Tuesday, 11 March 2014

Hollow, Tapered, Elliptical and Bent

And so the time has come, I can put it off no longer. I need to make the levers. Having all the conditions noted above makes them quite tricky, indeed if one of the conditions wasn't necessary then they would be considerably easier to make. You may recall that I've made elliptical tubing in abundance on this bike. I've also made bent tubing and I've also made tapered tubing. The handlebars are bent, tapered tubing which caused me much head scratching before I figured out how to do it in a shed with minimal tools. Of course I could cheat and make them an approximation of the originals but then I've spent 2 1/2 years on it so far so I may as well make facsimiles to the same standard as all the other bits.

I recently discovered that geared faciles had three styles of levers over the six years of production and there appears to have been some overlap. Being a relatively small concern, I imagine they would have made whatever you wanted if you had the cash. Of all the originals I have studied now, I've only seen two the same (actually nearly the same but that may be due to restoration). The earlier style of lever are the elegant curved style that I'm going to be making, also the hardest to make by some margin which is possibly why they were changed. At some point the levers changed to the later style which were flat with upturned ends, still hollow, tapered, elliptical and bent though. Then later, this same shape was changed from tubular to an 'I' beam section as in the photo above. The little upturn at the end, common to all styles is so that your toes have clearance when the lever is at the bottom of the stroke.

During the same research I discovered proof of something that I have long suspected. It turns out that the Percy Nix machine in the Coventry museum is not the machine that he did the record breaking ride on but the one that he was presented with by Ellis & Co. afterwards as a prize. Bartleet mentions this in his book but at some point the Coventry museum has mistakenly assumed it was the same machine. I have found two reports of his ride, one a transcript of an interview with Percy Nix himself less than a week afterwards, and both mention that the bike had a 42" wheel geared to 63". The Coventry museum bike has a 40" wheel. I wasn't aware of any 42" bikes being made but apparently, again if you asked nicely and had deep pockets, then the company would oblige. I also found evidence that Frank Shortland used a 42" on some of his record breaking rides. There is always something new to be learned. But I digress.

I've been thinking long and hard about how to fabricate these levers for months now and I've had several ideas.

1) Make them from solid. This is the easiest approach but the result would be very heavy and with bicycles you really do need to cut down on rotating or reciprocating weight.
2) Make the front part hollow and braze to a solid rear part. Better, but still too heavy.
3) Make the front part hollow and braze to a machined rear section with a minimal hole bored up the centre. Heat the rear section to bent to shape, then die grind the bore to remove as much weight as possible. This was my preferred solution for a while.
4) Make front and rear sections from hollow tube of different sizes with various gussets and slices taken out to make the tapers. Weld the parts together. Complex but possible, let's give it a go.

Since the levers will need to take a persons body weight, I've decided to use thicker tubing for them. All the tubing so far has been 0.049" (~1.2mm) chromoly, the levers are made from 0.065" (1.6mm) chromoly.

Start with a 7/8" tube and have two mandrel bends made in it at the appropriate radius and angle, this angle is too tight but will open up to the correct size when rolled elliptical.

Of course, I don't have the rollers for this ellipse so I need to make those first.

Then I can roll the tubing. This 0.065" wall tubing is really hard to manipulate in my manual roller. 
I needed to do this over two evenings. I tried to pay my children to do it but they simply don't have the strength yet.

I've made a short video of the rolling process. Of all the stuff I've made on the bike, elliptical tube rolling is by far the most common reason people find the blog through search engines. 

I took the pressure off the rollers for the purpose of the video, that why it appears so easy.

Then get a 3/4" tube mandrel bent. Autobend didn't have the correct radius I wanted for this size tube 
so I'm going to have to tweak it open manually as I roll it.

Roll it using the same rollers as for the 7/8" tube, it doesn't fit very well 
but it is going to be heavily worked afterwards anyway.

We can now see how the various shapes can be used to make the complete lever.

Mark the sliver to produce the taper at the foot end of the lever...

...and cut it out with a dremel cut off wheel. I love my dremel, I may possibly have mentioned this before.

Then close the gap to produce the taper. Cutting the sliver on the inside of a bend will tighten 
the radius and on the outside will open the radius. The inside cut is much easier to close.

You can see the produced taper in this comparison.

Next chop out half of the lap joint. These are very carefully measured to get both at the same angle.

Then cut the corresponding shape into the larger front part of the lever.

Nearly there but note the highlighted steps. Mr. Middleton wouldn't be bothered with these but I am.

A little nip and tuck, top and bottom...

... and we get the final complete shape.

Next mark the sliver on the front of the lever...

...and chop it out and close the gap.

I'll take these parts in to be TIGged this week.

In other news, we've had a little more weather last week. Lots of Christchurch has been flooded for days. On my commute home I successfully made it through a flooded street on two wheels that had cars turning around. I was on two wheels not the street. It was reported as a one in a hundred years storm. We seem to be getting these one in a hundred years storms several times a year at the moment. I should note that it was politicians not meteorologists that described it as such. The excellent mayor of Christchurch initially blamed the meteorologists for not forecasting it. Actually they did, well in advance. I knew about it at least two days before it happened and people in my office were discussing what we would do should it happen. In terms of rainfall, we had just under 100mm (4") over the three days, well short of records. I wouldn't dare to suggest that the reason for the flooding was the tardiness of the council in fixing the earthquake damaged infrastructure. That came out aloud didn't it? I keep doing that.

In more other news and on a lighter note, I think the space aliens I saw last week left something in my garden.

Seriously, WTF is it? I'd like to know. 

It looks like one of Ricky Gervais' flanimals.


  1. The purple things are footwear insulators. If you attach them to the top of a pair of shoes they afford a layer of warmth and prevent ingress by sandflies and other biting insects. While she is elsewhere, I would glue them to the top of one of your wife's pairs of court shoes, and when she returns home she will go into transports of delight at the improvement thus effected. - Kindly do so tomorrow, and report back to us all - there are 21 blog followers keen to know the result of this experiment.

  2. Is the purple thing the akebi fruit which ripens in the autumn in Japan? It must be autumn in your upside down world about now. Have a look at this picture...


    1. Hi Christian,

      I think we have a winner, you can have 10 points for your trouble. Thanks