Breaking Ground electric helicopter efficiency challenge

[Kergarin]

Hello, 

I was playing around with Breaking Ground's electric motors, and noticed they work verry well for building helicopters. 

But the question is: how much can we get out of them? 

 

I challenge you to build the heaviest possible electric helicopter - using the lowest possible electric power - using only breaking ground's electric motors.

 

The scoring will be: 

(Total takeoff weight of the craft in KG WITHOUT electric motors and rotors) divided by (the total rating of all used electric motors in kN added up) = your score

Additional kudos for heaviest, lightest, fastest, highest entry

 

Rules:

- only Breaking Ground electric motors

- craft needs to takeoff vertical and stay stable above 50 meters for at least 60 seconds

- no cheats, mods etc 

- craft needs to fit within the VAB or SPH

 

Have fun 

Edited June 3, 2019 by Kergarin

[Kergarin]

Just a quick proof of possibility. Definitely no top entry. Will add the data later.

EDIT:

0,791t without rotors

2x 75kN power

Score = 791kg / 150kN = 5,2733 points

Not verry good, but it's a start 

 

Edited June 2, 2019 by Kergarin

[Feradose]

Interesting. I expect a lot from this thread.

Let's see if I can come up with something.

[Kergarin]

4 hours ago, Feradose said:

Interesting. I expect a lot from this thread.

Let's see if I can come up with something.

I also did, but somehow there was no response since two weeks 

What's wrong?

[Guest]

Speaking for myself only, what's wrong is that this challenge doesn't really call for clever engineering, it just calls for patience to optimise for lifting power, and this process is rather tedious ATM for a number of QoL related reasons. Also rotors scale in efficiency with diameter so the problem is fundamentally pretty simple -- you just find the biggest diameter rotor that the motor can turn, then add to the payload to find how much you can lift, rinse, repeat, try with a different part for lifting surface, rinse, repeat until bored.

At this point I know I'm able to build a reasonably efficient rotor pretty quickly, but I just don't have the patience to iterate on it to attempt record lifts. Moreover in more realistic craft there are practical limits to rotor size, especially if you want to make the craft look somewhat credible (i.e., the rotor doesn't clip through parts of it), so the "make the biggest rotor you can" approach won't get you very far.

I'll present one in the light category anyway:

- Total mass: 2140 kg

- Mass without powered electric motor and rotors: 1681 kg

- Powered by 1 x 75 kN rotor (the other one is an unpowered freewheel)

Score: 1681 / 75 = 22.41

This could be further optimised by removing the small servos that adjust collective after finding the optimal blade pitch and using the deployment feature of the blades to get to that angle instead; this would lighten the rotor, and would allow us to add some payload. This also does the lift with relative ease so it ought to be possible to add at least a bit to the payload as it is. (Adding one notch more ballast is 300 kg and that's too much, but I think it ought to be able to lift 100 kg or so more.)

But as stated, I don't have the patience for that kind of tuning, it's tedious and not much fun.

Edited June 20, 2019 by Guest

[Pds314]

I don't know about efficiency, but I finally have a chopper that has working, realistic rotor controls for pitch and roll (even if they are the twitchiest controls ever).

It has full cyclic pitch control. It doesn't have collective pitch though because while it wouldn't be that much harder to implement it would be entirely unnecessary given the degree to which messing with the Torque and RPM % helps. Except if you are trying to do an autorotation but I don't think I would land it anyway.

It has at least 10 hinges, 4 control rod pistons, a rotor (duh), and at least four non-motorized rotors. (3 for the blade pitch and one for the swashplates, for a total of 19 moving parts.

With some more R&D I should be able to miniaturize it.

My guess is that I will be able to make a mk1 size version soon.

Edited June 23, 2019 by Pds314

[Kergarin]

On ‎6‎/‎20‎/‎2019 at 10:39 PM, Brikoleur said:

Speaking for myself only, what's wrong is that this challenge doesn't really call for clever engineering, it just calls for patience to optimise for lifting power, and this process is rather tedious ATM for a number of QoL related reasons. Also rotors scale in efficiency with diameter so the problem is fundamentally pretty simple -- you just find the biggest diameter rotor that the motor can turn, then add to the payload to find how much you can lift, rinse, repeat, try with a different part for lifting surface, rinse, repeat until bored.

At this point I know I'm able to build a reasonably efficient rotor pretty quickly, but I just don't have the patience to iterate on it to attempt record lifts. Moreover in more realistic craft there are practical limits to rotor size, especially if you want to make the craft look somewhat credible (i.e., the rotor doesn't clip through parts of it), so the "make the biggest rotor you can" approach won't get you very far.

I'll present one in the light category anyway:

- Total mass: 2140 kg

- Mass without powered electric motor and rotors: 1681 kg

- Powered by 1 x 75 kN rotor (the other one is an unpowered freewheel)

Score: 1681 / 75 = 22.41

This could be further optimised by removing the small servos that adjust collective after finding the optimal blade pitch and using the deployment feature of the blades to get to that angle instead; this would lighten the rotor, and would allow us to add some payload. This also does the lift with relative ease so it ought to be possible to add at least a bit to the payload as it is. (Adding one notch more ballast is 300 kg and that's too much, but I think it ought to be able to lift 100 kg or so more.)

But as stated, I don't have the patience for that kind of tuning, it's tedious and not much fun.

Well, Maybe you are Right, that's not really what I had in mind.

I guess I need to rethink this

On ‎6‎/‎23‎/‎2019 at 1:53 PM, Pds314 said:

I don't know about efficiency, but I finally have a chopper that has working, realistic rotor controls for pitch and roll (even if they are the twitchiest controls ever).

It has full cyclic pitch control. It doesn't have collective pitch though because while it wouldn't be that much harder to implement it would be entirely unnecessary given the degree to which messing with the Torque and RPM % helps. Except if you are trying to do an autorotation but I don't think I would land it anyway.

It has at least 10 hinges, 4 control rod pistons, a rotor (duh), and at least four non-motorized rotors. (3 for the blade pitch and one for the swashplates, for a total of 19 moving parts.

With some more R&D I should be able to miniaturize it.

My guess is that I will be able to make a mk1 size version soon.

Wow thats absolutely brilliant 

would love to see a video of this!

[Pds314]

I will do a video at some point. Although I want to try to streamline and improve the controls. Currently it is about as twitchy as you'd expect from being able to shove 25 tonnes of thrust from centered to a 6-meter offset in the blink of an eye. Instant MegaNewton meters of torque lol. So currently it is an unstable mess at low speeds and needs either SAS to have access to generous numbers of magic torque wheels (for SAS, not manual control), or me to have very good piloting skills or luck.

Edited June 28, 2019 by Pds314