Thursday, 3 November 2011

Handling the bars - Part 3

It's curious, is it not, that we refer to 'a pair of handlebars' to describe a bent piece of tubing. Where does this term come from? The answer of course is way back, as with all things bicycle related. Here is a photo of a pair of handle bars. They are detachable and each side is separate from it's twin. On the end of each is a handle. They are also solid, not hollow. They are bars, a pair of handle bars.

This particular example is an 1883 Bayliss, Thomas & Co. DEHF
(Duplex Excelsior Hollow Fork) although many other manufactures had similar arrangements
However, by the time that Ellis & Co. were making the geared faciles, hollow handlebars were the norm. A solid bar of the same OD as a tube (same material) will resist bending better, however a tube of the same weight (cross sectional area) as the bar will resist bending even betterer. The obvious result is that handlebars became hollow with a larger outer diameter and a thinner wall thickness. (A trend that continues to this day with the 'new' standard of 31.75mm - 1.25"). The geared facile has handlebars 27" wide that taper from 0.75" in the centre. So I need to replicate the handle bar mount with a 0.75" bore + clearance for braze.

The first job is to remove all the unnecessary material from around the head. The easy way is to drill a series of holes and then saw between them. I've found that the best way is to start with small holes and gradually increase, otherwise the drill bits can wander into a neighbouring hole. I've struggled to buy decent junior hacksaw blades for years. All the recent ones appear to be made of cheese and bend all too easily. But I digress.
Do you know what a versine is?
An easy way to remove excess
With all the excess removed I can now focus on shaping the handlebar mount into a nicely rounded shape. Strangely, I find it easier to get an accurate circle if I start with a square and attack a corner at a time. I'm going to mill/flycut the square shape and hand file the round shape. Pictures can describe the various steps better than I can.

My father taught me how to use a file many years ago. While an apprentice he was assigned an exercise to make an hexagonal hole in a piece of (unknown thickness) gauge plate and then make a hexagon to fit it accurately in all 12 orientations. All by hand using a file only. Apparently his was the only one that did, such is my upbringing.

The last two stages are to bore the 0.755" hole and then radius the edges of the mount.

Yet another boring photo, this time a boring head,
See if you can spot the mistake. Cross, me? not half.
Next week I'll cut the recess into the back of the head where the neck will insert.

In other news, on Saturday a few of us travelled to Akaroa with our bikes to take part in their french festival . Saturday was a beautiful day with high temperatures, no wind and not a cloud in the sky. The event was extremely enjoyable and we didn't leave until late in the afternoon.

In other other news, I've been given permission to buy a new pair of cycling shoes. This is indeed a momentous occasion since the last ones of I bought were a pair of Sidi Genius 2 in 1994. At the time they were the top of the line road shoes and mine are just about completely knackered after 17 years and more than 150,000 kms. Being a cheap retro grouch, I've been reluctant to replace them with any of the modern disco slippers. However, my very kind wife reminded me that I have a birthday in a couple of weeks and she never knows what to buy me... I've ordered a pair of Sidi Ergo 2 in bright shiny red (to match the bicycles). This pair should just about see me out...

1 comment:

  1. Bob, this is fascinating. I can't wait to see the finished article. What a great blog! Bob G.