I recall reading eons ago that using the sander (not Black & Decker) in a loco was ineffective above a speed circa 27 mph? Does that still hold? Is it in fact correct? Is it accurately rendered in TS20XX Is the sanding speed limit any different for Steam, DMU, EMU, Diesel, Electric, Hydrogen, etc? Any insights gratefully received. pH
I can't see how anyone can arrive at such a finite figure, as too many variable are at play, but the greater the speed, the less it would be required due to the momentum of the sheer mass involved. While I've not bothered to check speeds, Trains in TS do require less assistance once rolling, and that assistance required does seem to decrease with speed. From a physics point of view, it would depend on axle weight, and how many axles are powered, rather than specific types of traction. Technically, electric locomotives (including diesel electric and hydrogen as they all use electric motors) would require the most help, as an electric motor achieves maximum torque at zero rpm. I've no idea how steam compares. I've never had an interest in steam traction. That experimental hydrogen train... I'm assuming it uses hydrogen cells.. and therefore is just an electric train, yes?
I don't think the bolded part of the quote is quite correct. Available traction does not depend on momentum. It depends on mass (which is independent of velocity) or more specifically the normal force from any driving axle. As long as the tractive force is less than the (normal force) * (coefficient of friction) there won't be any wheel slip. The reason why you are less likely to encounter wheel slip at higher speeds is due to the tractive effort falling with increasing speed (power = force * speed, so force = power/speed). However, on some very "overpowered" locomotives or very light weight locos/multiple units you can still encounter wheel slip at high speeds because maximum tractive effort is achievable at higher speeds or because the normal force is low. The easiest way to test if the realism is accurate in TS2021 is to go into the locomotive folder and edit the "Tractiveeffortvsspeed.dcsv" file (after backing up of course) so that the power is unlimited (no tractive effort drop off), then you can test if it is possible to get wheel slipping at high speeds. I haven't done this myself but that there are problems with the way wheel slip is modelled in TS20xx is quite well known. It seems to be inversely dependent on the train mass (all wagons etc) which is very strange and I'm not sure how they even programmed it to be so wrong. I think it is a remnant of the Kuju Railsimulator engine though.
The game doesn't natively support simulation of synchronous wheelslip which is an issue at higher speeds with diesel electrics. (which is usually corrected by onboard sync slip sensors)
In-game sanding adds a certain amount of tractive effort, which is a close function of Amps displaying. Some locos seem to have different grip based on speed (ranges), some even lose grip as accelerating. Some scenarios have different rail sections, i.e. for the sake of fun, your first 200 meters have grip so that you can at least start. In other scenarios there is oil on the rails. When you mix different locos, particularly in the US, they have massively different traction curves and so you might experience funny. Donner Pass scenarios with a mix of SD40 and GP9 comes to mind - the GP9 has a ramp-up, but then above 3-5 mph drops drastically. So I learned I need to sand until 10mph but eventually figured the SD40 itself doesn't need sand at all. That 27mph might come from the idea that as the speed increases, sand doesn't last as long between the rail and the wheels, and so someone made a practical rule that it's pointless enough above this speed. People say various things about grip and spin, overall I think there are some practical misunderstandings (i.e. tractive effort equals acceleration) which lead to said experience.
