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Ever wondered if you could make those thrilling zoom movements without the jerkiness of freeholding the zoom? This simply 3-D printed rig gives the stability and the smoothness to transform your ordinary camera into a videographer's best friend. The best part is that this is fully customizable to your camera, and you can even have a second one to adjust the focus (at this point you are essentially a pro:)

• 3-D Printer and its related supplies (or a friend that has one)
• 1 motor (mine is 77 RMP at 6 volts)
• Wires
• 1 DPDT rocker switch, this stands for a double pole, double throw switch. Essentially two double pole (on, off, on) switches paired together.
• 1 Potentiometer (motor speed controller)
• Smooth shank screws or another form of shaft (I used 3mm and 4mm shafts)
• Drill Bits (preferably a complete numbered bit set, 1 - 60)
• Caliper (optional yet invaluable)
• Hollow Aluminum Pipe (I used an 18mm outer diameter pipe)
• Drill
• PLA filament
• Screw driver
• Soldering iron and solder (just for neat wiring)
• Shrink tube
• 3-48 Set screw
• 4 conductor wire
• 2mm pitch timing belt
• Wire connectors (optional)

If you just want to start printing and slapping parts together, then have at it, who am I to stop you. But if you want to see step by step instruction, read on.

The first step to any design is to decide what the parameters are so that the parts can be sized accordingly. I chose to use a cannon lens with a maximum outer diameter of 80mm, and an overall length of about 180mm. I then measured how much of an angle the zoom ring swept out when transitioning from fully zoomed out to the tightest field of vision, which ended up being approximately 45 degrees. I then decided that I wanted to make this transition in about 3 seconds with the motor at full speed. Since I had a motor and gear box that delivered a speed of 77 RPM at 6 volts I needed to step it down to 2.5 RPM to make 45 degrees in 3 seconds. This means that I needed approximately a 31:1 ratio.

Explore you options, don't let me tell you how to run your show. When I started thinking about this idea I made a decision matrix. That is where I assigned a weight to different metrics I wanted to get out of the design, and had these total to 1. I then rated each of my ideas in the categories, and then tallied up the scores.

This is the most difficult part, so it would be best to master this before the rest. I tried printing a worm with a pitch of 1.25mm, and it did not print well at all. I then tried a 0.5mm modulus and it turned out a little better. I printed it in halves and glued them together, but they then began to split. I stepped up to a 0.8 modulus and this printed better than all the others, and it was still small enough to accommodate a slim design. I found it on McMaster Carr so that I did not have to mess with CAD, helixes, pressure angles, involute curves, and all the other jargon that comes along with gears. After this I downloaded a 20:1 worm gear to match and slapped it on another gear that would act as the drive wheel for the zoom lens. Whew, now that the gears are done with, lets move to the fun part. Printing!

Now print the gears to make certain that the teeth print fine. You may have to take an exact-o knife to the teeth and "floss" them a little. Once you are content with the outcome, start on the powerhead casing.

This came by a bit of trial and error for me, but it does not have to be for you, yahoo! If you use the provided files for the worm, worm gear, and the same motor, shaft sizes, and guide rod, then all you have to do is download the provide .stl file for the front and back casing. Then bingo, it will all fit together like a glove. You will just have to ream out the holes for the shafts (in both the casing and the gears) with a reamer or simply with a drill bit. This is to ensure that you get a perfect fit so that the wheels move freely. Otherwise, you will have to lay out all your parts, fire up your CAD software of choice, and have at it.

Now you simply need to assemble the powerhead. Begin by soldering the wires to the motor if they are not already. Cut the 3mm shaft for the worm down to 19mm long and ensure that it slides freely in the gear. Next, cut the 4mm shaft to 17mm long and ensure that it too slides freely in the zoom drive wheel.

This is the tedious part, tapping the hole for the set screw. It is not as daunting as it sounds, just take care not to "wallow" out the hole as you are drilling it, and you can simply use the setscrew you are using as the "tap". Begin by stating a hole with a number 47 bit (0.078" dia.) about 5mm from the end of the worm (do this on the end with the worst printed teeth because this will not be engaged in any gears). Drill only until it breaks through the inner surface (i.e. only half way through the worm), and then back the bit out slowly. Now start the setscrew by applying a lot of pressure on it while twisting it clockwise, gently forcing it in the hole (it sounds contradictory but can be done). This will cause the threads to grab the plastic and pull itself in. If the screw is not taking to the hole, drill a slightly larger hole by stepping up the bit one size. Continue driving the setscrew in until it goes through the length of the drilled hole. Now back it out and drill through to the other side, ensuring not to let the bit touch the sides of the already threaded hole. Perform the same tapping operation on the other side of the worm so that two setscrews can be clamping on the motor shaft.

First, place the zoom drive wheel in its place (large gear side down), and insert the 4mm shaft through it, into the casing pocket designed for it. Secondly, insert the motor in the worm, tighten the set screws, and insert the adjoining 3mm shaft on the other side of the worm. Slip the shaft (with the worm on it) into its pocket on the casing, while guiding the motor into its resting place. With the gears and the motor situated, wiggle the zoom drive wheel to ensure that it does not have too much or too little play in it. If you are content with the way things fit together, ease the top of the case on, and fasten it with three screws in the appropriate holes.

These are my wiring schematics that show where the power is going. The basic breakdown is that the power goes from the battery, to the potentiometer, to the DPDT switch, and then to the powerhead. I have also shown how to wire the controller with the DPDT switch.

Now that the main chink of the work is done we can start on the controller. There are just two parts to print for a combined printing time of about 5 hours, just enough time to get the wiring prepared! While the casing and controller wheel are printing you can wire the DPDT rocker switch to the potentiometer. You will have four wires coming into the controller, tow for power in, and two for power out (to the powerhead). The power comes into the potentiometer, then out of it to the DPDT rocker switch, and then out to the power head. Just wire the DPDT for a polarity reversing operation. To do this, power goes in the two center terminals, run two jumpers catty corner between the far terminals, and then power goes out one set of the other four terminals. Once the parts are finished printing, fish the wires out the nose of the controller, throw the wiring harness in, tighten the screws, and gaze at your master piece.

I put this wiring harness together, so that the battery can be attached then have three outputs. Two are for two different controllers (one for zoom and the other for a focus control if desired), and the other is a combined power output for the zoom and focus powerheads.

I created this mounting rig that will accommodate a lens diameter between 65 and 70 mm. It is simply composed of two printed halves and a pin connecting them so that it can open up and then clamp down using a bolt and nut.

Now just slip the guide rod on the mounting rig and clamp it down. Next, clamp the mounting rig on the lens, and then slip the powerhead on. Wrap a 2mm pitch timing belt on the lens and fasten with a zip tie, for this is how the powerhead will grip the lens. Now, press the powerhead against the belt while twisting it about the guide rod a bit, and holding this position tighten the screw at the guide rod clamp on the powerhead to keep the torque in the powerhead. After this is all done, the rest is ready to attach the wires.

Just run the power from the battery to the controller, and then to the powerhead. Finally, turn the potentiometer knob and gaze with delight at your brand new powered zoom lens.

This tool has many uses that go beyond simply adjusting the zoom on a camera. This basic design can be used to make minute adjustments on many rotary tools, say to angle a ball shooter or potato cannon in a specific direction. This can also be improved on by adjusting the gear ratio to fit your specific requirements.