[steamer_ctn]

joe_star, on 28 November 2021 - 08:37 PM, said:

Into the equation above gives exactly the tractive force of 30.5klbf, which in my understanding would only be delivered when the boiler is actually at 160psi, not at lower pressures.....

The 0.85 factor is an arbitrary number, so it is possible in some instances that MTTE could actually be higher then this figure.

In your video can you highlight the time stamp where the TE jumps up to the MTE?

Thanks

[joe_star]

steamer_ctn, on 28 November 2021 - 09:53 PM, said:

The 0.85 factor is an arbitrary number, so it is possible in some instances that MTTE could actually be higher then this figure.

In your video can you highlight the time stamp where the TE jumps up to the MTE?

Thanks

Hello,

Please have a look from 10 sec onward. You can see the force (and HP) fluctuating. My boiler pressure is around 120psi at this point (down from the default 160psi, lost a good deal of steam ascending up to this point). The force changes between 22.8klbf (which matches the TE equation at approx 120psi) to 30.3klbf (which matches the TE equation at the design pressure of 160psi).

I did the TF calculation based on the boiler pressure available in my loco at that point (120psi). Even taking the TE equation without the 0.85 fudge factor only yields 26.9klbf at 120 psi boiler pressure. That from what I understand would be the maximum theoretical TE my locomotive be able to make at that only 120psi boiler pressure, not taking the losses that would be accounted for to give MEP.

Thanks

[steamer_ctn]

joe_star, on 29 November 2021 - 12:00 AM, said:

Please have a look from 10 sec onward. You can see the force (and HP) fluctuating. My boiler pressure is around 120psi at this point (down from the default 160psi, lost a good deal of steam ascending up to this point). The force changes between 22.8klbf (which matches the TE equation at approx 120psi) to 30.3klbf (which matches the TE equation at the design pressure of 160psi).

Ok, I can now see what you are saying.

I have applied a small patch to try and make the starting tractive effort more responsive to boiler pressure variation. It has been added to the unstable version.

[joe_star]

steamer_ctn, on 29 November 2021 - 01:38 AM, said:

Ok, I can now see what you are saying.

I have applied a small patch to try and make the starting tractive effort more responsive to boiler pressure variation. It has been added to the unstable version.

Hello

Yes it appears now the starting tractive effort is much more closely tied to the available boiler pressure, rather than the design boiler pressure as it appeared to be previously.

I suppose there has never been any attempt yet to imitate the changes in force that happen at every forward and reverse stroke.

[joe_star]

I also found the following article which gives some details into tractive effort and it's derivation

https://www.jghtech....cle-current.pdf

Interestingly, it mentions that the K factor of 0.85 also varies with cutoff, ranging down all the way 0.6 at 50% cutoff.