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keidal

2 mm Finescale loco chassis

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Can someone please tell me if the two can motors are back to back, rather than nose to tail as it were - can they still be wired in series to give each motor 6 volts and for the output shafts to be rotating in the same direction at the same time ? Or is there some jiggery-pokey with the positive and negative tails supplied with the motors please ?

If the two motors are back to back, then the shafts need to rotate in opposite directions (when viewed from the front of each motor), i.e. one motor running forwards and one in reverse.  This means the current needs to be flowing in opposite directions in each motor so the red lead of one motor needs to be connected to the red lead of the other and then each of the two black leads connected to one of the frames (or the other way round).  If the two are nose to tail, then one black lead is connected to the red of the other, with the other leads connected to a frame each.  If you find that the loco runs in reverse when you set it to run forwards, then swap the leads to the frames.

 

HTH,

 

Jim

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Or, it could be like a Webb 'Greater Britain' and have wheels going in opposite directions!

 

Tim

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The 2mm Association shop sells loco driving wheels as small as 7mm diameter. If I build a small industrial 0-6-0T loco with 7mm drivers how does it know it is a loco and not a six wheel powered tender? Or will such a loco not pull anything either?

 

It won't pull much, but as an Industrial loco it isn't expected to. A large passenger loco with a tender is going to have to pull more, not to mention pushing the loco itself along before adding any real stock.

 

There is soneone who models steam tender locos by using Dapol Terrier chassis as tender drives, That loco certainly doesn't know exactly what it is!

 

My experiments with the Farish tenders did show you need to retain the traction tyres, and get the loco itself very free running, but also I have since noted that Tim Watson and Bill Blackburn both (I believe) replaced the Farish motor with a low-revving can motor and this produced a much sweeter running mechanism. And don't forget there are Fleischmann tender drives out there that will pull more wagons than most of us could ever dream of owning. With traction tyres, naturally. I have been the proud owner of such a 2-10-0 for nearly fifty years now, which will out-pull anything Farish or Dapol have ever produced. People do retro-fit these with coreless motors and a replacement worm that doubles the gear ratio.

 

http://www.sb-modellbau.com/product_info.php?products_id=257&cPath=254_80_198

 

It would be possible perhaps to ignore the Association wheel range, buy some N gauge diesel wheels with traction tyres and have them turned down to 2FS.

 

All tender drives do suffer from a common weakness. Any dirt or oil that gets into the loco wheel bearings will cause them to skid, as they are not being driven. This both looks awful, and increases the friction that the tender drive has to overcome.

 

I have to say the mind boggles at motorising a bogie tender with what is in effect a very small diesel. Very few people scratch build diesels and with good reason. Certainly not what I would choose for my first foray into 2FS.

 

Chris

Edited by Chris Higgs

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So long as the brushes are both insulated from the motor frame there would be no problems. I remember my old Triang Jinty had a return path through the motor frame which would have been a problem.

I suspect most twin motored locos are wired in parallel using 12v motors. If you were to wire the two 6 volt motors in parallel it would work but you would be using only part of the controller range so wiring in series should work well with 6v motors. Which way the motors spin for the loco to go in the same direction depends on their orientation in the model so you have to connect the appropriate tags together.

 

Don 

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I am not hell-bent on tender drive or even putting a motor in it to drive the two coupled driving wheels, but there isn't a lot of space in the Small Ben's round-topped firebox.

The loco will be expected / required to pull a maximum five coaches.

There is relatively a lot of space in the 8 wheel tender and it is my intention to attempt to drive the four axles with gearing and not belts. I am investigating a] whether there's a suitable motor with a shaft at both ends, b] whether I can fit two decent sized motors - one for each bogie or, c] use four smaller 6v motors, in pairs side by side with each one driving an axle.

Whatever space is not used, it will be occupied with lead and some photographs show these locos with a good heap of coal on top. 

This is a pure "can it be done by me" exercise and if in my opinion it proves to be a nonsense, then I will revert to the firebox site for a single motor and reduction gearing.

Back to the drawing board.

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Smaller motors - I would look at the torque figures for the smaller motors.   Its a while since I did a thorough survey, but I recall that changing from a Faulhaber 10mm dia to 8mm dia halved the available torque.  So, a small change in diameter and the motor pulls half what it did with the larger version.    I'd expect a drop from 8mm to 6mm to be even greater (bigger drop in relative rota swept area).  Then add the annoyance that worm drives consume a lot of power through friction, and the small motor, even in multiple copies, might not be a good idea.    
If you can arrange a gearbox which is just spur gears (no worms) then the losses can be much lower: there was an interesting article in a recent 3mm Society magazine issue on off-the-shelf motor-gearbox sets with phenomenal output torque, but whilst they'll fit in a 3mm scale loco they are a little too big for most 2mm uses.    

 

Making the 8-wheel tender run.  There are two ways to make an 8-wheel tender, either as a rigid 8-wheel, or two four wheel bogies.  The former is a lot simpler, just a lot of gears driving things, its effectively, two of my DY1 chassis back-to-back (see 2mm website or magazine backnumbers).   Two four-wheel bogies introduces lots of issues around articulation which are found when scratchbuilding small Bo-Bo diesels, can be done but a lot of work. 

 

Keidal says "not much space" in the Small Ben round-topped firebox.  I wonder how much space is actually needed ?  Given the big tender, there is scope for a spur gear reduction before the output shaft if that's really needed (doubt it is needed), achieving as much as 3:1 in the tender.  The loco probably only needs a worm+wheel, and probably a final spur drive onto the forward driven axle.  The wormwheel can be behind the driven axle, raised very slightly, but its axle probably in line with footplate.  Then worm above that.   All very conventional and not taking up that much space. 

 

I'm sure a tender drive can be done,  if its a rigid 8-wheel then its not overly difficult, just a lot of spur gears.   But I'd expect a tender drive plus non-binding push-along loco will be more work than the regular motor in tender, driving the loco wheels.  

 

 

 

- Nigel

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I am not hell-bent on tender drive or even putting a motor in it to drive the two coupled driving wheels, but there isn't a lot of space in the Small Ben's round-topped firebox.

The loco will be expected / required to pull a maximum five coaches.

There is relatively a lot of space in the 8 wheel tender and it is my intention to attempt to drive the four axles with gearing and not belts. I am investigating a] whether there's a suitable motor with a shaft at both ends, b] whether I can fit two decent sized motors - one for each bogie or, c] use four smaller 6v motors, in pairs side by side with each one driving an axle.

Whatever space is not used, it will be occupied with lead and some photographs show these locos with a good heap of coal on top. 

This is a pure "can it be done by me" exercise and if in my opinion it proves to be a nonsense, then I will revert to the firebox site for a single motor and reduction gearing.

Back to the drawing board.

 

The 'standard' 2mm method of motor in tender with drive shaft to gearing in loco maximises the amount of space available, over any other methods where the whole mechnaism has to be fitted into either loco alone or tender alone. I seriously cannot imagine any tender - of a British prototype at least - that would have space for four motors that could produce any sort of decent torque plus four sets of gearing. Certainly my eyseight and dexterity would not be up to assembling such tiny components as would be required.

 

There are plenty of double-ended motors around, although typically not coreless. Coreless must exist I think, as DJ Models plan to use them in their upcoming diesels.

 

Regardless of drive style, 4-4-0s are tricky beasts to balance and might require the front of the tender bearing onto the loco to add weight. If you go for tender drive, consider how much weight you will need in the loco to make it run OK, and factor that into what your tender is going to have push along.

 

Chris

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I am not hell-bent on tender drive or even putting a motor in it to drive the two coupled driving wheels, but there isn't a lot of space in the Small Ben's round-topped firebox.

The loco will be expected / required to pull a maximum five coaches.

There is relatively a lot of space in the 8 wheel tender and it is my intention to attempt to drive the four axles with gearing and not belts. I am investigating a] whether there's a suitable motor with a shaft at both ends, b] whether I can fit two decent sized motors - one for each bogie or, c] use four smaller 6v motors, in pairs side by side with each one driving an axle.

Whatever space is not used, it will be occupied with lead and some photographs show these locos with a good heap of coal on top. 

This is a pure "can it be done by me" exercise and if in my opinion it proves to be a nonsense, then I will revert to the firebox site for a single motor and reduction gearing.

Back to the drawing board.

Hello Keidal,

 

I'm not sure if the comments below are of any use but I though I'd post them anyway.

 

I've attached a few pics of an 8 wheel tender I made recently. This uses the simple tender mounted drive to a 'gearbox' in the firebox. The motor is an Association flat can with a shaft at each end. As you can see from the first pic, the centrelines of the motor shafts are well above the tender wheels and how you'd connect the motor shafts to the wheels is somewhat problematic, though I'm not saying something couldn't be schemed out.

post-12813-0-72142400-1482919363_thumb.jpg

 

The motor would need moving back to the middle of the tender wheelbase too, and the second pic shows the cover over the motor.

post-12813-0-24227000-1482919456_thumb.jpg

You can see that there is not much scope to move the motor back as the bulkhead gets in the way. It seems that there are soon a number of conflicting constraints surfacing! I suspect that this would be the case whatever prototype you chose, and I've certainly found that each loco I've built has a set of problems to work out, some unique to that loco, some fairly common to all. You can also probably judge from this pic that there is not as much room for adding weight as one might first have thought. There is not much available space when the connections from the motor shafts to the tender wheels are included (if such a system can be devised), and I suspect that would be the case for the tender you want to build.

 

So, I'm not saying some sort of tender drive can't be devised, but I think there will be numerous issues that will need sorting out. I think you will find that the foremost loco builders in the 2mm SA would recommend that you keep things simple, and for that reason I strongly recommend that you go for a tender mounted motor driving a 'gearbox' in the firebox, as recommended by Jerry. Here is a pic of a 4-4-0 chassis that I built, very similar to the one Jerry made for his Midland Belpaire.

post-12813-0-27158900-1482920621_thumb.jpg

 

(The motor is araldited to the tender chassis with a female u/j housing glued to the motor shaft.)

 

Seasons greetings to all.

 

Nigel Hunt

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I've attached a few pics of an 8 wheel tender I made recently. This uses the simple tender mounted drive to a 'gearbox' in the firebox. The motor is an Association flat can with a shaft at each end. As you can see from the first pic, the centrelines of the motor shafts are well above the tender wheels and how you'd connect the motor shafts to the wheels is somewhat problematic, though I'm not saying something couldn't be schemed out.

attachicon.gifL & Y 0-8-0 construction shots (15a).jpg

 

 

A typical design of a RTR tender drive is a worm on the end of the motor shaft, a spur gear train (2-4 gears) down to the front wheel and then a chain of gears along under the footplate to the other axles. A lot of gears in total. The Association Class 08 kit allows for all-wheel drive using a spur gear chain, but it meant the motor had to be pitched high up to clear them, something you cannot do in a tender, even with a mountain of coal.

 

If you do pitch the motor low down, beware of magnetic attraction between it and steel tender wheels, or just use solid brass wheels instead.

 

Making the bogies pivot is a lot more complex, needs something like a diesel drive, where a coarse pitch worm allows the gear under it to pivot. The motor has to be short enough to fit between the two bogie centres for this type of design.

 

Two motors plus in that tender - forget it.

 

Chris

Edited by Chris Higgs

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Jerry and Nigel H are two of the most prolific and able constructors of locomotives that I know of in 2FS. Even with their vast experience and skills they tend to adopt the simplest solutions wherever possible. If I was just starting out (or even as a member of thirty odd years) I'd be inclined to follow their guidance.

Edited by Yorkshire Square
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I would agree with this to some extent. I have a Farish tender drive BR Standard 4 2-6-0 which runs well and also a Union Mills conversion which, whilst crude, runs ok. However, what they all have in common is rubber bands traction tyres, The wheels have been skimmed to thin the flanges and the BtoB opened out to run on 2FS track  but if the wheels are to retain the tyres they have to remain well over width which can bring clearance problems.

Chris Higgs did some experiments with 2FS wheels in Farish tender drives and he found that without the traction tyres they could barely pull themselves along, let alone a train!

 

Jerry 

 

My UM tender is fitted with replacement wheels supplied by Neil Ballantine, as is the loco  - er, I may have been working on this for some time... - and with the steel tyres it seems a capable enough hauler for what I'm going to ask of it.

 

Which, truth be told, isn't very much, trundling up and down a 6ft-ish plank with half a dozen wagons.

 

However, I'm realistic enough to accept that my attempts at a new chassis mightn't sort out my tender behind.

Edited by 2mmMark

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OK, I'll submit !

 

Right, now you can start scheming the chassis in detail - good luck.

 

Nig H

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My UM tender is fitted with replacement wheels supplied by Neil Ballantine, as is the loco  - er, I may have been working on this for some time... - and with the steel tyres it seems a capable enough hauler for what I'm going to ask of it.

 

Which, truth be told, isn't very much, trundling up and down a 6ft-ish plank with half a dozen wagons.

 

However, I'm realistic enough to accept that my attempts at a new chassis mightn't sort out my tender behind.

 

Actually, a Small Ben might not be required to pull too much either. A quick google produces at least one photo where it has just one coach on.

 

Chris

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Right, now you can start scheming the chassis in detail - good luck.

 

Nig H

 

A copy of this might be useful. ;)

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Actually, a Small Ben might not be required to pull too much either. A quick google produces at least one photo where it has just one coach on.

 

Chris

 

The Drummond family connection is clear to see, the  Small Ben isn't all that small, its essentially a T9 with smaller wheels. A very attractive loco, I look forward to seeing it progress.

 

Jerry

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Talking of T9's here's an example of a T9 with 10mm Maxon in tender driving gearbox in firebox.

Sorry it's still awaiting brake shoes and painting and lining.

As people have said 4-4-0's are tricky to get adequate weight on drivers but some weight transfers from front of tender to cab end of loco.

Has excellent haulage capacity as a result.

You can just see that it even has ballrace bearings in the gearbox.

post-12886-0-34460300-1483045639_thumb.jpg

post-12886-0-47477300-1483045659_thumb.jpg

post-12886-0-43168200-1483045751_thumb.jpg

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Talking of T9's here's an example of a T9 with 10mm Maxon in tender driving gearbox in firebox.

Sorry it's still awaiting brake shoes and painting and lining.

As people have said 4-4-0's are tricky to get adequate weight on drivers but some weight transfers from front of tender to cab end of loco.

Has excellent haulage capacity as a result.

You can just see that it even has ballrace bearings in the gearbox.

That's beautiful, wonderful modelling

 

Jerry

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Actually, a Small Ben might not be required to pull too much either. A quick google produces at least one photo where it has just one coach on.

I'm sure that, especially in the winter months, one coach and three or four wagons wouldn't have been unusual.  The wagons (unfitted) were often coupled inside the coach as it made shunting easier!  Far distant from London, what the BoT didn't see, the BoT didn't have to worry about! (though the HR did get caught out from time to time).

 

Jim

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I'm sure that, especially in the winter months, one coach and three or four wagons wouldn't have been unusual.  The wagons (unfitted) were often coupled inside the coach as it made shunting easier!  Far distant from London, what the BoT didn't see, the BoT didn't have to worry about! (though the HR did get caught out from time to time).

 

Jim

 

Not too bad if the single coach was a brake. If there were say three or four loaded wagons and no goods brake with the wagons behind the coach they would be jolting the coach when ever the train slowed. With the coach at the rear it would steady the wagons if the guard was on the ball.

Don

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I'm sure that, especially in the winter months, one coach and three or four wagons wouldn't have been unusual.  The wagons (unfitted) were often coupled inside the coach as it made shunting easier!  Far distant from London, what the BoT didn't see, the BoT didn't have to worry about! (though the HR did get caught out from time to time).

 

Jim

I suspect this happened on Stephens lines frequently 

 

Nick

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I suspect that 'local initiatives' were tried out wherever and whenever they could. It is human nature. It wasn't so much the railway companies, as the local employees who did these things. On a railway like the Highland, even Inverness was a long way from much of the system - never mind the BoT in London. The shame is that so much of this kind of thing has never been recorded, so has been lost to history as the people who saw them passed away. They only normally got recorded when the BoT investigated accidents, which were probably just the tip of an iceberg.

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This is a superb model of the SR / LSWR T9 loco, as is Nigel H's model of the 8 wheel tender - for an 0-8-0  loco perhaps ?

 

I'm wondering if the T9 was completely scratch built or whether it was produced from Worsley Works etches, whatever the build, the result is absolutely fantastic and what an encouragement for me to crack on !

 

Probably a daft question, but how do you keep the body from shorting the chassis please ? Do you rely on paint, or keep the loco eg. positive and the tender negative ? 

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This is a superb model of the SR / LSWR T9 loco, as is Nigel H's model of the 8 wheel tender - for an 0-8-0  loco perhaps ?

 

I'm wondering if the T9 was completely scratch built or whether it was produced from Worsley Works etches, whatever the build, the result is absolutely fantastic and what an encouragement for me to crack on !

 

Probably a daft question, but how do you keep the body from shorting the chassis please ? Do you rely on paint, or keep the loco eg. positive and the tender negative ? 

There are a few ways, some are easier than others. If you're using tufnol blocks as frame spacers, they can be positioned slightly proud of the frames giving a physical gap, but it can be hard to get them exactly where they should be. The easiest solution I've come across is to take a piece of cigarette paper and super glue it to the bottom of the footplate. It is very thin, but keeps the body isolated.

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There are a few ways, some are easier than others. If you're using tufnol blocks as frame spacers, they can be positioned slightly proud of the frames giving a physical gap, but it can be hard to get them exactly where they should be. The easiest solution I've come across is to take a piece of cigarette paper and super glue it to the bottom of the footplate. It is very thin, but keeps the body isolated.

I remember the missus asking what I was doing with a pack of Rizla in my modelling box. I'm not sure she believed me at first. :D

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