Helicopter Rotor Direct Drive

[dillwhacker]

I will if you want me to

Yes! Please do, I'd be very keen to see a project like this.

[trillian]

Aha, I see now what you mean.

The thing about efficiency is that you lose energy counteracting torque, whether it's with a single tailrotor or several smaller units of some kind, which is why tandem and co-ax etc. type twin rotors are used for full scale heavy lifting helicopters.

Kasama has a military drone that has a single rotor and two 'tail rotors' but I'm pretty sure the controls are conventional heli swash type and I'm guessing the twin tailrotor design is part of a design brief to keep it real durable and easy to pack up etc. who knows.

I have had in the back of my mind the thought of adding a ducted fan to a regular rc heli as an additional thrust or lift source but when I started looking at how much a fan unit with enough thrust weighs, it kinda killed my buzz.

[Quadrotor]

Aha, I see now what you mean.

The thing about efficiency is that you lose energy counteracting torque, whether it's with a single tailrotor or several smaller units of some kind, which is why tandem and co-ax etc. type twin rotors are used for full scale heavy lifting helicopters.

Kasama has a military drone that has a single rotor and two 'tail rotors' but I'm pretty sure the controls are conventional heli swash type and I'm guessing the twin tailrotor design is part of a design brief to keep it real durable and easy to pack up etc. who knows.

I have had in the back of my mind the thought of adding a ducted fan to a regular rc heli as an additional thrust or lift source but when I started looking at how much a fan unit with enough thrust weighs, it kinda killed my buzz.

The smaller props that i plan to use will add to the lifting ability but probably not a super amount, the will provide counter torque and also allow me to move around. Im hoping that i can make it quite agile but at the same time nice and controlled.
For instance when set to hover it ill be very still and maintain the same altitude. When i want to move away from a hover it will do so quickly.

I have looked at those ducted fans in 2 minds as to whether or not i could make use of one

[RcRotaryMadness]

I will if you want me to

Yes please =) Interested in seeing this..

As for ducted fans, I believe their only really efficient at higher air speeds. They have short but high pitched blades on them, making them useless of "low speed pull" but great for "high speed - speed"

Also anything with a rotor and rear facing prop is heading into the autogyro territory

[Boggy]

sounds interesting

[Disc]

sounds like it could be a Tri copter variant

So two front props and then the tail rotor could be a 450 type with ability to steer the aircraft

or you reverse it and have the 450 head/swash at the front of the Tri...

[dillwhacker]

I was imagining a tri-copter , but with a 450 rotor in the middle. 3 small props in a triangle all rotating the opposite way to the 450 rotor.
Makes me realise I'm not too sure how a normal tri-copter works...
With 2 spinning CW and 1 spinning CCW, then to drop the nose and raise the tail and move forward requires an input from the steerable 'tail' servo, cos you can't drop the nose & raise the tail without un-balancing the torque from the 3 motors...
Love this stuff!

[Quadrotor]

My main rotor and CF blades arrived today

I have assembled the rotor and figured out most of what i need to do. mostly modifying the swash plate. I only have use for collective pitch, so im planning on removing the swash plate that is provided and making my own fixed version.

I do however have a question looking at how the standard swash plate is made. There are 3 ball joints one has an anti rotation pin on it. In normal operation when you want to use your collective do the 3 servos all push up on the swash plate??

[dillwhacker]

My main rotor and CF blades arrived today

I have assembled the rotor and figured out most of what i need to do. mostly modifying the swash plate. I only have use for collective pitch, so im planning on removing the swash plate that is provided and making my own fixed version.

I do however have a question looking at how the standard swash plate is made. There are 3 ball joints one has an anti rotation pin on it. In normal operation when you want to use your collective do the 3 servos all push up on the swash plate??

Yes, all 3 up for coll pitch. The mix for elev, ail and collective pitch is done in the TX or the FBL controller.

[Quadrotor]

Thought it would be done that way, In that case i will most likely make a fixed plate that will allow for collective pitch using only 1 servo. Just have to figure out how first

[dillwhacker]

Thought it would be done that way, In that case i will most likely make a fixed plate that will allow for collective pitch using only 1 servo. Just have to figure out how first

Maybe take a normal swash and glue the ball in place horizontally so it can rotate and slide on the shaft but not tilt?

[Quadrotor]

Maybe take a normal swash and glue the ball in place horizontally so it can rotate and slide on the shaft but not tilt?

Thats not a bad idea.

I have just been looking at the blades and how they fit onto the rotor, there is a decent size gap when the blades are in the rotor. Is there a special type of shim to pack them out with that i need?

Im going to the model shop tomorrow to get some bearings and other bits and pieces so will pick these shims up too.

[dillwhacker]

Not sure I follow about the gap...
Thinking about it, I would probably stick with 3 servos to push the swash up and down - or at least a linkage that pushes on all 3 arms. A single servo on one arm will tend to try to tilt the swash and might make it sticky to slide up and down the shaft.

[Quadrotor]

I was thinking i might use the 3 servos. Firstly to stop it sticking as you suggested, also so that i have the ability in the future to use cyclic pitch if i wanted to add it in for any reason.

[dillwhacker]

I was thinking i might use the 3 servos. Firstly to stop it sticking as you suggested, also so that i have the ability in the future to use cyclic pitch if i wanted to add it in for any reason.

Yep, I would. Will give your PID routines something to REALLY think about if you control elev and ail and rudder and collective with a mix of the three propellors and cyclics.

Good luck with it and please post some pics & a build thread.
TTP