Forum Thread

Helicopters, Tricopters and Quadcopters

redpoint5 3,910 692 January 22, 2016 at 01:18 AM
For some reason I have recently been obsessed with the idea of aerial video and photography, and it got me thinking about what would be the ideal setup for me. Helicopters seem the logical choice since they are way more power efficient, having fewer motors and a larger lifting disc. For some reason, they don't seem to be very popular, and I don't see the same gyro stabilization utilized on quads. It's beyond me why they wouldn't have similar gyros and automatic systems. If they did, I would assume they would be the best platform since adjusting a swash plate is much faster than adjusting rotor speed, and the flight time would be much higher.

It seems the next best thing would be a tricopter, since it has 1 fewer blade for efficiency, and can turn with more agility. I'm tempted to build one myself, but then I see great deals on the DJI Phantom on SD. I like the built in features of the Phantom such as follow me, return to home, position hold, etc, but I don't like that it isn't very modular. I'd like to swap cameras as tech improves along with batteries and such. I also don't like the Apple-like restrictions they place on customers, such as altitude ceilings and such. Let me decide what is acceptable use of the product.

Can a Tricopter be built with some of the same features as the Phantom? I'm handy with electronics, but don't really know what is possible to build. I'd want return to home and position hold at minimum.

I finally got the guts to start flying a Blade CP Pro that a roommate gave to me. Today I hovered for the first time, but lost a tail skid in the process. Lots of fun, I just wish there was more automation available for the platform.

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Joined Aug 2005
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#2
I think quads are popular for their stability, and lifting power. From what I have read 4 motors running between 50-75% would be better than 3 motors running between 75-100%. I know there is a big DIY scene with quadcopters specifically for filming video/photography and racing if you want to go that route.

I know in my experience I am fine learning on the cheaper equipment first till I get my flying skills up there so I won't crash anything I get that is higher end.
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#3
Isn't the blade CP a micro? Their is a world of difference between the micros and the full size R/C copters. I can land a micro on top of a ceiling fan blade but just getting a full sized to hover without wrecking is a task.
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#4
There is a micro CP, but I've got an older CP Pro, which I believe is a 300 size. I don't know what the 300 represents though. Blade length in millimeters?

I did OK hovering yesterday, but the tail skid is just barely longer than the tail rotor. This causes the rotor to chop grass and gravel when landing. Finally the skid broke off. I'll have to fabricate a longer one.

Still, I don't see why choppers lack the gyros and auto-hold features of a quad. Quads are more complex in that 4 motors have to be coordinated, whereas a chopper just has collective, cyclic, and yaw.
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#5
Quote from redpoint5 View Post :
There is a micro CP, but I've got an older CP Pro, which I believe is a 300 size. I don't know what the 300 represents though. Blade length in millimeters?

I did OK hovering yesterday, but the tail skid is just barely longer than the tail rotor. This causes the rotor to chop grass and gravel when landing. Finally the skid broke off. I'll have to fabricate a longer one.

Still, I don't see why choppers lack the gyros and auto-hold features of a quad. Quads are more complex in that 4 motors have to be coordinated, whereas a chopper just has collective, cyclic, and yaw.
I think it's a case where the complexity of controlling a quad happens to be the sort of thing that computers do really well while simultaneously getting rid of elements that computers don't deal well with. In particular the fact that you can get a full range of motion on a quad copter with fixed motors.

I don't know much about tricopters, but as I understand it they need to rotate one of the engines to get a full range of motion. That's not the sort of thing you can automate with anywhere near the speed or precision of adjusting thrust to an electric motor.

The algorithms are pretty mature at this point. Academics were doing pretty crazy stuff with quads 10 years ago, and those algorithms have long since made it from papers to commodity hardware/firmware.
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#6
Quote from redpoint5 View Post :
300 size. I don't know what the 300 represents though. Blade length in millimeters?
close, but not quite - it's the largest distance between the center of any two propellers (in mm)
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#7
Quote from slapshot136 View Post :
close, but not quite - it's the largest distance between the center of any two propellers (in mm)
In the case of RC helicopters, that would refer to the distance between the center of the main rotor and the center of the center of the tail fan?
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#8
Quote from redpoint5 View Post :
In the case of RC helicopters, that would refer to the distance between the center of the main rotor and the center of the center of the tail fan?
more or less, usually the size is rounded to a nice even number - but do note that it's not very standardized, especially non-electric ones tend to give the motor size rather than the physical size
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Last edited by slapshot136 January 24, 2016 at 07:00 AM

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#9
Check out the forums on flite test and rcgroups. Lots of amazing stuff people do there..
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