Heavy Lifters - where are we up too?

R

remyd

Member
Hi all,

I am interested in building a heavy lifter (8kg payload + 4kg batteries (estimate)) so likely thrust up around the 30kg. I would love to know what people are lifting and their configurations/specs and suggestions. This might be a useful resource for others??? I know all things multirotor are moving fast but what new frames are out there or do i need to custom build? or would something like the SkyJib be ample? I currently run a CS8, Cinestar 2 axis gimbal + Nikon D800, Plettenberg Orbit 15-22, Maytech V1 Opto ESC's, DJI Wookong M 900Mhz groundstation, T8FG radio, R6208SB receiver, props Aerobot 13x6.5 or APC14.4.7., 5S Thunder Power 5000mA by 2 for 9 min flight). Although very spritely in its current configuration I don't think the CS8 is up to the task for such a heavy load but maybe i am wrong. I would need to expand the booms if i want to go any bigger that 14 inch props i am using now.

I will be using the platform for slow (1/2 m/s) straight runs (100-500m) at a height of about 50m but with a very 70K expensive camera. I have a turbine heli in the pipeline for longer duration work but my multirotor experience thus far has me convinced that it is doable especially after watching beer lift :). Given the camera value i will be doing lots of testing and will need excellent reliable equipment prior to putting the camera up.

Looking forward to comments, especially about motors, esc's, props (combos) related to any thrust data that people have looked at.

Cheers,
Remy
 

J

jes1111

Active Member
Without doing any "eCalc-ing", my guess is that you'll need some very big props to produce that sort of lift - perhaps 17", 18" or more. In which case, a flat layout will be infeasible: you'll be looking at a coax 8. That much thrust on each arm will require some seriously rigid arms - not necessarily bigger diameter but maybe thicker walled.
 

R

remyd

Member
I would rather keep it flat but yes i agree it will be a large frame (maybe custom) and very rigid to accommodate larger props.
 


R

remyd

Member
i am comfortable with flat and for no other reason. I haven't done anything with coaxial setups. i know the guys at aerobot are working on a coaxial setup and the early video looks good. It will only be flown in perfect weather on nice sunny days as these will be required for the camera. The eight is for some redundancy it the event of a motor failure.
 


J

jes1111

Active Member
Well, 18" props on a flat 8 would yield a frame diameter of 1.3 meters! As far as venturing into unknown territory is concerned, that's more scary IMO than exploring coax ;) The same 18" props would only require a 700mm minimum diameter - much more manageable, much less weight.
 

K

kristiaj

Member
jes1111 said:
Well, 18" props on a flat 8 would yield a frame diameter of 1.3 meters! As far as venturing into unknown territory is concerned, that's more scary IMO than exploring coax ;) The same 18" props would only require a 700mm minimum diameter - much more manageable, much less weight.
Click to expand...
Yes, I agree that a coaxial may be a better choice in this case.
 

R

remyd

Member
Thanks this is exactly the discussion i am hoping to provoke. So what frame would you utilise for a coaxial and setups are you proposing?
 

J

jes1111

Active Member
I'd approach this by starting with the prop choice, then motors, then batteries, then ESCs, then frame. CW/CCW choices are limited at these big sizes. JXF does some- but you might need to look at using all clockwise props and adding servo-controlled rudders to control yaw. You'll want big, low kV motors, probably running at 6S. Innov8tive have useful thrust/consumption charts for all the Cobra motors.

The other starting point will be your gimbal - find something that's man enough for your load, then imagine a vibe-free mounting capability - this may guide you to the 'fuselage' design.

This size has been done before, of course, though I haven't seen much detailed documentation on them.

Seen this one? http://www.cam-and-carrier.com/products/vario-quad-copter.html
 

R

remyd

Member
Thanks jes1111 - useful info - no gimbal required as the camera will be looking down at nadir "ish" mounted with some vibration isolation but no need for stabilsation provided the copter is relatively flat. I will use an excellent attitude sensor to work out the look angles of the camera.
 

J

jes1111

Active Member
Interesting... you might still want stabilisation on the camera since the angle of the frame will vary with airspeed. Hanging such a load below the frame is itself a source of potential issues, so for this particular application you could mount the downward-looking camera in the centre of the frame, in the same plane as the props. The gimbal could be a relatively simple double ring (with direct drive) to give attitude correction on roll and pitch axes. Many (but not all) flight controllers are perfectly tolerant of being mounted away from the CG. Such an arrangement should fly very well (with the mass of the camera coincident with the overall CG) and be easier to fly straight tracks. And it wouldn't need a truck to transport it to the flight site ;)
 

R

remyd

Member
jes1111 said:
Interesting... you might still want stabilisation on the camera since the angle of the frame will vary with airspeed. Hanging such a load below the frame is itself a source of potential issues, so for this particular application you could mount the downward-looking camera in the centre of the frame, in the same plane as the props. The gimbal could be a relatively simple double ring (with direct drive) to give attitude correction on roll and pitch axes. Many (but not all) flight controllers are perfectly tolerant of being mounted away from the CG. Such an arrangement should fly very well (with the mass of the camera coincident with the overall CG) and be easier to fly straight tracks. And it wouldn't need a truck to transport it to the flight site ;)
Click to expand...

hi jes1111, the angle of the camera (actually hypersepectral imaging sensor) will be fine. I prefer it fixed as trying to compensate for gimbal changes as well as aircraft changes is often complex. The attitude sensor that goes on board measures 800hz (800 per second) and to 0.01 degree 99% of the time. I would be trying to get the camera and data acquistion directly under the CG and IMU etc. The truck lol i already have a large double bogey trailer for carting gear around :) so transport isn't an issue. I guess my worry is if the Skyjib or similar frames could cope with a large payload or if it is better just to make my own with larger props than i need and start from scratch.

Still looking for comments from those that are using big lifters currently. Setups and payloads would be really useful.

Cheers,
Remy
 

J

jes1111

Active Member
Sounds cool - although I'd still be looking to place the "camera" within the frame, right at the CG. Having such a heavy sensor hanging well below the frame (and hence the plane of thrust) will slow the responsiveness right down, making the craft work harder and hence shortening flight times. Since you won't have the normal viewpoint restraints of a stabilised gimbal, the opportunity to place the camera at the CG point should be seriously considered in producing a better overall package.

Forgot to mention, in case you didn't examine it detail - that Vario machine uses all CW props (17" if I remember correctly). Yaw control is through servo-controlled "rudders". Works very well, apparently - there's some video around on YouTube of this and several similar Russian machines.

Are you familiar with eCalc? Great tool for ball-park estimations of lifting capability, flight times, etc.
 

R

remyd

Member
Thanks Jess1111 i need to explore ore and do the math in ecalc to get some ball park figures. I am still hoping the current heavy lifters chime in to give some advice.
 

J

jes1111

Active Member
Yeah - seems nobody else is wanting to contribute :apathy:

I presume you've seen this: http://www.droidworx.com.au/specifications.html

According to their own numbers, they are indicating that your AUW would exceed even their Skyjib 8.

Did you mention Aerobot at the beginning of this thread? So you've seen their new ring design? That would probably do the job, and not expensive - Simon said online somewhere the price for the frame would be well under $1000 IIRC. I presume it flies as a six-motor, splitting each channel to two motors.
 

R

remyd

Member
yes Jes1111 that was the aerobot ring that i mentioned. I am waiting to see what come out officially but in the meantime need to keep hunting around to see what is available.

I know there are heavy lifters on the forum was hoping that they would chime in with advice. I will keep waiting and perusing. Maybe i will just extend the booms of my CS8 to take bigger props and see what sort of amps i use with my current setup and larger props??? i still remain confident this is doable it just needs the right mix of parts and a suitable frame.

thanks for your comments.
 

redridinghood

redridinghood

Member
jes1111 said:
I presume you've seen this: http://www.droidworx.com.au/specifications.html

According to their own numbers, they are indicating that your AUW would exceed even their Skyjib 8.
Click to expand...

This is under the news section, the specs posted seem obsolete.

"30/3/2012 Skyjib 8 new center section The skyjib 8 has been upgraded to further strengthen the center section, now tested to 500 Kgs, the new construction also stiffens the booms laterally. Please contact Droidowrx if you are a skyjib 8 owner and want this upgrade."
 



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