Steering shear pin

[bobskinner]

Good morning everyone,
Last week I went shopping in the GPA (as one does). On attempting a left turn it would only turn a few degrees, no matter how hard the steering wheel was turned. Right was OK. I struggled it home and on investigation the cable had slipped off one of the pulleys in the rear and jammed tight. There was enough slack because of this to turn right but not left. My question is this, why did fhe shear pin not break as it is designed to? I guess someone in the past had changed it for a hard pin. Does anyone have original shear pins or know what they should be made of? I think I will try brass and see how that works. It is potentially a very dangerous situation.
All the best
Bob