Help (required force to move a sliding door weighing 100 kg with two rollers)

[johnpaul]

what is the required force to start moving a sliding door weighing 100 kg with two rollers.
what are the forces acting on the system?

shall i used rolling friction on this?

what formula to use?

thanks a lot.

 

[tiny-tim]

Welcome to PF!

Hi johnpaul! Welcome to PF!

There's no such thing as "rolling friction", since a pair of rolling surfaces don't move with respect to each other.

There's rolling resistance, which is essentially energy lost due to deformation of the wheel, but I shouldn't think three's much of that with steel.

The main problem will be friction between the wheel and the axle though its centre.

 

[Molydood]

Hi johnpaul! Welcome to PF!

There's no such thing as "rolling friction", since a pair of rolling surfaces don't move with respect to each other.

There's rolling resistance, which is essentially energy lost due to deformation of the wheel, but I shouldn't think three's much of that with steel.

The main problem will be friction between the wheel and the axle though its centre.

But wouldn't the bearings be subject to rolling resistance as opposed to friction?
Maybe you assumed no bearings whereas I assumed bearings :-)

 

[johnpaul]

hi tim, hi molydood,

please correct me if I am wrong.

here's my computation:

Weight of door=100 kg
Number of wheels= 2
Weight per wheel =(100kg)/(2)= 50kg

F1= αW / r

F1- resistant force of a single wheel
α - coefficient of rolling friction
W - weight
r - radius (0.015m)

F1≈(0.0005 m)(50 kg) / (0.015 m)
F1≈ 1.67 kg; say 2kg

F''≈(F1)(2 wheels)
F''≈(2kg)(2 wheels)
F''≈4 kg

Force to move the 100 kg door horizontally:
F≈ 4 kg



Values for rolling friction from various sources are not consistent and the following values should only be used for approximate calculations.

Steel on Steel α = 0.0005m

 

[johnpaul]

hi,

can anyone advise me what is the proper way in computing the friction between wheel and the axle? its just a simple door carrier(please refer to the drawings above).

thanks