Would it be easier to pull a train with flat wheels?

[student715]

Yes, I agree the weight of the machine will not hold in place with only gravity.
However, the coefficient equation implies that it will.

There's a balance to be struck in that situation, though. The larger the contact patch, the less weight each cm² of rubber experiences and this lowers the frictional force. That's why we switch to skinny tires in winter and is the principle behind snowshoes.
I still think that gravity alone will not hold your doodad in place, though.

 

[Danger]

I think that I just came up with the absolute most ridiculous and impractical solution to this that could ever cross someone's mind.
Carry equipment to weld the wheels to the track; then use a plasma torch to loosen them up when you want to move. (I challenge anyone to do worse...)

 

[Crazymechanic]

Challenge accepted , put an extra set of wheel pairs to the device and then repeat the last think mentioned by Danger... :d
Here is your worse.

And speaking about the friction part and holding , even without calculations just from common sense I can assure you that Danger is right the device having a weight of that mentioned above and a horizontal push with a force of 4 times the vertical weight probably won't hold it.
I suggest you need some clamp or brake added to the device to make it absolute.

 

[Integral]

Or reduce the pressure on your pneumatics.

 

[pumila]

If wheels are not slipping we are just interested in static friction. So looking at sliding alone...

1. Static friction is constant for a wide range of load areas.
2. At extreme loading (massive loads/tiny load areas) static friction climbs dramatically.

So tiny round wheels and massive loads would be the way to go, but conditions are such that distortion and wear would make for a very short wheel life.

 

[Danger]

Challenge accepted , put an extra set of wheel pairs to the device and then repeat the last think mentioned by Danger... :d
Here is your worse.

I stand defeated...

 

[a1call]

A phenomenon you might want to look into is Magnetic Damping
Lowering strong Rare-Earth magnets to proximity of conducting rails could be an effective means of reducing speed. This would assist in weight based friction braking.

 

[a1call]

I am not an engineer, but a car can stop faster with wider tires. Same rubber and same road and same weight, just different surface area..

As I mentioned before, friction is difficult to formulate.
An over inflated tire can take longer to stop than an under inflated tire mainly because the momentum would result in more of a skipping action rather than tire wear.
Think of a bouncing basketball moving along vs a flat ball being dragged.