Public Lab Research note

soda bottle rig for pendulum suspension

by tonyc | December 12, 2015 00:05 12 Dec 00:05 | #12502 | #12502

What I want to do

connect a point/shoot camera to the end of a dowel, protected for flight

My attempt and results

this is a quick prototype of an idea to simplify the soda bottle rig. Original soda bottle rig has rubber bands passing through the neck of the bottle. My design goal was to make it easy to mount this rig to the end of a dowel, without introducting wear or friction on the bands.

The tension is provided against the screen, which presents an obvious problem. I found on this model at least, a protective card could be inserted to add impact protection, just a standard credit card size works.


The basic rig:


Questions and next steps

fly it, see if it works

Test it on someone else's camera to see if it breaks

Why I'm interested

getting ready to introduce a pendulum kit in the kits store, and working to show good methods for use.


That looks like a good way to avoid passing the rubber bands out of the bottle top, especially if the shaft could slide easily so the camera can be readily accessed for adjustments. Are the bands knotted around the dowel?

What kind of dowels will you use? I found that wooden dowel legs for camera rigs made from anything other than oak are too prone to breaking. But legs can break and still do their job protecting the camera -- a pendulum cannot break. Fiberglass tubes 20 inches long cost only a dollar ( and are well worth it for a pendulum shaft. A 20 inch shaft with 200 grams on the end can generate of lot of whip on a kite line, and I would not trust wood for this.

It sure would be nice to avoid obscuring the LCD. If you can't readily check the camera settings right before launching, you are increasing the probability of sub-optimal settings. That's a strong argument against the soda bottle rig in general, and any further obscuring seems like asking for trouble.

Some point and shoot cameras (maybe many these days?) have touch screen LCDs. I don't know whether pressure on the LCD from the stopper will be a problem. Scratching the LCD will be a problem unless the stopper or card are always very clean.

It appears that the only thing attaching the camera (and shaft) to the soda bottle is a rubber stopper. If the rig lands hard on the bottle, that stopper can pop out and allow the camera to hit the ground. That might require a different arrangement, or some way to lock the shaft to the bottle.


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The dowel is just a birch dowel, cheap as they come. But the design case was to have everything ship in a standard kit box, so the pendulum is built out of 9" segments of this dowel, held together by PVC flexible tubing joint, pinned in place with simple thumb tacks.

the result is stronger than you'd think, since it can flex at the joint. Thrown the thing around with weight attached and it whips, but doesn't break, even on impact.

The stopper pressed into the neck makes a very strong connection, one that is actually difficult to remove. I think this has a lot to do with the particular rubber it's made of, likely won't work with the firmer white rubber ones I've seen. To really lock it down, you could just put another stopper on top of the bottle, tapered oppopsite direction

the bigger problem is the pressure on the screen, and directly transfer of force to the screen on impact. Obvious flaw, as well as obscuring the view. The view could be helped by including a clear card to use as protector, but I don't know if this angle is worth persuing.

Totally different approact to this uses nylon threaded rod. This is another material I've been playing with, as it's univerally handy to have the tripod thread rod as part of the mix. Allows you to attach a camera or ball head, or tie in to the mount from the pole mounting kit...

the nylon thread is very strong and flexible. Might be too flexible and introduce wobble.

Thinking a two-hole #3 stopper could allow for interesting pairings of threaded nylon rod with dowel/carbon fiber rigid drops.

My end goal on this is a general purpose DIY suspension kit with all the parts you need to try many configurations, based on notes like these.

So far, all thread, stoppers, rubber bands, dowels, tacks, PVC tubing, tripod ball head, zip ties, string, rigid wire for connection to flying line...what else should be part of a small-parts kit?

assuming soda bottles are already everywhere... :)

IMG_3570.JPG this is a trick I used to keep the all thread rig from bowing under weight of P/S camera, btw

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Added some stick legs. Inspired by a recent bike accident, I thought I'd try to make the camera roll, rather than try to actually stop itself rigidly. So the chopstick (dowel) legs roll the camera back and off to the side, away from the lens.

The rubber bands at the top give it some spring. It actually kinda hops, then rolls over.



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OK, this is now its own research note, but the chopstick leg model is winning out for me!


I added a little "butt" for it to land on.

Now it rolls like a judo champion. Well, like the second place Judo player who just got thrown, but knows how to land without hurting themselves...

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