebox, although I have a cunning plan which might make it easy to fit decoders into small locos, but I need to do more work on the idea to see whether it is practical before going public.

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Branchlines at the Manchester show had a new tram style enclosed gearbox. A bit like the old 17:1 thing I used in the Drewry railcar. That drives 8mm dia wheels so I wonder if you could use 2 of them, one on each of the front & rear axles with either an extended or articulated drive shaft?

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Many thanks to those who have added further ideas to this thread.

Katier and Nick H have both caused me to keep fiddling around with the idea of a 1015 and HighLevel gearbox. As Nick has demonstrated in his overlay, the combination more or less fits on the large Sharpie. (As an aside, I assume that the HighLevel overlay shows a sort of composite motor attached to their gearboxes. If I understand it correctly, the longer part is the outline of a 1020 and the shorter dumpier part measures out as about 14mm wide by 15 mm long, so it is more or less possible to work out where a 1015 would fit.)

However, the pieces that I have acquired are for a rather earlier and smaller loco on which the firebox reaches almost to the driving axle (note the arc on the front of the firebox casting). The photo below, grabbed between downpours this morning, shows the assorted pieces, laid out in more or less the right order.

post-9472-0-96185000-1351858824_thumb.jpg

The motor which is included for comparison is a 1020, which is waiting to be used on another project.

Ullypug's suggestion comes back to the idea of driving both the carrying axles and I may have to come back to this one. Possibly when the NWSEMGSAG next meets at Schloss Ullypug, I shall be looking for a tutorial on articulated driveshafts! Do Branchlines still have a website? The last thing I can find is the farewell blog from Andy Mullins which was written about 4 years ago.

Again, thanks for all the helpful suggestions.

Best wishes

Eric

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Rather then the Nigel Lawson motors try looking for a maxon motor. Maxon Motors are good quality but not cheap the 2mmSA sell the RE10 (16x10dia to members only) at £35. They were also selling an 8x10x16long flat can but I haven't tried it yet. Might be worth looking at the Maxon site.

Mind you if you like little locos the best advice would be to go 7mm Brian of ABC can provide motor gearboxes to suit most combinations and they are really good.

 

Don

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If it's an etched chassis, then a LRM single stage 38:1 or 50:1motormount with a Mashima 1020 or 1024 flatcan, with the motor underslung might suit with the motor in the ashpan. The attached shows a 1224 in a set of P4 frames for an LNWR Coal Tank with 4' 8" (19mm) wheels. The 10xx series will normally fit within 00 frames without a problem.

 

post-1191-0-88055200-1351934338_thumb.jpg

 

You can download an outline here.

 

http://www.scalefour...motormounts.pdf

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Thanks for all the further suggestions, which have been causing me to ponder over the weekend. They also caused me to do what I should have done at the outset - which was to sketch out the actual dimensions of the castings.

post-9472-0-92357400-1352235460_thumb.jpg

 

Apologies for the slightly crude drawing, which has been scanned from a full A4 sized sheet (and so should be easy to print if anyone is so minded).

I cannot be sure that my drawing is particularly accurate, but, playing with the HighLevel gearbox overlay, the only permutation which comes close to fitting is a 1015 motor mounted vertically in the firebox, with the gearbox sitting horizontally. Even here, the length of the motor seems to exceed the top of the inside of the firebox!

This is causing me to look again at the various axle hung motors that the CLAG website illustrates. Bill B has pointed out that there are no fixing points for the 16x8 motor, but does anyone by chance do mounting etches for these motors?

I did look at the Maxon website, but I must confess that it made my brain hurt when I tried to sort out the right permutation of size and voltage! :scratchhead:

I take LNW's point about dropping the motor down between the frames but I don't think that that option will help in this case (see comments about length above). However, the 12 wheeled carriage in the background does look rather nice!

Again, thanks for all the suggestions

Best wishes

Eric

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Another source of small-ish motors are the 5-pole skew wound units which Finney & Smith sell to 3mm scale modellers. They are an approximate replacement for the old Fleischmann N-gauge motor, and come in three lengths. Perhaps regard them as "slightly smaller than Mashima" options, whereas the Lawton and small Maxons are considerably lower torque and power.

 

- Nigel

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if you chose to go down the 'drive the carrying axles' route, could the 'faux driving' wheels mount on stub axles, leaving space for the motor between them

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