Posted by: DHE Rwanda | August 24, 2011

As Easy As Drilling Six Holes… Right?

Hey all, sorry for the delay on the post, we’ve had a fairly busy week trying to prepare everything for half the team’s return to Banda to do the repairs on the site, and looking for an internet connection reliable to put up all the photos in this post. Most of the work to the former end has been involved with the attempts to ready the mechanical parts (turbine, nozzle, casing) for implementation. They say a picture is worth a thousand words, so I’ll try to forgo my usual verbosity in favor of a more visual-heavy post. I’m bummed that we didn’t take any pictures of the Gakinjiro Market, where they sell wood, scrap metal, and other building materials, and where we purchased most of the material for the casing; like most of the other open air markets in Kigali, it’s huge and sprawling. A to the characteristic hustle and bustle the whine of many many angle grinders all running at once, the UV-spitting zaps of stick welders, and the smell of burning metal, all under the beating of the equatorial sun, and that’s the complete sensory overload that is Gakinjiro. Dickering with the scrap merchants in the midst of all this made for a very long day, let me tell you. The best way to get a fair price at the market is the “leaden butt” method of negotiation – basically, the longer you’re willing to stick it out in the market, the lower the merchants are willing to drop the price (though whether it’s worth the few dollars you save on a piece of scrap steel is something Collin and I wondered more than once that day)  – so you can end up spending a fair bit of time there.

The parts purchased, we headed to KIST the next day for the (usually) fun part: machining! The angle iron for the casing had to be cut up into the right size pieces (they come in 6 meter lengths as stock, which were just a bit too large for our purposes). Since KIST didn’t seem to have a bandsaw and using a hacksaw would have been miserable for the twenty-some cuts we had to make, they pulled out the shop’s only angle grinder, which is both the most terrifying and most fun piece of machinery I’ve ever used (see below). The burning shards of steel are also hell on your clothing, though not as painful on your skin as you might expect.

Resident hard guys Collin and Wouter grind some angles.

Collin and I keep track of the different length pieces, trying to machine them to spec (and generally failing by several millimeters). Fortunately the casing dimensions weren’t particularly important, so long as the pieces that needed to be equal lengths were sized accordingly, and a couple seconds’ work with the angle grinder were all it took to shave off the extra material.

After we cut the pieces at KIST, we took them to a rather more well-equipped garage, E.T.O. Muhima, in downtown to assemble the casing (we caught KIST at sort of a bad time – final projects were due around the time we were trying to machine, which is every bit as hectic as back at Thayer).

A mural outside E.T.O. Muhima. I took this picture mainly because Tintin’s in it1.

Machining at E.T.O. Muhima had its own set of problems, due to misinterpretation (and on a couple of occasions, disappearance) of the drawings. A couple corners from the pieces were cut incorrectly (undesirable but not a serious problem), and the casing nearly got assembled inside out (both undesirable and a serious problem since we wouldn’t have been able to bolt the top and bottom together). It was times like these when I would have given a great deal for an encyclopedic knowledge of Kinyarwanda. Most of the technicians didn’t speak English and the ones who did were frequently occupied with other tasks, so it usually fell to the machinists and the engineering students to try to discuss the finer points of casing construction using a combination of gestures and pidgin versions of each other’s languages. As to which of the above methods was more effective I couldn’t say, but all things considered, the casing came together amazingly well, though it took longer than we might have hoped. Of course, this was all in accordance with the first law of machining, which states that everything will take at least five times longer to make than you think it will. I think this must be some sort of corollary to the second law of thermodynamics, Murphy’s Law, or maybe both.

Yi and Emily inspect the partially completed casing.

No matter how you care to express the first law of machining, it manifest itself brutally when we tried to finish the final part of the turbine assembly. The turbine runner (for those of you who aren’t mechanically inclined, this is the part that catches the water jet) is attached to the shaft by means of a collar that bolts on to the runner and clamps onto the shaft.

We already had the bolt pattern drilled in the runner, so all we had to do was drill and tap (put threads in, for bolts or screws to attach) the holes in the collar flange. Simple, right? We certainly thought so, expecting maybe a hour’s work on the drill press at KIST. But the problem with what we were trying to do with drilling all those holes in the flange was that those holes were smaller than the holes in the runner (they have to be, otherwise the tap won’t fit and the hole will be useless), which we were using to determine the bolt pattern. Drilling a hole dead center inside a larger hole is hard enough when you have a solid machine with a digital readout and can clamp the pieces together so tightly that Hercules himself would get a hernia if he tried to pull them apart. When you have a drill press that moves around if you so much as look at it funny, no satisfactory clamp, and several holes that have to be aligned to within a fraction of a millimeter, you end up playing a game you can’t win. So we took this problem to E.T.O. Muhima as well to use a larger and more reliable press. Even so, we still had trouble aligning the holes, and after several futile attempts to do so, we decided to abort the current plan for fear of turning the flange into a hunk of metal Swiss cheese. By this point half the garage had turned up, all arguing vigorously in Kinyarwanda about the best way to proceed, which didn’t help the already palpable tension in the room one bit. Fortunately, while bemoaning the fact that we hadn’t just drilled the stupid holes in the flange back in the States, where we had a nice Bridgeport with a digital readout and a dial indicator, or better yet, drilled the holes in the flange and the runner all in one go, we realized that we could still do this. The current bolt pattern in the runner still left plenty of room for a new one, so we clamped the pieces together and started from square one. As it turned out, we spent far less time doing this than deliberating what to do, not to mention the hours we spent drilling all those useless holes in the flange.

The mechanical team (minus Collin, plus a couple Rwandan technicians) trying to figure out what to do. I’m hard at (totally pointless, as it turned out) work with a file.

 

In the meantime, the casing was coming along swimmingly.

An unorthodox but apparently effective method of steadying the casing for drilling holes.

Emily and Wouter with the technicians.

Whoops – looks like I’m well over a thousand words. I’d better stop now. More later. I’ll leave you all with this last picture that got accidentally left out of a previous post. I like to think of it as “Mama Ted and Baby Ted.”

Wiley

 

1 Personal note: I was kind of surprised to see Tintin here, considering that he’s the hero of an extremely racist comic book set in the country next door. It was titled “Tintin in the Congo,” but might as well have been called “Tintin Civilizes the Savages” or worse for all the cultural awareness it showed. Fortunately it’s not that well known these days; Herge, its author, at least had the grace to be ashamed of it later in life, and its presence in the pantheon of Tintin books has waned significantly. I still find it distressing, especially since I grew up on the Tintin books and looked to the fearless boy reporter as a sort of role model. The brute in the Congo barely resembles the pure, noble soul of the later books; only the sweater vest, plus-fours, and stupid little tuft of hair are the same. If I were a Rwandan, I probably wouldn’t want him on the wall of my garage, but I’ve noticed that many Africans are unaware of some of the uglier aspects of Western culture (the kid I saw in the Kimironko market wearing a Confederate flag T-shirt comes to mind), so maybe that’s why a onetime symbol of colonial oppression gets the place of honor on the garage wall.

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