Ensuring a Roller Rolls ?
Ensuring a Roller Rolls ?
(OP)
Help - does anyone know the formula, or ratio that will ensure that a round roller will roll on a flat surface - what is the maximum round axel shaft dia. ?? that will allow rolling and not sliding.
is there a ratio that is a guideline ??
Thanks a lot
Dave B.
is there a ratio that is a guideline ??
Thanks a lot
Dave B.





RE: Ensuring a Roller Rolls ?
Where:
F is the normal force against the surface that the roller is intended to roll on.
R is the roller radius.
A is the coeficient of adhesion between the roller and whatever it is supposed to roll on. This is not the same a the coeficient of friction, although it may be close.
T is the torque required to overcome the roller's bearing resistance.
RE: Ensuring a Roller Rolls ?
no length as a factor in the
given equation.
What is the length of travel of
the roller that you are disigning
for?
RE: Ensuring a Roller Rolls ?
condition for initial rolling:
Fn*fstatic*r>Bf=bearing frictional moment
condition for steady rolling:
Fn*fdynamic*r>Bf
Changing the inequality from > to < then gives the conditions for skidding or sliding.
RE: Ensuring a Roller Rolls ?
If the coefficient of rolling resistance is given, "a", then a roller of radius "r" and weight "W" will need a horizontal force of "F" such that:
F = Wa/r
Typical rolling resistances are 0.003 in for steel on steel to 4 inches for steel on soft ground. I have used 0.05 inches for steel on level pavement and got very close horizontal forces, i.e. realistic nominal values.
I guess the big question is to determine your resistance on a medium other than these listed.
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Ensuring a Roller Rolls ?
Mike Halloran
Pembroke Pines, FL, USA