ChrisOlson
Member
I've been wanting to experiment with a Direct Drive Fixed Pitch tail for some time on a bigger helicopter to get rid of the fragile and wear prone tail drive, servo, linkages, etc. I got it working on my Trex 500 using a Tiger 3510-630 spinning a 9 x 4 APC prop. Have tested it in 20-25 mph wind gusts with no blowouts.
I eventually want to put this system on my Trex 600. The tail response was a bit quick at first and been tuning it to get it smooth enough for UAV type flight, flying autopilot controlled mapping/survey flights with a 600 helicopter carrying a MAPIR Survey2 camera. The flight controller used on this 500DFC is a Pixhawk running AC3.4.6. There's a couple bugs in the code for tail rotor active state vs FC armed state that I'll look into as time permits. But I now have it working quite smoothly on the 500.
This would also be quite handy for scale builds where the tail rotor is located in the top of a vertical stab, or similar. Without using the quite messy angled tail drive kits for scale builds. The weight difference between the DDFP and standard tail is only 4 grams. I got rid of the tail unit, belt, drive gear, autorotation gear, servo, linkages, tail pitch mechanism, etc.. The setup I'm using on this 500 is way overkill and will give yaw rotation rate of ~700 degrees per second in the anti-torque direction, and about 400 degrees/sec in the torque direction. The maximum available thrust of the tail drive should match the torque direction to yield about the same 400 degrees/sec yaw rotation in the anti-torque direction. But I used some stuff I had laying around the shop to build it just to test it, and get it working.
This type of tail is quite common on little helicopters like the Blade MCPx. Not done too often on 500's and up.
Here's a vid that shows how well I got it working on the 500
I eventually want to put this system on my Trex 600. The tail response was a bit quick at first and been tuning it to get it smooth enough for UAV type flight, flying autopilot controlled mapping/survey flights with a 600 helicopter carrying a MAPIR Survey2 camera. The flight controller used on this 500DFC is a Pixhawk running AC3.4.6. There's a couple bugs in the code for tail rotor active state vs FC armed state that I'll look into as time permits. But I now have it working quite smoothly on the 500.
This would also be quite handy for scale builds where the tail rotor is located in the top of a vertical stab, or similar. Without using the quite messy angled tail drive kits for scale builds. The weight difference between the DDFP and standard tail is only 4 grams. I got rid of the tail unit, belt, drive gear, autorotation gear, servo, linkages, tail pitch mechanism, etc.. The setup I'm using on this 500 is way overkill and will give yaw rotation rate of ~700 degrees per second in the anti-torque direction, and about 400 degrees/sec in the torque direction. The maximum available thrust of the tail drive should match the torque direction to yield about the same 400 degrees/sec yaw rotation in the anti-torque direction. But I used some stuff I had laying around the shop to build it just to test it, and get it working.
This type of tail is quite common on little helicopters like the Blade MCPx. Not done too often on 500's and up.
Here's a vid that shows how well I got it working on the 500
