Heavy Duty Pull Cord Helicopter
by kasperfish in Living > Toys & Games
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Heavy Duty Pull Cord Helicopter
| Toys are fun especially if they can fly! A few days ago I was looking at the "Things That Fly Contest" here on instructables. After reading some fun instructables memories came back from when I was a child and when I had those pull string helicopters and how much fun they were. Sadly I also remembered how many I broke in my kids days. I figured that it was time to make a heavy duty pullcopter that can withstand my proportional increased force compared to when I was a child. I immediately Googled for "3D printed pull cord helicopters", that's what you do if you need something and have a 3D printer, but I only could find 100% plastic ones. That was obviously not what I wanted. So I opened my CAD software and started to make some sketches. I was so eager to pull my unmade pullcopter that I was printing and designing parts at the same time. Some hours later and after I disassembled my filament spool holder for bearings, I had my first prototype. Sadly I was not able to launch it properly because I did not have a good rope to wind it up. All of my cords were not strong enough and broke under the tension. The next day I went to the hardware store and bought some nylon cord. You can see the first launch with my new cord here at the right side. I did not expect to see that thing (45 grams) flying so high, so fast and so far, I even didn't pull with full strength. Read the next steps to make one yourself! |  ↓↓↓ See the video for more launches! ↓↓↓ ↓↓↓ Also watch a mega pull! ↓↓↓ |
List of Tools and Materials
Materials
Here is a picture with all the materials I used. You will need the heat-shrink tube (or electrical tape) if you don't have a grinding wheel to grind of the threads of the bolt. I used 1.5 mm nylon cord and made a pull handle from a 6.5cm piece of threaded rod (not pictured). The length of the PVC pipe is not critical, I used a 12cm long scrap piece.
Why the PVC pipe?
You can ask yourself why I used a piece of PVC pipe as a handle and not printed one. I have a 3D printer, right? First of all I like to combine printed parts with readily available hardware stuff like threaded rods, PVC pipes, empty bottles, timber, etc. These materials let you make modular (and bigger) things without the need to print that much and loose project time while waiting impatient for your print to finish. In this particular project I used PVC pipe to save time during the build but also to save time in the future when I want to do some modifications.
Tools
I used a few power tools but they can be replaced with hand tools. Use your creativity if you are missing one of the tools. You probably will be fine with a dremel and some extra patience.
| Tool | used for |
|---|---|
| drill press | making two pilot holes in the pvc pipe |
| dremel | cutting out a slot in the pvc pipe |
| grinding wheel + cordless drill | smoothing the threads of the M8 bolt |
| flat and round file | removing the brim after cutting the PVC pipe |
| crafts knife | cutting rope and cleaning the printed parts |
| lighter | heating up the nuts and heat-shrink tube |
| spanner | tightening the M8 nyloc nut |
Download and Print
Don't be discouraged if you don't have a 3D printer. You can print the parts with a 3D printing service. I highly recommend 3Dhubs. Check their website, you'll be amazed how many 3D printers are in your neigbourhood ready to print for 1/10th of the cost compared to a centralized 3D printing service. You should be able to get the parts for around 20-30 euro. BTW I'm a hub too!
Here are the STL files that you need to print. I printed them with 30% infill and 3 perimeters with PLA filament. All files are metric (in millimetres) and ready to print. This means that the models are manifold and orientated correct. None of the parts need support material.
You need
- minimum 1 propeller
- two bearing holders
- one transmission pin
Assembly
Now you have your printed parts it's time to assemble your own heavy duty pullcopter. Follow the pictures and read the blue boxes. If something is not clear you can leave me a comment!
First open the hole from the bearing holders. The hole is closed with a single "bridged" layer to prevent the need for support material. You also should clean the edge with a craft knife so the bearing can be fitted more easy.
Drill two holes in the PVC pipe. I marked two points 3 cm from each end and drilled with a 10mm drill. Next you need to cut out a slot by connecting the two holes. I used a dremel with cutting disc for this.
First screw the nut on the bolt. Also add two pieces of marking tape (top: 5cm, bottom: 4cm) and grind of the threads between them. I used a cordless drill and a grinding wheel. If you're not able to get a smooth rod I suggest adding a piece of heat-shrink tube to protect your precious nylon cord. However grinding of the threads is preferred because it also decreases the diameter a bit (smaller diameter = better leverage). Next push the head of the bolt into the transmission pin. You probably have to heat it up with a lighter to fit it more easily. It should be a tight fit.
Add a M8 washer to the bolt and slide on a bearing holder. Next tie the nylon cord to the bolt as seen in the picture. Push the bearing holders in the PVC handle and add a washer and a nyloc nut. Do not tighten the nut too much, the bolt must be able to spin freely.
I made a handle from a piece of M8 threaded rod from which I grinded of the threads. I also made a groove in the middle to hold the nylon cord.
Wind Up and Pull!
This pullcopter is designed for high speed. To unlock it's full potential you need to wind the spool properly. Unlike other pull cord helicopters you don't want overlapping windings. If all the windings are close to the (centre) shaft you have optimal leverage to get a high torque. My personal record is around 40 meters high and 7 neighbours further (LOL). It's really fun to have two or more pullcopters in different colours to challenge your friends!
Final note: This pullcopter is the best I ever had! It's extremely fast and very powerful. However it can also be very dangerous, the propeller can have such a high angular momentum that it can easily break your fingers (if not cut them of, I'm not kidding). Do not use this pullcopter inside and don't aim at people or animals. Also don't let kids play with it unattended. Just be careful, ok?