awesome laser-pointer-spinning thing
May 28, 2009 2:13 PM   Subscribe

Help me improve my awesome laser-pointer-spinning thing.

So, I built this awesome laser-pointer-spinning thing. It's a foot-long piece of 1x2, with holes drilled to accept 4 laser pointers. There's a bolt though the center, which I chucked into a cordless drill. When spun, it created amazing patterns in the misty night sky (and amazingly awesome patterns in campfire smoke).

Problem is, it's heavy, and produced a lot of torque when starting and stopping. After I started and stopped it several times, the bolt broke from the strain, sending the apparatus flying through the air. Not optimal for the delicate laser optics, or for the delicate optics of the human spectators.

I suppose I could be more careful about trying to ramp the speed up and down gradually, but my drill isn't really very good at that. Does anyone have suggestions about how to make the thing stronger, lighter, more awesome? Manual-powered modifications would be fine, too, but I found that it worked best at high rpms.
posted by MrMoonPie to Media & Arts (24 answers total) 5 users marked this as a favorite
Wood is heavy: try a piece of aluminum or hollow plastic tubing (bonus: whistling sound).

A cordless screwdriver (maybe not fast enough) or dremel (maybe not strong enough) would be a heck of a lot easier to carry around than a full-sized drill. Dremels are also variable speed (it's a dial or slider, not a trigger.)

Take your magic wand to a Lowe's or some place and try it out on every drill/driver/spinner combination they have.
posted by rokusan at 2:21 PM on May 28, 2009

Use a bigger bolt. Most cordless drills have 3/8" chucks. You're not going to break a 3/8" bolt.
posted by jon1270 at 2:24 PM on May 28, 2009

The first thing that occured to me was that you could use a blender base instead of a drill. Then you could slow it down in steps rather than all at once. I know it isn't cordless, but it might work well for a backyard lightshow.
posted by Brody's chum at 2:32 PM on May 28, 2009

Don't make it 4 feet long? If I remember my physics, which I don't, making it half as long should reduce the inertiasomething to a quarter of what was.

It's too big and too heavy is what I'm sayin'.
posted by chairface at 2:45 PM on May 28, 2009

It's one foot long, with 4 lasers.

Plastic tubing would help, but there's still the weight of the pointers themselves, spinning rapidly. I'm not worried about the overall weight, more the weight of the spinning part--I'd consider a bicycle wheel or something similar if I could figure out how to get it spinning fast enough. Gears? Belts? Something with mirrors or prisms or beam splitters? A hand-cranked ice-cream maker? I'm pretty handy, and can weld, and am willing to put a ridiculous amount of money and effort into this.
posted by MrMoonPie at 2:49 PM on May 28, 2009

You could take the laser pointers apart to the bare minimum (or use something like this) and use a remote battery (maybe even the drill battery). The tricky part would be a slip ring to get power over. As a plus you'd be down to one power switch.

Maybe even replace the wood with cordage (boot laces?) that gets flung out to take shape when spun. Or something a bit heavier like 5mm cord. On preview: siphon tubing could be used to house the wiring.

I'd be glad to lend a hand with the electrical aspects if you like, as I like to think of myself as the soldering ace of NE DC.
posted by exogenous at 3:07 PM on May 28, 2009

You are a man after my own heart. The first thing that I purchased with my very first paycheck was an overpriced, oscillating laser toy from Spencer's Gifts many years ago. As you probably know, spinning lasers are the future.

I think using a wheel as a base is a great idea. Something solid like a roller blade, but a maybe a couple inches larger. Smaller is definitely better, since it will be easier to spin. Also, get the smallest/lightest laser pointers that you can -- the type that are powered off of a single AAA, or a couple of watch batteries. You could drill through the rubber of the wheel and really wedge the pointers in there (as long as you can still access the batteries and the on/off switch). Connect them up to a small hobby motor, power source, and a rheostat (maybe RadioShack?), and you'd be all set.

Alternately, may I suggest the $5 laser show? This would be a bit more portable and the lasers would move by themselves, so that you could enjoy the show too, instead of manning the spinning laser array.
posted by mattybonez at 3:22 PM on May 28, 2009 [1 favorite]

If you wanted to put some work into it, you could mount all the lasers in the center, pointing along the length of the rod, and then mount mirrors at the end of the rod to reflect them perpendicular to it. This puts the weight of the lasers at the center, minimizing the moment of inertia of the assembly, but requires getting some mirrors and finding a good way to mount them.
posted by pombe at 3:33 PM on May 28, 2009

Make a flywheel/harmonic balancer where the shaft goes through the stick. That will balance the weight of the lazers more toward the center and put the load on the center axis instead of out toward the ends.

I'll think about this some more.
posted by snsranch at 3:41 PM on May 28, 2009

You could use a kind of clutch thingy (vocabulary is failing me) instead of a bolt. Something like on a bicycle rear wheel, then you only have the torque spinning it up, but it would just freewheel when stopping the drill.
posted by mmkhd at 3:45 PM on May 28, 2009

It doesn't look like it has a handle. A drilled out dowel or something on the shaft would make it less unwieldy and you could use a socket and socket extension as a quick release for the drill so you can wind it up, let it go and wind it up again.

Man, that thing sounds like fun!
posted by snsranch at 4:03 PM on May 28, 2009

Get one of those cheap box fans and take one of the grills off. Drill holes into the fan blades and insert the lasers where desired.
posted by orme at 4:03 PM on May 28, 2009

snsranch, the shaft goes into the drill like a bit would--that's what makes it spin. I'm interested to know what you have in mind, though; I don't quite see it.

One important feature is that, to use it in the venues where it'll be of most use, it needs to be cordless. I'm taking it to festival camping events to amaze the hippies; last weekend, I was thanked "for bringing the awesome." It won't be of much use in my DC backyard, what with light pollution and restricted airspace and such.
posted by MrMoonPie at 4:26 PM on May 28, 2009

Oh, and I actually do have a bicycle I could use for parts, if that'll help.
posted by MrMoonPie at 4:27 PM on May 28, 2009

Replace the wood with PVC pipe?
Get another drill, with adjustable torque?
posted by bartleby at 4:53 PM on May 28, 2009

Use a 3/8" bolt. Get one that has threads only in the last inch or so. Cut off the head. Clamp your piece of wood between two opposing nuts on the threaded section. You now have a plain, unthreaded shaft to fit into the drill chuck, which will give the chuck better purchase than gripping onto threads. Trim the shaft to the shortest length it can be while still reaching all the way into the back of the chuck. If you want, you can file three flats into the shaft 120° apart to engage the chuck jaws a little better still. Tighten the chuck with a chuck key, if it has one.
posted by flabdablet at 5:45 PM on May 28, 2009

Ok, you'll get this even without pics.

So, as I see on you're diagram you have a fairly long shaft/bolt that is going right into the chuck on your drill. So it sounds like the drill is actually what you're holding onto.

So as that light-show-machine is spinning it's probably pulling your drill and hand around quite a bit, probably in a circular motion. It's easy to see why the shaft broke before.

So find something, a tube, pipe, rubber hose to sheath the shaft and use as a handle over the shaft. I think they have dowels that are already drilled length wise at craft stores. The idea is that you can hold it like a shot gun or something, supporting the shaft and light bar with one hand while operating the drill with the other.

If that makes any sense, continue by putting a big washer at each end of the "handle" and use some graphite lubrication.
posted by snsranch at 5:52 PM on May 28, 2009

I got it now, snsranch. My drill is pretty stable--I didn't include in the diagram the balancing mechanism, adjustable (of course) for shifting around the variable-weighted laser pointers. And a little wobble adds to the effect.

And, yeah, it is fun. I ain't talking about the 5mW stuff you can get at the drugstore. I, uh, got my sources...
posted by MrMoonPie at 6:46 PM on May 28, 2009

The simplest way to fix it is to even the weight distribution so it's not as inclined to fly off at an angle. I would make a 2' long thing and add dummy weights on the non-laser side that are equal in weight to the laser pointers and distributed at the same places then mount the bolt/ flywheel in the center of the 2' long rod. That way it'll be like a propeller instead of like a slingshot. You will have to be careful not to make it into an actual propeller so shape the blades so that they provide as little "lift" as possible to reduce the strain on the center assembly.

An old fan assembly would probably work pretty well for this and the cage might be adapted to provide a safety shield of sorts.
posted by fshgrl at 7:21 PM on May 28, 2009

I would LOVE to see some photos of this in action!
posted by snsranch at 7:45 PM on May 28, 2009 [1 favorite]

Just checking in...

Lots of suggestions on how to lighten-up the assembly, which I may try. Right now, I'm heading towards the oppisite end of the spectrum. Yesterday, I cut up my daughter's old bike (she'd outgrown it), saving the rear fork, wheel, and crank assembly. I also cut off one side of the fork--my idea is to mount the whole thing (somehow), attach the lasers to the wheel, and crank the shit out of it. Not really sure how it'll work, but it'll be fun trying.

One of the things I liked about the original project is that it was so very low-tech and simple--I wasn't even careful about the angles of the holes, and it turned out great. There was a huge impressiveness/effort ratio, so to speak. I guess I'm destroying that.
posted by MrMoonPie at 7:57 AM on June 14, 2009

In the end, I used the original design, but with modifications. I used a slightly-less-than-footlong piece of 3/4 inch PVC pipe, with the lasers brounght in as close as possible to the center. I also built in some slip to the mounting, using fiber washers. This allowed the apparatus to ramp up and down when starting and stopping. Still pretty simple.
posted by MrMoonPie at 2:06 PM on September 26, 2009

I just ordered high-powered blue, green, and red pointers to fit the apparatus. I'll try to get video when I fire it up next time.
posted by MrMoonPie at 2:38 PM on April 16, 2010

Last time I used the device, I discovered that pointing it at things like tree lines was really impressive, creating spirograph-like intersecting circles. It gets a bit wobbly at high speed, but this adds to the effect, so I'm not worrying about that.

The diagonally-mounted lasers had to be turned off for this, or else they'd shoot into the spectators, so for the most recent iteration, I eliminated the diagonal mounts, thus giving me room for another pointer on each side. I didn't worry about getting the lasers perfectly vertically aligned, so the beams do intersect sort of randomly, but that's cool.

The PVC is working well. I'm now up to 6 lasers, in 3 colors, with a combined output of around 500 miliwatts. I'll see what I can do about pictures--I live in the city, so I can't play much outside. We're going camping this weekend, so I'll see if anyone can get a good shot.
posted by MrMoonPie at 1:42 PM on May 24, 2010

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