Introduction: Hamster to Mongolia
A couple of months ago I acquired a Roborovski hamster. I caved in, despite swearing that I will never keep rodents again. Those little dark, moist eyes, like jet beads, are the thing that makes rodents so hard to resist for me, add in the comical little noses in constant motion, tiny, human-like hands, and soft, delicate, semitransparent ears covered with velvety fuzz, like flower petals, and you've got a powerful combination indeed. The cuteness level is on par with kittens here! This time what really reeled me in was the Roborovski's incredibly small stature. At the adult size of about 3" they are the world's smallest hamster. And voila, I brought the little fuzzy home.
Over the time that followed, I've learned two things. One: my little Hamham REALLY likes her wheel! And two: humans (i.e. myself), are infinitely more trainable than hamsters. All my attempts to hand-tame the new critter seemed to amount to was holding a desperately squirming little fuzzball as she first attempted to wriggle free, then emptied her cheek pouches of all the seeds she'd been hoarding there, in an attempt to become slimmer, and therefore more effective at wriggling free, then finally starting to chirp in terror and desperation, while peeing and pooping herself the whole time. Had I been a child, I would probably have happily ignored every sign of her distress, and, at some point, finally persuaded her that I wasn't trying to have her for lunch. However, having developed a bleeding heart as an adult, I couldn't stand torturing the poor thing for long. Result: one tamed human has restricted hamster-handling to a minimum necessary to maintain a clean cage. The Hamham had her revenge, too, running in her wheel so much every night, that it was sliding all around the cage and banging on the sides (and conveniently keeping me awake) until I finally figured out how to mount it on the wall of the plexiglass cage (at least that stopped the banging, though she still runs in it all night every night, and I can still hear it). Nowadays, before turning in, I look in on her, watch her bounce in her beloved wheel, and tell her: "That's right, run-a-way-way little Hamham! Quick! Run back home to Mongolia!"
That got me wondering: Roborovski hamsters hail from the Goby Desert and the surrounding areas. If her little wheel wasn't securely fastened to the side of her cage, could she run all the way to her native Mongolia? There are, of course, a few oceans in the way, probably a couple of mountain ranges, but what the hell, even "as the crow flies" (or hamster runs, as it may be), could she make it to Mongolia if there was a straight line path to follow, minus the obstacles?
Nothing to do for it, but figure it out.
Step 1: Dollar Store Find
While browsing through the Dollar Tree, looking for things to take apart for another project, I stumbled on this cute little gadget: a pedometer! Of course, this is not the deluxe model that calculates how far you walked and how many calories you burned, this one just counts the steps. This one just has a reset button, to flip the counter back to zero. I wonder if I could get it to count wheel revolutions instead? Turns out, I can!
I took off the back cover and had a look at the mechanism. Ah-hah, that's how it works! Basically, there's this little rotator arm held suspended above a contact lead by a spring. When the gadget is motionless, the arm is in equilibrium, and the circuit is open. If you jerk it a little (as would happen when you took a step), the arm swings down briefly and touches the lead, thereby closing the circuit. It then swings back up again, and after oscillating slightly, is once again held poised above the contact by its spring. Ridiculously simple, really.
All I'd have to do is have the wheel move the arm on each revolution, and I can count how many times it spins!
Please forgive the blurry pics here -- the pedometer is quite small, and this is the best macro photography my camera can muster. I tried to outline the important parts...
Step 2: Pedometer Hacking, Part 1
My first thought was to attach a rare-earth magnet to the wheel, and move the pedometer arm without even touching it. I grabbed a little magnet and tried it out. Nope -- the arm isn't nearly magnetic enough to pull this off. Of course, I could hang one magnet on the arm, and another on the wheel... but no, that would make the arm weigh too much and throw off the balance created by the spring! Looks like I'll need a mechanical trigger.
But wait, the pedometer only counts when its arm swings down. That will work just fine for counting clockwise revolutions, but what if my hamster gets confused about where Mongolia is, and gets the wheel spinning counterclockwise? I can't hold poor sense of direction against her, after dispensing with the oceans and mountains!
Solution: solder a wire to the peg, creating another point of contact for when the arm swings upward from its equilibrium position. Done!
Step 3: Pedometer Hacking, Part 2
Now that the pedometer can count upswings as well as downswings, I could always just put the cover back on and use it for its intended purpose -- except now I'd be making twice as many steps wherever I went. Or I could avoid that inconvenience, and devise a way for the wheel to trigger it, so it could count revolutions.
After giving it some thought, I came up with two rules for the trigger. One: it has to be light! If a tiny magnet weighs enough to upset the equilibrium of the arm, soldering a wire to it probably wouldn't be much better. Two: it has to be flexible! Otherwise, once everything is properly mounted, the pedometer could hinder the weel's rotation, or the wheel could knock the pedometer out of place. And then I found the perfect material: the clear plastic packaging the pedometer came in!
Since I needed to attach something to the arm that would stick out at a 90 degree angle, I decided to use the bends already built into the package, and cut out a very thin strip of plastic that was bent as an "L", then attached it to the pedometer arm with a dot of superglue. I didn't even try taking a picture of this: it was tiny and transparent, and wouldn't show up well in the already blurry pics that were the best I could do so far.
Also, attaching the pedometer to the side of the cage might hinder the ability of the arm to move freely, so I used a bit of airdrying sculpting clay to build a support for the pedometer to rest against, creating free space between it and the cage. I suppose a piece of gum would have worked as well, but I wasn't chewing any just then.
Then I used some clear packing tape to attach the pedometer to the outside of the hamster's cage, making sure the trigger extended inside between the bars, and the arm could swing up and down freely.
The last thing to make it work: cutting out another, much wider section of plastic with a bend in it and supergluing it to the wheel so it would tap the trigger on each revolution. Done!
Step 4: Observation!
Now I'm going to see just how far the hamster runs every day. I plan on taking pedometer readings every day for a week, and then calculating an average. This is where the reset button will come handy -- I'll reset the counter back to zero after taking each reading!
So on the first day she made 14967 revolutions of her wheel.
Over the next two and a half days I was out of the house, and so didn't take daily readings and reset the counter every day. However, in those two and a half days, she ran through 40728 revolutions.
The day after that, I checked the pedometer to find that she made a whopping... 18!? For a second I actually feared the worst: the little creature must have pushed itself too far in her mad dash for her ancestral homeland and died of exhaustion! But no, upon closer examination of both the hamster and her wheel I realized that what actually happened was that she became wise to my spying ways, and circumvented my invention: both the pedometer trigger and the tripping mechanism were chewed to a nub!
Of course, at this point I could have just replaced the plastic pieces with some aluminum sheeting from a coke can. But I decided to respect her privacy instead (really, I was not being lazy, this didn't have anything to do with my getting a DS and becoming addicted to Zelda). So I'll be basing my calculations on three and a half days of observation, instead of the intended seven.
It's time to answer the burning question though!
Step 5: Mongolia?
So let's recap:
The distance from Winchester, Virginia, USA to Ulaanbaatar, Mongolia is 6413 miles.
The circumference of the hamster's wheel is 14 and 6/8"
14967 revolutions over 1 day + 40728 revolutions over 2.5 days = 55695 revolutions over 3.5 days, or an average of 15913 revolutions per day.
That is a distance of 234715" or 3.7miles (impressive!) per day.
Over her expected lifespan of 3 to 3.5 years years, or 1095 to 1278 days, she would run 4052 to 4727 miles... and NOT QUITE make it to Mongolia! About 2/3 of the way would probably land her someplace in Russia, competing with the local bigger, meaner hamsters. What an awful fate!
Perhaps it's a good thing she's safely in her cage, running in the little plastic wheel, trying so hard to get back home :)