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:


- Multistar

- Turnigy

- T-Motor

- Afro

- Motortron

- Quattro

- 3DR

- Spider



- Aris


- AutoQuad

- Exceed

- HobbyWing

- Lumenier

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.

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could you provide me with weblink to BLACK BOX ?

What data are recorded and saved ?

Is individual RPM saved for ESC with RPM sensor ?

Sponsor. That is an offer I'll make to other professional racers that have earned their stripes by winning a major FPV race or freestyle.

I don't care if you are pig-headed or arrogant as long as you are willing to try to improve the sport through testing various designs that:

- accelerate faster than anything you have flown before

- are more durable than anything you have flown before

- are disciplined in your approach to winning

The goal is to create a ship that can out-fly anything humans can control and survive when its pilot crashes into a concrete wall at full speed.

My purpose is simple. Get manufacturers of ship bodies, VDEPs, ESCs, motors, props, controllers, cameras, gimbals, transmitters, receivers, and video output devices to improve their technologies faster.

So if you have a friend that wants an anonymous sponsor, have them friend me.

The same goes to manufacturers that I also work with gratis and anonymously to help them improve their products directly.

 Sure, It is in the Beta Flight and Cleanflight software. Most of the F3 and some others like the naze 32 version 6 have onboard storage for black box. You can see it on the Cleanflight site also. It is a very very useful tool. It will show your input from the radio and will show all the things going on in the multirotor. You can configure your transmitter to turn it on and off.

Sorry I hadn't read the whole thread and had you re-post your wire size spreadsheet. Would you consider smaller wires for the AC side of the ESC? These wires would be very short since the ESC resides under the props, the wires themselves get better cooling, and there are 3 wires to carry the current rather than 2.

i apologize ... saw the question before and forgot to answer it.

wires need to be the same size. only two wires between the ESC and motors carry DC current at any given time so same as the input side of the ESC.  

interesting point on the cooling. you are right, cooler would result in lower wire temp and thus less resistance. The difference, however, would be less than a fraction of one wire size. So keep them the same size.

to save weight, i use magnetic motor wire. it is epoxy coated and thus weighs quite a bit less than the thick silicone or rubber insulation. on a FPV ship, however, use regular insulated wire as they take a lot of abuse and the distances (weight) doesn't result in much savings.

Another question. I don't want to mount my ESCs vertically. What do you think about mounting them FETs facing down against the aluminum arms, with heat conductive tape between, and the shrink wrap around the ESC and arm. The ESC will be mounted outside of the propeller arc, but the aluminum arm will get lots of cooling.
I am concerned that some of the FETs on the edge will not touch the aluminum since the ESC is wider than the 20mm arm. I also need to be careful about shorting out the ESC on the arm.

PS. Did you test the stock 20A 3DR ESCs? I have ten of them and they could also be stripped down. I'm wondering if the efficiency savings is significant enough to warrant swapping them out.
Paul, thank you for the pilot report. I'm running 8x 2216-850 at about 4KG like you said. It should only pull about 10A per motor but need headroom to continue in the event of a motor failure.
My goal here is efficency and reliability. I know you don't agree with Forrest's assessment of ESCs for racing, but for endurance he seems to make a solid argument that the 100g extra thrust from the subject ESC outweighs it's extra mass.

Are there any changes that should be made in BLheli to accommodate for low KV motors?

Brilliant to put the heat tape between the FETs and the Al arm and then wrap in shrink tape. just make sure nothing conductive on the FET side contacts the metal. I'd go the extra mile and put electrical tape around the arms under the ESC leads.

The 3DR ESCs are good. Use them. Unless you are trying to set a world record, you won't notice a difference.

P.S. I love it when people think outside the box. You put a big smile on my face.

Well,... I have to jump in at this point. Darius has his point here! What Forrest did is against any ...norm of electronics. Lets start from the beginning - What are the Al heat sink for?! To quickly suck out the high junction temp. The thermal conductivity of AL against air is magnitudes apart and as one poster said before is all about speed at which the temp. gets eliminated from the junction. And here the Al is perfect. Well Cu would do even better job, but the price would be prohibitive.

So once the thermal current is eliminated from the junction by "large" AL heat sink, comes the air. And heat sinks are large because the air is the problem here!! Because of the air's bad thermal conductivity. That's why we need large "radiators". And Forrest wrongly said that eventually AL heat sink have the same temperature as a FET core - allegedly because of a bad heat sink! NO! The air is the problem. To have the same thermal dissipation without a proper heat sink you need more air flow, thus more propeller wash. But the propeller has other job to do not tu cool your poorly thermally managed ESC!

I got the same idea though, but with a Intel NUC board. Well to "spray it" and sink it in a water coolant :-). But you see no AIR! So it is doable.


Good point! At least Darius has some backing-up from leading experts in the field (Fairchild of course is one of them!). I have the same problem with Mr. Forrest. Please, Forrest do not use such bombastic titles! And no matter how much I love one man's ingenuity, try to stick with what is already discovered to be good and scientifically proven. Don't invent a hot water, and don't use  a kitchen knife for puling carrots out of dirt. There are other tools to do so :-)


I do appreciate your effort. In a matter of fact with every discussion we learn something - in one way or another. 

What I don't understand in your article is what qualifies one ESC to be better than other? For me this is the best: (Herkules III 3-6s Brushless ESC OKTO XL). So for what type of "bird" is your ESC the best? For my 10kg bird... I don't think so. And one thing that no one mention in this discussion: What about 40A running through a 2mm wire? Really? Wire Gauges (AWG) Current Ratings

That kind of wire would support 15A at max.


Nice test-stand! I love the fact that you put it vertically. So the in-flow as well as the out-flow are unobstructed. Very nice job. Thumbs up!

That would be a good material for a discussion :-)

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