In late 2016, the drone world was enthralled by a new, super-small 4K drone by the Chinese company DJI - the Mavic Pro. Since I had already been interested in getting a drone for my youtube channel, I threw my hat into the drone ring and pre-ordered one. I've really been loving learning to fly this drone. While you can fly the drone using only the controller, if you want to see what you are filming you need to attach it to a smartphone. The phone slips inside two grips, which fold out from the bottom of the controller. This arrangement is really quite brilliant and ergonomically. However, the size of the phone/tablet is limited by the reach of the two grips. In this situation, size is important as a larger screen means you can more easily frame a shot and ensure you are getting exactly what you want. Ideally, I wanted to attach my iPad Air to the controller, but needed an adapter to make this happen - thus came about the solution in this Instructable.
Step 1: Design
The idea was to create a simple clamp to hold the iPad. This clamp would be attached to a metal plate inserted into the grips in place of a phone. There are two methods for creating an iPad clamp. The first is to make the clamp spring loaded. You simply pull back on the clamp, place the iPad inside and let it snap back. While this may initially seem ideal, in practice, loading and unloading the iPad can be quite cumbersome. You need to pull the clamp open using both hands, while simultaneously trying drop the iPad into it. The second clamp design utilizes a screw advance mechanism to move the clamp open and closed. This allows for one-handed operation of the clamp, while the second hand is free to place the iPad. I decided to go for this design. One side of the clamp would be fixed, while the second side would slide on two metal rods. A section of threaded rod in the middle would be used to move the clamp open and closed.
Step 2: Cutting the Wood
The main body of the clamp was made from a piece of 3.5" x 3/4" poplar. After cutting a 3.5" long section from the poplar, I set it aside and got to work on the clamps. Each clamp required a 7/16" wide by 1/4" deep groove to be cut in it. Since I don't have a table saw, I made a depth stop for my sliding compound miter saw, which allows me to create cuts partway through a board. After setting the correct depth, I made multiple passes until the grooves were 7/16" wide. With the grooves cut in both clamp blocks, the 1 5/8" tall blocks were cut from the board.
Step 3: Assembling the Wood
The stationary part of the clamp is made by attaching the one clamp to the end of the 3.5" x 3.5" block. After drilling two small holes in this clamp, I used two finishing screws to attach it to the square block.
Two 1/4" holes were drilled in the second (movable) clamp block for the slide rails (rods) to pass through. A third small hole in the middle of this clamp was used to temporarily attach it to the second end of the 3.5" x 3.5" block.
The most critical part of this build is accurately aligning the two rods for the clamp to slide on. These rods are slid into holes in the 3.5" x 3.5" block. If the holes for these rods are not precisely aligned, the rods will not be perfectly parallel and the clamp will not slide smoothly. I initially tried drilling these holes by hand, but was not successful and had to remake the blocks. Having learned my lesson, I decided to use my friend's drill press. After clamping the clamp assembly vertically in the drill press using a piece of steel u-channel, I was able to successfully drill the required holes for the rods.
Step 4: Bushings and Inserts
To allow the movable clamp to slide freely on the rods, I enlarged the holes for the rods and pressed brass bushings into them. The fit was tight enough to allow the bushing to be held in my friction alone.
Next, a hole was drilled most of the way though the center of the 3.5" x 3.5" block. The threaded 1/4-20 insert screwed into this hole will eventually be used to hold the end of the threaded rod used to move the clamp. This hole needs to be deep to ensure that the threaded rod can be freely screwed through the insert as the clamp is closed.
Step 5: The Slide Rails and Threaded Rod
The two slide rails were cut from a 1/4" solid steel rod. Each rail measures 8.5" long. A section of 1/4"-20 threaded rod was also cut to length to serve as the advance screw. The picture above shows the final assembled position of these rods in the clamp.
Step 6: Epoxy the Rails
The two steel rods were epoxied into the stationary clamp block. Before applying the epoxy, I roughened the end of each rod by chucking them into my drill and pressing the edge of a file onto them while rotating slowly.
Step 7: The Metal Plate
The metal plate for attaching the clamp to the controller was made by cutting two sections of 2" x 1/8" aluminum to length. While, there are numerous ways this plate could be attached to the clamp, I went with perhaps the simplest option. Two 3" bolts attached to the two aluminum plates directly screw into threaded inserts in the bottom of the clamp. After drilling the two holes for the inserts in the clamp, the aluminum plates were clamped to the bottom of the clamp and the holes were continued through the plates. The two holes in the wood clamp were enlarged and 1/4"-20 threaded inserts were screwed into them.
After assembling the plates, I realized that two 1/8" thick aluminum plates were a bit too thin to fit snuggly inside the controller grips. By placing two sheets of 1/32" balsa between the two plates, I was able to thicken the assembly so that it fit tightly. I also drilled the two bolt holes closer to the edge of the plates. This was to move the clamp slightly away from the controller to prevent it from overhanging the controller screen.
Step 8: Assemble
The two 3" screws were slipped through the aluminum plate assembly and nuts were loosely fastened onto them. Before tightening these nuts, the two screws were evenly threaded into the inserts in the clamp. With the plate attached to the clamp, the movable clamp was removed from the slide rails and the threaded rod was screwed into the threaded insert in the stationary clamp. I added two nuts a few inches from the free end of the threaded rod. By tightening these nuts against each other, they are "locked" onto the rod. After sliding a washer against these nuts, the movable clamp was slid back onto the rods and another washer and nut were added to the threaded rod on the other side of the movable clamp. By threading a knob down against this second nut, the knob and nut were "locked" to the threaded rod on the outside of the clamp. When the knob is turned, the threaded rod advances through the threaded insert in the 3.5" x 3.5" block, moving the movable clamp along with it.
Step 9: Finishing
Before applying stain and polyurethane to the clamp, I disassembled it and rounded all of the edges using my "new" belt sander that my friend graciously gave me. I finished up the sanding by hand.
Step 10: Using It
Using the finished clamp is quite simple. After the aluminum plate is securely slipped into the controller grips, the iPad is dropped into the clamp and the knob is turned clockwise to tighten the clamp. At this point, the iPad simply needs to be connected to the controller using a lighting cable and I am ready to go fly.
So far this mount has been super helpful when I take my drone out. I also like how the clamp could easily be adapted to work in different configurations. For instance, a minor change would allow the clamp to be mounted on a tripod. You could also use this clamp for many iPad-mounting situations besides a drone.