What causes steam locos to slip...?

[rkk01]

Back on the BMR, and I'm testing the Morlais Junction to Pontsticill section of the Merthyr Branch - 9F + 40No. 16T minerals

Anyhow, I can get the train moving from a standing start on 1:45, run through the loop / double track section at Morlais Jnc and through a sharpish curve following the Taf Fechan valley to Pontsticill. I can get the train going at 15-20mph, but then it starts slipping - bizarrely after the gradient has eased to 1:50.

Is it something in the model, or some track setting???

[michaelhendle]

with steam loco's it's a case of juggling the regulator and the cut off,usually slipping is caused by opening the regulator to much,you could try putting the sanders on,to get extra grip.

Mike

[rkk01]

Yes - but I don't understand how I can get moving on steeper section, only to spin out after the gradient has eased

Sanders and careful regulator / cutoff control are prerequisites...!

[Rockdoc2174]

I don't understand it fully but I know that the track used can offer different conditions, although it appears identical to the player. I've found on some routes, similar to the OP of this thread, that driving conditions that have given me good grip will change for no obvious reason and the loco will slip much more easily, returning to the previous conditions some time later.

Keith

[adburgess1992]

Yes - but I don't understand how I can get moving on steeper section, only to spin out after the gradient has eased

Sanders and careful regulator / cutoff control are prerequisites...!

My only guess is because you could get away with using more tractive effort uphill because of having to overcome the reistsance of the stock but less than the rail were as on a less steeper graident you are overcoming the tractive effort of the stock and track causing it to slip by putting to much power down, Thats my guess atleast anyway its one of them things like injectors we dont really understand why it works it just does. By no means claim to be an expert just that was always my understanding of it.

[AndiS]

Today it could be anything. Once upon a time, there were reliable physics calculations behind wheel slip. Then they messed it up and later engine and scenario creators jumped in, plugging in their best guess at the real thing which can be a different thing for different creators. If I understood this right, you can have surprise wheel slip now like you have fireworks and spooks.

All you can do is close the regulator, open the sander and whenever the wheels stop their spinning, open up the regulator with care and then stop the sanding. And say "thanks for the extra challenge, very entertaining".

[tialho]

Leaves on the line!

[rkk01]

Leaves on the line!

I really doubt that...

Haven't got around to planting all the trees yet

OTH, what AndiS says might be on the money. Might experiment with some other traction
[hopeful] comparison with 7202 would be excellent [\hopeful]

[metrobus]

Don't even try to comprehend the basic Railworks adhesion model, it is as illogical as it is incorrect which is to say very.
Edward

[Alicatt]

Isn't there a difference in starting the scenario uncoupled and then coupling up compared with starting coupled up from the start?

I did try that with a scenario for the 9f, I modified the start by uncoupling the loco and having to then couple up and pull the 40 wagons up the hill from the station, much less slip that way.

[karma99]

Don't even try to comprehend the basic Railworks adhesion model, it is as illogical as it is incorrect which is to say very.
Edward

Sadly, Ed is very correct about it being very incorrect! This is why many of us have scripted our own wheel slip physics to give something predictable and much closer to reality.

[rkk01]

Great to have input from some of the developers who are at the cutting edge for what can be done with steam loco models!

Seems like it may not be my driving after all

[ttjph]

Don't even try to comprehend the basic Railworks adhesion model, it is as illogical as it is incorrect which is to say very.
Edward

Sadly, Ed is very correct about it being very incorrect! This is why many of us have scripted our own wheel slip physics to give something predictable and much closer to reality.

And very convincing it looked too, the first time I got the DC Castle to slip!

[rkk01]

The old "starting coupled up" bug

The 9F had an embarrassing surplus of power and steam...