"Flip the main switch, Igor! WHAAAHAHAHA!!!"
Well, OK, not exactly like that - this started, oddly, with lost luggage...
When I arrived at friends of mine after one of my many trips, minus my luggage, they gave me one of their "standby" bags of toiletries. This one contained an intriguing item: a battery-operated toothbrush with no visible means of replacing either the battery or the head of the brush. When the battery finally gave out, I resolved to recover the motor from the toothbrush...
NOTE: This is a classical example of me setting out to do something and ending with a completely different result - so this will be a "use stuff that's similar" kind of instructable. This is my first try, so here goes!
Step 1: You Will Need...
A weird (to me at least) toothbrush that vibrates when you press a button on it*
A new, garden-variety (or is that bathroom-variety), ordinary toothbrush
Something to cut with. I used a junior hacksaw and what we call a "hobby" knife, the type with the retractable blade
Something else to clean edges with. I used the file from my multitool and some coarse sandpaper
A hole-making tool, like the drill bit I used
Some flexible plastic tubing of a diameter similar to or just slightly smaller than the toothbrush
*As I mentioned before, this toothbrush was a bit of a mystery: no way to change/charge the battery, no way to replace the head. I got the impression it was designed to be discarded. As a matter of fact, I have not seen another like it again. So, should you find yourself with an abundance of ingenuity and a complete absence of strange toothbrushes, improvise. I include a picture of the other thing in my collection of knick-knacks that could also work: a battery-operated razor. When you get rid of the "head" part of these items, they are both basically a stick the size of an over-enthusiastic pen that vibrates. Functionally synonymous.
Step 2: Examine the Patient
Since the original goal was to extract the motor, I started by looking for ways to get inside. I noticed a cap on the end (indicated by a seam about 20-25mm from the end), that seemed to be glued on. After some wiggling, I coaxed the seam open and the cap twisted off with little effort.
From this orifice, a AAA battery slid out. I realized that, if I replaced this with one of the rechargeable ones I have lying around, I could resurrect this toothbrush if I could find a way to replace the head.
(From the last picture in this step, you can see that the battery-operated razor is about the same size, but takes a AA battery, which is often easier to come by)
Step 3: Off With His Head!
On further examination, I saw a similar seam between the brush head and the flexible neck of the toothbrush. The same procedure was followed: after wiggling it sideways a bit to crack open the glued seam, the head twisted off rather easily, leaving me with the main body (and the now exposed vibrator motor) and the vaguely cone-shaped brush head attachment.
At this point, the plan was to simply chop a segment off the new toothbrush and bore a hole into it that would fit the stub where the previous head was attached. Blasted Murphy...
Step 4: Foiled! Really?
Next, I seperated the old brush head from it's cone-shaped appendage. I then cut through the new toothbrush in a section I thought would be thick enough to accommodate the stub of the cone. I didn't want to glue it in place, as I figured I could re-incarnate the toothbrush everytime by merely transplanting the head.
I made the cuts, smotthed the edges over with my file and sandpaper, then made an appropriately deep hole with the drill bit, by hand. When I did a test-fit, however, the new "head" did not take well to pressure being applied to the brush. I soon found why...
If you look carefully at the last picture in this step, you'll notice that the white, hard plastic is interrupted on the right-hand side by the blue, rubbery part. This weakness happens to be exactly were it will cause the brush to fall off when brushing with even the least bit of vigour. Thus, instead of having resurrected a toothbrush, I now had two "dead" patients on my hands... What do to?
Step 5: Shrink It and Go! Tube to the Rescue!
Luckily, my eye caught a piece of clear plastic tubing that I had lying about the place. It happened to be just thinner than the handle on the toothbrush. I cut off an appropriate length of tube, boiled some water and submerged the tube in the boiled water until it became quite soft. I first fit this around the new head's bottom, allowing it the cool to test the fit.* Next, I reheated the water, softened up the tube again and wedged the cone-shaped attachment in there, with the tip slotting into the previously made hole. After it cooled, I tested the fit again.
*I'd like to mention here that I had to cut a small slit into the tubing, to allow it to fit around the bottom part of the head.
Step 6: The FrankenToothbrush
After putting a newly charged AAA battery into the handle, I reassembled all the parts of tested it. It works! The head doesn't fall off (a major plus) and it works just like before, albeit being quite bit longer (just over 9"...)
"It's alive! IT'S ALIVE!!!"
"Wrong switch, Igor..."
Step 7: Epilogue
Of course, there are many ways to skin a cat...
As mentioned before, you don't need two toothbrushes to create a FrankenToothbrush; any object that vibrates and is easy to hold will do. There are undoubtedly also a myriad ways to attach the new head. The point is, get out there and mix and match until you find something that works.
What of the old, discarded head and the handle of the donor toothbrush? Well, this is one I'd like to throw out there for the community. What would you use it for? Which crucial component of your dastardly scheme for world domination would this be?
Last but not least, if you've enjoyed this instructable in any way, please consider voted for it using the button located at the top-right corner... ;)
Step 8: Caveat Constructor...
"Common sense is not as common as we are led to believe..."
In paying homage to this maxim, the author would like to point out that the risk of recreating this instructable lies completely with the person(s) attempting it. The author assumes no responsibility for any cuts, bruises, amputations or fatalities resulting from such attempts. Any dental expenses for broken teeth, resulting from attempts to recreate this project withoversized power tools, is for the maker's own account. The author also exempts himself from any electrocutions/fires/global destruction that might result from connecting versions of this device to any high-voltage power source. In addition, should your attempt result in a device with a length similar to or exceeding that of the device in this instructable, the author will not be held responsible for the ferocity of your gag-reflex when you put it too far down your throat. He will probably snigger a bit...