Nether Madder and Green Soudley Rly

[Nearholmer]

I’m slowly forgetting basic engineering knowledge here, but isnt the coefficient of friction (COH) independent of area of contact?

 

Leaving that aside, if it is true that modern RTR 00 locos really can’t pull the skin off a rice pudding (COH variable according to chef), that feels like a topic to be delved into and solved.

 

The wheel material will definitely be important, it being very well known, for instance, that bright-plated wheels on nickel-silver rail have a very low COH.

 

The old 0 scale favourite is cast iron for wheels, but modern sintered steel (not plated) seems very good too, it retaining a very tiny amount of roughness. 

Edited October 23, 2019 by Nearholmer

[Edwardian]

It seems to me, for whom electricity is frightening magic, that steel laid above the sleepers or iron filings is fraught with the possibility of a short circuit. 

 

The prudent alternatives would seem to be the continuous plates beneath the track, as DCC Concepts intended, or your suggestion of plates between the sleepers, which sounds as if yo could keep them well away from rails and flanges.  Would it matter that the magnetic material was not continuous?

 

I've just picked up on the fact that you've had a visit from the Black Dog, and I'm glad to read that you are shaking it off.  I had a rather bleak but mercifully brief episode on Saturday, until Mahler and Broad Gauge gave me the hand-holds to pull clear, so I do sympathise.  We must keep our chins up. The last temptation is despair!

[chuffinghell]

6 minutes ago, Edwardian said:

It seems to me, for whom electricity is frightening magic, that steel laid above the sleepers or iron filings is fraught with the possibility of a short circuit. 

 

Electrickery is most definitely a form of witchcraft!

 

7 minutes ago, Edwardian said:

I've just picked up on the fact that you've had a visit from the Black Dog, and I'm glad to read that you are shaking it off.

 

Agreed

 

8 minutes ago, Edwardian said:

I had a rather bleak but mercifully brief episode on Saturday, until Mahler and Broad Gauge gave me the hand-holds to pull clear.

 

Pleased you too have managed to shake off the black dog

 

I suffer with the black dog but I've found that modelling has become both my escape and therapy

[brylonscamel]

11 hours ago, Martin S-C said:

Colin, its the DCC Concepts Power Base, so its ferric steel, about 0.3 to 0.5mm thick. It slides under the sleepers. I can definitely feel the magnetic attraction when lifting the loco wheels from the rails.

I am wondering if the steel strips could be cut in half lengthways and laid atop the sleepers between the rails. I have plans to lay an ash ballast effect, burying the sleepers so that's a possibility.

 

I am filing this discussion under 'useful research that others are doing, so you don't have to' .. I have shied away from inclines in small spaces but appreciate the joy of an elevated railway.

[Nick C]

On 20/10/2019 at 01:46, Martin S-C said:

Thanks for the comments Nick. I haven't used trap points anywhere on the layout, so using them here would look odd. I had a long think about whether I wanted to include them, even dummy ones but in the end decided against it. How does this look?

 

 

Looks good - the only thing I'd do is reorder some of the levers - make the crossover outside the box 18, outer home 19, goods starter 28 - that way all the inbound signals are grouped together, as are all the outbound ones. I'd probably swap 4, 6, 7, 8 around as well to read in numerical order, but that's just me...

[Stubby47]

Silly idea time...

 

Have you tried puttIng a line of magnets under the track/between the sleepers and putting a steel strip under the loco ?

Edited October 23, 2019 by Stubby47

[Harlequin]

Magnets on the track and under the loco: Maglev!

 

Edited October 23, 2019 by Harlequin

[Regularity]

3 hours ago, Harlequin said:

On another thread (Wright writes?) there has been talk recently of the profile of the wheel treads being important for traction. People have had wheels re-treaded or re-ground and got improved pulling power.

 

That makes sense intuitively: If the tread is angled at all then it will only have a tiny contact patch with the rail but if it's flat then it will make much better contact and the coeff. of friction should be consequently greater.

Another reason why I don't read that thread.

 

The coning is essential to getting round the curves properly, as it means the wheels can adopt slight different diameters to suit the difference in radii between the rails (hence, railways do not use a differential drive) and also to keep the outer flange away from the inside edge of the railhead, if possible. It also serves (all other things being equal) to "centre" the wheelsets on plain straight track, so that the flanges don't rub against the rail head. Also, bullhead track is (on the prototype) laid with the rail inclined at 1:20, to match the coning. Flat bottom track can be laid this way, too, with baseplates, but isn't always - if laid vertical, then the gauge was narrowed by 3mm (4' 8 3/8"): "modern image" P4 layouts need to reduce the gauge to 18.79mm if using vertical FB rail...

 

Tri-ang used "Magnadhesion" on their locos, with a steel block between a wheelset, alloy wheel centres, steel tyres and steel rail. This is presumably a variant on this idea, but there is the risk of preventing the loco from loosing its feet rather than stalling the motor: the latter will burn it out.

 

There are essentially four possible cause of the problem, but they may (may? almost certainly are!) interrelated:

1) Rolling resistance;

2) Gradient too steep;

3) Curves too tight; and

4) Lack of power at the rail.

 

Prototype locos typically have a "factor of adhesion" of about 4, or put another way, a coefficient of adhesion of 25%. (And yes, that's a vague yardstick, for the point of illustration). This means that, for example, the tractive effort put down at the rail is roughly a quarter of the weight on the drivers (we will stick with locos without bogies and pony trucks - on most models, these are purely cosmetic anyway). Too much weight, and the loco will stall, too little, and it will slip. A steel plate under the rails and a magnet under the loco will use magnatism to increase the effective coefficient of friction, but there may be a cost if the loco cannot slip.

 

We are using electric motors and things are slightly different, as proportionately they are capable of putting much more power down at the rail, and with a light model loco, therefore much more likely to slip and engaged in wheel spin. That's ok: as stated above, that is a safety mechanism that stops the motor from stalling under load and rapidly becoming a generator of localised heat.

 

The easiest two things to look at because you have laid your track are, as mentioned, to look at the resistance in your rolling stock, and then to look at the weight of your engines. You want less and more, respectively!

 

IIRC, you tested curves and gradients before construction, and they don't look any sharper than on other model railways, so I suspect that wheelsets and weight are your recipe for improvement - add the steel plates and magnets after addressing these issues.

 

Have you standardised on a specific brand of wheels and bearing? I remember Alan Gibson telling me 20 years ago just how many 00 wagon and carriage wheels he shifted every month to people replacing the ones which came fitted to RTR models. Steel/metal tyres and pin point bearings should help. Using a single brand ensures a consistency of profile, which will mean you have removed a variable from the set up.

(The Ultrascale wheels have nickel silver tyres to a slightly "better" - technically - profile, but the Gibson wheels are fine.)

Edited October 23, 2019 by Regularity
Gauge narrowing

[Regularity]

39 minutes ago, Harlequin said:

Magnets on the track and under the loco: Maglev!

Which is fine provided the rolling stock is similarly fitted, otherwise there is virtually no friction and no tractive force...

[Nearholmer]

Tractive force in a maglev system is achieved by causing the magnetic field to move, which is going to be quite a challenge with permanent magnets.

[RedGemAlchemist]

2 hours ago, chuffinghell said:

I suffer with the black dog but I've found that modelling has become both my escape and therapy

Amen to that. 

 

And all this stuff about magnets is straight over my head. 

[Nearholmer]

Actually, thinking about it, one could make a steam-powered contraption to move permanent magnets so as to create tractive force in a maglev system.

 

it would be inefficient, inelegant, and immensely amusing.

 

I'm thinking of a sort of paddle-steamer, with water replaced by magnetic fields, which makes me wonder whether the equivalent of a screw-propeller might be possible using magnets. Failing that. Just use the maglev bit, create magna-canals, and use a horse to provide tractive force to the barges.

Edited October 23, 2019 by Nearholmer

[RedGemAlchemist]

1 minute ago, Nearholmer said:

inefficient, inelegant, and immensely amusing.

Best kind of engineering that. 

[DonB]

4 minutes ago, Nearholmer said:

Actually, thinking about it, one could make a steam-powered contraption to move permanent magnets so as to create tractive force in a maglev system.

 

it would be inefficient, inelegant, and immensely amusing.

 

are you any relation of Heath-Robinson ? 

[Stubby47]

2 hours ago, Stubby47 said:

Silly idea time...

 

Have you tried puttIng a line of magnets under the track/between the sleepers and putting a steel strip under the loco ?

 

I take it back, obviously there are much more silly ideas...

[Nearholmer]

Design continues apace:

 

The way a linear induction motor field works has some similarities to the way a cuttlefish swims through water, so I’m proposing to use a series of oar-like structures along either side of the mag-barge, arranging them to rise and fall in an undulating sweep, like the cuttlefish fins.

 

Given that cuttlefish are incredibly agile manoeuvring in tight spaces, reversing direction very quickly etc, I have high-hopes that the mag-barge will prove you be a very useful vessel.  

[Harlequin]

1 minute ago, Nearholmer said:

Design continues apace:

 

The way a linear induction motor field works has some similarities to the way a cuttlefish swims through water, so I’m proposing to use a series of oar-like structures along either side of the mag-barge, arranging them to rise and fall in an undulating sweep, like the cuttlefish fins.

 

Given that cuttlefish are incredibly agile manoeuvring in tight spaces, reversing direction very quickly etc, I have high-hopes that the mag-barge will prove you be a very useful vessel.  

 

I assume you have a daVinci-like sketch of your revolutionary invention on the back of a fag-packet? Can we see it, please?

 

Tangentially: I was on the Eskdale and Ravenglass last week and as we proceeded forwards down the line the sounds of the wheels on the rail joints came first from the back of the train and moved forwards past us up towards the loco. I tried to explain the concept of strobing to my companion but I don't think she got it. The wavy motion of your mag-barge oars would do something similar when filmed...

 

[DonB]

Regularity, above, details the possible sources of your "stiction". ...A quick check .... will an individual wagon roll freely, unaided, down your inclines?  one of Mikkel's blogs details his wagons rolling across his near level work table,  

[Nearholmer]

Mechanical cuttlefish robot https://ethz.ch/en/news-and-events/eth-news/news/2014/05/robotic-squid-and-honeycomb-turbines.html

 

OK, this one swims in boring old water, rather than magnetic fields, but you get the idea.

[Northroader]

Looking at that picture reminds me of a rude story about an octopus and some bagpipes.

[Martin S-C]

18 hours ago, DonB said:

Trying to think "outside the box", It occurred to me that an alternative to the suggested thin steel sheet at track level for the magnets to be attracted to, you could consider mixing the commercial grade of Iron filings (as used in BWsTrains demonstration picture) mixed in your ballast and WELL GLUED in place. The magnets ideally need to have (all, if more than one) of their poles aimed at the ballast and as near as possible to it.

Quite a good idea. I appreciate the 'well glued' caveat. I can still forsee endless cleaning of metal particles off the magnets though, well laid plans and all that.
 

16 hours ago, St Enodoc said:

Martin, I think it would be worth trying some thin magnets with the poles perpendicular to the faces. Small disc magnets are available:

 

https://www.frenergy.com.au/rare-earth-discs.html?p=4

 

I've used magnets for other applications - e.g. loco lamps, as you know - from this firm (usual disclaimer) but I'm sure there will be suppliers of similar items in the UK.

Yes, discs may be the way to go. Bearing in mind that under some locos like the Beattie 2-4-0 there's only 1mm of space to play with before the magnets foul point switch blades. However magnets this thin are available, its just they have lower and lower power the smaller their mass (obviously). But correct orientation of the magnet poles should help.
 

9 hours ago, Nearholmer said:

I'm still a bit foxed by the haulage problems that you are experiencing, and wonder if an underlying issue might be the rolling resistance of the wagons.

 

it bothers me, because it seems plain morally wrong that a model loco can't do the work of its real-life peer, especially a newly made model loco, because if it can't, that feels like a design failure on the part of Bachmann, Hornby, or whoever.

 

Have you tried measuring the drawbar pull needed to shift the wagons on level, tangent track? Someone on here (it might have been you!) was using some sort of tiny spring balance to measure drawbar pull, accepting that it wouldn't give very accurate measurements, but would allow meaningful before vs after (lubrication, bearing de-crudding etc) comparisons.

 

As a rule of thumb, I think that a loco ought to be able to shift on level, tangent track a load that requires drawbar pull of about one fifth of its mass (others feel free to contribute/contradict), and the effect of gradient is calculable, given knowledge of a load of variables that you probably can't access! But, if you can measure pull on level, tangent track you could also measure it on curving gradient.

I am not sure how heavy a load a Beattie well tank could haul up a 1:32 grade on an extremely tight curve. The curve is tighter than any real railway so perhaps therein lies the answer.

I have selected some of the freest running wagons I have and am adding weight to them as a test. I should probably try again using a more empirical route and use as few wagons as possible, each carrying a heavier load. Ideally I should use 1 wagon and load it up with a huge weight. I have some lead pieces in my 'weights for rolling stock' box I can use to investigate via this route. This then brings the issue down to one of mass and reduces the effect of rolling resistance. I have noticed that a loco can almost always haul, on a curve, a greater weight in 4 wheel wagons than it can in bogie coaches. I presume this is because a bogie coach suffers a higher value of angular forces over its length vs its wheelbase. The rear bogie is being pulled sideways more by the body of the vehicle and so more energy is converted into friction by the flanges, etc.

I would need my hand holding and step by step guidance through the conduct of a drawbar load test. I haven't done such a thing before.

 

8 hours ago, Harlequin said:

On another thread (Wright writes?) there has been talk recently of the profile of the wheel treads being important for traction. People have had wheels re-treaded or re-ground and got improved pulling power.

 

That makes sense intuitively: If the tread is angled at all then it will only have a tiny contact patch with the rail but if it's flat then it will make much better contact and the coeff. of friction should be consequently greater.

 

Martin: How do you feel about gluing magnets to your locos and iron plates to your track and having to disguise both???

 

Thanks for the info but replacing wheels on locos or re-grinding them is not for me. My model railway interests stop a good way short of miniature engineering. If I get a loco whose pulling power is almost useless and I cannot find a duty for it on the level it will go in the resales box!

 

Gluing magnets to locos and steel plates under track is what I'm doing now. I haven't found a less time consuming or disruptive method yet. This option came after a discussion several months back of banking or pilot engines which I discarded as looking silly on such short trains.

I'm sure this is going to work, I just happen to have selected a poor loco as my first test engine.

 

I am leaving tomorrow morning to go away to France over the weekend partaking in my other hobby - wargaming, where I and some mates are continuing our Eastern Front 1941 campaign that we've been playing for many years using 15mm miniatures. Back on Monday and I will see how the J15 performs. I'll also try to bypass rolling resistance by using the shortest train I can while adding greater weight to it.

 

Soviet forces roll (and canter) forwards in a counter attack near Borisov.

A Soviet headquarters occupies a small forest village.

Wehrmacht armour and motorized infantry move out of a forest past a burning railway station towards a Soviet fortified line.

 

And before you ask, yes, when we lay the scenery I am usually tasked with properly laying out the railway lines! These are TT track pieces laid on a hard foam base and ballasted and look fairly effective. The game's ground scale is 1" to 100 yds so TT pointwork is very over scale and we usually represent junctions by just butting up one track piece to another as you can see in the burning station above. The game scale also use bases of infantry mounted in pairs to represent a platoon of 30~60 men and vehicles represent a platoon or battery of 4~6 vehicles or weapons.

 

The Henschel 126 artillery spotter plane in the pic above was mounted using magnets on a clear plastic pole standing on a flock covered round base but I photoshopped that out.

Edited October 23, 2019 by Martin S-C

[Martin S-C]

7 hours ago, Edwardian said:

It seems to me, for whom electricity is frightening magic, that steel laid above the sleepers or iron filings is fraught with the possibility of a short circuit. 

 

The prudent alternatives would seem to be the continuous plates beneath the track, as DCC Concepts intended, or your suggestion of plates between the sleepers, which sounds as if yo could keep them well away from rails and flanges.  Would it matter that the magnetic material was not continuous?

 

I've just picked up on the fact that you've had a visit from the Black Dog, and I'm glad to read that you are shaking it off.  I had a rather bleak but mercifully brief episode on Saturday, until Mahler and Broad Gauge gave me the hand-holds to pull clear, so I do sympathise.  We must keep our chins up. The last temptation is despair!

I hadn't spotted that issue with the iron filings mixed in ballast, but while that suggestion is well outside the box, I am not sure I want to go there, it seems to bring in some negative possibilities the thin steel sheet system (below or above sleepers) does not.

No, the ferric material does not need to be continuous. There will be at least 2 magnets under each loco so gaps in the sheets can be bridged. It saves cost of steel sheet parts too.

An alternative to steel sheets is steel flat headed nails inserted between the sleepers and just below the level of their upper surface. More work but it gets the steel attractant for the magnets a critical couple of millimetres higher without covering the sleepers entirely, which on second thoughts is something I am not sure I want to do in the visible areas. In the tunnels its fine. Of the 7 gradients in question, 3 are in tunnels.

 

5 hours ago, Stubby47 said:

Silly idea time...

 

Have you tried puttIng a line of magnets under the track/between the sleepers and putting a steel strip under the loco ?

I hadn't but that method strikes me it would push the cost up by several orders of magnitude! You can't stick steel strip under the locos anyway as the undersides are rarely flat and brake gear
gets in the way.

 

4 hours ago, Regularity said:

The easiest two things to look at because you have laid your track are, as mentioned, to look at the resistance in your rolling stock, and then to look at the weight of your engines. You want less and more, respectively!
 

Have you standardised on a specific brand of wheels and bearing?

 

I am a good way down the investigative road and have gone past all the mileposts you're highlighted already. All plastic wheels are removed and Bachmann metal ones fitted. I don't alter RTR axle bearings, my experience is these are extremely free rolling. All my kits use brass bearings. After models are weathered I pop the axles out and check for free rolling, cleaning where needed. There are a couple of iffy kit builds I bought second hand but if I can improve loco hauling power up the grades these single vehicles should not be a problem.

My conclusion several months back was that lack of loco power and weight was the issue, which is what I'm addressing. Weight has been added where it can be which is frequently none due to lack of room.

Of course the root of the problem is the steepness of the gradients but now that my poor planning has come home to roost I must press on with methods to overcome my earlier mistakes.
 

2 hours ago, DonB said:

Regularity, above, details the possible sources of your "stiction". ...A quick check .... will an individual wagon roll freely, unaided, down your inclines?  one of Mikkel's blogs details his wagons rolling across his near level work table,  

My wagons roll fairly well, though of course some better than others. The newer RTR offerings are particularly good runners.

To clarify and focus things, there is no problem on the level, whether straight or curved. My trains will be short and light. No more than 2 bogie coaches and a couple of vans or 4 four wheelers and a couple of vans in passenger trains and the freight train maximum is 8 short wheelbase wagons plus brake. Several passing loops have been arranged specifically with these lengths in mind. A typical RTR coal wagon weighs only 20 grams, this rises to 40 grams with my standard coal load added. So a loaded coal train is only about 360 grams if we allow 40 grams for the brake van.

Only a few of my locos have haulage problems. I have a 1950s set of rolling stock as well including many diesels and since these models are very heavy they can haul huge trains up my 1:30 grades. Even the DJM J94 at 165 grams that some claim is underpowered can haul 590 grams up a 1 in 60. The problem lies with a few very light engines in my Victorian/Edwardian era collection and then only on the worst grades. The steel plate method is only being used under the gradients, not elsewhere.

[Nearholmer]

“Of course the root of the problem is the steepness of the gradients but now that my poor planning has come home to roost ”
 

Don’t beat yourself up (not yet anyway).

 

on the level, on tangent track, a loco only has to overcome starting friction, then rolling resistance.

 

Add a model-railway type curve, and we get flange friction to overcome. 
 

Add a gradient, and a proportion of the mass of the train is attempting to pull it down that hill - the steeper the hill, the greater the proportion of the mass.

 

We've explored starting friction, sort of touched on flange friction, and talked about rolling resistance.

 

Your trains are of modest numbers of vehicles.

 

Which leaves mass.

Are your wagons perhaps a bit heavy? Have you ballasted them? Have you tried the haulage test with empty wagons?

 

If that doesn’t sort it, I advocate that you pension-off the engines that are too featherweight for the job, and use heavier ones instead.

 

I honestly think that your gradient, train length, and curvature combination should be within the capacity of any respectable loco. 
 

Personally, I wouldn’t advocate magnedhesion or traction tyres - highly unrailwaylike the both. 
 

PS: the speed of a real train on your grade/curve would probably be down to walking pace, probably with some sand (plus spectacular exhaust). Does going dead-slow help on the model? Have you tried abusing the loco wheels to get rid of any over-shiny surface?

Edited October 23, 2019 by Nearholmer

[Ruston]

49 minutes ago, Martin S-C said:

To clarify and focus things, there is no problem on the level, whether straight or curved. My trains will be short and light. No more than 2 bogie coaches and a couple of vans or 4 four wheelers and a couple of vans in passenger trains and the freight train maximum is 8 short wheelbase wagons plus brake. Several passing loops have been arranged specifically with these lengths in mind. A typical RTR coal wagon weighs only 20 grams, this rises to 40 grams with my standard coal load added. So a loaded coal train is only about 360 grams if we allow 40 grams for the brake van.

Only a few of my locos have haulage problems. I have a 1950s set of rolling stock as well including many diesels and since these models are very heavy they can haul huge trains up my 1:30 grades. Even the DJM J94 at 165 grams that some claim is underpowered can haul 590 grams up a 1 in 60. The problem lies with a few very light engines in my Victorian/Edwardian era collection and then only on the worst grades. The steel plate method is only being used under the gradients, not elsewhere.

Out of interest, which of your engines are unable to get up your gradients with the maximum load what do they weigh and what is the steepest gradient?

[Martin S-C]

That would take me a while to answer, I have numerous ones but am planning to work through the entire stock and check each one.