Wright writes.....

[Lecorbusier]

I think Frank brings out an important and sometimes under-appreciated point. That is, adding more driven wheels doesn't increase tractive effort one bit. The engineers who designed full-scale locomotives only added more driven wheels to keep the civil engineering department happy by spreading the load over a greater area of track. If they could have got away with always using single or double driven axles, they probably would have.

 

But because track loading doesn't scale, we can use much higher axle-loads and build everything as an effective 0-4-0 even though it might look like, for example, a 2-10-0.

 

Hope this makes sense

I am now somewhat confused. I was always under the impression that more driven wheels meant more contact with the rails and so less chance of slippage? I have in mind the specialist goods engines such as the 2-8-0s on the S & D and the 9Fs for example? Wouldn't the Victorian Singles have continued if number of axles had no bearing? ... Genuine question?

Edited October 28, 2018 by Lecorbusier

[Northmoor]

I am know somewhat confused. I was always under the impression that more driven wheels meant more contact with the rails and so less chance of slippage? I have in mind the specialist goods engines such as the 2-8-0s on the S & D and the 9Fs for example? Wouldn't the Victorian Singles have continued if number of axles had no bearing? ... Genuine question?

You're right, more contact points with the rails does reduce risk of slippage, which might mean you can make use of more tractive effort, not that you inherently have more.  That is largely a function of how much steam you can generate and convert to force on the piston(s).

 

Large freight engines tended to have more axles because:

• to produce more power, they had a larger boiler, which;
• meant more weight, so you have to divide it over more axles to reduce the axle loading and;
• to allow the wheels to fit within the length of the frames, the wheels have to be smaller than for a passenger loco (which would need to run faster anyway), while also;
• increasing the starting tractive effort and;
• keeping conrod speeds and forces within acceptable limits.

[St Enodoc]

Tony,

 

Is there a link to the source of the medium-sized Canon motors, please?

 

Though the Mitsumis are fine for small to medium locos, I would be interested in trying a Canon in something larger - 10100 'The Fell' for instance !!

 

Regards,

John Isherwood.

Wouldn't you need five of 'em for that?

[Headstock]

The whole engines, I think.

 

Anyway, I'll settle the issue by putting the tractor on a 'Lowfit'. 

 

Evening Tony,

 

a lowfit sounds like a safe bet, I don't know if Conflats were used or not for the transport of tractors. I was more interested to see if anybody had a picture of one, just to see how it was strapped on from a modeling point of view.

 

 

I am know somewhat confused. I was always under the impression that more driven wheels meant more contact with the rails and so less chance of slippage? I have in mind the specialist goods engines such as the 2-8-0s on the S & D and the 9Fs for example? Wouldn't the Victorian Singles have continued if number of axles had no bearing? ... Genuine question?

 

There are a whole load of advantages in having more driving axles beyond that stated in the original post. Trying to concentrate a higher proportion of a locomotives total weight (or for that matter length) on less driving axles in order  to give more weight for adhesion is a mugs game, even if you had no weight limit on the individual driving axle.

Edited October 27, 2018 by Headstock

[AndyID]

I am know somewhat confused. I was always under the impression that more driven wheels meant more contact with the rails and so less chance of slippage?

 

 

Hi Tim,

 

It's a bit counter-intuitive I know, but it neither increases nor decreases the total amount of friction (and therefore the tendency to slip). That's determined only by the total pressure between the two surfaces and the frictional properties of the combination of the two surfaces (characterized by what they call the "coefficient of friction".)

 

I was lucky to have a really good physics teacher (alas, no longer with us). He had us run a lot of experiments that clearly demonstrated that the contact area had nothing to do with it, despite the fact that we all thought it would

 

There are lots of reasons for using multiple drivers on full-scale locomotives but the avoidance of slip isn't one of them, and that applies to model locomotives too.

 

Cheers,

Andy

[St Enodoc]

Hi Tim,

 

It's a bit counter-intuitive I know, but it neither increases nor decreases the total amount of friction (and therefore the tendency to slip). That's determined only by the total pressure between the two surfaces and the frictional properties of the combination of the two surfaces (characterized by what they call the "coefficient of friction".)

 

I was lucky to have a really good physics teacher (alas, no longer with us). He had us run a lot of experiments that clearly demonstrated that the contact area had nothing to do with it, despite the fact that we all thought it would

 

There are lots of reasons for using multiple drivers on full-scale locomotives but the avoidance of slip isn't one of them, and that applies to model locomotives too.

 

Cheers,

Andy

Andy, that's not quite right. The force that drives the loco is generated by the torque at the wheel rim, either through the force of the pistons through the cranks (on steam locos) or the torque of the motors (on locos with electric motors). If the driving force exceeds that which can be transferred to the rails by friction, then the loco will slip.

 

Everything else being equal (which of course it never is), the more driving axles there are the more of the driving force can be transferred to the rails.

 

If the coefficient of friction is 20%, the maximum driving force that can be transferred is 20% of the weight (downward force) on each driving axle. If the maximum allowable axle weight is 20 tons and there is a single driving axle, then the maximum driving force that can be transferred will be 20 x 20% = 4 tons. If, however, there are two driving axles, it is doubled to 2 x 20 x 20% = 8 tons and so on.

[AndyID]

Andy, that's not quite right. The force that drives the loco is generated by the torque at the wheel rim, either through the force of the pistons through the cranks (on steam locos) or the torque of the motors (on locos with electric motors). If the driving force exceeds that which can be transferred to the rails by friction, then the loco will slip.

 

Everything else being equal (which of course it never is), the more driving axles there are the more of the driving force can be transferred to the rails.

 

If the coefficient of friction is 20%, the maximum driving force that can be transferred is 20% of the weight (downward force) on each driving axle. If the maximum allowable axle weight is 20 tons and there is a single driving axle, then the maximum driving force that can be transferred will be 20 x 20% = 4 tons. If, however, there are two driving axles, it is doubled to 2 x 20 x 20% = 8 tons and so on.

 

As i said, it's a bit counter-intuitive.

 

However, this is not my theory. This is stuff that's been well understood for at least 150 years (and probably quite a bit longer.)

 

If you double the number of axles you've also halved the force exerted between each wheel and the rail. As friction is proportional to that force you've halved it too, so the total friction remains the same.

 

The best way to get around this is to change the coefficient of friction. People have tried to do this by using rubber tires etc, but I'll say no more about that.

 

Anyway, I'm only pointing this out so that people don't spend a lot of time trying to perfect the suspension of a model 4-12-4. It will perform just as well as an 0-4-0.

 

Cheers,

Andy

[jwealleans]

Tractors. A quick Google only turned up the photo Andrew posted, but I have now located the picture I used. It is one of Paul Bartlett's, link here. The link isn't working at this ungodly time of the morning, but if in doubt, search for 'tractors on Lowfits'. Google will bring up a small version so you can see how they're secured.

 

 

 

I did a rake for Thurston, mainly on Lowfits although for variety one is on an ex-LMD D.1986 and another in a 3 plank open. They aren't glued on either (I hate seeing little pools of glue round wheels), the roping works in 4mm.

 

I was mulling on chains last night - a tractor isn't heavy enough to require chains over ropes and they'd have to use sacking or something to protect the paintwork. I'm sure ropes would be the easier option.

 

Also, when I did mine I was taken to task about them having exhaust fitted. New ones travelled without to avoid damage, I was told. Paul Bartlett's photo contradicts that, but if asked I just say they're second hand and being taken for auction.

 

 

Andrew, that coach is beatutiful. I wish I could do teak half that good.

 

 

Tony, thank you for your efforts on behalf of 2372 and I'm sorry you were put to the inconvenience. I was always confident it had left Ally Pally with me, so under LB or in someone else's kit was always the lost likely scenario. Selfishly, I'm pleased it turned up before I trailed down there and wasted more of your time (and mine) searching. The DJH one can go back into the 'waiting works' queue.

Edited October 28, 2018 by jwealleans

[St Enodoc]

As i said, it's a bit counter-intuitive.

 

However, this is not my theory. This is stuff that's been well understood for at least 150 years (and probably quite a bit longer.)

 

If you double the number of axles you've also halved the force exerted between each wheel and the rail. As friction is proportional to that force you've halved it too, so the total friction remains the same.

 

The best way to get around this is to change the coefficient of friction. People have tried to do this by using rubber tires etc, but I'll say no more about that.

 

Anyway, I'm only pointing this out so that people don't spend a lot of time trying to perfect the suspension of a model 4-12-4. It will perform just as well as an 0-4-0.

 

Cheers,

Andy

Andy, this will be my last posting on the subject, as we are straying off topic.

 

"If you double the number of axles you've also halved the force exerted between each wheel and the rail".

 

This is only true if you don't change the total weight. As I said above, if you increase the number of axles you can increase the total weight accordingly, provided that the maximum weight per axle is not exceeded.

 

If both your hypothetical locos have a weight on each driving axle of 20 tons, then the 4-12-4 will have an adhesive weight of 120 tons and the 0-4-0 will have an adhesive weight of 40 tons. The driving force at the rail will therefore be three times greater for the 4-12-4 than the 0-4-0.

[AndyID]

This is only true if you don't change the total weight.

 

No disagreement there. I was making the huge mistake of assuming the weight of a particular locomotive was approximately constant. If you can load it up with a lot of lead you'll definitely change the total weight, and the adhesion.

[jamie92208]

As far as I know the Victorians abandoned singles and went to 2-4-0's as locos got larger and more power needed transmitting. I believe that it was the invention of steam sanding that brought back the beautiful Midland and GN singles (I'm sure there were others as well). Also by that time rails had got stronger and higher axle loadings were allowed.

 

Jamie

[SJR]

Re the discussion on tractor loads. Taken at Quainton Road in 2006. Definitely chains in use on the Conflat but not sure how representative it is

[Major Clanger]

The Wizard website is now fixed. The motor gearbox combination Tony refers to is Canon CA1620 plus GB8/15. Due to different fixing screw spacings, this gearbox is the only Comet one suitable for use with this motor, and vice versa. On a related theme, we still have plenty of Mashima motors, except 1620 (sold out) and 1024 and 1833, both of which are almost down to single figures. 

[Tony Wright]

I have fitted the Canon/Comet combination to a SEF J38 I have just finished.It is the quietest and smoothest drive train I have used.I haven't tested its haulage capabilities but I am confident from the "feel" of its torque that it would be fit for duty on LB.It will also move at an almost imperceptible crawl.In future this will be my preferred drive train.

 

Tony, it was good to meet you and Mo in Sydney and thank you again for being such an enthusiastic and involved presenter in our convention.

Thanks Ron,

 

It was good to meet you, and all the others as well.

 

I'm delighted my talks went well, and may I thank all those at the convention for their enthusiastic responses, please? 

 

We really did have a fantastic time. 

 

Regards,

 

Tony. 

[cctransuk]

Wouldn't you need five of 'em for that?

 

I'm not that committed to (internal) prototype fidelity - but my intended power train will be quite 'eccentric' (not literally I hope)!

 

 

The motor shaft and RH gearbox shaft will be joined within the flywheel, which will act as a sleeve joint. Success or failure will depend upon the fit of the shafts within the flywheel.

 

You will see that the design includes a Mashima 1630 - which I have in stock - but I may well substitute one of the Canons as an experiment.

 

Regards,

John Isherwood.

Edited October 28, 2018 by cctransuk

[Headstock]

The second carriage has had its paint work finished yesterday. A somewhat protracted affair for this GC corridor third as I had to priorities some locomotive work while the layout was available for testing in the club rooms. I'm quite pleased with how its come out, as it it was resurrected from a derelict condition, found neglected in a dusty scrap box at an exhibition. It has acquired a new scratch built roof, a new chassis, bogies and much detail work to the sides, such as door hinges and drop light safety bars. I also drilled and filed out the recesses for the door and grab handles. I'm always a sucker for a hard look story if I can see genuine potential, it is immensely satisfying that this one will  be heading back to the tracks rather than the scrap bin. When the paint is dry, it requires the fitting of corridor grab handrails and gangways.

[Tony Wright]

Tractors. A quick Google only turned up the photo Andrew posted, but I have now located the picture I used. It is one of Paul Bartlett's, link here. The link isn't working at this ungodly time of the morning, but if in doubt, search for 'tractors on Lowfits'. Google will bring up a small version so you can see how they're secured.

 

 

 

I did a rake for Thurston, mainly on Lowfits although for variety one is on an ex-LMD D.1986 and another in a 3 plank open. They aren't glued on either (I hate seeing little pools of glue round wheels), the roping works in 4mm.

 

I was mulling on chains last night - a tractor isn't heavy enough to require chains over ropes and they'd have to use sacking or something to protect the paintwork. I'm sure ropes would be the easier option.

 

Also, when I did mine I was taken to task about them having exhaust fitted. New ones travelled without to avoid damage, I was told. Paul Bartlett's photo contradicts that, but if asked I just say they're second hand and being taken for auction.

 

 

Andrew, that coach is beatutiful. I wish I could do teak half that good.

 

 

Tony, thank you for your efforts on behalf of 2372 and I'm sorry you were put to the inconvenience. I was always confident it had left Ally Pally with me, so under LB or in someone else's kit was always the lost likely scenario. Selfishly, I'm pleased it turned up before I trailed down there and wasted more of your time (and mine) searching. The DJH one can go back into the 'waiting works' queue.

Thanks Jonathan,

 

I'll rope my two tractors down (when I get round to it). The reason they're in that little freight is because, in the WTT, there was a daily pick-up freight from Peterborough to Grantham (and the other way), which would have stopped at all the intermediate stations (if required) on the way. There was a tractor/agricultural machinery factory at Essendine (Alice Chalmers, I believe - or a similar name); hence the pair (though neither are of that make - modeller's licence). It's probably unlikely that just a pair would be present, but there you go. Any pictures I have show longer trains of tractors, such as yours. 

 

There's really no need to apologise for the 'inconvenience' about the B16 (though more-diligent immediate searching would have made my scrambling around task superfluous). My fear was it had been nicked at Ally Pally (but not its box), because I've found a rather shabby blue box - actually loads of shabby boxes, of all colours! I've also found several forgotten-about kits, and even some locos and stock! And, of course, Mo (quite rightly) made me tidy up the floor afterwards. 

 

As for 2372, don't forget she's guaranteed for the rest of my life (as with all the locos I've built). I'm delighted she'll continue to work on Grantham. 

 

Regards,

 

Tony. 

[The Stationmaster]

Re the discussion on tractor loads. Taken at Quainton Road in 2006. Definitely chains in use on the Conflat but not sure how representative it is

 

That won't work - for several reasons, viz -

 

1. The chain round the tractor itself will cause damage to the tractor because it is not padded with straw pads so will rub simply as a consequence of normal movement,

2.The chains are not tensioned so will move and not correctly secure the load,

3. Because the chains are not tensioned they will cause even more damage to the tractor because both they and the tractor will be liable to move during shunting and normal train running.

 

Summary - don't necessarily take notice of the ideas of preservationists as a guide to the real railway.  Overall chains would only be used to secure very heavy loads and would in any case have to be tensioned using bottle tensioners.  Special chains were used for traction engines and steam rollers but tractors were roped until more modern fastening straps with tensioners became available, and of course anything with wheels loaded for normal freight train movement had to be scotched.

 

Overall securing with chains was something of a nuisance as they could be awkward to get right and unless used very carefully and properly tensioned they could 'work' and damage the load or even fail to properly secure it.   it was a great day when modern high tensile strength strapping with its own tensioners appeared to succeed chaining, at a place (a steelworks) where I was working we had some for early experimental use the staff loved it compared with chaining - easier and quicker.  Roping was always easier than chaining but equally obviously still had to be done properly.

[APOLLO]

Tony you may not need to tie down your tractors, but you MUST tie your Kangaroo down mate !!!!!

 

 

Brit15

[Clem]

The second carriage has had its paint work finished yesterday. A somewhat protracted affair for this GC corridor third as I had to priorities some locomotive work while the layout was available for testing in the club rooms. I'm quite pleased with how its come out, as it it was resurrected from a derelict condition, found neglected in a dusty scrap box at an exhibition. It has acquired a new scratch built roof, a new chassis, bogies and much detail work to the sides, such as door hinges and drop light safety bars. I also drilled and filed out the recesses for the door and grab handles. I'm always a sucker for a hard look story if I can see genuine potential, it is immensely satisfying that this one will  be heading back to the tracks rather than the scrap bin. When the paint is dry, it requires the fitting of corridor grab handrails and gangways.

 

Hi Andrew.

I very much like the way you make and finish coaches. The Thompson was beautiful and this is also. A GC corridor third is on my list to build one day, too. I was wondering.. who produced these kits? Perseverance ?  

 

Clem

[Headstock]

Hi Andrew.

I very much like the way you make and finish coaches. The Thompson was beautiful and this is also. A GC corridor third is on my list to build one day, too. I was wondering.. who produced these kits? Perseverance ?  

 

Clem

 

Afternoon Clem,

 

Unfortunately, it's a case of picking them up were you can find them. The consensus of opinion is that mine is Jidenco (Falcon Brass) I don't think that any are still in production. The bogies are D&S, I had a set in stock awaiting a suitable subject. I replaced the Underframes as the original was very basic and attached to the body, I prefer my carriages to separate between the underframe and body. The replacement underframe is from MJT. I also modified various MJT underframe components to GC style fittings. Other sources of GC carriages of this style that I can think of  were D&S and John Fozzard. Both are very difficult to get hold of, the latter almost impossible due to John Fozard's untimely death.

 

The D&S kits come up on eBay on occasion, but go for silly money. However, It is still worth trawling through the scrap boxes at shows, little gems can still be had.

[MarkC]

Wouldn't you need five of 'em for that?

Weren't there actually 6 engines? 4 for traction and 2 for ancilleries?

[Headstock]

With LSGC off the exhibition circuit next year (unless anything new is booked in) I may take the opportunity to learn how to produce my own brass etchings. In todays climate it makes sense a lot of sense to get control over what you require.

[cctransuk]

The motor shaft and RH gearbox shaft will be joined within the flywheel, which will act as a sleeve joint. Success or failure will depend upon the fit of the shafts within the flywheel.

 

You will see that the design includes a Mashima 1630 - which I have in stock - but I may well substitute one of the Canons as an experiment.

 

Regards,

John Isherwood.

 

Ah - just spotted a possible obstacle to using the Canon 1620 motor in place of the Mashima 1630 - is the Canon motor double ended; ie. does the shaft protrude at both ends?

 

Virtually all of my recently built locos have a flywheel on the free end of the motor - and a double-ended motor is essential for my 10100 project.

 

Regards,

John Isherwood.

[gr.king]

Afternoon Clem,

 

Unfortunately, it's a case of picking them up were you can find them. The consensus of opinion is that mine is Jidenco (Falcon Brass) I don't think that any are still in production. The bogies are D&S, I had a set in stock awaiting a suitable subject. I replaced the Underframes as the original was very basic and attached to the body, I prefer my carriages to separate between the underframe and body. The replacement underframe is from MJT. I also modified various MJT underframe components to GC style fittings. Other sources of GC carriages of this style that I can think of  were D&S and John Fozzard. Both are very difficult to get hold of, the latter almost impossible due to John Fozard's untimely death.

 

The D&S kits come up on eBay on occasion, but go for silly money. However, It is still worth trawling through the scrap boxes at shows, little gems can still be had.

 

It's shame this didn't crop up two years ago. I had temporary possession of some D & S "loads of little pieces of plastic" original GC matchboard coach kits that an acquaintance was trying to sell and I could find no buyers amongst those known to me. The owner has almost certainly managed to dispose of them by now.....