3D Printed Micro Quadcopter
On Friday afternoon we managed to get a 3D printed micro quadcopter frame built so that I could do some testing over the weekend. I'm quite impressed with how the 3D printing turned out, as you can see from the two pictures below. Don't try cleaning your 3D printed PLA with hot water like we did, though, as it does tend to make the plastic go soft and warp. Our first frame isn't exactly straight any more.
The reason for doing this is that we're running a workshop in about a month's time where we're going to get a class of year nine's to build quadcopters. After looking into the feasibility of building one from scratch which could run CleanFlight, we decided that the simplest option was just to modify the HubSan X4 with our own 3D printed frame. The main reasoning behind this is the distinct lack of availability of parts in the UK. Everything I wanted to buy had to be imported from the US, otherwise I would have used a Quanum Pico 32 board from HobbyKing.
After cleaning up the 3D printing with a file and drill bits, I added four brand new replacement HubSan X4 motors (approx £15). These are just a push fit into the holes, but I had to add sellotape around the motor cans to get a tight fit due to the inaccuracy of the 3D printed hole diameters. The motors come as either a black/white wire, or red/blue wire pair. Looking at the original HubSan, I made sure to copy the orientation, with red/blue top right and bottom left. The red and white wires are the +ve connection, while blue and black are the -ve. Strangely for a quadcopter, the front right motor rotates clockwise. The motor wires were soldered directly onto 0.1 inch pitch PCB header pins, with heat shrink tubing to add some mechanical strength. This is only a test of concept, so the final design evolution will have to use better connectors.
Then I set about de-soldering the PCB from my partially broken HubSan X4. This is relatively easy if you are careful with the soldering iron.
The PCB is tiny once it is removed - it's only about 30mm long and 20mm wide.
The next job was to solder the 8 connectors for the motors, which only took about 5 minutes as I was able to re-use some wires which already had servo plug connectors attached. I've used Futaba style servo plugs quite a lot as the Dupont connectors fit over regular PCB pins very securely. All you have to do is to crimp or solder the wire to the connector and then heat shrink over it to insulate. The only problem is that they tend to be a bit long, so I'll replace this on the final design.
All that's left now is to add it to the frame, a job which requires a number of strategically placed elastic bands. That's what the holes were for.
The all up weight with everything ready to fly is 42g. The original HubSan X4 is only about 33g, so we've added 9g which is 27% in weight. The white 3D printed frame on its own weights 12g. I'm hoping this doesn't make too much of a difference as there is nothing we can do about the PID values.
OK, it's all connected up and ready to go, but this is where I ran into a little problem. My HubSan X4 hadn't been working for a long time, which was why I was willing to sacrifice it for this test. Sometimes it would work perfectly, sometimes it was just dead. Occasionally you could spin up the props and it stopped working, and sometimes you would be flying around happily when suddenly it would just go dead. I could not get this blasted thing to work until out of the blue on Saturday evening when it decided to work perfectly. Unfortunately, I had taken the PCB off of the frame, so all I could do was sort out the prop rotation directions and see the frame flip itself over. It definitely has the power to lift itself off the ground. In fact, I had forgotten how much these little props "bite" your fingers. You think it's got the power to cut you when actually it hasn't, so you're careful of it because it hurts but it's actually completely safe. Perfect for some 13 year old students.
Now I just have prove it can actually fly.
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| A 3D printed frame designed by en-topia and printed by CASA's Director (digitalurban). On its own, this weighs 12g. |
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| The HubSan X4 props are 55mm diameter and the ruler gives a sense of scale. The diagonals are 100mm. |
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| The four replacement HubSan X4 motors are a push fit in the holes, using sellotape around the motor cans where necessary to ensure a tight fit. The connectors are 0.1 in pitch PCB pins soldered directly to the motor wires with heat shrink tubing added. |
After cleaning up the 3D printing with a file and drill bits, I added four brand new replacement HubSan X4 motors (approx £15). These are just a push fit into the holes, but I had to add sellotape around the motor cans to get a tight fit due to the inaccuracy of the 3D printed hole diameters. The motors come as either a black/white wire, or red/blue wire pair. Looking at the original HubSan, I made sure to copy the orientation, with red/blue top right and bottom left. The red and white wires are the +ve connection, while blue and black are the -ve. Strangely for a quadcopter, the front right motor rotates clockwise. The motor wires were soldered directly onto 0.1 inch pitch PCB header pins, with heat shrink tubing to add some mechanical strength. This is only a test of concept, so the final design evolution will have to use better connectors.
Then I set about de-soldering the PCB from my partially broken HubSan X4. This is relatively easy if you are careful with the soldering iron.
The PCB is tiny once it is removed - it's only about 30mm long and 20mm wide.
The next job was to solder the 8 connectors for the motors, which only took about 5 minutes as I was able to re-use some wires which already had servo plug connectors attached. I've used Futaba style servo plugs quite a lot as the Dupont connectors fit over regular PCB pins very securely. All you have to do is to crimp or solder the wire to the connector and then heat shrink over it to insulate. The only problem is that they tend to be a bit long, so I'll replace this on the final design.
All that's left now is to add it to the frame, a job which requires a number of strategically placed elastic bands. That's what the holes were for.
The all up weight with everything ready to fly is 42g. The original HubSan X4 is only about 33g, so we've added 9g which is 27% in weight. The white 3D printed frame on its own weights 12g. I'm hoping this doesn't make too much of a difference as there is nothing we can do about the PID values.
OK, it's all connected up and ready to go, but this is where I ran into a little problem. My HubSan X4 hadn't been working for a long time, which was why I was willing to sacrifice it for this test. Sometimes it would work perfectly, sometimes it was just dead. Occasionally you could spin up the props and it stopped working, and sometimes you would be flying around happily when suddenly it would just go dead. I could not get this blasted thing to work until out of the blue on Saturday evening when it decided to work perfectly. Unfortunately, I had taken the PCB off of the frame, so all I could do was sort out the prop rotation directions and see the frame flip itself over. It definitely has the power to lift itself off the ground. In fact, I had forgotten how much these little props "bite" your fingers. You think it's got the power to cut you when actually it hasn't, so you're careful of it because it hurts but it's actually completely safe. Perfect for some 13 year old students.
Now I just have prove it can actually fly.
Thanks
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