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August 25, 2003

I Came, I Broke, I Learned

Just ask my wife how much patience I have for things that aren't working for me. I have become a bit better over the past many years, but I'm still far from being cool and level headed in the face of an inanimate object that is being stubborn. My typical reaction is quite predictably linear: first I become frustrated, then annoyed, and if things keep escalating I tend to start swearing. Make me really mad (in other words, if I persist and the inanimate object remains stubborn) and I'll start heaving things. It's certainly not pretty, which is exactly why I'm trying hard to change.

The other night, however, something very strange happened. I screwed something up, tried to fix it, screwed it up more, tried again to fix it, screwed it up worse, and now it sits in pieces in a little box. So now you're wondering if the pieces are the broken chunks of what's left over, and whether my neighbours thought some sailors stopped over at my house, right? Well, don't. The more broken it got, the more interesting it became. And when it did break - in spectacular fashion, I might add - I laughed. I was really enjoying working on this obtuse piece of hardware that wasn't co-operating. And do you know why? I approached it as fun. And it turned out to be!

I'll cut the suspense and let you know that what I was working on was a tape measure. I have (had?) a spare green-bodied 12'/4m tape measure downstairs, and after writing about tape racing I decided that I had to start learning this sport regardless of how much interest was immediately generated, and so decided to start up the learning curve of Tape Racing.

This was not my first foray into figuring out how a tape measure works. A few nights before (much to my wife's shock/incredulity/amazement/dismay) I took apart my other silver measuring tape, a full-Imperial 12' model. I took the case off, and got my first look at what the rewind mechanism is in a cheap tape measure. Satisfied, and without time to further poke and prod I put the cover back on. That just wasn't enough, however. I needed to know way more about the nitty-gritty details of the rewind mechanism if I was to go racing. That's when I decided to sacrifice my green tape measure, as I almost never use it (and certainly can't now).

Just taking the two different ones apart has shown me quite a lot. It is obvious that these are economy tape measures. They certainly aren't meant to be serviced, let alone hopped up in any meaningful way. (Of course, that won't stop me.) I also found the highly varied lock mechanisms interesting. My silver tape has a lock that requires manual engagement, a feat performed by a simple rocker switch and a sliding piece of plastic. The green tape, on the other hand, is always in "locked" mode, and requires depressing the button to allow it to rewind. The lock mechanism on this is incredibly interesting, involving a 3-piece link mechanism and spring. I'm suitably impressed with the amount of engineering that went into this simple tape measure.

Before I go any further, I should take time out to warn you. Tape measures may be deceptively simple, but they are dangerous when being taken apart. Any time you have energy stored up in a spring, no matter the size, it can be released very quickly in an uncontrolled manner. If the spring is a thin, almost sharp, metal sheet, you have the recipe for a sliced finger or two as well. When you're working with the spring, please wear safety glasses or goggles! I was thinking this exact thought when working with the coiled spring, and suddenly it got away from me and the reel launched itself across the room, out of my hand. Luckily, it didn't hit my eye (or anything else delicate for that matter), but it highlighted the fact that a loaded spring is dangerous. I could have been seriously sliced or scratched my cornea or worse. Safety first next time for me, and safety first right from the start for you, OK?

My primary reasons for taking apart these tapes were to gain a better understanding of the underlying mechanisms and also to assess how one might start going about improving the mechanism and making the tape faster and stronger. I have some preliminary ideas based on what I saw. The two tapes are identical internally, with spools of thin spring steel coiled around a fixed point encased in a reel. As the tape is drawn out, the spring is wound up, providing the necessary force to rewind the tape. The first thing I noticed is that all the internals of the tape are plastic, save for the spring and tape itself. What's more, very little effort has been made to ensure that the reel mechanism operates smoothly over a lifetime; the plastic reel is held in place by plastic bosses, no bearing surfaces or lubrication at all. Another factor is that over a period of time, the internals of these devices will pick up dirt and lint and get clogged and sticky. Even with my relatively unused green tape there was a substantial amount of pocket fluff that I cleaned out. I can only imagine what a contractor's measuring tape would look like after a couple of months on the job.

So, where would I start improving the 0-12' performance of a tape measure? First, I'd clean and lubricate everything. The steel spring was lightly oiled, but still had some very mild surface rust on it. I'd wipe it down and perhaps lubricate it with a dry lithium or graphite grease to ensure that it doesn't bind and that no viscous liquid makes it stick to itself. Next, I might try incorporating ball bearings into the reel. Ball bearings would do two things for the reel: it would allow the reel to be placed quite accurately within the body and thereby not rub on anything, and also provide a smooth rolling surface, as opposed to the plastic-on-plastic that exists now. If space is limited, thrust bearings might work well.

Another modification I would make would be to remove the fixed point the reel spring winds around from the body to an independent component. To wind the reel spring now I have to lock it into a spindle on the body, and then gently rotate the reel and half of the body around each other. This is, to put it mildly, a pain. (No, really - my thumb started cramping up.) Of course, if you let go it spins out of control and you lose everything you just did. Making it such that I could wind the reel without it being mounted in the body would make life a lot easier.

For the record, I believe the reel is large enough that replacing it with an electric motor is a real possibility. Getting enough electrical power to the motor might be another issue, however. I'm sure I'd have to try both batteries and capacitors, but I can't imagine either being easy to work with on such a scale.

The most important fact I learned during this exercise was that tape racing is within the realm of the possible. Even with a modest budget and mechanical abilities, just about anyone with the will and desire to enter tape racing will be able to hone, tweak, and improve their tape. It will take time for a body of knowledge to amass, but from what little I've seen I have no reason to doubt the possibility of that happening. I've taken the first step, and learned quite a bit. I'm ready and eager to learn more.

Hopefully, one of the next things I'll learn is to actually put my tape back together and get it working....

mr.ska
nft@myrealbox.com  


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