ULSRS Low Rotor Speed RC Heli Teetering Head and crash
This is a video showing some attempted hover tests of a fully teetering flybarless rotor system. The flybarless stability system was shut off so there wouldn’t be any problems from the stabilizer getting in the way of the basic flight feel of the rotor system.
Didn’t work well at all! Every time I attempted to lift the heli into the air, it would suddenly lean in a random direction.
Thinking that the problem was being caused by the skids not being able to freely slide on the grass, I placed a smooth sheet of plywood on the ground with which the skids wouldn’t have much friction. Didn’t help one bit and the inevitable happened – a crash.
During the slow-motion portion of the clip, watch the main frames and try to count the number of times they performed complete rotations.It’s pretty horrifying.
The closeup shots of the tail boom show something important that went missing; the tail servo. The force of the spinning/flipping heli threw the poor servo over 100ft away from the point of ground contact. Note the remains of the servo arm still connected to the forward end of the tail pushrod!
This is the same heli and head seen in the long video shot recently at the Hodges Hobbies All Electric Fly-In 2010. Extra stiffening was added back to the head to remove the freedom to teeter as seen in this video.
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10 Responses to “ULSRS Low Rotor Speed RC Heli Teetering Head and crash”
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why rc helicopters do not work with semi rigid teeterig rotor head and are they too unstable?
Doesn't work…gee ya think.
Raise the teeter location (fulcrum) or add some dehedral, dehydral, an upward angle, also a delta hinge might work. 2 bladed choppers in particular are very needy of high rpms to counteract any weight that moves outside of the blades length wise. Bell does it with very slight dehydral, and a very high twist to the blades. There is super low drag because only inner half of each blade has over 1° of pitch and a wide chord for very focused lift towards center of mast, not in center, or in your case evenly through blades. As soon as there is an unbalance a fight occurs, and the mast is forced to follow the forces, while spinning. Good carnage though. Interesting direction towards low rpm physics, with less centrifical force throwing the blades horizontal, to keep them from flapping like a sail to it's own lift force. Helicopters are a massive gyroscope, that has just enough extra power to provide lift and thrust to locked solid gyroscopic, centrifugal and precise rate control of these forces through throttle control and an efficient power supply. Airplanes fly, a Helicopter beats all physics into submission, and are quite a bit more expensive.
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no the problem was a teetering head with as much teeter as you had as a scale machine was to much and the heli got tail drag in other words , could not lift its own weight and remain linner ,head speed would had helped and half an inch teeter at max , teeter is only there to ease the machanics when the heli gets put through tight manuvers and in long flights to ease side draft and eddies etc but well done for the effort and keep going , i like experental stuff trys thanks
i remove the fly bar off my Pantera 50 helicopter,although its posible to be fly.its very sensitive and i though of tettering head and wood flexible blades (I also believe you have too much free tettering)
What really frustrated me while trying to fly this head was the fact that Bell 206 Jet Rangers use basically the same design. I thought, "If the real one can fly so smooth, the model should too." Wrong! Three years later I'm talking to a friend that had stick time in a Jet Ranger and he said it was a horrible handing machine requiring constant cyclic inputs to keep it from shooting away. I wish someone had told me that bit of info sooner…
@MarioIArguello
RE: Too much teeter – No, just enough to allow the blades to flap without bumping into the flap stop, that's all. I've yet to edit and post lots of other testing video of this rotorhead where I tried all sorts of neg and pos delta 3. The teetering was slightly restricted and flight was wobbly but possible. The best handling was with…………………………………..wait for it…………………………………ZERO DELTA! Yes, I'm shocked too.
Hi Max, I could tell you had too much teeter , at the start of the video when you teetered the blade up and down.
But I am glad you got it working and really enjoyed your other fliying video!
I learned the hard way, also, while designing a flybarless MIA House FLY back almost ten years ago, but luckly my fail attempts, before I finally got it right, were at almost no cost . Most important thing is not to have too much deflection of the control links, and I employed delta 3. I made the control arm on the rotor head really short, so I didn't have to use dual rates, or special TX settings, and just the right amount of damping.