I would like to introduce the DIYD community to my project, the T1000. This is a tandem rotor helicopter based on T-Rex 450 parts, with custom 425mm asymmetrical blades. The initial goal for the project (in 2011) was to have a fpv platform that could fly for over 1/2 hour. I now think we can now achieve a 1+hr flight time with a 1kg payload. This is similar to the twin-rex, and indeed utilizes their TH2 for the moment for servo mixing. Our project differs in many ways from the twin-rex though. First of all, we are using a large diameter thin walled carbon timing shaft through a square carbon torque tube. We also use custom designed 2mm carbon nacell plates, along with our in-house manufactured asymmetrical 425mm blades. The third requirement for us getting 1+hr flight times with this platform is the 18650b battery. Though this drawing only indicates a 45 cell pack, I plan on using a 69 cell, or 3s23p custom Li pack. The orientation of the battery pack, and the landing gear have yet to be determined.
Please post any questions or comments (I will not be offended by negative comments, please be honest)
Comments
There are a few other advantages to the tandem rotor system vs a single rotor. First is there is a lot of area for mounting payloads. Another benefit is with a center mounted payload, the motors and gears are located over 1 foot away from the payload/APM sensors. That, along with the proper mounding of batteries and APM should help when it comes to vibration isolation and dampening.
Interesting info, thx.
Hugues: that is a very complicated question to answer.
A traditional helicopter has the lowest frame weight per total disk area.
A tandem heli will have the smallest frame size, per total disk area. This benefits to "How much payload can I lift with an aircraft that fits in the back of a pickup" type of design problems. You could probably lift 200lbs payload with a machine that would fit in the back of an 8' pickup bed. It also solves a few problems with single-rotor system. But it does bring with it some new design challenges.
It should be noted that in the full-size world, the largest transport helicopters are single rotor, not dual (or multi). The very largest helicopter ever, was a non-intermeshing transverse-tandem. But it never went into production.
@Huges, a brushless motor system will at the very best have up to 90% efficiency. And there is lots of loss in the propeller also, especially during static hover. So adding more motors and propellers only adds up and increases the efficiency loss. Ideally you want a single motor and as big a propeller as possible.. In other words, a helicopter..
@Hugues: The two rotor will cost about half as much as a 4 rotor version as far as prototyping, while still serving as a proof of concept. We do have a 4 rotor version of this on the drawing board as well. Aerodynamically the two rotor should be a little more efficient while traveling than a 4 rotor. The 4 rotor would have about twice the lifting capacity, and will should be more stable when hovering. One interesting thing, is while the 2 rotor should be more efficient while traveling, the 4 rotor actually should have a higher theoretical top speed.
@ Hugues: Not sure there is an advantage (aerodynamically) when increasing the number of rotors.... Rob explains it well here: https://www.youtube.com/watch?v=HywcbNHroQg
What are the advantages of two rotors versus 3,4,6,8...?
Gary, I believe the Chinook is built that way because it is optimized for forward flight. With the airframe level, the rotors are tipped forward about 7 degrees or so. So that the body is streamlined while at speed. But, the rear rotor needed to be higher, so that the blades don't clip the fuselage on their forward arc. The front rotor does not need to be raised. There may be other reasons as well.
But the rotors do intermesh, and are geared together to no collide with eachother. I don't think the vertical stagger plays into that however.
Sean, cool project. Keep me posted.
Our secondary goal was redundancy. When the payload is often worth more than the craft these things seem prudent.
-
1
-
2
-
3
of 3 Next