horsepower vs rolling resistance

[conveyorbud]

steel wheel on steel rail. horsepower calculation per the attached sketch

 

[JStephen]

Do you know the resistance? Or is that what you're trying to find?

I think there is a railroad engineering forum here as well.

 

[Timelord]

conveyorbud,

Check out:

http://en.wikipedia.org/wiki/Rolling_friction

The value of rolling friction for a steel wheel on a steel rail is given in the table.

Timelord

 

[GregLocock]

Are you sure the rail is horizontal? (Clue)

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[hydtools]

See this setup. Calculate force to overcome rolling resistance. Calculate the wheel torque for this force. Plug torque into your horsepower formula.

http://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html

Ted

 

[desertfox]

hi conveyorbud

Were using metric units over here so I did the calculation and converted to horse power afterwards, this gave me an answer of 0.02245 horse power.
Firstly I took CRF to be 0.0006 for steel on steel which I then multiplied normal force of the wheel to find the force to overcome friction.
To find the power required I simply multiplied the force to overcome friction by the velocity which gave the answer above.

regards

desertfox

 

[GregLocock]

Yeah, I can see a 20W electric motor pushing 25 tons of railway wagon around. (That clue is getting bigger)




Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[desertfox]

hi Greglocock

I don't think a 20w motor will do it, but thats whats needed
just to overcome the friction and maintain the existing velocity given for one wheel, what you need to get it started in the first place etc is another question entirely.

desertfox

 

[BiPolarMoment]

Greg... perhaps you should get to the point .

 

[MJCronin]

Ummmm

Are we doing someone's homework problem here ?


-MJC

 

[BiPolarMoment]

It certainly looks like one MJC.

 

[desertfox]

Hi MJC

Check his profile he as been a member for 4 years I doubt this is homework.

regards

desertfox

 

[MintJulep]

Not nearly enough information on the sketch to solve.

 

[dvd]

Well, if the poster is using the wheel on a conveyor, someone will figure out a way to make it need to be more robust. If the wheel is rolling on a level surface then the place to start negotiations is

HP = (22 fpm * 56,000 lb) / 33,000 ft-lb/min-HP = 37.3 HP

rolling friction will decrease this value; dirty environment, defects, grades, etc. will increase it.

 

[GregLocock]

So, we've got one answer that is ~1500 times the other.

I'd hazard a guess the real answer is somewhere in between!

Perhaps the OP could tell us what he is really trying to do, while I agree that desertfox did answer the exact question as posed, I don't think it is a real world solution.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[chicopee]

Something is wrong with the free body diagram--Driving force is not where it is shown unless the rail was moving the wheel then friction would not be where it is shown unless the rail is sliding as well as moving???

 

[desertfox]

Hi Greg

The reason dvd got a different number to mine was he didn't multiply the normal force by any CRF.
I agree its not a real world answer it only addresses the amount of power to maintain one rolling wheel in equilibrium. Maybe the op will come back with some more info.

regards

desertfox

 

[hydtools]

Why isn't it real world? If you had four wheels, each would carry 1/4 the load and therefore 1/4 the rolling friction force. Total force would be the sum of the four; the same as the example showing only one wheel carrying all the force. The 'quess' is the value to use for coefficient of rolling friction; somewhere between .001 and .0025. This is just the power to keep the load moving. Nothing was asked about getting the load started and how long to reach speed.

What may not be real world is not including bearing/bushing friction.

Ted

 

[GregLocock]

Why isn't it real world? Because in the real world a 20W electric motor, roughly the one you have in your windscreen washer pump, is not enough to push a 25 tonne railway wagon around.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Bribyk]

From a Constructor magazine online article about the Arizona football stadium's rolling field:

"The 18.9-million-lb, 3.5-ft-deep dish takes about 65 minutes to roll outdoors for sunlight and grooming...
...The tray moves over 13 rails using 542 steel wheels, 76 of which are driven by 1-hp motors."

Looks like about 150W will move a 25t railcar, just not very fast.