B Brake shoe orientation?

[SilentUnicorn]

Tube type axle. 77b
Which way is correct?
As you can see they seem to fit either way.
where does the cut out in the shoe belong?


ahhh the things you find from previous mechanics.

Left side

Right side

 

[bob67bgt]

I would go with the one in the bottom pic. bob

 

[DrEntropy]

Yup... the "leading" shoe should be at the top. Rotation and ~arresting~ it would be the function of the leading shoe.

 

[Roger]

The convenience of routing the pipes and cables has much more to do with the way they're oriented than anything else. Some say that keeping the leading shoe low (as illustrated) is easier on wheel bearings but it's marginal.
Or maybe it wasn't the orientation of cylinders you meant! The shoes should be oriented as the bottom photo, with the cutout on the trailing edge of the shoe.
The leading edge of the leading shoe is at the bottom in both your pics.

 

[DrEntropy]

The handbrake actuator lever in the bottom photo is right. But the spring "tang" (on the one behind the shoe) should be resting on the lever. And the top spring is upside-down. Top spring in the left side is mounted correctly.

 

[SilentUnicorn]

Nice catch Doc, Had not noticed that yet. Found a pitcher on the inter-net. This looks correct for right side.

Can any one explain the theory behind the leading edge on the shoe?

Thanks for the replies all


m

 

[DrEntropy]

It's a balance twixt adjustment and the hydraulic bit. The leading shoe is no more "important" than the following one. All depends on the adjuster to be right... if it is less-than correct, the contact across BOTH shoes is biased toward the edges where the hydraulic cylinder applies the pressure.

You want the adjustment to allow the entire surface of each shoe (or as much as possible) to contact the drum equally.

 

[JPSmit]

Some of the science here:

https://www.engineeringinspiration.co.uk/drumbrakes.html

 

[SilentUnicorn]

and here they are mounted correctly.

m

 

[DrEntropy]

Mark, again, the "leg" of the bottom inside spring should be on top of the handbrake link, holding it downward in the slot of the shoe. And in photo two the top spring (adjuster) is upside-down.

 

[SilentUnicorn]

ahhh... I thought it went underneath, holding the hand brake up. I will fix it today.

Thank you


m