In this Instructable I'm going to show you have to make a remote control drop mechanism. It can be used for several different applications. However, I use it mostly for dropping things from drones and radio controlled airplanes.

Step 1: Materials

In order to control the drop mechanism from a far distance (>1km), I decided to use a 2.4GHz radio system. The 2.4GHz control system includes a transmitter and a receiver. The transmitter is held by the user (you), and the receiver is an electronic part of the drop mechanism system.

The receiver is powered from an electronic speed controller, also called ESC. The electronic speed controller can supply the receiver with a maximum of 4 amps, this translates to 5 servos.

A lithium polymer battery is used to power the circuit. A small 500mAh 2S (7.2V) is enough to power one servo for several hours.

Control system: http://www.ebay.com/itm/RadioLink-2-4G-6Ch-6-Chan...
Servo: http://www.ebay.com/itm/Micro-Servo-Motor-RC-toy-...
ESC/BEC: http://www.ebay.com/itm/Micro-Servo-Motor-RC-toy-...
Battery: http://www.ebay.com/itm/Micro-Servo-Motor-RC-toy-...

You also need this:

2mm steel rod
15x15mm square wooden dowel
Piece of plexiglass (foam or wood also works)
Heat shrink 40mm (optional)

Step 2: Building the Frame

Cut the 15x15 square wooden dowel to a proper length. This depends on the length of your rudder horn, but 25mm should be enough.

Use a screwdriver and drill a hole larger than the steel rod. If you're usnig a 2mm steel rod, use a drillbit with a diameter of 2.5mm. This will ensure the servo will move freely without additional friction against the wood. The hole should be place fairly close to the edge.

Take your piece of plexiglass (or whatever) and use a moderate amount of glue. Place it in one of the corners. I used hot glue, and it seems to hold up great!

Step 3: Steel Rod and Servo Installation

Bend one end of the 2mm steel rod into a Z-shape. This end will be connected to one of the rudder horn holes, and will make sure we don't lose the steel rod once the drop mechanism is activated.

You may have to increase the diameter of the holes on the rudder horn in order to fit the steel rod.

Insert the steel rod as shown in picture number 4. Glue it to the plexiglass sheet's other corner, while the rod is inserted through the square wooden piece. The steel rod will most likely be too long, you will have to cut it using a plier or saw. Cut it to a length were it goes half the distance through the 15x15 dowel.

Step 4: Connections

The receiver will have multiple ports, connect the servo to a port called "GEAR" (usually channel 5) and connect the ESC to the throttle port. Power on the transmitter and connect the battery. A small LED light will indicate a connection between the transmitter and receiver.

Depending on the control system used, you may have to do some minor programming to make it work. Don't worry about it, comment below and I'll help you out! Once the system works properly you should be able to flip a switch on your transmitter and the servo should pull out the steel rod. By attaching/hanging stuff from the steel rod, it will release once the servo pulls the rod out from the wooden dowel.

Step 5: Component Management

To protect the electric components, and avoid long wires to get caught you can use heat shrink to insulate the system very nicely. This will also make it easier to attach velcro. Put some velcro on the battery too, and put everything on top of eachother. You are now done, good job! Let's try it out!

Works like a charm...

Step 6: Usage

As mentioned before, I'm going to drop stuff from my DJI Phantom 3. In this first test I successfully dropped a tennis ball.

One can't help wondering how many water balloons you could drop? Remeber to be responsible, don't drop dangerous things!

Step 7: 3D-Printed Version

In case you have access to a 3D-printer you can easily print a 3D-version of the drop mechanism. You can find it here: http://www.thingiverse.com/thing:920725

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