Thread: floating lantern - low rpm motor?

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Hey folks,

I just got my hands on two low rpm motors that I want to use to twist a few lanterns, but then I got to thinking...would it be possible to add an arm off of this motor to give a much more dramatic look to this prop?

The box isn't specific as to how many rpm's, but its low. It also says that it can hold up to 2kg, which I believe is roughly 4.4lbs.

So do you guys think it can be done? If so, how would you suggest I connect a arm to the rotating pin?

Here's a picture:

The diameter of that crank suggests that the "overhang" rating would be pretty low. I'd be surprised if you could place much of an offset on it without burning the bearing or armature.

It looks like theres that's a hole though the shaft - perhaps you could try using a small cotter pin to hold a very light plastic arm after molding it over the end.

Thanks KevinS

I was thinking maybe something along these lines:



But was concerned about exactly what you suggested might happen. The upside is that I got the motor in a two pack. LOL One to test and most likely burn out, and one to use on the day as recommended by the manufacturer. haha

Dminor - with a counter-weight, as you have in the drawing, you should be just fine (as long as the total weight of lantern, armature, and counter-weight don't exceed the 2kg limit).

The counter-weight will eliminate any lateral torque the armature would be exerting on the shaft, which I believe was KevinS's concern. I don't believe the additional rotational torque exerted by the extended arm will be too much for the motor to handle, once it's all in motion (it may need a gentle push from you to get going, perhaps, but that should be it).

Very cool! Now I just need to figure out how to attach the arm and make it pivot. LOL

Any suggestions on selecting a weight? The lantern is 15oz.

Nevermind, I just read a tutorial about weight and how to attach the arm.

I figured I'd have about a 4' swing circumference (with the lantern 2' from the fulcrum and a 2lb. weight 1' from the fulcrum) and just use a small bucket that I could fill with sand or similar to make the balancing act easier.

Thanks again for you help guys!

I agree that a counter weight system would be the answer. Given the small circumference, I'd make the arm the same length on both ends and use fishing weights.

Please post a link to thaetutorial - I collect that sort of info

Nice set up, but you might want to add one more level of suspension.

As you have it, the lantern will only go in a predictable, circular path (you might get some up and down motion, tho). Thus the effect is easy to figure out.

If you were to add one more level of suspension, thus another pivot point, your lantern will, while staying in a 'roughly' circular pat, will tend to 'wander' more. Much more effective.

Good instructions for this can be found at GHOST SONGS: Music From Beyond The Grave....

This is the basic desing you want from that site:

Grim Spirit, thanks for the input! I reviewed that site last night which helped me come up with the rig I'll be building today.

The predictability of the "flight pattern" doesn't bother me too much, as the prop will be in somewhat of a small area, so a small rig is the right choice for this year.

In the future I hope to have more space (this year I'm doing my setup in the courtyard of the apartment complex I live in) and have bookmarked the Ghost Songs website for future use.

I'll write up a tutorial once I'm done with lunch. :-)

Ok, first things first. I bought a bunch of bits and pieces that I ended up not using. So you can thank me later. lol

Parts:
1 - low rpm motor (i.e. disco ball motor)
1 - lantern (1lbs.)
1 - LED flicker candle
1 - 1/2" diameter aluminum rod
2 - 10-24x2" eye bolts
2 - 10-24 nuts
1 - 10-24 hex nut
1 - m4-12 pitch .7 pan head phillips head screw
1 - 2lbs. fishing weight
1 - ball bearing swivel
2 - lanyard clips
1 - zinc swivel mirror holder - 2 hole

1. determine the width of the circle you'd like your lantern to travel and select an appropriate length of rod.

In my case, I have a very small space to pull off this effect, so my circumference was only 4'.

2. Take your eye bolts and screw the nuts onto them and insert them into the end of your aluminum rod. The 1/2" diameter rod was slightly smaller than the size of the nut, so it's a snug fit. Once you've got the nut positioned, unscrew the eye bolt and hammer the nut flush with the end of the aluminum rod.

3. Attach your lanyard clips to the eye bolts. Then attach your weight to one end and your lantern to the other. Be sure to insert your LED candle so that your lantern is at its final weight.

4. place the swivel mirror holder around the rod. Take the M4 screw and nut and tighten it around the rod roughly where you have determined the fulcrum or balance point is for your prop.

This step has a little trial and error as you may need to move the swivel mirror holder until your weight and lantern are even balanced.

5. Attach the ball bearing swivel between your low rpm motor and the swivel mirror holder and turn on the power.

At this point I would advise that you should paint every surface matte black to help hide all of your mechanisms.