"World's First Hydraulic Drone Promises Six-Hour, Non-Stop Flights Over 500 Miles"

ElPaso Pilot

ElPaso Pilot

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ElPaso Pilot
Welp, here's a solution I would have expected in a 1960's Popular Mechanics magazine, not in 2022...

Gas engine powered, with 4 stump grinder hydraulic motors.

https://gizmodo.com/worlds-first-hydraulic-drone-can-fly-500-miles-1848587714
https://flowcopter.com/technology/


DSC_5920-scaled-owws6yl51xcxq65s49fdb4s9a1tvu4j5lcmz6uvqww.jpg
 
That surprises me, I would think that the hydraulic energy losses would be far greater than electrical losses, but if it works it works. I suppose the need to not have heavy electrical windings for motors and a generator could make some sort of alloy hydraulic pump and motors lighter.
 
Sac Arrow said:
That surprises me, I would think that the hydraulic energy losses would be far greater than electrical losses, but if it works it works. I suppose the need to not have heavy electrical windings for motors and a generator could make some sort of alloy hydraulic pump and motors lighter.
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The losses in the hydraulic system are huge, compared to electric.

I think they're betting their farm on the much higher energy value per pound of gas vs. battery tech., and tankering extra fuel to make up for inefficiencies.
 
What's the gain of this from building a drone like a conventional helicopter? A heck of a lot simpler and much more efficient as well.
 
'I'll just swing by at Fleet&Farm for a bucket of hydraulic fluid for the drone...'

Interesting concept. I would think that directly linking the props to the prime mover via carbon fiber driveshafts is a lower loss and lower weight approach.
 
weilke said:
'I'll just swing by at Fleet&Farm for a bucket of hydraulic fluid for the drone...'

Interesting concept. I would think that directly linking the props to the prime mover via carbon fiber driveshafts is a lower loss and lower weight approach.
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Except to be a functional quadcopter, each rotor is continually changing speeds to keep it stabilized.
 
I guess multi-copters are cool, so multi-copter it is. Damn the inefficiency, full speed ahead...
 
As someone with a lot of experience working around hydraulic systems at construction sites, there is NFW I'm trusting my life in flight to a hydraulic drive system. MTBF is way to short for hydraulic connections.
 
Jeff Oslick said:
As someone with a lot of experience working around hydraulic systems at construction sites, there is NFW I'm trusting my life in flight to a hydraulic drive system. MTBF is way to short for hydraulic connections.
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It may be that they're not interested in attracting people who will trust their life to the system. More likely they're looking to attract investors.
 
ElPaso Pilot said:
The losses in the hydraulic system are huge, compared to electric.

I think they're betting their farm on the much higher energy value per pound of gas vs. battery tech., and tankering extra fuel to make up for inefficiencies.
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Then electrical generation and electric motors would be better, if not cheaper.
 
weilke said:
It needs to continuously change lift, not necessarily speed.
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That would be challenging with all the props spinning the same speed.
 
Jeff Oslick said:
As someone with a lot of experience working around hydraulic systems at construction sites, there is NFW I'm trusting my life in flight to a hydraulic drive system. MTBF is way to short for hydraulic connections.
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The thermal camera this thing is going to move down a Powerline wont have that hangup.
 
Salty said:
That would be challenging with all the props spinning the same speed.
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Helicopters change their lift around the course of every revolution of their single rotor.
 
ElPaso Pilot said:
Gas engine powered, with 4 stump grinder hydraulic motors.
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Sure seems like a step backwards going the hydraulic route. Sticking a Honda 2200 generator in there with 4 AC motors would seem more a step in a positive direction with electrical vs hydraulic speed controls for the motors. I wonder what type control valve set up was used.
 
Bell206 said:
Sure seems like a step backwards going the hydraulic route. Sticking a Honda 2200 generator in there with 4 AC motors would seem more a step in a positive direction with electrical vs hydraulic speed controls for the motors. I wonder what type control valve set up was used.
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“Digital Displacement® Pump
A new type of hydraulic pump:

– Extremely efficient.
– Features high bandwidth control of 4 independent motors for attitude control.
– Robust: Designed for harsh environments.
– Better power to weight ratio of equivalent ‘best in class’ PM electric motor.”
 
ElPaso Pilot said:
A new type of hydraulic pump:
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I saw the pump type but they don't get into how they control the hyd flow, i.e., speed, to each motor. I see the hyd manifold in the pics but thats about it.
 
Bell206 said:
I saw the pump type but they don't get into how they control the hyd flow, i.e., speed, to each motor. I see the hyd manifold in the pics but thats about it.
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1 servo on the swash plate for volume and 4 servo valves for proportions with some control logic magic?

No idea.
 
ElPaso Pilot said:
1 servo on the swash plate for volume and 4 servo valves for proportions with some control logic magic?
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Except most multirotor craft (quad drones) use fixed pitch props and control things by varying the props speed, i.e., thrust/lift, and tilt the whole vehicle for directional control. "Conventional" variable pitch rotors/swashplate/servo set ups are usually limited to 2 rotors. Plus I don't see any of the same in the vids/pics. Its definitely an interesting conception but the hydraulics add a second level of complexity that an electrical motor turning those props does not. Now there are some drones flying out there with what they call a "virtual" swashplate which is very simple but it is electric, adjusts speed for pitch control, and requires a computer to make all the control input.
 
Bell206 said:
Except most multirotor craft (quad drones) use fixed pitch props and control things by varying the props speed, i.e., thrust/lift, and tilt the whole vehicle for directional control. "Conventional" variable pitch rotors/swashplate/servo set ups are usually limited to 2 rotors. Plus I don't see any of the same in the vids/pics. Its definitely an interesting conception but the hydraulics add a second level of complexity that an electrical motor turning those props does not. Now there are some drones flying out there with what they call a "virtual" swashplate which is very simple but it is electric, adjusts speed for pitch control, and requires a computer to make all the control input.
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Guestimating about a swash plate within the hydraulic unit -- not on the rotors. Controlling total volume to four servo valves within the manifold, one for each rotor motor.

Not sure how they're getting 4 independantly controlled circuits out of the pump.

Hydraulics_03042016_Schematic3.png
 
Friend of mine said once what the world needs is a hydraulic TV Set. That way when picture goes FUBAR, you find the leak and fix it.

Same logic here I suppose :rolleyes:

Cheers
 
ElPaso Pilot said:
Guestimating about a swash plate within the hydraulic unit -- not on the rotors.
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Okay, I think I got it. First we need separate the "swashplate" terminologies. The picture you have is a cross section of a hydraulic wobble or "swashplate" pump. The swashplate I was referring to is a rotor flight control. No comparison. What I missed was the "digital" or electrical words in the type of hyd pump which is basically an electro-mechanical hydraulic pump where the control valves are internal and located at the head of each pump piston. However, the pump is a radial type pump with each pump piston a separate hydraulic pressure supply system. In other words its completely different than your picture and conventional hyd systems I'm familiar with. So each internal pump piston supplies pressure to each rotor motor and is independent controlled by a variable electric valve mount internally at each pump piston head assembly. Now that's a mouthful. Basically, each rotor speed is changed independently by open/close of the internal ports which in turns allows for direction control. Seems these type electro-mechanical hydraulic pumps are all the rage in the heavy equipment industry and are used on excavators, etc and have made conventional mechanical hydraulic control through spooler valves, etc. obsolete.
 
On a multicopter you don't need a swashplate as you can vary the thrust of the rotors independently. To do so you need to vary the rpm, which needs a very light propeller, or you can very the propeller pitch, which is a much simpler mechanism than the swashplate for cyclic pitch used on helicopters. If you can control the pitch, then rigid driveshafts would work and be a lot more efficient than hydraulic transmissions... but then of course you have to consider the reliability of the pitch change mechanism.
 
Bell206 said:
Okay, I think I got it. First we need separate the "swashplate" terminologies. The picture you have is a cross section of a hydraulic wobble or "swashplate" pump. The swashplate I was referring to is a rotor flight control. No comparison. What I missed was the "digital" or electrical words in the type of hyd pump which is basically an electro-mechanical hydraulic pump where the control valves are internal and located at the head of each pump piston. However, the pump is a radial type pump with each pump piston a separate hydraulic pressure supply system. In other words its completely different than your picture and conventional hyd systems I'm familiar with. So each internal pump piston supplies pressure to each rotor motor and is independent controlled by a variable electric valve mount internally at each pump piston head assembly. Now that's a mouthful. Basically, each rotor speed is changed independently by open/close of the internal ports which in turns allows for direction control. Seems these type electro-mechanical hydraulic pumps are all the rage in the heavy equipment industry and are used on excavators, etc and have made conventional mechanical hydraulic control through spooler valves, etc. obsolete.
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Well, there you go. It's been awhile since I've been inside a hydraulic pump.

https://fluidpowerjournal.com/digital-displacement-pumps/

Fig-1-DD.gif
displacement-pump2.jpg
 
ElPaso Pilot said:
It's been awhile since I've been inside a hydraulic pump.
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Interesting. I dont think I've ever been around a radial piston pump. So the electronic version of the one above would basically be 6 seperate single piston "pumps" driven by a common drive.
 
weilke said:
Helicopters change their lift around the course of every revolution of their single rotor.
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Helicopters also add power when increasing the collective. Powering all the props from the same source would mean they’d all be the same rpm, despite the pitch of the various props being different. That would be “challenging” to make work well.
 
The overarching concept of this design is to not use electric motors or batteries.

A "Certified airworthy Engine" driving sync shafts to the rotors would add tremendous complexity and points of failure because of the need for transmissions, flex couplings and swashplates.

By simply varying the speed of the rotors using control valves, the motors can be located directly connected to the rotors and only hoses used to transfer the power. What makes this "New technology" is the ability of those valves to respond quick enough to match the low inertia RPM changes of electric motors!

I have always thought a hydrostatic powertrain could be adapted to an aircraft to avoid the need for running driveshafts through the cockpit and permitting a wide choice of locations for the engine. This is sort of that way of thinking, but with a better chance of it working well enough to have enough control authority.

Efficiency could be a tradeoff for light weight and maneuverability in this case.
 
Which ring of Hell does the 6 hour, 500 mile flight belong in, and how do I sign up?
 
kyleb said:
Which ring of Hell does the 6 hour, 500 mile flight belong in, and how do I sign up?
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Like all such promises made by aircraft entrepreneurs seeking investors, it falls into the imaginary one.
 
Somebody's just having fun with this.

In the 80's, an engineer friend of mine asked how I'd power the door locks for a car. I said electric, maybe a solenoid or motor. He said nope, guess something else. Well, maybe vacuum? Ford did a lot of vacuum powered stuff in the 70's cars. Nope! Pneumatic? Nope! So I gave up. He said, what's the worst way to do it? I guessed - hydraulic? He said yep!!! Meet my new (BMW or Audi - I don't remember). Apparently they made the door locks hydraulic, and if you parked a cool car in the sun, it would sometimes heat up and the pressure change would pop all the locks open.
 
DaleB said:
You’re partly right, but I feel some of your information is speculative.

:D
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What information do you mean? He's right that lithium ion won't get us to electric flight. There are other chemistries being developed more suitable for flight, and some are in production. Lithium sulfur is available now, which is why I feel it is the most likely choice for electric flight, but it isn't the only possibility. At potentially 5x the capacity of lithium ion, LiS is the most practical choice that I know of at this time for small aircraft. People are working on metal-air batteries that, if they get them working, will have energy densities similar to gasoline. Those are a long way off. Hydrogen could work, but he alluded to one problem when he mentioned "big, heavy tanks in the fuselage"- it takes a large volume of hydrogen, even as a cryogenic liquid, to have any range even when using it as a fuel cell. Scientists are working on ways to improve the amount of hydrogen that can be stuffed into a given volume but there haven't been breakthroughs that I know about recently.

My information isn't very speculative, and is grounded in current science and reality.
 
DaleB said:
I never said it was very speculative, just speculative.
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And a lot less speculative than the posts that claim electric aviation will never be practical in any form ;)
 
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