Monday, February 2, 2009

reconfiguring project: wheel

When Will constructed his prototype for a detachable grain mill, there were a few unforseen technical challenges that came up. Yesterday i decided to get started on one of them.

Because of the way the wheel needed to spin (pre Will welding the cog to it) the grain mill had to be placed accordingly off to one side, throwing off the balance of the bike. Though not a huge problem, i thought it might be the simplest place to start. Will suggested that, since welded, the wheel could be flipped around and the grinder put more centrally. While i was at it, i decided that i would flip the fork around and use the other side, envisioning a possible future swapping of the wheel for the much smaller rubber hub-covering (mentioned in the previous post).

You can see here the fork is flipped over and i´ve welded two new pieces of rebar to the fresh side.

Here it is with the new base welded on. And below a close up of the weld- you can see i´m pretty new at this.

Since i was welding a whole new set up any way i decided to move the base structure that i was attaching much closer to the wheel. I roughly marked it, and came a hair too close. The rebar and a little of the new platform had to be grinded off. No problemo.

(What was really interesting, was that when i finally attached it to the bike, the mill was closer to the bike seat than it had been before, weird.)

So with the new base put on, i tried attaching the mill to see how things looked. It appeared at first that everything was fine. So I tried putting on the chain. Doesn´t fit. What? Why wouldn´t it fit, its closer, if anything it should be looser, not tighter. So i broke the chain, with this nifty little device that pops out the pin between chains- lets call it a chainbreaker. It took me a few times of adding and subtracting to get the right number of links, and the breaker was harder to use than it looked, though definitely easier than trying to pop them out with a thin wire and a hammer(what i was doing when i decided there must be a special tool for this).

Once i got the chain on it became pretty clear that the mill was too central, as the chain was rubbing pretty hard on the fork, and needed to go back toward the right. The problem with this is that it would place the underside of the mill directly above the tong of the fork, meaning the bolts would no longer fit underneath. I decided the best thing to do would be to build a little table to raise it up.

I welded the table out of flat iron that was kicking around, cut off the the other base since it would be in the way and used it as a template to drill the holes for the new base. After welding the new base together i ground out, roughly, the shape of the tong it would sit on top of. This was to create more contact between the metal pieces and encourage a stronger weld. It worked pretty well and the mill sat exactly as it was supposed to.

However, when i attached the whole device it sat even more off-kilter than it had before. And further, when the bike pedaled it spun the device right off to the side wher it would fall with a thud and hang uselessly next to the wheel. I tried a few things, like loosening and changing the angle of the stem where it makes contact with the seat post, but nothing seemed to work. And at 11:00 pm i felt better prepared to tackle my pillow than this next challenge. So in a tired daze i wondered upstairs and fell right asleep.

No comments:

Post a Comment