Thursday, 30 May 2013

The Spoon Brake

I've spent this shedweek making the spoon. Of the various original geared faciles that I've personally seen, I've yet to find one with it's original brake. Even the one I am copying has a modern replacement, it's just a rough casting that still requires finishing. I've seen a few others that look like they are made from the same casting but never an original. So this week I have been in touch with a well known collector from the States who has owned two originals and still has one of them. I discovered that he is the source of the castings that I've been finding scattered around the planet. He had them cast using one of his originals as a pattern. He also very kindly sent me some good clear photos of how his looks when mounted. My lever will be slightly different since I have the deep drop bars but I can adapt the style to suit. I was also interested to discover that his estimate for the total surviving number of geared faciles is only 12+ worldwide. In return for all of this information, I've promised to send him a scan of an original 1885 Ellis & Co. brochure from my own archive.

When I measured the original bike I traced the outline of the lever and spoon even though they weren't original parts. This was fortunate since they were cast from originals and so are accurate (if slightly too small) to copy. What I wasn't sure on was how the lever and spoon interacted, the photos cleared this up. Choice of material is important when making these parts. Even though you are only applying hand pressure, the force at the spoon, due to mechanical advantage, is considerably (3 times in this case) higher. I'm pretty confident that I could bend mild steel of this gauge with 3 times my hand force. I searched around for some higher tensile plate that would take the force, I ended up buying some 1/4" Bisalloy 80 (roughly 3X yield strength of mild steel) mostly because the local supplier had some offcuts and it was cheap. Except when I got it home I found it was 6mm. Unless I use shims I'll have that authentic brake rattle common to most antique bicycles.

First mark out the shape of the spoon using the original as a pattern and roughly cut it out. Then drill the pivot hole. Bisalloy 80 is hard to drill, the manufacturer recommends cobalt drills. I just used HSS at a lower speed and it was OK. Then assemble and mark where the spoon will sit so that it contacts the tyre with as much surface area as possible.

The spoon itself is made from a scrap piece of thick wall water pipe.

Make a jig to hold it all in the right place...

...and take it to Tweed Pete to weld up. 
I asked him to build up a decent fillet so that...

...I could then dress it off and make it look organic and beautiful. 
Like melted cheese or something.

Then make the top pivot pin, this is machined in the lathe from a high tensile bolt and then the upright is shaped so that it sits at the correct angle relative to the lever. This angle is important, the angle when it is in the off position should be the same as the angle in the on position relative to the brake lever it passes through.

Reuse the same jig and take it back to Pete... get it welded up. The thread is just used to hold it in the jig.

A stunningly bad photo of the finished spoon in situ.

Next week I'll start on the lever itself. It's a little more complicated than the spoon.

In other news, I was riding the motorbike to work this morning. Taking a right hand bend into a T junction when, accompanied by a loud report, the rear tyre parted company with the rim. As you can imagine this is not an ideal situation to be in when leant over on two wheels on a frosty morning. For safety reasons, I tend to prefer my tyres to be firmly attached to my rims. By sheer skilliance I was able to not fall off. I pushed the bike home, changed my underpants and then had to spent the morning running around like a blue arsed fly trying to get the tyre replaced. It's an odd size (of course). Unfortunately this time I can't blame Mr. Middleton for my two wheeled misadventure.

I've also lashed out on some modern riding gear. I last bought a motorcycle jacket when I was 17, a long time ago. I still think it's the height of fashion, an opinion not shared by my children. Or my lovely wife. This new one has all sorts of body armour and such like contrivances to assist your comfort level when sliding down the road. My wimp glands decided it may be prudent to invest in suchlike technology.

The bike has been causing me some trouble just lately, first new chain and sprockets, then new front tyre, then the starter motor packed up and now this. I'm having to bump start every day since I'm still waiting for a moron on Trademe to send me a replacement starter motor but that's a story for another day...

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