[copperpen]

I will try the Atlantic at some point, but this was run using the Hall OR Adv from your site, with a rake of the default OE cars.

[copperpen]

While testing various combinations of locomotive and rolling stock I noticed something strange on the Forces HUD. Using Alt+P to change the weather I noticed that changing to snow has an effect on the displayed friction which becomes about 3 times higher than dry or rain. Sometimes this does not affect the locomotive but does alter the tender. I have only found one set of equipment that is not affected, the default OE cars which retain the same friction whatever the weather.

[steamer_ctn]

copperpen, on 03 May 2016 - 09:33 AM, said:

While testing various combinations of locomotive and rolling stock I noticed something strange on the Forces HUD. Using Alt+P to change the weather I noticed that changing to snow has an effect on the displayed friction which becomes about 3 times higher than dry or rain. Sometimes this does not affect the locomotive but does alter the tender. I have only found one set of equipment that is not affected, the default OE cars which retain the same friction whatever the weather.

Is this the rail/wheel friction (called WAG and Loco Adhesion) in top of forces HUD or the Brk Frict against each wagon?

The code at the moment only changes the wheel/rail friction value with the different weather seasons. The Brk Friction should not vary with season, only speed.

Can you give me a series of screenshots as you vary the season (hopefully at the same approximate speed?

Thanks

[copperpen]

First of all, it is the friction in the forces table that is affected, not the rail/wheel friction. The change to the friction only happens when the consist is at rest. The friction at rest in falling snow is triple that of dry or rain which is why it is very easy to get wheelslip while starting on falling snow and not so easy in the other two conditions. Once the consist is rolling there is no difference in friction levels between the three weather conditions.

[steamer_ctn]

copperpen, on 06 May 2016 - 02:15 AM, said:

First of all, it is the friction in the forces table that is affected, not the rail/wheel friction. The change to the friction only happens when the consist is at rest. The friction at rest in falling snow is triple that of dry or rain which is why it is very easy to get wheelslip while starting on falling snow and not so easy in the other two conditions. Once the consist is rolling there is no difference in friction levels between the three weather conditions.

Are these the coefficient of friction values that you are referring to, or the "Friction Force" figures in the 5th column? I can see the friction force figures varying with weather, but not the brakeshoe friction.

If it is the Friction Force, then these values will be higher in cold weather due to the bearings and/or the axles being "frozen". As the train moves, these items warm up, and the friction reduces.

If it is not the Friction Forces, can you please add some screen shots so that I can see what the issue is, as I cannot understand it at the moment.

Thanks

[copperpen]

It is the friction forces, but I would not expect those to triple in cold weather.

[steamer_ctn]

copperpen, on 10 May 2016 - 04:19 AM, said:

It is the friction forces, but I would not expect those to triple in cold weather.

The book Steam Locomotive by Ralph P Johnson describes the impact of cold conditions on the journal bearing as follows:

"Journal friction at the instant of starting is generally assumed to be about 20 pounds per ton (US), diminishing rapidly to a minimum at 5 to 10 miles per hour, and remaining constant at higher speeds.
Temperatures below freezing increase journal resistance at starting to 30-35 pounds per ton (US), and the most favorable conditions mentioned above are not attained until the train has been running some time."

The OR starting friction model is based on this, and a number of similar statements. So the starting friction at zero speed should not exceed 35 lbs per US ton for journal bearings. Roller bearings have a similar approach, but have lower values.

Using the above figure the starting friction can be calculated and confirmed against the HUD values. As far as I can see so far the figures appear to be being calculated correctly.

If you have an example where a figure of greater then 35lbs has been used, then please provide me with the details.

Thanks