info: friction is probably mass

[spacek531]

Consider the following observations:

1. The friction value of a train is the sum of all the friction values of the cars.

2. The acceleration and deceleration of a powered car positively correlates with horsepower but negatively correlates with friction.

3. The speed a powered car climbs a hill positively correlates with horsepower, but negatively correlates with friction. This is the friction of the train, not the front car. If a car has enough horsepower, it will asymptote to a velocity when traveling up a hill.

4. Peeps add to the friction value of the train.

5. Cars are given friction values roughly according to their length.

There are a number of explanations, but I believe the simplest is that the "friction" value is mass.

One cannot really add friction - friction is a constant determined by the interaction between two specific surfaces. Video games approximate this all the time, but there is a simpler explanation that fits rudimentary physics: the mass of a whole body is exactly the sum of its parts.

Acceleration and deceleration both negatively correlate with friction. This is important: if friction really was friction, deceleration would positively correlate with friction, not negatively! A rudimentary physics equation explains both acceleration and deceleration behaviors: acceleration = torque*constant/mass. This equation says that we can expect faster acceleration with more torque (which is a linear function of horsepower), and slower acceleration with more mass. This relation is observed ingame.

If a car has enough horsepower, it will asymptote to a velocity, which the following rudimentary physics equation explains: horsepower/(mass*gravity*cos(theta))=velocity. With higher horsepower, the car goes up the hill faster, and with higher mass, the car goes up the hill slower. This relation is observed ingame.

The model breaks down when simplifying the equation for ideal friction, where F = u*N, N = g*m: F = u*g*m -> F = k*m, a = F/m ->a = k*m/m -> a = k, ergo trains decelerate at a rate not influenced by mass, but this I assume the friction coefficient is a function of mass like torque is a function of horsepower.

Observation 5 is seen in ARRT1.DAT: the front car has a friction of 550, the middle cars have a mass of 500, and the rear car has a friction of 50.

If the friction value is actually mass, then peeps add mass to the train and cars are assigned mass roughly according to their length, something which sounds perfectly normal.

The assumption does not fit every case perfectly, as some variables are unexplained except by educated guesswork (that the power property in powered rides controls horsepower and torque at the same time). That said, with the above guesses, several observations are described by rudimentary physics equations under this assumption, which I believe is a strong argument in its favor.