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.

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