Over the last three years I have been monitoring the web for evidence of large, heavy lift, commercially capable systems, for loads in excess of 10Kg
As many of you may know, there are a lack of larger frames on the market, that can handle more than 10Kg.
Rimcopters can manage 40Kg loads, and more!!!
From my research, I have found that many "heavy lift" frames are lacking one thing or the other. Either they are too heavy, or they are not strong enough. In both cases the frames are made using "tube and plate" style assemblies.
Three years ago I began developing a new type of multirotor frame. The basic idea came from my experiments with Aluminum extruded tubing as a core frame...bike rims.
This may sound quaint, perhaps even a bit tacky...bike rims for Commercial sUAS and UAV's...
I admit, its easy to get the wrong idea... I am not out in the dump collecting old bike parts to make recycled cheap frames! Stick with me for a bit, and discover why I kept going with this idea, and where I ended up :)
First, let me say that I am not here to bash anyone... There are millions of dollars invested into various manufactured designs, and those dollars are worth protecting!
It is not my desire to obliterate others hard work! My goal here is simple : make the best multirotor possible ! The fact that what I have made is less expensive, and easy to buy and build... That it is made entirely of stock components... And can be reproduced in any part of the world may be concerning to some... I am only here to show that what I have made has value, is useful, and may help some of you in your goals.
Please, if you are offended, or don't have anything useful to add... Please refrain from offering any comments!
If you are an operator, and individual or company that see's value in the work, please contribute !!!
I do not sell frames, or systems... I learned that lesson!
I do not have a business, nor do I intend to create one... So relax! Just enjoy the ride, and take from it what you can... If you intend to take this idea, and make a business... Beware ! I will not tolerate it, and ultimately, it would be better to just ask me to use the design, and pay for that use.
Individuals, who would like to reproduce my results may do so, for their own use... Make one, use it, and prosper! However, if you intend to make them for commercial use... Please remember that this is my intellectual property... And I can and will protect it :)
Now, onto the good stuff
Rimcopter is a TYPE of multi rotor frame, not a brand. To be honest, I didn't even coin the phrase. The name simply denotes what it is... A multirotor made from bike rims.
WHY BIKE RIMS?
Thanks to 100+ yrs of production and development, the bike rim is lighter, stronger.. Less expensive than custom designed parts to do a similar job.
Tube and plate designs could never create the same strength to weight ratio's apparent in my designs, nor can the tube and plates adequately deal with Vibration and Deflection issues... The truth is, Tube and Plates could never be expected to hold the weight, and as a result of the design, they suffer from vibrations effects... Jello, lack of resolution, and over loaded flight controllers, trying desperately to over come the errors created due to motor deflections and stray vibrations!
Rimcopters are completely different. The flight controller and loads are completely isolated from the drive system. In addition, the strength to weight offered in the frame reduces the load to the motors substantially. The result is longer flights, with greater flight ability and performance... Without any complications from stray high frequency oscillations or motors moving all over the place...
When I say lighter, I mean MUCH lighter... In any given example, our frame design will be lighter. Sure, you can make a light tube and plate, however, it would never been strong enough to handle the loads!
AS an example, the 1000mm X8 Aluminum design, AUW of 1.2Kg including 30mm CF Landing gear (can take 200Lbs !!)
Y6 Carbon 900mm... 780g
In both cases the frames can take well over 150Lbs force, before ANY movement / deflection.
AS comparison, I can deflect the motors of a s900 with just two fingers... Less than 10Lbs force.
Too good to be true?
Not at all... The strength of this design is that ANYONE can produce one for them selves, and because of that, it is unlikely that any larger corporation will attempt to produce it.
So, you can see, its not marginally lighter... less than 1/2 the weight in many cases!
not slightly stronger... Exponentially stronger!
Not slightly less expensive... Frames can be made for as little as $75 - $150.
So then, what are you waiting for ?
Need a larger, stronger, less expensive frame ?
Of course you do!!!
What I can offer...Two formats ( X* and Y6 ) , in two sizes, from three materials ( carbon, aluminum or steel)
Welded, bonded, or bolted...
the torsional effect is the issue... vertical flex, if not associated with torsional deflection is fine.
In this design, due to the way the rims are designed to clamp on the tube ( clincher) there is little flex or deflection whatsoever at all... this is mostly due to the short booms lenght.
Tube and plates would need to make massive plates to cover the area ( think Ricopter) and that results in a a HEAVY frame, that still loads the FC with stray vibrations.
The original rimcopter was a single rim... its a design shared by a few, including another member of this group.
have a look at my original thread, from RCgroups:
What I did with that design was make it more usefull... modular, scaleable... and so on.
There is no perfect design. It's all a balance act between weight, strength, cost and being easy to build/repair.
The "plate and tube" design is very common because it utilize mass produced CF parts to lower cost and make manufacturing easier. And you will be hard pressed to find other workable materials with the strength to weight ratio of CF.
Also keep in mind that the traditional center plate design, is only one of many possible "tube and plate" solutions. Once you start to size up, it makes more sense to open up the center area to make room for equipment.
And from my experience I have found that payload capacity is not limited by frame strength, but mostly propeller size and overall propulsion system lift capacity.
So the real questions before you even start looking for a new design then becomes.
- Is the "tube and plate" design strong enough for you application (heavy lifter)?
- Can you make an alternative design that is cheaper to manufacture, and still has equal or better strength to weight ratio?