Drone Efficiency

[redpoint5]

As freebeard points out, a tandem rotor heli would be most efficient. Conventional helis waste about 15% of their power just counteracting the twisting motion the rotor imparts on the fuselage. Tandem rotors counter-rotate to offset the twisting.

Helicopters are inherently stable and require no electronics to fly. Having the blades above, lifting the chassis keeps everything upright. Quadcopters on the other hand are inherently very unstable, which is why they weren't popular until recently. They all require computer controlled gyro stabilization as they would just flip otherwise.

This is why I'm perplexed as to how GPS, accelerometers, sonar, etc made it to quadcopters well before helis. Quadcopters are mechanically simple though, requiring only 4 motors and no gearing. Helis require at least 1 motor, gearing, rotor head, and swashplate, and then there is still the tail rotor to consider.

[samwichse]

But again, for the most efficient drone...

Fixed wing.

[freebeard]

Steam/hot hydrogen-lifted airship.

The hot hydrogen cell (a rigid tensegrity structure) would look like this inside the Zeppelin shaped blimp aerobody. The steam has more lift than hot air but less than helium. It insulates the hot hydrogen, which is essentially a vacuum.



edit: thinking about powering it, I lean toward single ducted fans on the tips of the nose and tail that tilt and nod like an helicopter rotor. The varying clearance to the envelope would create thrust vectoring.

[redpoint5]

Originally Posted by freebeard

thinking about powering it, I lean toward single ducted fans on the tips of the nose and tail that tilt and nod like an helicopter rotor. The varying clearance to the envelope would create thrust vectoring.

Just to clarify, you mean vary the pitch of the blades, just like a helicopter? The rotor does not move in a conventional helicopter except to spin.

[LibertyMKiii]

Off from the current discussion but was mentioned in your first post for signal strength one of the best modifications to the transmitter is boosting the signal. I'm not certain what power is broadcasted with drone Tx but there are many 2W signal boosters on the market for 2.4ghz radios. (I use one for my RC car)

Have you looked into prop pitch? I know the drone racers play allot with their motor kv and prop pitch. This may be a good area to gain efficiency in.

-Liberty

[freebeard]

Bad example. The thrusters on ships?

The whole duct would gimbal so that the thrust is biased by being occluded on one side. Plus, I guess, variable/reversible pitch.

[redpoint5]

Originally Posted by LibertyMKiii

Off from the current discussion but was mentioned in your first post for signal strength one of the best modifications to the transmitter is boosting the signal. I'm not certain what power is broadcasted with drone Tx but there are many 2W signal boosters on the market for 2.4ghz radios. (I use one for my RC car)

Have you looked into prop pitch? I know the drone racers play allot with their motor kv and prop pitch. This may be a good area to gain efficiency in.

-Liberty

As it is, the range is already sufficient to send further than I can fly and return. Just learned that the signal is 5GHz. Prop pitch looks to be ideal from what I can see (maximum length without touching other props, heavy pitch from center and tapering out to flat at tip), although they sure make a lot of noise, like a swarm of angry wasps.

[freebeard]

(maximum length without touching other props, heavy pitch from center and tapering out to flat at tip)

Aha! So, no room for improvement there.

You're constrained by the legal line-of-sight requirement. Attack the maximum orbit speed.

For the acoustic problem, look to the 'black helicopters'. A solid center disk and odd shaped tips. Are you 3D printing your own propellers yet since they're expendable?

[redpoint5]

Originally Posted by freebeard

Aha! So, no room for improvement there.

You're constrained by the legal line-of-sight requirement. Attack the maximum orbit speed.

For the acoustic problem, look to the 'black helicopters'. A solid center disk and odd shaped tips. Are you 3D printing your own propellers yet since they're expendable?

I may stretch the legal requirements, but I fly over farm fields and technically, light reflecting from the drone reaches my eye. My controls don't work if I don't have line of sight.

The props are somewhat proprietary considering the twist locking mechanism, and I have gone through 8 of 'em so far. They only set me back about $2ea when shipped from China. I order spares ahead of needing the replacements.

My flight that ended up in ditching 0.8 miles from home lasted 30 minutes. If I fly 30 MPH, I should be able to cover 15 miles in half an hour, or 7.5 in 15 minutes.

I can't see getting less than 20 minutes of flight time regardless of how hard I fly, so maybe I can cover 8 miles roundtrip on a charge given a 30 MPH speed.

[freebeard]

http://www.zdnet.com/article/silent-rotor-blades-could-lead-to-true-stealth-helicopters/

According to this, the noise comes from blade encountering vortexes shed off the preceding blade.