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).
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.
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