PUSH FORCE CALCULATION
PUSH FORCE CALCULATION
(OP)
CAN ANYBODY HELP TO DETERMINE THE FOLLOWING MORE PRECISELY:
HAVE A SHAFT OF 4 MM DIAMETER
ASEMBLING A COLLAR ON SHAFT WITH TWO DIFFERENT MATERIALS
BRASS AND STEEL
THE THICKNESS OF COLLAR IS 3MM
THE INTERFERENCE MAXIMUM BETWEEN BRASS COLLAR AND SHAFT IS 20MICRON
THE INTERFERENE MAXIMUM BETWEEN STEEL COLLAR AND SHAFT IS 4 MICRON
WHAT IS THE GENERAL METHOD TO DETERMINE THE PUSH FORCE UNDER ABOVE CONDITION
HAVE A SHAFT OF 4 MM DIAMETER
ASEMBLING A COLLAR ON SHAFT WITH TWO DIFFERENT MATERIALS
BRASS AND STEEL
THE THICKNESS OF COLLAR IS 3MM
THE INTERFERENCE MAXIMUM BETWEEN BRASS COLLAR AND SHAFT IS 20MICRON
THE INTERFERENE MAXIMUM BETWEEN STEEL COLLAR AND SHAFT IS 4 MICRON
WHAT IS THE GENERAL METHOD TO DETERMINE THE PUSH FORCE UNDER ABOVE CONDITION





RE: PUSH FORCE CALCULATION
Here are the formula you need:-
Pa= f*3.142*d*L*Pc
where f=friction coefficient
Pc=contact pressure between the two members
d= nominal shaft dia
L=length of external member.
Pa= axial force required to interference fit
to calculate Pc for a given interference use the formula:-
Pc=x/[Dc*[((Dc^2+Di^2)/(Ei(Dc^2-Di^2))+....................
((Do^2+Dc^2)/(Eo*(Do^2-Dc^2))-((Ui/Ei)+
Ui/Eo))]
where x = total interference
Dc=dia of shaft
Di = dia of inner member(this is zero for solid shaft)
Do= outside dia of collar
Uo=poissons ratio for outer member
Ui=poissons ratio for inner member
Eo=modulus of elasticity for outer member
Ei=modulus of elasticity for inner member
This formula for Pc will simplify if the materials are the same.
Hope this helps
regards desertfox
RE: PUSH FORCE CALCULATION
RE: PUSH FORCE CALCULATION
The formula that I gave you earlier were for obtaining the force required to make the assembly at room temperature.
I would point out that now you have added a temperature range, at the upper temperature of 170degrees C I calculate
that the brass collar will be loose on the shaft as you have
insufficient intereference between the steel and brass.
Brass expands 1.45 times that of steel for the same temperature rise.
exp coeff of steel= 11x10^-6 /K
exp coeff of brass= 16x10^6 / K
where K=Kelvin
You need to base your intereference between your brass and steel shaft on your maximum working temperature.
I can perphaps help you further if you require, but I will need more information about exactly what your trying to achieve.
regards desertfox
RE: PUSH FORCE CALCULATION
Having re-checked my calculation it appears that there would still be some interference at 170 degrees C however
at this temperature the axial force required to move the brass collar along the shaft would be reduced.
regards
desertfox