also posted this suggestion on minecraftforum
anyways, would be lovely if a modder was interested in creating something like this:

Granted, there are already multiple vehicle mods.
But those are generally vehicles that look completely different from minecraft objects while having the odd steering and motion physics of some undefined ridable minecraft entity.
To me that is the worst of both worlds

Instead, what i am proposing is something that, while looking like minecraft and being crafted in a way that fits minecraft, but at the same time is steered smoothly and behaves dynamically like an actual four wheeled vehicle



[spoiler=how could it be crafted?]wheels from iron and slime ball
[b][b][b]
[b][j][b] ------> [w]
[b][b][b]
kart from 4 wheels, iron bars, a stair to sit on, and a redstone block to power it
[w][j][w]
[j][x][r] -------> [Kart]
[w][j][w][/spoiler]

[spoiler=how would you steer it?]you turn it the one way in minecraft that gives you a direct connection of direction and on screen display:
the view direction controls it
this means the front wheels turn according to where you look
the forward and backward keys ([W] [S]) give you a forward/backward force going into the rear wheels
the force is straight forward/backward in the direction the kart faces, not rotated by your view
since the wheels have finite stickiness to the ground the kart will start to slip when you try too forceful maneuvers
optionally the kart spinning may turn your view with it, if there is a smooth and reasonably effective way to program it[/spoiler]

[spoiler=how could it work technically?]the kart has a mass (inertia working against changes of momentum), center of gravity and average mass distance from the center (inertia working against changes of rotational momentum)
each wheel touching the ground have forces working on them, changing the momentum of the kart, and through their position relative to the center of gravity the rotational momentum
those forces are:
rolling friction working against whichever direction the wheel is rolling
slipping friction against whereever the wheel tries to slide, or is sliding if the force put through it exceeds that friction, the steering also works by the turned front wheels pushing the kart into rotation through that friction
acceleration forward or backward through the rear wheels, this just like steering may cause slipping
optionally the frictions against rolling and slipping may depend on the material (block) the wheel is on[/spoiler]

should you like the idea, please spread the word
should you be a programmer willing to do it, even better
in case you don"t like the idea, please comment on what can be improved