Quadcopter / Drone / RC Helicopter Automatic Deploying & Retracting Payload Hook

thingiverse

Here at H5 labs, we like neat things such as 3D printers, quad-copters, Robots, lasers - you know, the usual geek fare. We have enjoyed our DJI Phantom 3 drone, but we wanted to do more than just take nice pictures with it. So, we came up with a payload hook system so that we can deliver small items to "remote" areas - all without requiring any additional radio channels. We got to thinking about a hook hanging from the bottom of the aircraft, but quickly realized it would be a problem for take-offs and landings; not to mention the difficulty in "dropping" the load at the drop-off site. A lot of thought went into designing our payload hook to make it automatically deploy on take-off (yet, automatically retract, should we immediately need to land) and be able to automatically swing out of the way when dropping off the payload to help minimize any maneuvering required to release it and to make it possible to land again without interference. The design we came up with is relatively simple, light weight, and met our desired design goals (yes, we have tested it successfully). We have used it on a DJI Phantom 3, but it should just as easily work on any aerial vehicle capable of carrying a payload and hovering. Parts Needed: 1- Payload hook bracket 1- Hook; choose the long or short one (we prefer the long one for the DJI Phantom 3) 2- Re-usable anti-drop pins and clips (http://www.thingiverse.com/thing:1255296). 1- Rubber Band 2- Small zip-ties Additionally, if you attach this payload hook to a DJI Phantom 3, you will need to add landing gear extensions to clear the payload hook bracket. We recommend our http://www.thingiverse.com/thing:1274193 design (NOTE: this also requires Tanemahuta's http://www.thingiverse.com/thing:909566), but anything that provides an additional 25mm or more will do. To assemble: Use one of the re-usable anti-drop pins/clips to attach the hook to the bracket at the pivot point (reference attached photos for details). Be sure to note the proper direction of the hook (yes, it does matter which way it goes) - the hook should be pointed towards the end of the bracket that has three (not four) holes on the mounting plate. Next, attach the rubber band to the back of the mounting plate (the end with four holes in it) and the hook. There are many ways one can attach a rubber band to the bracket and the hook. However, we found it works best to minimize the number of band "strings" used; two is the minimum we could get and you get it by inserting a rubber band through the two middle holes on the back end of the mounting plate (this is the end with four holes). Once both ends of the rubber band are threaded through two separate holes (the two middle holes), take one end of the rubber band and pass it through the loop of the other end of the rubber band and pull it tight. This provides a single loop (two band "strings") that you then wrap around the second re-usable anti-drop pin/clip. Tension on the rubber band can be set by moving the re-usable anti-drop pin/clip in different holes along the hook and/or by simply wrapping another turn around the re-usable anti-drop pin. It is important to get the tension provided by the rubber band just right. If it is too tight, the load may not activate the hook (sometimes a quick drop/rise of the aircraft with the payload on the hook may be required to activate it). If it is too loose, the hook may not properly swing out of the way when depositing the payload. For proper operation, the rubber band MUST be under at least a small amount of tension with the hook in the retracted (i.e. payload dropped) position. This is best achieved by positioning the tensioning pin further down the hook rather than higher up. Our photos show a setting we found to work very well with the rubber band we used, in case it helps. Once the rubber band is attached and the tension set, it is time to attach the payload hook assembly to the aircraft. Attachment: The four outer holes on the brackets mounting plate are intended for use in attaching the payload hook to the aircraft. Zip-ties worked well for us - but you are free to use anything that works for you with your aircraft. It is important for the mounting plate to be mounted such that it is parallel with the ground during takeoff and landing. This insures proper operation of the automatic deployment and retracting features of the design. On our DJI Phantom 3, we used the following additional thingiverse designs to attach and use our payload hook:http://www.thingiverse.com/thing:1274193 - Landing gear extensions (used to provide clearance for the payload hook bracket)http://www.thingiverse.com/thing:909566 - Gimbal guard to go (used for the frame and main mount)http://www.thingiverse.com/thing:1259506 - Payload basket (used to haul loot) With this setup, we were able to successfully deliver a bottle of Gatorade to a thirsty test subject with our DJI Phantom 3. If you mount your payload hook on a DJI Phantom 3 the same way we did, you will be able to use the camera to view the payload and verify proper payload detachment remotely - really cool! NOTE: Flying with a payload can SIGNIFICANTLY alter the flight characteristics of your aerial vehicle. We recommend lots of practice in a wide open area (not in a small lab space like we did at first - yeah, bad things can happen). This will help you get used to the different flight dynamics of carrying and dropping a payload. Also, carrying a payload WILL reduce your flight time as it requires more energy to lift and move the extra weight. Be sure to take this into account when flying with a payload. If you use this payload hook system on an aerial vehicle other than the DJI Phantom OR if you use a different attachment system on a DJI Phantom, please post your unique build in the "I made one" section - we would all LOVE to see it! Please refer to the print settings section on our recommendations for print settings. Print Settings Printer Brand: MakerGear Printer: M2 Rafts: No Supports: Yes Notes: Filament used: MakerGear PLA, 70C bed temp, 220C Extruder temp. Hook (long or short one): 0.3mm layer height, 60% infill. Print in orientation shown in model file. Supports are needed in four areas (reference one of the attached photos for more detail); The hook tip, the two rounded pivot ends (needed to keep the plastic from lifting and warping the pivot holes), the inner "latch" ledge near the pivot (reference photo for better detail). Bracket: 0.3mm layer height, 60% infill. Print in orientation shown in model file. Supports are usually needed in one area; the elongated pivot hole on the vertical "shark fin". Refer to the printing recommendations for additional things in their respective thing pages.