Mechanical disc brake issue

[Ninedriver]

So I’m working on my manco 710. Starting from the brake pedal there is a short length of approximately 1/4” rod which goes to a hand parking brake lever and coupled to that is a longer length of rod that attaches to the mechanical disc brake caliper. The longer rod is flat running along the floor board under the drivers seat and then there is a slight bend in the rod to angle it down to the caliper and clearance the rear subframe. I’ve cleaned and adjusted the caliper to allow quick engagement and plenty of travel.
When I press on the brake pedal the caliper clamps but as I press harder on the pedal, instead of the caliper clamping harder, the bend in the longer rod just stretches out. When I release the pedal, the rod springs back into shape. Unfortunately, as a result, I have very weak clamping pressure, very weak brakes, and a looong stopping distance.
Any thoughts on how to address this and get better braking? I’d like to make this system work instead of going hydraulic.

 

[landuse]

Coukd you maybe post some pics? It could be that the brake system was put in by someone else who didn't know what they were doing. In that case we could have a look and help you out to fix it.

If it was factory original, then there is something missong. Usually the rod goes through tabs with holes in them for the rod to stay in a straight line.

Anyhoo, post some pics