[OpenRelief Developer] Airframe design (was: Re: introduction post)

[Karl Lattimer]

On 15 Jun 2012, at 10:13, Shane Coughlan wrote:

> Hi Mohammad
> 
> On Jun 10, 2012, at 10:34 AM, Mohammad Athar wrote:
>> Why was Blender chosen for airframe design?
>> http://openrelief.org/pipermail/developer_openrelief.org/2012-April/000048.html
>> It doesn't seem like there are many analysis tools in blender (FEA, fluid dynamics, etc).
>> What advantages does it offer over solidworks?
>> Any input on this would be appreciated.
> 
> First of all, our prototypes are using off-the-shelf airframes, and we are learning from that. Step two is to create a open hardware airframe, and Karl has begun the brainstorming process on that.
> 
> As part of this Karl is using Blender to put together thoughts regarding the shape of the airframe. I am sure he would appreciate your contribution if you have experience in fluid dynamics (etc.) and access to other tools that are more targeted towards detailed models.

At the moment the airframe model is simply a shape design which takes some aspects of our existing airframe and extends and improves on it. We're using blender because I don't have any decent CAD software and its been a long time since i used CAD. 

The idea is to effectively build a scale model of the airframe for testing - we will hopefully be able to print it shortly and test it with some basic materials. 

I've tried to model the shape on a dragon fly as it would give us a unique appearance and a very slippery shape. The wings are a slightly improved version of the FPV 168 in that they have a slightly sharper rise to the ends and longer and wider elevators/ailerons - we also opted for a V-Shaped tail to reduce complexity and simplify the build.

What I'm missing :-

* The capability to slice and section the airframe accurately
* The capability to produce high quality graphics of the airframe 
* Vorlax or similar tool for testing the pressure zones around the airframe 
* A laser cutter for cutting plywood 

What needs to be done :-

* Design of wing attachment parts - a piece which attaches the wing to the fuselage, it must be strong enough to hold the weight of the wing
* Design of tail attachment parts - similar deal with holding the two tail wings to the central column 
* Design of the overall fuselage internal structure
* Design of the internal ribbing and structure of the wing
* Detailing the assembly process from the above parts. 
* Design of camera mounts (two or three cameras possibly with IR/RGB Fisheyes underneath and a nose mounted first person view)
* Design of servo mounts, preferably OpenSCAD printable parts - constructed from two pieces, one is the holder the second is the cover, these two parts screw together and into the wing.

Specifications :- 

* Aircraft must fit into a box no larger that 50cm x 30cm x 80cm
* Aircraft should be able to carry some weight in the tail section
* Aircraft should be able to carry some weight under the fuselage
* Total maximum load to carry should be no more than 2kg - excluding what is needed to make it fly (computers etc...)


Variations on this basic design, re-using the wing sections are also in the works, I haven't managed to settled on those airframe configurations as yet.

> 
>> It seems the UAV is in production
>> http://openrelief.org/pipermail/developer_openrelief.org/2012-April/000047.html
>> http://openrelief.org/pipermail/developer_openrelief.org/2012-April/000025.html
>> Where can I get specs on this model?  (I.E. maximum payload, maximum speed, estimated endurance, etc.)
>> http://openrelief.org/pipermail/developer_openrelief.org/2012-May/000146.html
>> is a design report available?
> 
> The first two prototypes have been made. I believe Karl has documented the build process and intends to publish that documentation. The lessons learned can probably be usefully shared, so everyone can know what went wrong, what went right, and why that was.

Assembly of the FPV 168 will be documented when I find time. 

We don't have specifics for lifting capacity or endurance yet, we hope to find that out in testing.


> 
>> in regards to: http://openrelief.org/pipermail/developer_openrelief.org/2012-April/000040.html
>> Could prototyping-level processes be employed?
>> If so, we could provide instructions for people to go build their own UAV at local shops/hackerpaces/garages.
>> The other parts seem easy enough to source, and being able to build it would make for a less expensive entry cost.
> 
> OpenRelief is a design project, so what we intend to do is provide the instructions for people or companies to build the various parts to make some or all of a drone.
> 
>> Plasti-dip isn't right.
>> http://openrelief.org/pipermail/developer_openrelief.org/2012-May/000152.html
>> We need something lightweight.  Decent results can be achieved by carbon fiber.  The best way to manufacture that is in an autoclave, but you can also use a negative cast to create the needed pressure.
>> http://openrelief.org/pipermail/developer_openrelief.org/2012-May/000126.html
>> http://openrelief.org/pipermail/developer_openrelief.org/2012-May/000114.html
> 
> At the moment we are looking at airframe prototyping from fibreglass. It's not an ideal material but it can be sourced around the world, and it is pretty tough.


BR, 
Karl
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