First off, id like to say I have been hooked on this forum for hours of the past few days. You guys have a great thing going here with info and fun!


My question is, I took off the front wheel and drum to inspect the brakes on my 60 F500. I cannot for the life of me figure out how this setup works.....it looks like an other drum setup but has a single sided wheel cylinder on the top facing forwards.....I played around with this a bit and cant figure out how it works. How is pressure applied to the trailing shoe??

 

Well, the circle formed by the shoes gets bigger inside the drum when pressure is applied

 

Right. I understand the concept of how drum brakes operate. What I'm asking is why the wheel cylinder only pushes one shoe and not both at the top.

 

I've wondered that for years. About 35 yrs ago I had a boat trailer with surge brakes. They had a single sided wheel cylinder like that. It was the first I'd ever seen, and I never figured out what good the rear shoe served. It can move a little from the bottom, but I can't imagine it providing much stopping power.

 

I bet if you measured and did the math, it takes about the same amount of fluid to activate as a dual one. And if you stop and realize in a dual one, the fluid displaced might only move one side anyway, and probably does. One side or the other is up against the anchor pin depending on rotation. The only downside I see to the single design is that it might not be as effective backing up.

 

The picture shows a uni-servo brake. When you are going forward the piston pushes out on the shoe it is connected to and it contacts the drum. The reaction force on the shoe acts through the bottom link (adjuster) to force the other shoe against the drum with much more force than the piston can exert. so both shoes produce braking torque with the shoe without the piston producing more than the other. You will notice that the non piston shoe has a longer lining. And you will get less brake torque when backing up, but you will generally be going much slower anyway.