Would a locomotive on ice (like in The Polar Express) move?

Question

In the Polar Express film, there is a scene where the Polar Express runs off the tracks onto a frozen-over lake, which supports it and doesn't collapse even after the locomotive tilting and hitting the ice with force twice. (This is disregarding the crack from the pin.)

This Reddit post calculates out that

it would take at maximum 2.895 m (9 ft. 5.95 in) of clear freshwater ice to support the Polar Express weighing in at its maximum 825 US tons ["the fully fueled Pere Marquette 1225 @ ~425 US tons and 5 passenger cars high-balled @ 80 tons each"].

Would a standard-gauge locomotive like Pere Marquette 1225 (either steam or diesel), placed on sufficiently thick ice, and its throttle applied, move? Or would it stay in place and have wheel slip?

Answer 1

Starting from rest, it will slip, but not because the friction coefficient is too small, but because:

• the ice will slowly melt from the friction of the motor wheels (and be ejected) the wheels will slowly sink to the point in which climbing out of the hole with the available friction is impossible - with a low friction coefficient, it doesn't take large depths to reach that point
• the locomotive is heavy enough to cause the ice become liquid water based on the pressure alone. It will continue to stay liquid until the wheel descends and the surface of the contact is high enough to lower the pressure under the point increased pressure liquefies water (have a look on the phase diagram of water - at 0C, a pressure of 10MPa will transit the water from solid into liquid. Not unexpected, since water freezing is accompanied by an increased in volume)
• the liminal layer separating the ice with the environment behaves more like liquid water up to a temperature of -35C (and a thickness of 12nm for fresh water, thicker for salt water). A layman explanation goes like: very much like the equivalent of the surface tension, the water molecules in ice are bound more strongly with their neighbors than the ones at the surface, the latter interact with the rest of the environment like any water molecule will do. But do read the linked PDF, it's fascinating - the hypothesis was advanced by James Thomson, confirmed by his brother William Thompson (Lord Kelvin), dismissed by Michael Faraday, reconfirmed and investigated by experiments in modern era.

If the train is already in move, it is a guess for how long it will continue to do so, the dynamics of interaction between wheels and ice and the aerodynamic friction is complicated enough.

Answer 2

It's very likely it will not move and simply slip.

Snow and ice are known for causing slippery rails

Winter can provide problems of low adhesion when snow and ice are deposited on running lines. Just as with road vehicles, black ice can cause trains to encounter difficulty when starting away, or can initiate wheel slide during braking.

The loss of friction between wheels and rail results in loss of tractive force: the wheels begin to spin, and in some instances the train is unable to move. In braking, substantial loss of friction results in reduced braking force. Braking distances are considerably longer, and in extreme cases the wheels may even lock up, causing the train to slide.

Trains use sandboxes to improve traction in difficult situations

A sandbox is a container on most locomotives, multiple units and trams that holds sand, which is dropped on the rail in front of the driving wheels in wet and slippery conditions and on steep grades to improve traction.