That's a bold statement ... Worlds Best. But it's even larger than that. Not just Worlds Best, but best for most all applications less than 30 Amps (limit of the tests). That means:
- duration ships that only pull 2 to 8 amps per rotor
- most all 6S and smaller ships (exception of nano-ships)
- any-size FPV racer
- any other ship in between
Why almost any size? Shouldn't a small FPV racer use a smaller and lighter ESC for response? Yes, if it does better on a net-lift response test. In other words, when you penalize the ESC for it's weight, is it still better and faster? What i continue to see is ESC manufacturers downsizing critical components of the ESC at a net loss. They weight savings is lost because of greater thrust loss and response. In other words, this heavier ESC will out accelerate, in the real world, a smaller and lighter ESC.
Why post this? To move technology forward, we need to report to industry what works and what doesn't. For some reason (i don't know why), this ESC works better than all others tested:
- for generating maximum thrust from the motor***
- for net-lift efficiency or the grams of weight it can lift (after it lifts the rotor) per watt
- for response (how fast it can generate targeted lift)
These tests were conducted on multiple days on multiple rotors of highly variant size, always being immediately compared back to another DYS 40A multicopter test to ensure that the baseline wasn't changing.
The ESC that dominated is a DYS 40A OPTO Multicopter using SimonK. The photo is included because there are two others that carry a similar or same name.
- Not the white cover DYS BLHeli 40A
- Not the one that is says "Programmable" versus "Multicopter" in the blue/purple band across the front
Have i tested all ESCs? No, but if you are convinced you know of one that would work better, let me know. I've tested most all of the following and one or more of their variants:
To do a test like this, a highly repeatable and finite test stand is needed. It took a while to develop one but what works is one that:
- measures (at a minimum) volts, amps, thrust, motor temp (shoots IR up the aft end of the motor)
- eliminates harmonics between the rotor and load sensor (this proved difficult but achievable)
- is calibrated and proves repeatable within 1.5%
- controlled by a system that can precisely repeat a rotor test (uses a Audurino Mega)
- directly feeds the data into Excel for analysis (uses DATAQ)
- uses a test script that produces repeatable results
- uses a test procedure that minimizes repeatability error (used average of multiple tests)
How much better is this ESC? On average:
- 4.4% higher net lift (after it lifts itself)
- 2.3% more net-lift efficient (usually the larger the better)
- from more than twice the response or the same response as other ESCs (usually the larger the better)
So how to make it better?
Step 1: Strip it naked. See photo below.
... remove the cover
... remove the heat plate (better to locate the ESC under prop wash to run cooler, see below)
Step 2: Right-Size the bullet connectors or wires (see above where heavy wires are replaced by 2mm bullets)
... remove the large bullet connectors or wires
... replace them with ones that are the most net-lift efficient (where heat loss = weight loss)
Step 3: Seal the ESC. Seal it with Electrical Sealant to protect from moisture and conductive dust
... tape or plug connectors and wires
... repeatedly spray each side from different angles
... a mistake i made was not sealing the bullet connectors and solder
- don't tape them off like i did
- insert a male connector into the end of bullets so sealant doesn't get inside them
Step 4: Locate ESCs under Prop Wash. See photos below. The turbulence generated by the prop does not adversely affect lift when the ESC is placed on edge to the prop wash.
... Use something non-conductive like hot glue to bond the ESCs to the motor mast or spar
... Face the FETS (the little square warehouses or Fire Emitting Transistors) to open air
... Protect the ESCs from below from ground contact (not needed here because of clearance)
back-side with hot glue
front-side with FETs completely exposed to open prop wash
Step 5: Tie up wiring. Use dental floss to secure wiring away from the prop.
***Note: The T-motor Air 40 in high-timing mode (an option) generated higher thrust, but at the sacrifice of efficiency and motor temp. Also, the T-Motor Air 40 was 2nd best and close in performance. If you are using an Air40, it probably isn't worth switching.
Great question for the King trying to figure out how much gold is in the goblet.
"Fake" carbon usually suffers from one or more of the following:
- has a high epoxy content (large impact on strength to weight)
- dyed glass (moderate impact on strength to weight)
- advertised as woven or fabric but is twill coated extruded carbon (less durable)
- not enough resin (too fragile)
I buy from trusted aerospace sources and perform a "hammer" test on a short piece (while wearing eye protection ... carbon splinters are not nice).
it depends on amps. fly in hover or if a FPV racer, at race speed. check your log and see what your typical ship amps are. Then enter that value into the attached worksheet in cell E4.
The color area will immediately change. pick the lowest number (the most green) and look back across at column D for the wire size.
Thank's Forrest, aerospace here mmm.....
some pieces I bought in China looks heavier than others to be CF, I thought that something like you explain was happening.
Race ESCs use 16ga for 40A, 16-18ga for 30A, and 18-20 ga for 20A versions. Wire gauge depends directly on run length; typically these ESCs will have BATT leads less than 100mm long. If you need longer than they come with, always step up to the next larger ga wires than come on the ESCs.
We recommend for racing to mount ESCs as close to the motors as possible, directly under propwash with motor leads in the 15-30mm range if possible as it helps eliminate desync with smaller, high-speed props, and to never extend the wires longer than the manufacturer ships the motor with. Always solder motor leads directly to the ESCs without bullets; RACE ESC vendors know you will be doing this so it will not void your warranty.
If you're not racing... meh. It's a matter of preference. Bullets are okay, and convenient to replace ESCs & motors in the field. I use 'em on my AP rigs. On the other hand, I've NEVER, EVER, had to replace an ESC on my AP rigs; I usually overbuild by a factor of at least 2X. The only times I've ever needed to replace a motor, I was already replacing a lot more than just a motor, so soldering was the least of my worries. ;)
Yes, it's a PITA to have to re-shrink-wrap your ESCs, but it's part of racing. And you can change the colors while you're at it, if you care about such things. A couple of the latest model ESCs now come with a snap-together nylon shell so you can do away with all that mess; it looks more finished than heat-shrink and weighs less too.
I'm not that sure I believe they'll hold up as well as polyolefin heat-shrink, but they will probably hold up better than the thin PVC heat-shrink we usually re-wrap in to shave a few grams and improve heat transfer for cooling.
With modern FETs cooling is typically a moot point anyways; their on-resistance is so low, and they spend so little time switching states in the commutation phase that very little heat is generated even at maximum load.
Typical heat-sinking provided by the copper pour is multiple times what they need anyways; the mounting in the propwash thing is really more to make us feel better because we know we're abusing our ESCs. ;)
I'm going to go out on a limb and assume you...how do I say it...play a lot of video games? Just a hunch... :)
Hmm... I just "upgraded" to XBOX 360... so, no, not likely. :rolleyes:
I build and fly as a hobby. I'm retired from the life now. ;)
Dilbert can suck it; I got out with my sanity intact.
Martin - I can tell that you are a scientist, and a precise one, if not in trade, then in at least in hobby. With that in mind ...
With electric motors, Torque is Proportional to Amps. If you want higher response, you need higher torque. Thus anything that reduces Amps, reduces response. Of the things that reduce Amps, one, as you know, is resistance.
In comparing the ESCs, we aren't talking about a 30% difference in performance (well in most of the cases). So it doesn't take much heat to create the less than 5% difference seen across the top ESCs.
To get precise, Ohm's law I (amps) = V (volts) / R (resistance)
P.S. An ampere is defined as 6.241*1018 electrons, but who's counting :-)
I can tell you have never drag raced before.
It's fun. Try it with your friends and stand back and away from any spectators because ... the best description i can think of is ... fireworks. This is how it works.
- start from the ground with props running
- on go, go to full throttle
- attempt to do a controlled take-off at full throttle
- then transition into forward flight while still at full throttle
- control the direction and end up between cones (or trees) about 50 meters out that are about 10 meters apart
Do that, and then tell me you still believe what you just wrote above. I'm all grins because this will shock you and make you laugh at the same time. But be forewarned. It takes time for the Adrenalin to wear off and time for your sudden attack of humility to sink in as you laugh at yourself and your friends. I was foolish enough to volunteer for being at the finish line to judge who won. Never do that again!
I raced BMX then MX, then Can-Am, I've bracket raced street stock IRL, raced Sportsman class irl, and raced 1/10 scale AA class and dirt Oval WoO.
I know more than a little about adrenaline junkie-ing dumping massive current in a few seconds. ;)
THIS is what I think is fun NOW; all the adrenaline, but it lasts for minutes, not seconds.
I can only dream of being this good some day; but I'm not going to stop trying.
Right now, this style of racing is the fasted growing, best monetized aspect of model aviation. It is well on its way to being the next X-Games.
For THIS kind of racing, or ANY kind of Acro Proximity FPV flight, you NEED faster, stronger, smarter ESCs than the ones you're working with.
If you look at the latest stuff that's out there, you'll see that we don't NEED huge ESCs with oodles of stacked FETs to drop the overall IR; modern FETs have 1/10th the on-resistance of the FETs in that old design. Added to that, they have a fast enough processor that they can actually turn the ungodly high E-RPMs modern 14-18 pole motors need to max out on small, high-pitch props to OR to pull bigger props on 4S-6S.
RS2K is the guy who made OneShot125 happen, and he's the guy writing MultiShot. He's one of those FFF adrenaline junkies; he loves 6S and 6045s. I think he's nucking futs; it's all I can do to keep 4S and 5045s in the air. ;)
This is how ESC Response data is collected and summarized into statistics.
- The upper line shows when the command to change throttle was given, which starts the clock.
- The lower line shows real thrust.
- Each vertical line clocks 200 ms.
- The data collection rate is 100Hz
- An up or down cycle completes in about 5 to 20Hz depending on the rotor and voltage
- To get accurate statistics, 251 cycles of an up and 251 cycles of a down command are logged and averaged
- A 3rd order polynomial is then sent through an x/y plot of thrust change versus time
- The commanded change is about 250 net grams (grams after it moves the ESC first, thus ESC weight is a penalty)
- The evaluation point is when 80% of that command is achieved or 200 net-grams.
This is a typical chart showing how thrust changes with time (0.02 s = 20 ms). As one can see, despite our best wishes, nothing happens on the Mega Hz scale (a million Hz or 1/1000 of a ms). It's not until milli-second range, 0.01 seconds, that one can see a noticeable impact on thrust, but still only 5ish% of the commanded thrust change. The reality for those that subject themselves to hype.
Note that the blue line, Throttle Down, reacts faster than the red line, Throttle Up. So was this a spectacular demonstration of active braking?
Unfortunately for the hypees, this is passive prop drag reacting faster than the up stroke of a fairly good size motor. When i've tested ESCs with active braking, i can see it on the charts. But not on the thrust chart. Only on the volt chart as battery takes a quick charge and V spikes. By the laws of physics, there has to be an impact on thrust. But it apparently is extremely small relative to prop drag. As the technology matures, i'll keep checking. I know I'll see it someday. As a note, FPV Racer props are extremely high in drag. My efficiency ships, however, run lower drag carbon props so i think i'll first notice it there.
With this data, one then does two things:
1) calculate acceleration over the first 200 ms (in this case 4.53 g/ms^2 on up and 4.64 g/ms^2 on down)
2) calculate how quickly it achieves 80% of a 250g change in thrust (in this case 16.7 Hz on up and 19.3 Hz on down)
Hope this provides FPV Racers a bit of a reality check.
As a side note, 5Hz appears to be about the minimum for controlled flight in light winds when the ship is well made (mass close to the center of the prop plane for ease of rotation).
way too much fun ... what they need is a durable ship :-)
Yeah... well... a lot of us have settled on the ZMR250. It's cheap as beans, supports 6" props and 22xx motors stock, and is essentially disposable at ~$20 if we buy the China direct versions.
They're made of 'glas with a CF skin and are actually quite a bit more durable than 100% 3K CF twill. I've flown mine into steel lightpoles and concrete at full throttle... 30-40 MPH... and it survived with a chunked corner or cracked top plate that's still serviceable. The weight penalty is 25-30 grams over 100% CF.
When we get good enough to need the lower weight and higher rigidity of 100% CF, we have a number of trustworthy vendors we can go to for a 100% 3K CF twill version at about $35-45 depending on options. Several of them have taken up the mantle of design improvement; We have inverted H and true X versions that are really popular with the Hyper FFF crowd.
Multirotormania.com is run by a friend of mine and he's a regular on the ZMR250 thread; one of the most popular on RCG. He developed the Zeus20A/FVT LittleBee 20A ESCs that are still one of the benchmark ESCs for racing, and right now I'm building a MRM250 V3... the third version they've released since we started way back almost 3 years ago.
We've got good gear for cheap; because you can't buy experience. ;)
We know that if you aren't crashing you aren't pushing your limits, and you need stick time to get good. You can't do that if you're replacing a $150 frame every time you break something.
Really... these little quads are more fun than DisneyWorld. And a lot more bang for the buck. :D