Pivoting W-irons and Brake Shoes

[Lacathedrale]

I've dug out a wagon to finish up (see Imperial Workbench and/or S-scale area).

 

It has an etched underframe the comes with a one-sided set of brakes which look wonderful, and one pivoting W-iron.  However, when the the W-iron pivots, it causes the wheel face/flange to rub against one or the other side of the fixed brake shoes, which then adds a little drag/rotation which causes a vertical deflection between the body and the W-iron, which then causes it to rub more, etc. etc. causing a waddle. Stiffening the pivot may make the initial state less likely to occur, but it feels like I'm missing something fundamental here - should the brake shoe be far enough away either horizontally (or in depth, or both?) that it cannot touch the wheel face/flange?

 

I have already shaved a wedge off the back of the brake shoe to give clearance, but no joy.

 

This feels like it must be a solved issue, after all - the same problem would manifest in EM, P4 or S7 with the same principal - and I would like to know what can do or have done wrong...

 

For the sake of prettiness, here's an otherwised unused photo of the offending wagon:

 

[Paul Cram]

I file the brake shoes so that the profile matches the wheel profile and ensure that thee is enough clearance top and bottom. I also restrict the amount of rock as .5mm either way is sufficient. I model in P4.

[Lacathedrale]

Maybe reducing the rock is a solution, it's at least a couple of of mm currently. The shoe does match the profile, it's just very close. Thank you, I will check it out.

[5050]

If your wheels rock to the extent of a couple of mm - then it's time to check your track laying!  Whilst running, the amount of 'rock' should be negligible, only enough to follow slight irregularities in the track.  In P4, I just file the brake shoe to provide a bit of clearance but quite often, depending on the kit, I find that the shoes could do with a bit of thickening!

[Lacathedrale]

Ah, I don't mean that my track varies - just that when pushing it along the workbench. I'm not pushing perfectly perpendicular to the axis of the wheels, which seems to start off a slight rock that is then exaggerated as the wheels alternately 'brake' on the inside of the shoe and increase the waddle, just that the design of the pivot permits a couple of mm maximum pivoting.

[Lacathedrale]

I bent the shoe very slightly away from the wheel face, and packed out the pivoting W-iron - and it works great. Thank you @5050