Introduction: Drone Build, Stranded, Rescued and Crashed.
Though this particular drone came to a tragic end, as you will see in the video, the ideas tested here were a success. This project explores the use of blue foam in an effort to lower the weight and cost of a home built drone frame. Low weight in flying machines translates into less power consumption and longer flight times. It is not my intention to do a step by step for this particular model, or produce plans, but to demonstrate the use of the materials. Dimensions will be included if anyone wants to copy this particular design. I won't go into great detail on setting up flight controllers and radio systems. This instructable was to be about the frame and construction technique. There are many you tube videos detailing setup of the electronics of each particular brand of flight controller and radio control systems.
Step 1: Materials
For this project I used the following:
3 sheets of balsa 1/8 inch thick 3" x 36" from Hobby Lobby
2 sheets of balsa 1/32 inch thick 3" x 36" from Hobby Lobby
Yellow carpenters glue, also from hobby Lobby
Dow insulation foam from Lowe's about 1/8 inch thick.
White foam art board from Hobby Lobby could be substituted for Dow foam
Talcum powder as filler for finishing (optional)
Testor brand spray paint bright yellow #2917 from Hobby Lobby
Wire zip ties from Harbor Frieght
1/8 inch plywood sheet 6"x12" from Hobby Lobby
Flip 32 flight controller from BangGood.com
JR xp6102 radio
4 speed controllers Afro esc 20 amp from HobbyKing.com
4 brushless motors D2822/14 from HobbyKing.com
4 props 7 inch 3.5 pitch, 2 right hand and 2 left hand rotation
1 Nano-tech 12 lipo battery from HobbyKing.com
1 Mobius action cam from HobbyKing.com
X-Acto knife from Hobby Lobby
"T" pins to pin things together, from Walmart
Sandpaper, 320 and 600 grit from Lowe's
A flat surface to work on.
Foam art board to pin parts down. Got mine from Hobby Lobby.
Wax paper from the grocery store.
Assorted clothes pins/clamps.
Fine point Sharpie pen or pencil.
Small carpenter's triangle.
Drill or drill press.
Hot glue gun
Step 2: Why Use Blue Fan Fold Foam to Build a Drone?
Blue insulation foam is a lightweight material obtained from most home improvement box stores. The thickness is about 3/16 inches. I got mine from Lowe's. I bought the stuff a few years ago, it was a large number of sheets. If unavailable, the white art board from Hobby Lobby will work too. It has a layer of white paper on each side of a thin layer of foam. The system I used was to frame the edges of the foam parts with 1/8 balsa sticks. This gives the foam stiffness and an edge that can accept common carpenters glue. Foam does not allow glue like Elmers white glue to evaporate the water, so a foam to foam bond tends to dry slowly, or not at all. A balsa to foam bond works ok, since the balsa is porous and will cure normally. The blue foam used here has a clear plastic vapor barrier layer that needs to be peeled off. At first, it seems like it is a good idea to leave on, but it isn't bonded well and peels away at the edges anyway. I tried some superglue products, the foam reacts and melts. Maybe some of the foam safe super glue will work, just test a piece first. The economy and availability led me to use the Gorilla Glue brand of yellow carpenters glue.
Step 3: Building the Frame From Foam
Here I cut the major parts from foam using the steel ruler as a guide for a straight cut. The X-Acto knife is really sharp so be careful and deliberate with each cut. I used a foam art board as a work surface and covered it with wax paper to prevent the parts from sticking to the work board.
The major parts consist of 2 "Bulls Horns" motor arm assemblies, the "box" 2 sides and a top and bottom pieces, and 4 diagonal motor arm pieces. I measured these parts out and cut them from the foam sheet. I usually peel the clear vapor barrier sheet off after I cut out each part. After I cut 1 Bulls Horns, I laid it down and traced it onto the next foam piece and cut it out too.
Step 4: Add the Balsa Edge to the Foam.
I cut the 1/8" thick balsa sheet into strips about 3/16 inch wide or roughly the same width as the foam is thick. If the balsa is a bit thicker, it can be sanded even after the glue is dry. The Bulls Horns are trimmed around the edges with the 1/8 sheet balsa sticks. I cut each stick to length and glued the pieces together with carpenters glue. After drying, the Bulls Horns are sanded flat.and sheeted with the 1/32" balsa. These support the motors and need to be sturdy. I laid the Bulls Horns down on the 1/32" sheet and mark around the edges. I cut out the traces part and spread a thin coat of glue on the foam. I clamped my parts with clothes pins. Only the Bulls Horns get the sheeting of 1/32" balsa. The side pieces of the Box are straight and are simply trimmed around the edges with the 1/8" balsa sticks. I pinned mine together with edge pin as shown.
Step 5: Sheet the Bulls Horns
A very thin sheet of balsa was applied here, making the Bulls Horns strong and light. I laid the Bulls Horns down on the 1/32" balsa sheet and mark around the edges. I cut out the traced part and spread a thin coat of glue on the foam. I clamped my parts with clothes pins. I sheet both sides. Only the Bulls Horns get the sheeting of 1/32" balsa.
The side pieces of the Box are straight and are simply trimmed around the edges with the 1/8" balsa sticks. I pinned mine together with edge pin as shown.
Step 6: Build the Box
I stood the sides up and pinned them down to the work surface spaced 2 1/2" apart. Add carpenters glue and pin them in. I kept checking alignment with a triangle and eyeballing it. The glue dries slow, so it's easy to make adjustments. Notice in these example pictures, all the glue joints are foam to balsa and not foam to foam. Only small areas are foam to foam contact. The cross pieces on the top ends are then added.
Step 7: Add the Electronics Deck
Here I added a sub level to the box where the flight controller board and radio receiver sit. I used a small wire spool as a support to mark the position of the deck before applying glue. I then applied the glued and pinned it in place.
Step 8: Glue the Bulls Horns to the Box
In this step I glued a square foam piece into the end of the box, closing the ends off. After that was dry, I glued one end to one of the Bulls Horns. Once this was secured with pins, I turned it upside down and glued the other Bulls Horns to the other end and secured this end with pins too. I set the assembly upside down and checked that the ends of the horns were flat on the building surface. This is important to the motor alignment. I did have to unpin one end and adjust until the Bulls Horns set flat. I was experimenting with paint so some parts are already painted and seem out of sequence.
Step 9: Add the Motor Plates
I cut 4 plates from 1/8" plywood. The motor is set and a plate measured with about 1/4 inch clearance around the edge of the mounting holes. The holes are marked and drilled out. I did this before I glued them to the frame. I used a flat board and put the plates down and then the frame upside down on tip. Gluing upside down like this keeps the plates flat and true. The motor plates need to be as straight as we can get them. After this was dry, I added a small scrap piece in the seam making a tough glue joint between the Bulls Horns and motor plates. I cleaned up any roughness with sandpaper.
Step 10: Mounting the Motors
I set the motors on the mounting plates with the wires facing back along the Bulls Horns. The motors were held on with wire zip ties. They are plenty strong and are much easier to cut off if need be.
Step 11: Diagnal Braces
These parts were an afterthought. At this point, I felt the arms were strong enough, but not stiff enough to dampen vibration. They are just foam capped on the top and bottom sanded to a bevel and glued on. They are held in place with pins until dry.
Step 12: Let's Weigh the Frame
Using my antique spring scale, the naked frame without gear came out less than 4 ounces. I have had some of the cheap plastic frames of the same size weigh in at 15 ounces or more. I know some of the carbon fiber frames are super sturdy and are really light, but I feel there is still a place for this construction technique. Pictures above have the major dimensions.
Step 13: Installing Electronics
My flight controller and radio receiver were mounted to the sub floor using double sided foam tape. Most flight controllers are mounted as close to the center of the frame as possible. The also have to face the right direction. In mine, the radio receiver is to the front. The blue foam model in the above pictures shows all the basic components. I just used zip ties to mount the speed controllers.
The battery is held on the bottom with rubber bands. I used bamboo skewers pushed through the box as shown in the photo. Rubber bands are great as they flex in the event of a crash.
I made a wire harness to power each speed controller from the 1 battery plug. It was routed under the flight controller.
Step 14: Landing Gear
I also made some simple landing gear from scrap paverbase foam. EPP foam or even styrofoam could be substituted. It just had to hold the craft up high enough to let the battery clear the ground. It provides a nice shock absorbing effect on those tough landings. It was cut to shape with the X-acto knife. The bottom of the box fits snugly into the top of the "H" shaped landing gear piece and is held on with hot glue.
Step 15: Camera Mount
I am showing the camera mount but won't go into great detail. It is made of braided wire and lets the battery and camera hang below the drone in an effort to isolate vibration. Maybe i can do this in another instructable. I used a Mobius Action Cam. I paid about $75 for mine. This is a great little cam. This drone went on several missions but Instructable Fail can happen to anyone.
Step 16: Fail!
So, having a drone and a camera means you have to get some pictures. I flew my new drone up to get a shot of the steam rising near a local power plant. I misjudged the power lines and bonk. Stranded! I know I acted poorly and ended up embarrassed and stranded on a power line, a bad situation at best.
John, a fellow drone enthusiast, came to the rescue with his Iris drone. He attached a pool noodle to his drone (non conductive) to attempt to dislodge my drone from the line. He ended up nearly crunching his expensive drone as his drone fell with mine, but got it slowed down enough before impact with no serious damage. My drone did not fare so well. I recovered most of the gear, but the frame was totaled.
The morale of this story is I got dumb and took a chance by flying close to power lines. I was lucky it only cost a drone frame and nothing more. Oh, John got a model plane kit as thanks for saving my camera and gear!