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.
obviously not enough coffee this morning :-(
your brain waves are way ahead of me so obviously i missed your main point. so what i did was put the ESC under the prop and then took it away from under the prop and measured recorded thrust in both cases.
..........OH!!!..... just woke up ... you mean does the thrust output from the rotor also change. So i need to risk my life again? Geeezzz.
But this is a great point. Props benefit from ground effect. Is there a measurable benefit from something like an ESC close to the underside of a prop? That's worth checking ... and risking life and limb :-)
Done. Looking at 100 observations each, a 2.5 g improvement with the ESC under the prop. I'd put a portion of that amount down to measurement error as we are talking less than 0.5% of the thrust.
if i had to guess, i'd say that the ESC has 1ish gram of drag with 0.15ish grams of lift for a net of .85ish g loss ... something like that.
That was fun!
does someone have one they can send me? i'm seeing back ordered.
Oopps ... before you write you might want to read. Further back is this link:
1) Net-Lift Efficiency (nothing that FPV Racers care about)
2) Maximum Net-Lift (what impacts acceleration of the ship when you floor it)
3) Responsiveness (how fast thrust is developed)
Ground effect start to matter at around 1/10 wingspan from the ground.
In ground effect the motor and propeller would spin faster and produce more thrust for the same power input than normally.
The side area of the ESC is so small and the inertia of the motor and propeller so great that it's unlikely that the ground effect would have any effect.
agree ... like how many angles dance on the tip of a needle? the number doesn't exist or is small.
didn't know about the 1/10th. interesting. have a reference on that?
Most of the arguments here about thrust being blocked by the ESC under the prop overlook the fact that thrust is being blocked by the arm anyway. Is the ESC wider than the arm? Not standing on edge. Is the ESC less aerodynamic than the arm? Yes, but is that enough to bother measuring???
Here you go -->
Source, page 382 -->
Ah ... that's entirely different. Thanks for clearing it up.
This is what we were talking about.
There is a difference between a pilot feeling ground effect versus the ground effect being there as a percentage of lift. You can see this when lifting off. At about 10% of a prop length you see "feel" the ship start to glide in the prop wash. But, closer to the ground (within limits) the stronger the prop wash effect.
To understand this consider the following cases. And think about taking off slowly with your multicopter and how you work the throttle.
- If stationary at 10% of prop length from the ground, then that means that the ship is at a specific RPM or throttle and wattage.
- If stationary at 50% high relative to prop length, then that means the ship has to be at a higher throttle, RPM, and wattage.
- It follows from experience and logic that the above chart is correct. We all know from experience if we very slowly throttle up, that if at 1% prop length from the ground (hard to do), then the ship is at a lower throttle, RPM, and wattage. Otherwise, it would be impossible to stabilize a ship at 1% rotor height because the ship would just magically rise if ground effect got stronger at 10% rotor height and then rise more until .... you get the idea.
Percent increase in rotor thrust is not to be confused with drag reduction caused by ground effect. So i guess we were talking about different things. Thanks for the education and reference on drag reduction.
It's not different. A rotary wing is still a wing.
If you decrease the induced drag (load) then the motor RPM will increase and so will thrust.
There's also an increase in lift (thrust) really close to the ground.I really don't see how what you said is different from what was said in my source.
agreed. i'm just saying, maybe differently, that it takes less RPM, throttle, and watts to hover at 5mm (5%) than 10mm (10%) when using a 100mm prop. so we agree on that?
Congrats for the Arizona Open, any video? :)
somewhere ... no idea where
but here is Martin flying in Arizona having a little fun with catus and tumbleweed ...