Can someone please recommend a prop maker and size for my hexa: 880kv motors, 30 amp esc, APM 2, cameral mount and camera: total weight with lipos 2.7kg. I'm looking for stability and long flight times for aerial photography and FPV. Also, can you elaborate on how to calculate all of this in terms of efficiency and thrust? Please help a newbie. Thanks. Please see photo attachment below.
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I have did some major research on products and there manufactures, as I was looking for companies to manufacture our products in large numbers. Nothing against jdrones but they carry the same props that come from the same factory's in the same country as you will find distributed on ebay. I am how ever surprised that you were able to get you quad off the ground> I broke 2 props just finger tightening and that was enough to switch not to mention the balance was so far of on them that there was way to much tape needed and drilling is just not a good idea. We are in the process of producing carbon Kevlar props that will come with our models.... Hunters just seem to think our quads are a new species of waterfowl.
The EPP props are junk. I've had two come apart in mid-flight on my 3DR Quad with 880kv motors. The material is just too brittle. I ordered some Gemfan carbon-core props and they look exactly the same as the EPPs, and make the same "popping" sound when spinning up. I'm looking to move to APC Slo-fly props this week. I can't take another crash!
GP(great planes) or GRAUPNER 1045 for rcTimmer 2836 or 11x6 you will get the best amp draw and max thrust.
Hi guys, I'm quite new to the world of multirotor drones, but I'm currently developing an heavy-lift for aerial photography, and recently I've read a lot of stuff concerning many topics to reach some basic knowledge and carry on my project (a total of 5Kg of flying drone with included equipment)
I read with interest this discussion, because it deals with many of my current issues and I'd like to add a question here, without open a new thread, just because it's very affine to mine and it's quite recent too;
I tried to use the mentioned calculator eCalc to figure out what my drone can do before to spend money, but actually the shown results don't convince me at all. Instead of using my project, which is still only imaginary, to expose my doubt I'd like you to consider this (probably well-known) heavy-lift hexacopter
http://www.rcgroups.com/forums/showthread.php?t=1372744
It's capable of flying with a total weight of almost 10Kg using APC 12x3.8 SF and some powerful motors not much different from AXI 2826/10 present in eCalc and 3s batteries
According to eCalc this should fly only up to 7Kg, but...
...here is my main doubt: accepting the fact that eCalc probably is not so accurate for such very extreme systems, even with lower loads and other motor/battery configuration it shows results (with apc 12x3.8SF propellers) largely exceeding the 5400 maximum rpm rated by APC manufacturer through the formula 65000/diameter; is it possible to spin a SF propeller up to 8000-9000 rpm without incurring in broken props or drastically lowered fliying efficiency? Or... is the guy of the video spinning them within or not much over the APC suggested limit? (this would means that eCalc totally fails)
Thanks to anyone would like to add a comment!
@James: A couple things pop into my head.
I ranted a bit about aerodynamics in another thread, and if you really want to calculate what's going on, understand the fundamental physics involved, and also check out some real-world data, please read this:
http://www.diydrones.com/forum/topics/the-case-for-large-scale-elec...
I dare say it's better than relying on "rules of thumb", although there's no argument with something that works. Beware of turning the props too slowly at this scale, however, as the UofI wind-tunnel data proves that sometimes achieving a higher Reynolds number is more important than the drag coefficient theory. The efficiency of props they tested was actually greater at higher RPMs for the most part. It might be counter-intuitive, but much below 100K Re, the drag coefficient goes down as the speed goes up, so the usual energy cubed law doesn't apply in this region.
Also, 6061 is NOT aircraft grade aluminum; it is actually the most common alloy around. While it is better than the highly corrosion resistant, and otherwise uselessly soft 6063 "architectural" grade for our purposes, it is hardly the best choice. 2024 (or 7075) is the good stuff, but it's 3 times the price and hard to find in a variety of extruded shapes. I am an avid customer of this site for materials:
http://www.onlinemetals.com/aluminumguide.cfm
My only relationship with them is one of highly satisfied customer. And I have purchased quite a bit of aluminum.
I am not a mechanical engineer, but the consensus seems to be that torsional rigidity is highly important in multicopter thrust unit arms, suggesting that round tubes are the best shape for strength-to-weight. Others who are more expert in this area than I are encouraged to weigh in (pun intended).
One of these days, I'm going to post pictures of a wire cutter and an aluminum-bodied turnbuckle that came into contact with each other for a few milliseconds while I was working on my full-sized ship, which has a fault-current of at least 4,000 amps (10S X 36P 3700 mAh 20C). Managing my best Crocodile Dundee imitation, "That's not a plasma, THIS is a plasma!" The wirecutter was scarred, but the turnbuckle barely still exists in a recognizable form (this was a full-sized quarter inch open-frame job too). I escaped with nary a scratch, but have a newly rediscovered respect for high currents.
P.S. The UofI site is here, and you'll note that they tested nearly everything mentioned:
http://www.ae.illinois.edu/m-selig/props/propDB.html
From an efficiency perspective, a lower speed higher torque motor is recommended running with higher voltage. Look at the MD4-1000 for instance, It's all a matter of how much money, and what engineering decisions you want to make. A quad is usually more efficient than hexa or octo, since you're carrying less dead motor weight, and the requisite larger cap batteries. But with his hexa configuration and those 880kv motors, there are limitations.
Your motors look like these RCTimer 880kv ones, here.
As everyone else mentioned, they were tested with 12x6 props for the 3s battery and 9x6 props for the 4s battery, according to the specs above. But, seeing as how your hexa is short on prop space, you could go with these 10x4.5 props with a 4s battery. Really nice props, and carbon reinforced. Good prop for the price, and not cheepo plastic props, like from HK. They're 10" instead of 9" for the reference props, but the pitch is lower, so should be similar loading to the 9x6.
That poor little APM2 needs some holes to get accurate barometric pressure... let it breath a bit! :)
For props I am experimenting with these lately and found them a lot better.
They are 10X4.5 carbon re-enforced nylon. yes as a result they are heavier (12grams each instead of 8 for cheap black ones) but they perform really well for me.
http://www.canadadrones.com/Propeller-set-10X45-EPP-Style-carbon-fi...
Dany
www.canadadrones.com
the short answer (at least for me) is: APC 12x3.8 Slow Flyer, theyre a huge improvement over the cheap 12x4.5 props. APC also make 14x4.7 and have (quite recently it seems) released a 13x4.7, i dont know what the current draw would be on those motors with the 13 or 14" props. the 12x3.8 will definitely work and in my experience could give you a 25% increase in flight time over the cheap 12x4.5s.
regards,
james
hi, great post on the the working out what size props to use, , James be careful when using cable ties on Ur esc aye, if to tight u might damage the, love the go pro box for damage control
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