How do I build a hand cranked projector?
March 27, 2009 9:51 AM   Subscribe

How do I build a hand cranked projector?

I'd like to build (as easy as possible!) a hand cranked projector to show a simple 30-second film (no sound). It's for a Green project so I'm trying to use no electricity to show the film(s) and I think it would be fun if it used something like bike pedals or some such to crank away. I can't seem to find anything online like this...any suggestions?
posted by tealeaf522 to Technology (6 answers total) 1 user marked this as a favorite
How I would do it would be to get an old hand-crank projector (like this) and a carbide bicycle lamp (like this) off ebay and replace the electric bulb in the projector with the carbide lamp, separated from the film gate by a fair amount of sheet metal tube, so as not to catch the film on fire. No electricity required at all.

A modified Gakken 8mm projector could also work, with a bicycle-crank-driven generator powering the LED and driving the film transport.
posted by hades at 10:24 AM on March 27, 2009

On the Gakken projector... Make sell this in the US, and it's a fair bit cheaper to boot.
Gakken Super 8mm mini-projector @ Make
posted by mattybonez at 11:12 AM on March 27, 2009

It's for a Green project so I'm trying to use no electricity to show the film(s) and I think it would be fun if it used something like bike pedals or some such to crank away.

I hate to sound like That Guy that knocks on efforts to go green, but I am genuinely interested in figuring out how to make tech greener, and this isn't it - using electricity from the mains is orders of magnitude more green than a pedal generator - no-matter how dirty the mains power station is. At the scale the power station operates, the environmental cost of the grid power for the projector for its lifetime is orders or magnitude less than the environmental cost of the resources involved in adding a pedal generator to the project.

That equation goes out the window if you need to be able to show this projection in a place where the grid is simply not available. In this case, all your options are environmentally demanding, and pedal power is not a clear loser any more. But the distinction should be clear to avoid perpetuating ideas that lead to muddle-headed good-intentioned environmental harm.

As to how to do it, and genuinely make it green, I would go to the dump or a thrift store and find a broken cordless powerdrill. It will be free or cheap because it doesn't work. Chances are it doesn't work because the battery pack is ruined, but the motor and gearbox is fine, and more importantly, it's a solid and durable gearbox and DC motor. The battery pack is made of toxic NiCd cells instead of decent stuff, so it's important that you drop them off at a proper recycling station (but don't make a special trip in a car to do it). Now you're ahead of the game because you've reduced potential landfill, and properly disposed of cadmium that was probably going to end up leaching into the ground.

You want a drill with as high a voltage as possible, because when you use it as a generator, you're may only get a lower voltage out of it (you should get at least half though). So find an 18V or higher cordless drill if possible.

Bike parts likewise come from a junker bike destined for landfill. replace the rear wheel with the power drill. That's the tricky part - power tools are likely going to eat more power than the projector will ever need, but your time is also valuable. So I'd use power tools and spend the karma from the recycled cadmium :)

This will give you enough power to run a lamp, though projector bulbs can spit out a lot of power, so don't bet the house on being able to match that brightness - maybe you can, maybe you can't, it depends on the components you use and how well you build it all.

You'll need either a bulb designed for the lower voltage from the drill, or a car-accessory 12v-to-mains power inverter. The inverter need not be counted against the environment as it is not used up by the project - you can just borrow one for the project, and return it afterwards in the same condition as when your borrowed it.
posted by -harlequin- at 2:07 PM on March 27, 2009 [1 favorite]

For reference, I would think you could get 20 watts out of the drill. That means you won't be out of breath in 30 seconds, but not a lot of power to play with as regards a projector lamp. If you want to tap power more in the 500W range (which, unless you are a cyclist, really will bust your ass in 30 seconds), you would go to a scrapyard for the alternator out of a car, though this will be more complex to use.
For something in the middle, the DC motor out of a broken treadmill or motorized wheelchair.
posted by -harlequin- at 2:28 PM on March 27, 2009

Armstrong can ride up the mountains in France generating about 500 watts of power for 20 minutes, something a typical 25-year-old could do for only 30 seconds. A professional hockey player might last three minutes and then throw up. (ref)
A typical 8mm projector has a lamp that takes between 50 and 500 watts. I think the one my family had when I was a kid took a 150 watt lamp. I really don't think that trying to directly produce power sufficient to drive the lamp and motor in an automatic projector's the way to go. I mean, unless you've got the generator hooked up to a nice beefy battery and inverter, in which case you're really only be pedaling for show anyway.

Powering an LED like the one in the Gakken would be totally feasible, though. Heck, you could do it with off the shelf parts by using a cheap bicycle generator set.

As for genuinely green, well, film's probably out entirely. Sidewalk chalk storyboards, maybe?
posted by hades at 11:18 PM on March 27, 2009

wow. thanks so much for the tips. reading all the responses is making me re-think doing this project. i think i might go with something a little more manageable with my limited tech skills :

but thank you so much for chiming in!
posted by tealeaf522 at 6:56 AM on March 28, 2009

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