Monthly Archives: June 2010

FiveFingers

I just got a pair of Vibram FiveFingers KSO barefoot shoes. I’d had several friends extol the virtues of FiveFingers, but was never sold on the $75-85 price tag. Then I saw that my favorite sketchy Chinese export company, DealExtreme, was carrying the whole line, for less than half of the MSRP, apparently with complete Vibram branding. It took about a month for the damn things to ship, but they are exactly as promised, and not only do they look exactly like the “real thing” down to the branding, they even have the tags and manual stuffed in the packaging. They almost certainly came out of the same factory as the $85 ones from the “legit” vendors.
I’ve been wearing them around this evening, including a walk around the neighborhood, and have to say they’re pretty comfortable. Fitting is a little weird (based on length in inches, not shoe size), and mine are a hair snug, but it means they grip my feet really well and don’t rub much. There is a little bit of irritation on my heels, in particular I chafed the hell out of my right heel, but I suspect that has more to do with where the calluses on my feet are, the particular shape of my feet, and not quite having adjustment down than anything intrinsic to the shoe. The biggest indicator that they work as advertised is that when I took them off my feet didn’t feel stiff. I ran through the park just to see how it would feel earlier; the lack of impact cushioning would take some getting used to, but the ability to naturally roll your foot is excellent, and it definitely feels better than usual.
So:
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* Do they feel like being barefoot? – Kind of. There is a constant awareness of “Stuff between my toes,” some stiffness, and a little excess warmth, but it is definitely more like barefoot than even my customary hiking sandals, or anything else I’ve worn. The tactile feedback off the ground really is great- you can feel every little bump of the surface, but it can’t hurt you.
* Do they protect your feet? – I feel like they provide a little more protection than my usual sandals, but it’s no skate shoe or work boot.
* Do they look weird – Hell yes they look weird, thats half the fun. You could probably avoid notice with the all black KSOs in most situations (at least until you wiggled your toes), but lets be honest; people wear weird shit all the time and no one worries about it.
* Are they worth $85? – Absolutely not, but I’m pretty convinced they are worth $30-40, and our unscrupulous friends in China can make that happen.

UPDATE:
Just wore them for a little less than a normal day’s walking… and shredded my heels (left is just a little raw, nickel-sized blister on the right). I’m not sure if it’s a fitting problem or unusually shaped heels or simple break-in period, but OUCH!

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The Death and Life of the Great American School System

I just finished Diane Ravitch’s The Death and Life of the Great American School System, which I’ve been working through in fits and starts for several months now. It’s an excellent book, which methodically eviscerates every major educational reform movement since the 1960s, written by someone who was party to many of those same reforms. The writing style is really what makes the book; most chapters begin with an upbeat passage on the exciting potential of the reform movement under scrutiny, often clearly pulled from the author’s feelings at the time, then darken in both style and content as they move into implementation issues, and finally take on an almost sardonic tone as they cover the long term studies which demonstrate a negligible or negative net effect. Another very strong point is that almost every claim is clearly referenced, in a well-integrated way, which results in a nearly 30 page bibliography for a < 300 page book. The absence of references for the few unsubstantiated clams is jarring enough to make them stand out as opinions.

Perhaps the most depressing portion of the book is about the “apply business principles to education” (accountability + “choice”, which in this context means privatization) movement which has recently been institutionalized and adopted on a far greater scale than any of the reforms before it, most of which showed more promise and potential validity than this one. There are an absurd number of good arguments with which to object to such policies, many of which are covered, but perhaps the best impact is the simplest: Does anyone remember what just collapsed, based on decisions made on business principles? The whole god damn world economy? Right, let’s not introduce more of that into education.

The book also seems to support my pet theory that the real good accomplished by Teach For America and similar programs is supplying a steady stream of bodies, who are unlikely stay for long enough to become effective anyway, into the high turnover positions, allowing more potential career educators to make it through their first few years. Helpful? Yes, but not in any of the ways they claim to be.

Her suggestions for alternatives in the closing are mostly very solid as far as I’m concerned: she advocates for adequate funding (duh), efforts to attract well qualified teachers and retain them for long enough to become experienced (duh), and a holistic understanding of learning which broadly evaluates learning progress in a universally comparable way, and takes into account the effects of externalities, rather than fixating on a few easily quantified factors (duh). Most significantly, she advocates a universal base curriculum, which is sequential, holistic, and scientifically and pedagogically sound. The one point that caught me off guard is that she argues for letting the old fashioned private and religious schools be in the same breath as advocating a standardized curricula to prevent the same from imposing their quirks and bigotry on another generation, a position which seems entirely incongruous to me.

It is a little bit onerous in places, as required to maintain it’s extensive rigor, but a very good read. Highly recommended for anyone interested in education.

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Drive Nuts

Another bit of progress on the CNC project: Better drive nuts!

The design is attempting to avoid expensive, difficult-to-source, or chicken-and-egg problem machined parts. The biggest issues because of that policy come from the couplers which attach the lead screws to the motors, and the drive nuts which attach the axes to the lead screw. Because my leadscrews are 3/8-16 Unified Coarse thread, there isn’t a “proper” solution to the problem, as any professional mill would be using Acme or Ball threads for the leadscrews. Therefore it has been hobby engineering all the way on those parts.

The current couplers (with which I am becoming ever more unsatisfied; they slip badly on direction reversals) are constructed by seizing a 3/8” coupling nut onto the end of the rod, drilling a 1/4” hole through the rod/nut assembly, and drilling and tapping a hole for a set screw into the side of the nut to grab the flat of the motor shaft. Because the frame won’t accommodate Lovejoy-type couplers (the canonical solution for such things), I suspect the eventual replacements may look something like the nested fuel line couplers this and other similar designs employ. I don’t like the lack of stiffness in those configurations, but things don’t appear to be tightly enough aligned for the inflexible couplers, and the slippage problem will be a show-stopper for actually milling with it.

The old solution for the drive nuts was roughly-bent steel brackets, wrapped around coupling nuts. The theory was that the steel would be springy enough to pull things into alignment, and malliable enough to beat, bend, twist, or otherwise adjust the fit. In actual fact, no amount of adjustment could get them to align perfectly, and the springiness wasn’t enough to prevent them from contributing to the axes walking in their rails. That design was eventually abandoned, and no good alternative came to mind, so one of my collaborators and I performed one of the best techniques for mechanical problem solving; we wandered around a home improvement store until we found parts to make something that would work. The solution? — Pairs of Tee nuts (the kind with screw holes, not tacks), attached together with machine screws (adjusting the tightness of the screws controls the preload, which gives free anti-backlash effects), mounted in blocks of Trex (A plastic/wood fiber composite material), which is cheap, easy to obtain, and works similarly to HDPE (Which is to say, wonderfully. Think soft, forgiving wood with no grain). These seem to be better than the old ones, and (possibly with a bit of shimming) workable for a usable mill.

Check out deez nutz:
Rough-fit Outside the block (that is a bar of Trex stock next to it):
drivenutopen_sm.jpg
and one nut complete and sitting in place:
drivenutcomplete_sm.jpg
There is a fair amount of fiddly fitting and drilling to putting those together, but nothing too awful. The machine screws have been trimmed and the edges of the block dressed a bit with a file after the other one went together, so they look pretty solid. In addition to better nuts, the other good discovery is that I suspect that Trex will make excellent, low cost, easily available material to mill objects without any particular material constraints from once the machine is working, I just wish it didn’t have tacky looking faux-woodgrain molded into the stock.

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Cherry Jam

One of the better parts of having old DIY-ful hippie types for parents is getting do nifty things that people just don’t do anymore. One of the better examples is the yearly ritual of making jam from the North Star Cherry tree in my parent’s front yard. The tree was productive this year (and not so much last year) so we ended up making somewhere around four gallons of the stuff over two days last weekend.

Onward, to Jam Making pictures:
Pitting cherries, which is hand-staining and labor intensive:
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To make double-batch sized vats of cherries:
cherry_sm.jpg
Which get cooked down, sweetened, and thickened to make jam:
jam_sm.jpg
Which is then put into bottles:
jambottle_sm.jpg

Way better than the store bought stuff, and fun (if hot, tiring, and messy) to boot.

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DIY Molex Y-Cable

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I think this thing might hold the record for the most times I used the phrase “Don’t do this” in a single fabrication.
It’s a 20-pin ATX Y-cable (for running two motherboards off a single power supply), built from two dead power supplies and a dead motherboard. The cables are available commercially, and if it works out will be ordered in bulk, but the research group needed a quick test cable, and all the necessary components were just sitting there in the dead parts pile…
The plan for these is to double up old Athlon (Thunderbred and Barton) machines on single power supplies, to reduce the number of power supplies (and total power budget. Related facts: 1. Switch mode power supplies are way more efficient when heavily loaded. 2. Power supplies and fans are by far the most fragile parts on disc-less machines) on a 128 node cluster built from scraps from KASY0 and some machines we recently inherited from the Computational Fluid Dynamics group in Mechanical Engineering. This cluster will be for testing network topologies (particularly Fractional Flat Neighborhood Networks), so the important thing is that it have lots of independent nodes, and not much else.

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