Handbrake Pivot

Stephen Blakey · Posted: Mon Jul 25, 2016 10:08 am Post subject: Handbrake Pivot

Dear all,

I wonder if I could trouble you for help with reading the handbrake drawing as I need to make one for my special? A few questions re the above;

"TAP 1/8" GAS" Google reckons Gas is the same as BSP. Is that right?

What's the idea with the taper pin? Do I tighten the 3/4" BSF nut then remove it and drill the pin-hole in the most likely looking pair of flats? How is the end-float controlled?

"LOCK NUT A.GS....etc" Any ideas what that means?

Thanks in advance

Stephen

Christopher Carnley · Posted: Mon Jul 25, 2016 1:02 pm Post subject:

An odd mixture of units, and 1/8" Gas is the same as BSPP, 28 tpi and about 3/8" in diameter.

It is the diameter of the bore of the pipe.

What does the part swivel on?

Stephen Blakey · Posted: Mon Jul 25, 2016 8:43 pm Post subject:

Here's some more views in a more traditional colour scheme;

It's the pivot for the handbrake. The lop-ear bits are where the ends of the twin ratchets attach.

The units are typical of Bentley Motors drawings. Basically the designs were done in mm but WO had to accept that his suppliers would not have metric taps and dies so the threads are imperial. Alan Smith is working up an article for the Review in which he suggests that WO's use of metric units was one of the many factors leading the demise of BM, as the suppliers had imperial machinery and would have had to convert the drawings to imperial units at BM's expense.

It's worth reminding ourselves that there was great enthusiasm for metrication in the late 1800's. For example in 1895 a Commons Select Committee recommended immediate authorising of metric units for all purposes, that the metric system become compulsory after 2 years and that the metric system be taught in elementary schools.

Took a little longer than 2 years.

AnthonyEssington8982 · Posted: Mon Aug 22, 2016 12:38 pm Post subject:

I have one you can borrow if you need to

Stephen Blakey · Posted: Mon Aug 22, 2016 7:50 pm Post subject:

Hi Anthony,

That's very kind of you, but I'm OK for examples. My barrel-scraping has yielded an original that's had its lop-ears amputated (why?) and a repro that looks like it was made with the pin as a separate piece which is missing.

It's a pretty simple job for my pal the machinist to make a new pin for me to weld on and keep the project moving forward. Alan sent me a set of handbrake drawings and I have made scans of them.

At some point I'd like to have a go at forging a new pair of ears for the original as the repro is a bit of an approximation. I may take you up then but, in the meantime, I need to follow the quickest route to completion (well, least slow anyway).

That 1mm thick brass bush seems a bit of a funny idea. It has been suggested that was railway practice? I wouldn't know.

Best wishes,

Stephen