2 mm Finescale loco chassis

[keidal]

I have tried to make sense of the various dimensions / tolerances etc on the 2 mm Society's suggested loco chassis page - and I'm struggling !

 

I am hoping to have a go at making a model of a Highland Railway Small Ben loco.

 

If I use 0.010" Nickel silver for the chassis frames, together with the Society's wheels / axles and insulating muffs, could someone please tell me what I should make the overall width of the chassis ? The loco would not be expected to to negotiate tight radius curves.

 

Is the 9/16 Mashima motor supplied by the Society, a suitable motor for using in the tender and possibly using a flexible shaft [incorporating gears] below fall-plate level ? A shaft above this level looks a bit awkward for the driver and the fireman to negotiate !

What gearing would be appropriate for the 6' 0" driving wheels please ?

 

Any help would be greatly appreciated - thank you.

[Orange Cat]

From the dimensions on the web site I make it that the chassis should be a maximum of 7.3mm overall. I stand to be corrected.

Looking at the useful page on motors and gear ratios on the EM Gauge Society's website I would suggest a ratio in the order of 50:1 would be appropriate with the Mashima motor. I would tend on the higher side of that figure as you want the loco to be able to pull a decent train along.

Looking at the dimensions on that page and making a quick comparison with the drawing in Peter Tatlow's book it looks as if that motor would just fit into the coal space of the Small Ben tender if you don't mind having a full load of coal to hide it with. 

[nick_bastable]

From the dimensions on the web site I make it that the chassis should be a maximum of 7.3mm overall. I stand to be corrected.

 

Looking at the useful page on motors and gear ratios on the EM Gauge Society's website I would suggest a ratio in the order of 50:1 would be appropriate with the Mashima motor. I would tend on the higher side of that figure as you want the loco to be able to pull a decent train along.

 

Looking at the dimensions on that page and making a quick comparison with the drawing in Peter Tatlow's book it looks as if that motor would just fit into the coal space of the Small Ben tender if you don't mind having a full load of coal to hide it with. 

topic should be moved  to the 2mm area lots of help there

 

Nick

[queensquare]

Bit confused as to why you have posted this in the DCC section and not the 2FS area.

 

Overall width of chassis around 7.5mm would be fine.

 

For 6' drivers the simplest gearing would be single stage 38:1 on the driven axle. You can arrange gearing to go below the footplate if you want, some Association members such as Jim Watt do this to great effect although personally I don't bother. A straight shaft between loco and tender is much simpler and all but invisible. The crew are plastic/metal and don't seem to mind!

 

There are much better, and smaller motors than the Mashima 9/16 available now such as the Nigel Lawton 8/16 or the 7mm Coreless that Farish use in their latest models.

 

Jerry

[Andy Y]

Now moved.

[keidal]

Thank you for all this information, which is greatly appreciated.

I have had a look at Nigel Lawton's motors etc and these look very promising.

My intention is to model the HR Achanalt station which is very small and very basic, near Garve [ Dingwall - Kyle of Lochalsh ]. It has two platforms on the single line incorporating a passing loop and a single siding. It did originally have a signal box though.

The Small Ben 4-4-0 loco was used on this line and because presumably it would only have 2 or 3 coaches [Lochgorm Kits ?, great hauling power and speed are not required.

I'm thinking that a gearing of at least 60 :1 would be adequate for such a loco to trundle along a single track. How I could achieve this sort of ratio or lower using the 2 mm Association's products, I'm not certain.

If I achieved building a 2mm scale Small Ben loco, this would encourage me to have a go at a HR Barney 0-6-0 goods loco complete with an 8 wheel tender.

One problem however is that the wheelbase of both locos includes a 9' 0" section and I'm wondering if I could butcher / splice someone's etched coupling rods ?  

[Orange Cat]

 

One problem however is that the wheelbase of both locos includes a 9' 0" section and I'm wondering if I could butcher / splice someone's etched coupling rods ?  

 

The 9' section isn't a problem as the 2mm Scale Association's coupling rod etch has a 16+18mm one on the sheet. (Cut off the 16mm bit for the Small Ben) but the Barney needs 15+18mm and there's not a 15mm spacing on the sheet. I don't know what the spacings on the replacements for the Farish and Dapol locos are. 

 

For your gearing, and the way you plan to do it, I would drop down to below the footplate with a reduction, then a similar reduction to take the drive above the axle and a worm on the driven axle. I prefer a higher ratio and the shaft out of sight too. If Association gears won't fit then have a look here there's something that will work in that range. They also have small motors. 

[queensquare]

The 9' section isn't a problem as the 2mm Scale Association's coupling rod etch has a 16+18mm one on the sheet. (Cut off the 16mm bit for the Small Ben) but the Barney needs 15+18mm and there's not a 15mm spacing on the sheet. I don't know what the spacings on the replacements for the Farish and Dapol locos are. 

 

For your gearing, and the way you plan to do it, I would drop down to below the footplate with a reduction, then a similar reduction to take the drive above the axle and a worm on the driven axle. I prefer a higher ratio and the shaft out of sight too. If Association gears won't fit then have a look here there's something that will work in that range. They also have small motors. 

 

You can follow this route if you wish but its far more complex than is neccesary, particularly if this is your first loco in 2FS. A 9 or 10 thou drive shaft is all but invisible and 60;1 a much higher ratio than is needed for a passenger loco. My MR and SDJR 4-4-0s and my 0-4-4-T all use the 100DP 38;1 gearset that the Association shop used to sell (still available from Ultrascale) as do John Greenwoods T9s and K11 - all are perfectly controllable down to a crawl.

 

Jerry

[Caley Jim]

Looking at the useful page on motors and gear ratios on the EM Gauge Society's website I would suggest a ratio in the order of 50:1 would be appropriate with the Mashima motor. I would tend on the higher side of that figure as you want the loco to be able to pull a decent train along.

 

I wouldn't worry too much abut getting a high gearing.  The haulage capacity of small locos such as the Small Ben is more likely to be limited by it's adhesive weight than by the power of the motor or the gear ratios, in my experience.

 

If you do decide to go down the route of dropping the drive down below the footplate, at the loco end, put the worm in the bottom of the firebox with the wormwheel above it, then have a lay gear between that and the drive gear on the axle, Thus:

 

 

This my arrangement for a Crewe type 7ft 2-4-0 with a 4 wheeled tender.  The motor is a Faulhaber 0816.  The driveshaft had to be angled downwards slightly to go under the rear coupled axle, but on something like the Ben it should be possible to run it between the axle and the footplate.

 

Jim

 

Edited for typo.

[keidal]

This is all fascinating to a 2mm scale complete novice !

Just throwing ideas around, has anyone been able to fit the motor in the loco somehow [partly down the boiler tube ?] and have a drive shaft back to the tender with gears on one or possibly two [or even three axles ?] and some lead for good measure.

Re. the 9' 0" coupling rods, the Association's 16 + 18 mm etchings unfortunately have the "joint" in the 18 mm portion.

I'm not sure what DP stands for, or how to calculate gear ratios ?

Is there a favourite controller to use successfully with these high revving small motors and relatively high gear ratios please ?

Thank you all very much.

[Orange Cat]

 

Re. the 9' 0" coupling rods, the Association's 16 + 18 mm etchings unfortunately have the "joint" in the 18 mm portion.

I'm not sure what DP stands for, or how to calculate gear ratios ?

 

 

Can you simply file the joint off. The Small Ben has plain rods so you will be using them with the fluting on the insides anyway and the joint detail won't be seen. Could you file them flat, top and bottom? Alternatively fold a bit of Nickel Silver sheet in two, drill two small holes 18mm apart and cut and file to shape. It is very easy to get caught up in the way of thinking that because something is widely available, then you are stuck if it doesn't happen to be available in the form you need. If you can scratch build a loco, coupling rods are one of the simpler tasks.

 

DP is basically an imperial measure of the size of teeth a gear has. It stands for Diametral Pitch and refers to the number of teeth per inch of diameter. The Association has (while stocks last, apparently) 100DP and 64DP gears. A one inch diameter 64DP gear wheel would have 64 teeth, while the same diameter 100DP gear wheel would have 100 teeth, so the 100DP gear has "finer" teeth than the 64DP one. The metric equivalent is Mod or Module which is the pitch diameter, in millimetres, of the gear divided by the number of teeth on the gear. The "coarser" gears are, in theory, easier to mesh but the finer ones take up less space for the same reduction. 

 

Gear ratio is the ratio of the input speed of a gear train relative to the output speed. For example if you had a 12 tooth gear on the input shaft (say the motor in the tender) driving an 18 tooth output gear (on the shaft to the loco) then for every 18 revolutions of the input gear the output gear would turn 12 revolutions, so the ratio is 18:12 or 1.5:1. Each time you add a pair of gears on the train then you multiply the ratio. For example if you then drove a 38:1 worm gear from that output shaft the total ratio would be (38 x 1.5):1 or 57:1. If you put another 12 x 18 reduction in the train (say, to lift the drive to the worm above the driven axle) you would then have an overall ration of (38 x 1.5 x 1.5):1 or 85.5:1. Basically to calculate the ratio of the drive train divide the number of teeth on the output gear by the number of teeth on the input. Do that for each pair of gears in the gear train and then multiply the results of the pairs of gears to get the overall ratio.

 

Note that intermediate gears don't affect the ratio, so if you were to put a third gear between the 12 tooth input gear and the 18 tooth output gear, the ratio would remain the same regardless of the number of teeth of the intermediate gear.

[keidal]

Thank you for taking all this trouble to show this doddery old geezer how to do things - I'm most grateful.

I had found this on the 'net in the meantime and it did make some sense :-

Spur Gear Terms and Concepts - Gears Educational

[keidal]

Is there a stockist in the UK for the Faulhaber 0816 motor please ?

[queensquare]

Is there a stockist in the UK for the Faulhaber 0816 motor please ?

 

Yes Brian at Branchlines stocks them - no website but phone number and email can be found on UK Modelshops. Be warned, they are over £40 a pop these days. The 8/16 coreless motor that Nigel Lawton  sells is excellent and only £6.50. I can also recommend the Farish 7mm coreless motor, available from them as spares for around £15

 

Jerry

[Orange Cat]

You can also get a very nice Maxon 8mm diameter motor, and if you think the Faulhauber is expensive... Although if you buy 20+ the price comes down a bit. They are also shipped from the factory in Switzerland so you have to pay VAT and Post Office processing charges on top. Very nice motor, though, if you feel you want to indulge. It's a smaller diameter version of the 10mm one that is out of stock in the Association shop.

 

[DLT]

You can follow this route if you wish but its far more complex than is neccesary, particularly if this is your first loco in 2FS. A 9 or 10 thou drive shaft is all but invisible and 60;1 a much higher ratio than is needed for a passenger loco. My MR and SDJR 4-4-0s and my 0-4-4-T all use the 100DP 38;1 gearset that the Association shop used to sell (still available from Ultrascale) as do John Greenwoods T9s and K11 - all are perfectly controllable down to a crawl.

 

Jerry

 

I can vouch for the fact that Jerry's locos run beautifully, like the proverbial "Swiss Watch".

Dave.

[keidal]

Having spent several hours drawing options for putting the motor and gears in the firebox, rather than in the tender, I came to the conclusion that using a 6mm x 10mm long can motor and a 38:1 direct drive as suggested, I would order the necessary items from the 2mm Association.

I had referred to the Gear Data Tables on page 26 in the 2016 Yearbook, which I received a few days ago.

Now the real problem starts or I'm going bonkers ? After all, I'm 80+ years and nothing would surprise me.

Under Dimensions of Association Worm Gear Sets, the reference number for the 38:1 gear set is 3-363.

Looking at the Shop 3 Price list on page 40,  reference number 3-363 is a Gear Set MO.25 21:1 item and no mention of a 38:i Gear Set !

Back to the drawing board.

[Yorkshire Square]

See Jerry's post above. The Association started moving to metric gears over two years ago. The 100DP 38:1 gearset is still available from Ultrascale. A metric version is available via Mikroantreib, the Polish manufacturer of our metric gears; they are easily Googled.

[Llangerisech]

Having spent several hours drawing options for putting the motor and gears in the firebox, rather than in the tender, I came to the conclusion that using a 6mm x 10mm long can motor and a 38:1 direct drive as suggested, I would order the necessary items from the 2mm Association.

I had referred to the Gear Data Tables on page 26 in the 2016 Yearbook, which I received a few days ago.

Now the real problem starts or I'm going bonkers ? After all, I'm 80+ years and nothing would surprise me.

Under Dimensions of Association Worm Gear Sets, the reference number for the 38:1 gear set is 3-363.

Looking at the Shop 3 Price list on page 40,  reference number 3-363 is a Gear Set MO.25 21:1 item and no mention of a 38:i Gear Set !

Back to the drawing board.

Hi,

 

As Jerry has said, the 38:1 used to be sold by the Association but isn't any more. The main option now is the 30:1 Metric gear. The 38:1 is available from Ultrascale but will require the stepped gear muff to allow the imperial bore of the worm gear set to also use the metric MO range for subsequent drive gears. If you use the 30:1 set from the Association shop, that is metric and can use a standard gear muff with other gears.

 

All this happened a couple of years back when gear supplies had to go metric to get decent prices. We even had to re-design kits around the new range of gears after starting with imperial standards. The 30:1 gear is of course smaller, but you can use it with something like a 14tooth and 22 tooth reduction and get around the 40: overall reduction. Any of the coreless motors mentioned should be fine with that.

 

Best to use the on line listing for shops now as keeping the yearbook up to date was a problem. Unfortunately, the gear tables are correct in that they refer to the old numbers for the imperial gears, but of course you have to look at the metric gear tables for the stuff that is currently available. The 30:1 centres however are the same for the metric version. I think it is an area for review in the next year book. Some folk may have old gears in stock in which case an old year book would be more appropriate. I will feed this back via the committee.

 

We want to encourage new members, not confuse them, but I think it's managed it here! You are not going mad. Try to re-work things around the 30:1, but if that doesn't fly, go to Ultrascale and mix and match. Their turn round time can be really quick or really long depending on stock levels of the batches produced.

 

Best of luck

Nigel

[keidal]

That is so kind of you all to take the considerable trouble to explain in simple terms, the current position re gears etc - and that is greatly appreciated because I've no engineering background at all. I am keen to really have a go at 2 mm modelling while the eyesight is willing !

 

I'd had a look at Ultrascale's site and was impressed with their gears, but when I saw delivery times mentioned I scurried off.

 

Just two probably obvious questions - do the various gears have grub screws to fix them in place or should I use some sort of adhesive / Loctite please ?

 

Is it possible with a long tender to place a motor [hopefully with a shaft at both ends] say centrally on the wheel base and drive the outer pairs of wheels, if muffs are available for fixing gears to their axles ? I've no idea if such a motor exists which would fit in a tender [just above the centre axle perhaps] ?

 

I'm determined to make this happen and hopefully use 0.005" brass for the body !

 

Thanks once again.

 

Keith   [ O7 Kits from decades ago ! ]

[Nigelcliffe]

Keith - fix metal gears with Loctite (or similar).  Plastic gears are best with grip fix.    

And one important tip (which I must get round to putting on the website) -  the metal gears need to be de-burred before use.  This is done with a few strokes of a **very** fine file (read the article on the 2mm website on files) or piece of folded fine wet&dry abrasive paper, on all corners of each tooth.   The burrs can be seen and felt on the edges of each tooth, one might need good magnification to see it, but its present. The size of burr is pot-luck from manufacture.  With worm-sets, removing the burr is critical, if the worm engages at the edge of the worm-wheel, the burr will cut into the worm and destroy it fairly quickly.   

 

 

When the metric wormsets were introduced, I went to some lengths to get the same centres as the imperial versions.   This was done by adjusting the worm diameter to deal with the slight difference in worm-wheel diameter between imperial and metric sizes.   Its not a perfect match because the data for the imperial wormsets is internally inconsistent - somewhere there is an error in the dimensions when one takes it back to theoretical gear centre sizes. 

I can't remember whether the 38:1 worm-wheel is beyond the production sizes at our Polish manufacturer, possibly when the next round of stock is required the shop or product officer could enquire. 

 

The course metric spur gears (M0.4) are near enough same centres as the course imperial (64DP) gears, certainly within the distances which a hand-hewn chassis would need to allow for drifting gear alignment.   The finer metric gears (M0.3) are totally different to the fine imperial (100DP) - we'd need a different metric design, such as M0.25 to be a close equivalent to imperial 100DP.   KKPMO in Poland list vastly more gears than the Association stocks, including M0.25, M0.2 and other sizes requiring very high levels of precision in meshing. 

 

My emails on metric wormset production are all 2012, so four years ago when the switch was made.  The changes to metric spur gears was from 2010 onwards, so six years ago.

 

 

- Nigel   (now retired from gear sourcing )

[JohnBS]

Hello Keith,

Welcome.

Concerning the last points in your email of this morning, I think that 0.005" brass is too thin. I use 0.010 hard brass or, preferably, nickel silver, both of which are readily available, around a heavier-gauge structural box.

It may be possible to drive the front and back axles of a long-wheelbase tender but the big problem would be adhesion weight, or rather lack of it. There just won't be enough space to pack with enough lead (and depleted uranium is a bit difficult to obtain). That is why most scratch built tender locos, and even Dapol proprietary ones, transfer the drive from a tender-mounted motor to the loco which is packed with as much weight as possible (suitable balanced). The drive shaft doesn't have to be a great big lump of plastic or metal but just a dumbbell-shaped piece of piano wire or guitar string, housed in slotted sleeves at either end. As such, it is pretty well invisible in use, particularly if chemically blackened.

Best wishes,

John

[keidal]

Thank you for all this invaluable information.

For some unknown reason, i have a calling to produce a 2 mm scale model of Achanalt station and approaches [on the Highland Railway] and as it was in the early 20c. before it was decimated, sorry modernized relatively recently.

This is why I'm determined to build a 4-4-0 Small Ben loco and then who knows, possibly an 0-6-0 Barney goods loco.

The station building was rudimentary to say the least, it's on a single line with a passing loop serving two platforms. There was one siding, a signal box and with the local Post Office was on one platform.

Fortunately Lochgorm Kits produces a couple of coach kits in 2 mm scale, so that's an added incentive and Worsley Works produces a basic Barney kit.

So that's my programme for the next few months.

Can anyone please tell me the normal thickness of boiler cleading / cladding - I'm assuming it's about 2 1/2" ? Also the sectional dimensions of coupling rods, because single etched rods don't look right to my eyes ?

[Caley Jim]

If you are a member of the Highland Railway Association, contact Alisdair Campbell, a 2MM SA member, who is the drawings archivist. He should be able to give you the details off GA drawings. I'm pretty sure they will be similar to CR ones, but I'm not at home at the moment. I'll have a look for you later. I could also send you the drawing I did for the chassis of my CR Jumbo, which will be very similar to the Barney, though with beam compensation it might be a bit complex for a first loco. I would agree that a driven tender is not a good idea. It's hard enough to get adhesive weight in a small loco, never mind in a tender. Remember that with a driven tender the loco becomes 'train weight' and with the coupled wheels is not particularly free running. This may not be relevant in the larger scales, but becomes significant in 2FS.

 

Jim

 

Edited for typos

[Caley Jim]

Now back home and had a chance to look at the GA drawing for the Jumbo.

 

Boiler given as 4'4" inside plates; 4'9½" over cladding.   Unfortunately the coupling rods are only shown in the sectional plan view and are not dimensioned, nor can I find any dimensions quoted in Campbell Cornwell's book on the class.  If it's any help, i made mine 1mm deep by c0.5mm thick.  I say c0.5 as they were filed from 30thou steel strip (an old hacksaw blade) and thinned down to just over half thickness except at the bosses.  They look OK to me.  How precise do you need to be with the dimensions of these in 2mm scale?

 

HTH,

 

Jim