Gradients

[newbryford]

Important point about the state of the wheels. Probably why my Pannier tanks give different results. I guess the same applies to the track in as much as old dirty track is not good for electrical contact but grips better.

 

In the same vein, steel track is better than N/S track for grip.

 

One word Magnadhesion, or perhaps Magnatraction depending on your side of the pond!  Certainly helps!

 

Brian.

 

Another word - powerbase.

 

(As in DCC Concepts Powerbase)

 

Cheers,

Mick

[peterfgf]

Hi,

 

I've just done some tests on a Bachmann Jubilee I've been lent for conversion to DCC. I tested the tractive effort on a slip track with the coupling connected to a load cell. I then weighed the loco.

 

I put the tractive effort and loco weight into my experimental gradient and curve calculator.

 

I then took the number of coaches your Jubilee could haul on the flat from your graph in post #1 of this topic in order to estimate the friction of the coaches.

 

I put the estimated friction of the coaches into my calculator.

 

The calculator predicted that my Jubilee would haul 4 of your coaches up a 1 in 50 gradient but not 6 coaches.

Bachmann PATRIOT GRADIENT A 1.PNG

Above shows 4 coaches, calc was run again with 6 coaches and at 1 in 50 the loco traction was less than drag due gradient and friction.

 

I haven't tested any other locos on your graph but I was relieved my calculator/predictor wasn't way out.

 

Could you send a link if possible for 71000's article on gradient tests as I couldn't find it under post #567.

 

 

Many thanks

 

Nick

Nick,

 

The original post from 71000 appears to have disappeared.  There were three graphs showing the haulage results.

However, the original post, including links to the graphs, has been included as the preamble to my reply (post 578)  http://www.rmweb.co.uk/community/index.php?/topic/92905-Heljan-gwr-47xx-night-owl/page-24

 

I'm rather taken with your calculations, after thinking they would be too difficult (see my reply to Frank of Shipley MRS in post 26 above), and will see if I can repeat them.  I'm very pleased that we have some sort of agreement.  Prediction plus confirmation by measurement is a good way to go.

 

Peterfgf

[34theletterbetweenB&D]

...Seems to be too many variables to be dogmatic.

 It is getting on top of all the significant variables by measurement that is the way forward.

 

 

Important point about the state of the wheels. Probably why my Pannier tanks give different results. I guess the same applies to the track in as much as old dirty track is not good for electrical contact but grips better.

 Condition of the two surfaces involved in the adhesion is a significant variable. New rail is significantly outperformed by long in service rail (nickel silver) and it takes significant running time before newly installed rail is up to full adhesion. If you measure, you get to know this information

 

Based on a similar testing concept to that described in this thread, I run a weighting scheme for steam locos by power class, to reflect their capability on my layout's ruling gradient of 1 in 80. No point sending off a class 4 on a class 7 job, it will slip to a stand. (In brief everything up to power class 3 has 250g on the driven wheels, and then the baseline rule is increments of 50g per power class, thus class 8 pacifics have 500g, All done with lead, often requires mazak to be removed and replaced in lead as already described.) The centre motor diesel traction is all hopelessly overweight as supplied.

 

The most significant variable controlled by measurement is rolling resistance of the stock. Everything must roll away from rest on 1 in 100;  an ancient rule acquired as a teenager from my first model railway club experience. Ideally stock should do better than that. That way even an 0-4-4T will realistically slowly move 12 coaches on the level, with a nice realistic half turn or two of wheelslip as it overcomes the inertia on starting.

[DCB]

 

 

The most significant variable controlled by measurement is rolling resistance of the stock. Everything must roll away from rest on 1 in 100;  an ancient rule acquired as a teenager from my first model railway club experience. Ideally stock should do better than that. That way even an 0-4-4T will realistically slowly move 12 coaches on the level, with a nice realistic half turn or two of wheelslip as it overcomes the inertia on starting.

Having stock roll on a 1 in 100 is great if your layout is actually level, however most of us aren't that lucky and rakes of stock rolling away is a very real problem. So much so that I am working on a working handbrake to allow a B set to be run round.   As regards realistic haulage a Jubilee was allowed 3 coaches unassisted on the Lickey 1 in 35, but a similar size GWR County was able to haul 12 well filled coaches from Newton Abbott to Plymouth in BR days up a 1 in 38.  Proving what GJ Churchward said, "One of ours would pull two of theirs backwards,"

[Ian_H]

In the same vein, steel track is better than N/S track for grip.

 

 

Another word - powerbase.

 

(As in DCC Concepts Powerbase)

 

Cheers,

Mick

As Mick has mentioned, the DDC Concepts Powerbase seems to be an answer to gradients down to 1 in 30, here's a video that I've seen before, you may find it of interest.

 

 

I've no experience of DCC Concepts Powerbase ................ but I am interested.

[Nearholmer]

Fascinating. I wonder whether they’ve managed to implement creep-control in miniature, or perhaps its some sort of conductive paint, doped with fine particles of metal, on the tyres.

 

Anyway ....... this is a very good thread!

 

I’ve long wondered why there aren’t a standard set of tests of model loco haulage capability, including gradients and curves, and the two together. The information gleaned would be very useful, especially if included in product reviews, and itmight cause manufacturers to focus on the too-often-forgotten business of hauling trains, instead of just obsessing about cosmetic detail.

 

The number of variables is, indeed, large, but that is true of many things that are subject to test, and the ‘trick’ is to define the test setup very tightly, so that the quality that is being sought dominates the outcomes.

 

Please, please move on to devise a standard setup that is more transferable than “it hauls N coaches round our loft layout”, which is the Peco favourite.

 

One suggestion to add is that micro-arcing might explain why NS gets ‘stickier’ with time when used as rail and tyre. Current transfer is always imperfect in rolling contact (which is why ‘real’ electrical devices, even those that appear on first inspection to use another mechanism, use sliding contact), and running current via bearings is a recipe for bearing damage. Even at the very low currents and voltages in question, micro-arcing will occur, and it will erode/pit both surfaces.

[NIK]

Hi,

 

I've tried to expand my experimental gradient and curve predictor I mentioned in a previous post on this topic to cover trying to predict the speed a train will go up a gradient and round a curve.

 

I tested a Heljan OO class 16 diesel chassis whose speed varied noticeably depending how many coaches were behind it when going round 3rd radius curves on my test track. I tested it with the most Mk1 coaches I had (9) and also with 5* Mk1s.

 

* I'm considering using a class 16 chassis in a 6 car Hastings unit.

 

The gradient and curve I want the Hastings unit to go up is a 1 in 40 with a 36" radius curve. Its on a scenic part of the layout so I don't want it to slow down too much.

 

The gradient/curve predictor had said the chassis plus 5 Mk1s should just make it up the gradient/curve.

 

The drag predicted for the chassis plus 5 Mk1s on the 1 in 40 with a 36" radius curve was very similar to the chassis plus 9 Mk1s on the flat test track with 3rd radius curves.

 

So I thought the speeds measured on the test track might equate to those on the gradient/curve of a club layout.

The min speed was 43 scale mph (chassis cold, pickups & track not cleaned) and the max 62 scale mph (chassis warmed up, pickups cleaned up by running, track cleaned).

 

The measured speed for the chassis plus 5 Mk1s on the layout's gradient/curve was 53 scale mph - in the middle (the track had been cleaned for an open day, but the chassis was cold and the pickups had not been cleaned). No slipping was observed.

 

I'm going to build a test helix to do more gradient/curve drag tests but if I can make it long enough I could do some speed tests.

 

 

Regards

 

Nick

 

 

 

 

[GregusGWR]

Magnadhesion was the old Hornby way. DCC Concepts sell small metal plates that fit under the track sleepers and powerful magnets to fit under the loco. Supposed to add traction. I have not tried that. I add lead sheet or liquid lead in all my locos and they pull better. My 0-4-0 Class 6 diesel shunter (Pullman) will haul 5Mk1 coaches up a   1:46 gradient with a level 2nd radius bend in it.

[NIK]

Hi,

 

In my last post I mentioned a comparison between speeds on my test track and on a club layout.

 

I've since fitted a local speedometer to my test track so I can see the speed over the seven inches between two Infra red detectors.

 

The speed shown by the local speedometer is up to 10 mph faster than the average speed round a lap.

 

I've checked the local speedometer with a stopwatch and an oscilloscope and the lap speedometer with a stopwatch. Both appear to be reading true.

 

So it seems as though the train is going considerable slower round parts of the lap than it is where I put the local speedometer (towards the end of a 90 degree curve).

 

When I have time I will try adding track feeds to every piece of set track rather than relying on any fishplates and see if that makes a difference.

 

Also the club layout I compared my test track with has feeds to every piece of track so the similarity in characteristics may have been less than I thought.

 

 

Regards

 

Nick

[NIK]

Hi,

 

Now that the heat that included the Basingstoke Bodgers has been shown on the Great Model Railway Challenge TV show I thought I could mention that I was asked to give them a copy of my experimental Gradient and Curve predictor. Their heat layout 'Santa's Holiday' had the main tracks on a dumbbell with gradients but I don't know whether they used my predictor as their trains were fairly short (you get a lot of elves in one wagon).

 

 

Regards

 

Nick (Basingstoke and North Hants Model Railway Society member. The society is looking for new members).