hw 35 leaking breech fix

[T 20]

I am quite sure you got the results you were after but how can you maintain any vacuum by withdrawing the piston if the breech weld is porous? Sorry for my pedantry

The cylinder doesn't leak to outside through the braze --- what you are doing is filling a void within the braze on the inside of the cylinder.

If the braze is porous inside the cylinder between the breech plug and cylinder tube then the pressurised air can pass through the porous braze into the voids in the breech plug.

Here's a debrazed cylinder showing the voids :-

image.jpeg

The voids are machined into the breech plug to hold a mix of brass and flux, this is then pushed into the tube and then heated up to form the brazed joint.

A slight cockup on heating and a porous braze can form allowing air from the cylinder side to enter the void left by the brass and flux.


Hope this helps




All the best Mick