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

[Crazymechanic]

Well considering the device on the wheels doesn't weigh that much I would say if when stopped a cylinder is pushing against something horizontally it would probably make the wheels slip because with a little weight solid smooth metal against another solid smooth metal has very little friction - well that's the whole idea behind train being a very efficient transport.

By the way a simple dc coil operating a single rod that pushes something in or out doesn't count to my mind as a huge complexity b the way.
But forget the brake pad maybe you can combine Danger's idea with the coil for say the coil pushes in or out a rod that anchors the whole device after any given intervals that you make on the rails.
I can't imagine how would you make this anchor without a electrical coil or device considering that this whole machine I guess will run pretty automated or controlled from a computer like a CNC machine I guess.

 

[student715]

Danger.. You're killin me!
That was a prototype in the first picture. The entire machine will be a weldment after all the bugs are worked out.

Here is another image.
I added a mock weight for reference and the cylinder will produce approximately 20,000lbs of force against a stationary object.

Didn't I kill you in a previous thread?

Student, that is a beautiful drawing. I still think that my previous suggestion of a clamp is the most practical one, but I'll think on it some more.
You won't hear from me for a few minutes; I have to get myself out to my doorway because there's a beer delivery coming and it takes me 5 minutes to get there.
By the bye, that thing seems to have an awful hell of a lot of bolts for something that you claim is welded...

edit: I just realized upon rechecking something that I suggested tapping your hydraulics for the clamp mechanism, whereas you stated that you are using pneumatics. My bad.

 

[256bits]

Something doesn't add up here with the figures you give, for your light rail system.
5000 pound weight of the 'weldment' , and a 20,000 pushing force for the 'pneumatics'??

You stated earlier:
"The engineer i am working under has completed several coefficient calculations using steel on steel and decided the weight of the weldment alone, will be enough to allow the brake to keep the weldment from being pushed my the cylinders"

With an assumption of an approxiamate coeficient of friction for dirty or somewhat greasy ( ie not clean ) steel on steel of 0.1, your static friction force to hold the car in place in only 500 pounds, with no safety facture.
Or your car needs to weigh more than 200,000 pounds.

Something is not so genius as you say, or your forces are incorrect.

20,000 pounds supplied by pneumatics.
What bore and pressure are you using?

 

[student715]

There is more then 1 pneumatic cylinder.
I removed the top of the assembly including all other cylinders from this image.
The total force produced from the cylinders is going to be about 20,000lbs.
The tracks and wheels will be covered to eliminate any chance of oil.

The answer i am searching for is to the question of friction.. I think?

When finding the coefficient of steel ( he used.8) this calculation does not take into account the surface area. I am baffled by this because the logically the bigger surface area the more traction.

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..

Something doesn't add up here with the figures you give, for your light rail system.
5000 pound weight of the 'weldment' , and a 20,000 pushing force for the 'pneumatics'??

You stated earlier:
"The engineer i am working under has completed several coefficient calculations using steel on steel and decided the weight of the weldment alone, will be enough to allow the brake to keep the weldment from being pushed my the cylinders"

With an assumption of an approxiamate coeficient of friction for dirty or somewhat greasy ( ie not clean ) steel on steel of 0.1, your static friction force to hold the car in place in only 500 pounds, with no safety facture.
Or your car needs to weigh more than 200,000 pounds.

Something is not so genius as you say, or your forces are incorrect.

20,000 pounds supplied by pneumatics.
What bore and pressure are you using?

 

[Danger]

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..

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.

 

[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.