Health and safety aside, the principle has stood the test of time. Sentinel 7109's original handbrake screw thread was clearly beyond use when it first arrived at Midsomer Norton. I never took a photo of it but the square shaped 'Acme' thread bore a strong resemblance to the 60 degree angles of a metric thread profile! As the last resort for stopping, it did not provide much in the way of confidence!
The way the handbrake works is quite simple. It's a big vertical bolt with a handle and a nut that's linked to a crank. When the handle is turned, it pulls on the crank which pulls on the brake. (There's some more about it here: Steam Brake Cylinder).
|Handbrake Nut and Linkage (below cab floor)|
|Handbrake Handle (above cab floor)|
It worked initially as in the video below (Also on YouTube).
However, after a while, the cutting tool decided it wanted to dig a little deeper and pulled off some of the metal causing a complete write-off of the original shaft.
Mendip Steam Restorations were tasked with the job and completed both the finishing of a new nut (with posh phosphor bronze 'Top-Hat' insert) and a new handle shaft.
|New Handbrake Shaft and Nut|
|Roller Thrust bearing below the handle|
|New nut & insert from below|
|New nut & insert from above|
One feature which I do intend to add is a shield of some sort to prevent grit getting into the thread; hopefully this will prevent the damage that happened to the old one.