Drum Brake Analysis 1

[Tagger]

I have an application for a drum brake where the brake shoes contacts the drum over an arc greater than 45°. The brake shoes pivot on the brake arms. Where is there literature with equations and analytical porcedures to determine forces (torques) applied to the drum face?
Thanks

 

[desertfox]

Hi Tagger

I have formula here for variuos types of brakes, for internally expanding shoe brakes usually found in vehicles,
which I think is what your after, the formula are as follows

torque for left hand shoe = TL = K*u*a*r*F/(b+K*u*c)

torque for right hand shoe = TR= K*u*a*r*F/(b-K*u*c)

total torque = TR+TL

where K= 4*sin q /(2*q + sin 2*q)

the shoe subtends an angle in side the drum of 2*q

K is a factor which is a function of angle of
contact.

a = lever arm distance ie from pivot to where load
is applied to the shoe

b = is from shoe pivot to centre of the drum

c = horizontal distance from shoe pivot to the
inside dia of drum

r = drum radius

u = coeff of friction

F = force applied



max pressure applied by shoe = Pm = TR/(2*u*w*r^2* sin q)


where w = width of shoe

average pressure applied by shoe = Pa = Pm/K

The drum in the example shown in my reference book is turning clockwise whilst looking directly inside the drum with cover removed.


hope this helps

regards desertfox

 

[Tagger]

Thanks for the help desertfox but this is an external brake that clamps onto the OD of a drum. It is a Long hinged shoe brake where two brake arms clamp on the drum at the 3:00 and 9:00 positions. Can you help me on that?
Thanks

 

[desertfox]

Hi Tagger

I have formula for a double block brake, with blocks external to the drum, formula as follows:

friction torque = T=F*a*r*u*[(1/(c+u*b))+(1/(c-u*b))]

maxium pressure = P= F*a/((c-u*b)*A)

where F = force applied

a = lever arm distance ie pivot point to force
applied F

c= lever arm pivot point to centre of brake block

b = offset between pivot point of lever arm and
tangential point on drum o.d.

A = block contact area

u = coefficient of friction


regards desertfox

 

[uwi]

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