Wednesday, 26 March 2014

Levers Part 3 (another pivotal moment)

This shedweek I've made the lever pivot mounts, these are the bits at the very front of the levers through which the pivots bolt.

They turned out to be relatively easy to make after I'd worked out how to do it and I was able to knock them out in just a couple of evenings.

First job is to realise that I don't have any bar stock big enough so I do a raid on Kung Fu Pete's metal stash for some 2" bar to cut into salami.

Mark and drill opposite centres. All will become clear...

Machine the outer face, this recess is to accommodate the special locknut.

Then flip around and machine the inner edge, this 
locates against the pivot on the end of the fork extension.

Hacksaw diet.

Mount between those centres and machine the trunnions to be a tight fit inside the front ends of the levers.

I only need one of the trunnions, the other only serves as a temporary way to...

... hold the work whilst I bore the trunnion to make it easier to braze...

...and feather the edge to reduce a stress riser.

Then chop off the spare trunnion.

Mount directly onto the mill bed to create the round shape. I machined some very accurate spacers so that I could bolt up securely and yet still turn the work easily. I searched high and low for a piece of tubing of the right size to act as a handle to rotate the pivot. I then realised I had exactly the right size sitting on the workbench next to me. Duh.

These little needles of swarf are deadly sharp and have got everywhere. 
I'm still picking them out of my hands.


Next week I'll make the pedals, these will be the last actual parts to make. I have a folder of photos of the original bike on my computer, whenever I finish a part and have no further use for the photos of it I move them to a different folder. I started with 264 photos and I only have 9 left, all of the pedals. I'm ignoring the rear mudguard for now.

In other news, I knocked the bike over this week. I had the front wheel slightly overlapping the workshop door and when I pushed the door shut it gently pushed the bike off balance. I was mildly annoyed and may possibly have taught the children three doors down some exciting new grown up words. It fell on the right hand side and fortunately didn't do too much damage, there is some scuffing to the hand grip and the lever pivot. But the con rod suffered the most, getting badly bent. It turns out that the brazed joints aren't strong enough after all. I'm going to chop out the centre section and ask Kung Fu Pete to weld in a new bit. I should have done this from the start I guess. The left hand side is OK at present so I'll leave it for now. We learn by our mistakes.

Tuesday, 18 March 2014

Levers part 2 - Beefy Bottom Mounts

Hoorah, I got the welded levers back from Pete.

As usual, he has done a brilliant job TIGing them together for me. I have some reservations about strength and the nature of welded 4130 so I'm going to get them normalised before I go too much further. If they break in use I'll have a re think about how to make them again.

This week I'm going to make these bits.

They are the bottom mounts for the con rods and are really quite beefy.

Starting with some scrap 3/4" mild steel plate, mark out and bore a counter sink at the correct depth.

Then using a series of drilled holes remove most of the excess metal from the mounts. 
Drill bits are cheap compared to milling cutters...

Then bolt directly to the bed and mill the final thicknesses of the mounts. 
The top part is just a tad thicker than the lever at 0.675" and the bottom part that the conrod bolts to is 0.375".

Next flip the mounts over and again bolt down square to the bed. Mill the sides to the correct width.

Then using these new milled surfaces as the reference, mount in the machine vice and mill the top of the mounts.

Next mill the slots for the lower con rod bolts. 
Recall that these bolts had flats machined on them. These flats locate into these slots.

Next mount at 45 degrees and mill away most of the excess of the upper thicker section...

...tidy up with files.

Then mark out the outer shape of the mounts and get busy with the hacksaw and files.

The last operation is to machine a curved slot into the upper thicker section so that the levers are wrapped by the mount, this needs to be a nice fit so that the brazed joint will be strong. Careful measuring of my Myford and the lever radius means that I can just turn these by mounting on the faceplate. It really is pushing the lathe to it's limits though. Simply bolting the mounts to the faceplate won't be rigid enough, the interrupted cut will soon knock the mounts out of alignment and make me a bit grumpier. In one of those rare moments of serendipity, I discovered that the slots in the faceplate are the same width as the slots in the mounts, This means that I can make some spacers that will rigidly locate the mounts onto the faceplate. By drilling a hole through, I can very securely bolt the mounts at the correct radial distance so that the bottom of the cut is the inner radius of the levers.

Very securely held in place, the correct radius can be adjusted by sliding in or out...

...and then bolting up.

With such a large diameter of cut, I needed to slow the lathe right down to successfully machine the groove. The interrupted cut meant that the feed in had to be very gentle.

I was also cutting almost blind, in that it was very hard to see where the tool was contacting at any time. 
I found that placing some white paper beneath the tool and viewing directly downwards with one 
eye shut wearing magnifying glasses and standing on one leg helped a lot.

Once I got close to final size and depth, I used the same trick that I used when filing the neck to fit into the backbone. The levers were coated with engineer's blue and slid around the groove, the marked high spots were then machined off and the process repeated.

I'll start on the lever pivots next week.

In other news, the strange fruit that was discovered in my garden has correctly been identified as an Akebi fruit. Thanks for that Christian. I found the vine that it grew on (we have a big garden) and discovered a few more, they don't grew on top but underneath a top layer of leaves which is why I've never seen them before. The plant, known as a chocolate vine, is classified as a noxious weed here in NZ. In the interests of scientific discovery I immediately ate one of the fruits, seeds and all. It wasn't too unpleasant, a little like melon, but had a bitter after taste. Later that evening I became slightly disorientated and nauseous. The following morning I had a mild headache and slept in a little later than usual, I seemed to be sensitive to light and loud noise. It must have been the space fruit, it couldn't possibly have anything to do with the beer I'd drunk to get rid of the bitter taste.

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.