So after playing around with the OG Pull Copter, I felt that you should be able to get more speed, without increasing the pulling handle (stroke) or the speed you pull with. So what can you do? Well, add more gears to make a gear train! 

How to build: This model can be stacked as far as you want. You start by constructing the base, which uses a unique base and lid/first plate combination, with two unique axles (first and second) and one of each gear. After that you add more gears (note: alternate the bigger and smaller gear so each layer reduces your gearing ratio), the extending plate 1 & 2 and the extending axle. The extending plate 1 & 2 also needs to be altered for the extending axle to fit through it's hole. 

When you are done, you add the final axle instead of the extending axle and put either extending plate 1 or 2 to close it up. Use two M3 screws and tighten it moderatly. 

I hope you enjoy building this! I recommend starting as the picture with three layers of gearing. This gives you a gear ratio of 10:1 on the output axle! 

How to print: I've only tried this with PLA so far and it's working fine. Print settings I've used on my Sovol SV07 and Orca are: 

• 10% gyroid infill on all the plates/handles
• 25% gyroid infill on gears and axles
• 50-75% gyroid infill on the pulling cord
• 0.20mm layer height 
• 3 wall loops 
• Supports: Tree (auto) on handle, everything else is printed without supports! 

Tips:

• A tiny drop of oil on every axle and on each side of every gear is almost a must! It's a massive difference in friction on an oiled vs not-oiled assembly! 
• All of the stacking plates are numbered on the bottom! 
• The rotation of the output axle reverses with each new layer. This means that you need to pull the pulling cord from the other way around if you stop at an even layer 
• For three layers - like the image above - an M3x30 screw works perfect! 

Some future improvements: 

• The final axle relies staying in place solely by the press fit between itself and the gear. It should be remade so it's locked with the top plate in some way.
• The pulling cord has a rather ugly handle and transition from it's “cord”. It works just fine, but it could be alot better imo. 
• The propellers can get stuck in the screw heads. I've raised the final axle 2mm above the top, but another solution should be done. Making countersunk holes are an option, but then there's almost too little space between the hole and the edge…
• More handle design could be done, both for the pulling cord and the ordinary handle. I would like to make a cool hollow pattern in the larger main handle, but I don't really know how to do that yet
• More gear designs! Right now I've only tried it with the 12 toothed and 26 toothed gears that come with the model, but you could probably get the smaller gear down to 6 teeth and still maintain proper contact. This would increase your ratio much quicker! 

Please feel free to leave a comment and maybe a picture of the finished design if you try this! I've spent almost three days on this and I'd be stoked to hear your thoughts, both the good and bad ones!