Hey Everyone

I've been messing with making a quad to carry a GoPro for indoor commercial use. I wanted one that was not necessarily 'finger safe' but 'impact safe' and after several iterations including a 'Bucket Copter' (Yep made out of kids toy buckets - Flew for 15 seconds then never stayed up again) I hit on the idea of using 8" PC Fan Guards mounted on Poly Screws to solve the issue.

I started with the super cheap frames from China. The current version has Emax MT2213 motors and 30amp ESCs. The mount for the GoPro is two Carbon Sheets and dampers with ear plugs in them. Its Rock Solid to the frame so needs smooth control but the platform is very stable in itself. APM 2.5 Board of course. LiPo 2200mah 4S 45c Battery. Props are 3 blade 6". Flight time is currently at 8mins to about 25% on the battery

My problem is that I have no fabrication or design experience but have a degree from the university of 'How Hard Can it Be?' Right now its getting pretty hard. The ESCs get pretty hot as do the motors after about 8mins. I'm pretty much tied to the 6" props because the largest Fan Guards I can find are 8". I want to go to bigger motors but am restricted to the props size and weight increase quite a lot with the Turnigy series. The other issue is that bigger motors are making the gap on the guards over 50mm and the screw system is only rigid up to that distance (broke a few)

I moulded some guards out of plastic but they were incredibly brittle and reduced airflow quite a bit. Also they weight benefit was not enough to get worried about.

So...any suggestions as to how to get this thing to have more grunt, not start smoking, have bigger props (with bigger guards) and more. I'd be grateful of any input you guys can have as I've hit a bit of a brick wall. Nothing I try at the moment improves on the current spec. Total cost of the rig was around $250 so I have a little more budget to throw at it but the aim was to come up with a viable rig I can use for work that wasn't the cost of my DSLR Octocopter.

Thanks


Ewen

Views: 3615

Comment by Project Nadar on August 11, 2013 at 5:38am

you can also use 3 bladed props. Not that efficient but it will increase your lift capability. 

Comment by R. D. Starwalt on August 11, 2013 at 7:51am

Those fan guards are the real weight burden on the aircraft. Plated metal guards are were not designed for the aircraft but you get A+ for originality! I imagine the guards weigh nearly as much as the bare airframe.

You could consider minimizing the guards, taking out multiple round sections, reducing weight but also providing the protection you like. If you have a Dremel (or something like it), use the thin, ceramic cut-off wheels to make them look like below -- or whatever you feel comfortable with.

This will still provide the security you are looking for but cut the weight substantially down.

-=Doug

Comment by Austin Suhler on August 11, 2013 at 8:17am

Also, if you plan on having a APM board that works in your near future, might be a good idea to get a KK2.0 board to use while you're testing. I've had to work with 2 broken APM's for that reason alone; The people before me were testing, and it didn't end so well. Really nice idea though! Didn't think of using that size of a quad indoors specifically because of the large prop requirement, keep us updated!

Comment by Sam on August 11, 2013 at 8:30am

more blades on the props!!!

Comment by Ewen Rankin on August 11, 2013 at 11:30am

Great Idea RD. The ones I bought arent as continuous as yours but they certainly can stand some chopping out.

Thanks Austin. The whole point of the system was that it fitted through doorways...and it does

Comment by Oliver on August 11, 2013 at 11:59am

Well those grills are a clever idea but you have a bunch of things working against you here. Those guards are heavy and are occluding/interrupting airflow through the props. Three-blade props are notoriously inefficient. They're also too small and too slow. 

Suggestions: Remove the guards and check performance/heat. Weigh the guards and add dead weight temporarily  and check performance, to see how much of the hit is from occlusion and how much is from weight. Replace the props with the biggest two-blade props that will fit and check performance.

If guarded props are absolutely essential I would think about a perimeter styrofoam structure along the lines of the "indoor" one that comes with the AR Parrot "drone." It could be a simple square shape attached (for example) to projecting CF rods from the arms. It would guard against edge-wise prop strikes which are the potentially really nasty ones. It would be easy to remove in low-risk situations. It could act as crash protection for the quad as well. And it would allow setup of the quad itself to current best practice in regard to motor/prop/esc combos.

Comment by earthpatrol on August 11, 2013 at 6:07pm

As Oliver mentioned, keeping the airflow shadow to a minimum is a good idea. Also, the idea of cutting 4 holes out of a large enough piece of foam that you could attach and detach to your airframe seems reasonable as well. It will be light and you can tweak the design easily.

I too wanted to fly my GoPro in environments where safety is more of an issue. I have been having great success with my HooperFly Racer-PEX design. It's light, strong and has plenty of power to lug around my GoPro. I integrated the prop guards into the body design to reduce weight and as an exercise in having a frame without any straight arms.

Good luck on prop guard quest, it can be frustrating at times.

Comment by Cre8it on August 11, 2013 at 7:54pm

You need a set of my landing gear.  Super light and crazy strong.  no more landing on your camera.  quick zip tie on.

Comment by mP1 on August 11, 2013 at 7:58pm

@Ewen

I use wire about 3ish mm thick, its rigid enuff to support the hex, it should be sufficiently strong as a guard between props and some other object.

Comment by mP1 on August 11, 2013 at 8:00pm

@Cre8bit

Where did you get those legs ? Can they handle a fall from 4-5m without breaking ?

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