[Lamplighter]

It really depends on many factors that the drive wheels start to slip. Even on the number and coupling of the drive axles. Therefore, locomotives with five drive axles were used on the slope-demanding tracks of the part - mountain locomotives.
Five coupled axles for better starting with the load.
I see the problem elsewhere: In OR the event of wheel slip, the unloader (reverser) must be completely reset to zero.
In reality, it is enough for the driver to remove a small part and the wheels will get out of trouble. It is not possible to get the reverser to zero quickly.
Sample: https://youtu.be/E5pqQBf_EgA

[ATSF3751]

Its really the throttle you want to get to 0 not the reverser.

[Lamplighter]

 ATSF3751, on 15 March 2022 - 05:10 PM, said:

Its really the throttle you want to get to 0 not the reverser.

Yes i admit it , i replaced the reverser and throttle (steam cylinder filling and steam control).
But that doesn't change a thing. Wheel slip immediately switches to high speeds and fine steam control won't stop it. The moving off must be repeated from zero.

[Jonatan]

 Lamplighter, on 14 March 2022 - 01:53 AM, said:

Sample: https://youtu.be/E5pqQBf_EgA

This isn't the escape velocity we experience in OR.

[Lamplighter]

Here are some more examples:

https://youtu.be/5J91kqASNO4?t=215
https://youtu.be/iKzRNrDH5AU?t=140
https://youtu.be/ByjXCarKjmY
https://youtu.be/6bH7-6bjPVA?t=153

This is a difference compared to the current start-up of a loaded steam locomotive in the OR. There, the wheels only spin uncontrollably.

[ATSF3751]

So I have been thinking about what all effects wheel slips on steam locomotives and here is a list of what I have thought of. Most of these can be used for all locomotives when it comes to wheel slips though.

1. Factor of Adhesion- Weight on the drivers and weight of drivers.
2. Weather- Rain and snow.
3. Train- Weight of train behind the locomotive.
4. Power output- How much the throttle is opened when you start.
5. Grades- How steep the grade is the locomotive is encountering.
6. Other factors- Grease, leaves or vegetation on the rail, rusty or old track along with starting on a switch.


If I have left anything else out please feel free to add onto it. You can not just go off of one or two things when it comes to wheel slips like Open Rails currently does.

Here is another good video of a steam locomotive slipping. https://www.youtube....h?v=FH6knmorArw


Brandon

[steamer_ctn]

To facilitate further investigation of this operational feature I have configured two locomotives (see BR Merchant Navy locomotive).

In real life this locomotive was originally built with a Factor of Adhesion (FoA) of 3.76. As this value was less then the rule of thumb value of 4, it meant that the locomotive was prone to wheel slip if the driver was not paying attention. Later in its life the locomotive was rebuilt to correct a number of poorly performing features with the original design. As a consequence the rebuilt version had a FoA of 4.3, which reduced the likely hood of it slipping. The main factor changed to improve the slip characteristics and FoA was to reduce the boiler pressure, and the resulting tractive effort (force). For the purposes of this model, I have reduced the Adhesion of the models so that slip can be induced if not started smoothly.

Typically if the throttle is opened as quickly as possible, with full reverser setting, then the original version will slip. If the throttle is opened more slowly and smoothly, then both locomotives should start without slipping.

A brief description of how wheel slip occurs is shown on this page. If the throttle is not reduced when wheel slip occurs, then eventually the locomotive will end up with uncontrolled wheel slip. Ideally when wheel slip occurs the throttle should be sufficiently closed to reduce the force applied to the wheels to be less then the wheel slip adhesive force.

Further investigation may continue.

[ATSF3751]

Thank You Peter along with all of your other hard work to try and make steam locomotives as realistic as possible in Open Rails.

Brandon

[scottb613]

Hi Folks,

I'll take a look - thanks much Peter.

As mentioned previously - I've been conducting a bit of a reconnaissance foray into the bowels of the enemy camp.
:p

I think we can learn a great deal from how others tackle issues.

There's a new BigBoy over in TS2022 - it's made by an exceptionally masterful modeler called "SmokeBox" that does a great deal outside of the normal realm of the core TS2022 program via LUA. This appears to be the most sophisticated steam locomotive model ever made. Check out his wheel slip - this is what I'm envisioning wheel slip should be and it appears to jive with real world footage. Note the fully animated valve gear and EVERYTHING else.


Smokebox Big Boy - Wheel Slip
https://youtu.be/0GpHP0Gkxpo


Steam Aficionados - Driving and Firing the Smokebox Big Boy
https://youtu.be/IkTUd0faCaE


Regards,
Scott

[Jonatan]

Quarter-slip is very realistic. They do that. The wheelslip simulation on that model is excellent, exactly what we hope to see in Open Rails.