(07-May-2017, 07:53 PM)unseen Wrote: I'm not convinced that 13x4.7 slow fly props will deliver the extra thrust needed at 3S to fly a 6kg AUW safely.

Those are impressive motors looking at the specs, very beefy and capable of tolerating up to 1kW of power!

The specs say the 12x6 props will give 2075g thrust at full throttle which is probably more like 1450g in reality. The 13x4.7 give 2194g, which is a minor improvement. Then again, none of this tells us much about what they'll do at 50% throttle, which is what really matters.

Realistically, 4S is going to be what gets you the thrust that you need. Out of interest, I'll see if eCalc has those motors listed and see what might work with an AUW of 6kg.

Bob, I'm puzzled by what you said about being able to go to 100% throttle without lifting off if you raise the throttle slowly. What flight controller and firmware are you using on this craft?

Hi Unseen, and all others who have pitched in to help, many thanks. I am using the Hero FC with Dshot 300 30A esc and Hyperion LiHV batteries. I am also puzzled by that slow throttle response. I cannot see any reason for it. I was hoping that there was a setting somewhere to adjust this parameter.
Re battery voltage, I am now resigned to the fact that I need to go to 14.8V with the biggest props I can fit. How to fit it all in is the problem.

(07-May-2017, 09:56 PM)sloscotty Wrote: What does eCalc say bout the 12 x 6 SF that he's trying to use now?

That if the actual all up weight is increased to 6kg that the craft won't even get off the ground.

I'll fire it up again and grab a screen shot...

Here is what it says will happen at 6kg AUW with 12x6 SF and 3S power:

With 4S and the 12x6 props, it will lift, but at 77% throttle...

Just as a matter of interest and to illustrate some points raised in previous comments by responders, I have attached a photo of my test stand which I used to test various motors, ESC and props. I spent several months on this testing and for your interest the four motors fitted with 12 x 6SF props delivered between 2.0 - 2.2 kg of thrust, exactly as predicted by e-calc and the Scorpion calculator.
There was a huge difference in thrust with the SF props as against all other props tested. Various 12" props tested between 1.2 - 1.7kg of thrust whereas the 12 x 6SF delivered on average 2.1kg.
During testing I came to rely on the e-calculators as the results pretty well matched actual performance.

Nice stand! Very practical.

The slow fly props do have a much greater surface area than other shapes which would explain the significant increase in thrust.

It's a shame that static thrust tests can be so misleading though. As soon as you actually start moving and the propeller unloads, actual thrust is no longer the same as static thrust. I always knock off 30% to be on the safe side. And of course, while it's interesting to know what you can expect at maximum, the thrust at hover throttle is even more interesting.

When I need to do some thrust testing, I connect up to this:



The RCBenchmark 1520 thrust stand. It's available from HobbyKing (here) or directly from the manufacturer in Canada at rcbenchmark.com

It's a very useful device which lets you construct your own test procedure and control the throttle signal to the ESC. As test test runs, it collects readings of the current drawn, the voltage, the motor's RPM and the thrust generated and logs them automatically as a .csv file on the attached PC.

The best part of this is that I can click on 'Start Test' and then retire to a safe location outside the room where the test is running. Having exploded a few GemFan props during testing, keeping a safe distance is a very good idea!

It will measure up to 5kg, so it's more than enough for any of my needs.

I've seen some criticism of eCalc and in the case of smaller propellers and high kv motors on a racing quadcopter, that criticism might be justified. In the end though, a racing quad flies for no more than five minutes, so working that out with eCalc seems rather pointless.

For larger builds, I've found it to be pretty much on the mark. I used it to select the propulsion for my camera ship. That has an all up weight of 2.8kg and uses 530 kv motors spinning 15x5.5 carbon fibre props on 4S power. The calculated flight time was within minutes of what I achieved in testing.

Hello again All, I must say I am really impressed with this forum. The help you have all given me is invaluable. I just wish I had known about it 12 months ago and joined then.
Unseen, I posted my last reply before I noticed your postings with the e-calc results. I have not had a chance all day to look closely at those results nor will I until later tonight. But thanks a lot for the effort you have put in.
I also wish that I had found that test stand you showed. Standing outside the room is a good idea. When I tested the first 12 x 6SF prop things that had never moved in previous tests started flying around the room, Scared the living daylights out of me let me tell you. I could not get over how much more powerful  those SF props were.
Anyway I am off out again shortly but when I have a chance I will look at those e-calc results.
Regards,
KK
PS I have attached a screen grab from the Hefei King Kong ESC data log showing results for the test of Motor 3. This may be of some interest. The batteries used in this test were older ordinary LiPOs.

The most powerful setup I've tested on the RCBenchmark stand was a 10x4.5 carbon fibre prop on a 2610 920kv motor with 4S. That produced 1.5kg of thrust at a cost of nearly 450W and was pretty scary, even though I was standing outside my living room during the test.

If I ever tried testing the 15x5 props, I think I'd prefer to be outside the apartment with a steel door between me and the test. I can imagine that your 2.1kg test was quite terrifying to be anywhere nearby.

Given that we're likely to achieve higher than real life thrust in a static test, I'd say it was prudent to always consider a motor and propeller under test to be as dangerous as a loaded gun, especially once you move up to the big props. When I destroyed a GemFan 5030 triblade by foolishly testing it on 4S, the prop started to resonate as the throttle passed 80%. The noise was utterly deafening! Then, as the throttle signal started to increase to maximum, the propeller suddenly exploded into fragments. If that was a carbon fibre prop, it would probably have taken out my windows!

The telemetry from that HiFei ESC is impressive! I might have to get one of the 100A ones to mount permanently on my thrust stand. Even though it would duplicate some of the data that the stand generates, having a second data source is always good for verification.

Unseen, testing those big motors in a small workroom is a real worry. The full quad with four of those motors is even scarier.
During initial tethered testing in my garage I accidentally reversed the throttle instead of the elevator whilst the quad was armed. I had my back to the quad at the time and all I heard was a roar and a smash and I turned around to see the quad hit the ground with pieces of the garage light fixture falling all around it. That was a valuable lesson. I was lucky I was not seriously injured.
These days I am obsessive about arming/disarming, Tx adjustments etc.
I even use a wooden prop lock to capture the props whilst I am under the quad plugging in the batteries.
Flying that quad is a very serious business.
And believe me I am very experienced in handling large UAV aircraft but this quad worries me more than any large aircraft I have flown.
As a matter of interest I have attached a photo of some of the UAVs I used to manufacture. These are 4m wingspan aircraft with 3.8hp motors, 16" props and they were pussycats compared to this quad.

Those are some beautiful aeroplanes Bob! I forget that you are an industry legend sometimes - it must be the misleading user name.

I'd much rather be next to one of your fixed wing craft with the propeller spinning than my camera ship:



Just at hover, the tips of those 15 inch props are moving at about 250 km/h.

I'm sure some people think I'm far too paranoid about safety when I (for example) tell them off for arming a quad with 5" props indoors and holding it in their hand so that they can tilt it this way and that to feel how the flight controller attempts to fight against the movement. The problem here is underestimating the speed of the propellers and the amount of thrust they can develop almost instantly. A sudden unintended movement while you have an armed quad in your hand can produce a violent correction with enough torque to simply rip the craft out of your hand. At full speed, the tips of a 5" prop will be moving at around 500 km/h. Plastic or not, at that speed they have a lot in common with the blades of a food blender!

As your "I reversed the wrong channel while the craft was armed" story shows, if a well seasoned veteran like yourself can accidentally create a situation where horrifying consequences are just a split second away, then anyone can. Even three inch propellers on powerful, high kv motors are more than capable of inflicting serious injuries and anything above ten inches should rightly be viewed as potentially lethal.

I'm religious about not powering up anything that has propellers fitted unless I'm outside and in a controlled situation. As I try to explain to people, safety procedures are about minimising the risks when something unexpected happens. The unexpected nature of most accidents means that it's never OK to skip safety at any time. It's when you make assumptions and take things for granted that the unexpected is most likely! And of course, when things do go wrong, everything happens so quickly that having time to react just isn't going to happen.

I'd hate to see our hobby get banned because some irresponsible fool gets themselves or someone else killed through their stupidity. So I'll carry on preaching in the hope that those who take needless risks think twice about it and change their ways before something nasty happens.

Hi Unseen, sorry for the long delay in answering your last post but we have been working down on my son's farm in Joadja near Berrima NSW for the past few days. That farm is where I do my quad flying, well away from people. See photo attached.
Where are you located if you do not mind me asking. You seem to indiicate that you know me from your very nice compliment about me being an industry legend. I am not too sure about that but thanks anyway.
With regards to your crusading about safety, please do not stop. I have seen some very nasty accidents on flying fields over the years so you cannot be too careful. One never knows when it may happen or why it may happen. Equipment failure, a moments lack of concentration, people clowning around or just simply errors in judgement. From the moment we walk onto that flying field we must be ever alert to the potential for danger.
One final matter. Do you mind if I ask you a series of questions on technical matters over the next few posts?
Regards,
Bob

Unseen, I also forgot to thank you for the kind remarks about the Flamingos. I am completely biased of course but I also think the Flamingo is a very nice looking aircraft. Not only nice looking but a dream to fly.
My favourite photo of the Flamingo is attached for your interest. It is of the Flamingo we used in the 2007 Outback Challenge, before fitting the water bottle to be dropped.

(11-May-2017, 01:58 AM)Keyboard Kid Wrote: Hi Unseen, sorry for the long delay in answering your last post but we have been working down on my son's farm in Joadja near Berrima NSW for the past few days. That farm is where I do my quad flying, well away from people. See photo attached.
Where are you located if you do not mind me asking. You seem to indiicate that you know me from your very nice compliment about me being an industry legend. I am not too sure about that but thanks anyway.

I'm on the other side of the planet to you in Stockholm, Sweden. I don't know you personally, but anyone who knows anything about the history of RC flight knows the contributions that you and Silvertone made to the hobby.

(11-May-2017, 01:58 AM)Keyboard Kid Wrote: With regards to your crusading about safety, please do not stop. I have seen some very nasty accidents on flying fields over the years so you cannot be too careful. One never knows when it may happen or why it may happen. Equipment failure, a moments lack of concentration, people clowning around or just simply errors in judgement. From the moment we walk onto that flying field we must be ever alert to the potential for danger.
One final matter. Do you mind if I ask you a series of questions on technical matters over the next few posts?
Regards,
Bob

Ask away! I'll do my best to answer.

I am a bit late here, but. Welcome to the forums Bob! Glad to have someone with your years of experience.