This is an open source (almost fully) printable helicopter. It should be compatible with any of trex-450 rotor heads. DFC rotor head included with this model is fully printable, but it needs to be tested yet. If you would like to print and fly it, consider using DFC swashplate to avoid damage caused by blade holder linkage coming off the swashplate. Direct drive fixed pitch tail rotor is used to reduce mechanical complexity of the frame. I printed everything except a motor frame (which had been printed in ABS so it would not melt) in PLA, and it seems rigid enough. THPA20S 90w 2800kv motor fitted with a 5x5 propeller is used for a tail rotor, you can change it to any similar one.

To assemble this, you would need m3 and m4 hardware of various sizes, aluminum square pipe 400x10x10x1mm, aluminum round pipe 8x1mm, 4x8x3mm bearings for the head, 5х11х5 bearings for main rotor shaft, trex450 swashplate, main gear assembly and a 5mm main rotor shaft.

--UPD 14.10.2016

Brought it to a hover today. A printed head really works! Had to tune controls sensitivity down to 60%. Be careful with servo endpoints, limit them ~65% and test without blades to reduce damage should a linkage come off the ball end. Consider using very soft blades. Also, you may want to use longer blades. Uploaded modified head linkages (solid_v2 and solid_v2_long). It is strong enough, but the head becomes a pain to set up. Will work on it further.

--UPD 30.07.2017
Tested it with an hk450v2 stock head from hobbyking today, and it flies great! Added some photos of the heli in action. I think it's totally safe to fly with trex compatible heads. Haven't tried if an FBL one will fit though (it should if you can fit it on an original), hope to test it soon and make necessary adjustments if any.

--UPD 30.09.2017
New parts added: new one-piece tail with rotor guard and stabilizer, new landing gear in 2 variants.

SAFETY NOTICE

THIS IS NOT A TOY!

Please be extremely careful when flying helicopters! This is not a quadcopter, blade strike may cause a serious injury! Do not fly this thing with people around! The printed rotor head or entire transmission frame may blow up in a case of linkage failure! Never fly over people, cars or other objects you can harm! Keep out of reach of children!

The printed head included in the archive may require one's piloting skills to be higher than average to fly without electronic stabilization.

FLY SAFE