Friday, January 30, 2009

exciting new projects!

While i was supine, some interesting developments took place. Carlos finally did show, and augmented an existing corn masher to be run by bike. And Will began constructing a prototype of an add-on device he designed- titled "project: wheel"

I didn´t get to take too many shots of this while i was up, it was pretty quickly whisked away to a far off jungle. I´m not sure how it works, but the pedals spin the big fly wheel (which is just a bike wheel poured full of cement) and that turns something which grinds or mashes corn into a pulp useable for making tortillas. I wish i knew what all of the associated trays and containers do, but no one seemed to know, and Carlos was far to busy to explain.

Will´s design came out of a discussion we had with MP´s Volunteer Coordinator Rubin. We learned in this discussion that the bicimaquinas are not donated, as previously believed, but they are sold. Generally sold at a loss, but still too high for most to afford.

All of us came here to learn about bicimaquinas, to aid in their creation and donation to the masses. So this news was a good impetus to get thinking of ways to reduce costs, increase revenue, and encourage monetary and bicycle donations.

Will, a mechanical engineer by training, almost immediately began designing a grain mill model that could be connected to an existing bike. His design would reduced the need for materials, save labor time, and was simple enough that any of the volunteers (i.e. free labor) could produce them. Its small size makes it portable, and inexpensively mailed, thus extending the range of places it gan go within the country. Its immediate downsides would be that you can´t see or reach what you´re grinding, necessitating another person for the most efficient grinding possible. Also, without the fly wheel, it has less power and may not grind as well (Will didn´t seem to think so though).

It didn´t take him too long to mock up a prototype. It worked almost exactly as he envisioned. The small wheel you see is attached to a bike fork, the part that holds the front wheel of a bicycle. The fork is hinged to a stem (?) the part that hold the handle bars to the rest of the bike. The stem can then be attached with screws to the seat post, as you see below.

Because of the inherent friction of the rubber, the two bike wheels act like cogs which turn the chain and spin the grinder.

The grain mill is clamped to two pieces of rebar which are welded onto the top of the fork. The mill can be removed and a corn de-kerneler can be swapped into its place. Presumably other similarly sized devices could as well. The strap you see in the above picture is to increase the pressure between the two wheels to ensure solid contact. Also, the back axel needs to be propped up in order to keep yourself from biking away.

There were, of course, a few unforseen problems with Will´s design. The first was that the chain cog, or whatever its called, wouldn´t necessarily spin with the wheel. Will welded it on. Problem solved.

The next was that the angle of the prototype required the seat to come way up, okay for 6 foot-something Will, but not for your average Guatemalan.

I dont know what Will´s thouhgts are on how to fix this, but i thought perhaps a longer stem, also one that´s angled slightly up, in addition to one or two more pivot points, would allow the device to slip under the seat at a comfortable height, or any height, and it would conform a little more naturally to the shape of the bike. It would also get the gear of the mill a little further away from the bike seat.

Another problem was that the angle of the fork wasn´t quite right, and the whole thing sat slightly askew. Still workable, but less efficient and definitely not as nice to look at. I suggested to Will that perhaps during the construction of the model, that the stem have welded to it a threaded piece (threaded as in a screw). The fork could have welded to it the corresponding threaded piece and the two could be manually twisted into place until perfectly alligned and then tack welded right there (tack weld being a quick holding weld, to make due until you do a real weld). Will thought this was a good idea and could simplify getting the angles right, especially for less skilled workers.

Will commented that the wheel was too large, a smaller one would be better- more rotations per minute. I suggested that the wheel could be stripped entirely and the hub covered in rubber just like the liquadora (from a previous post). That would increase the RPM dramatically. But Will thought too dramatically.

Its a great start. I´m really excited by Will´s design, i think he´s really onto something. It will be awesome to keep working on it and see how it can be improved and implemented.

No comments:

Post a Comment