How did you come up with that number? Seems awful low…
If you have an all up weight of 225lb and an overall 8:1 glide ratio you only need 28.125lb thrust or roughly 12.6kg thrust to fly. (225*1/8=28.125)
8:1 is awfully optimistic. A lot of A wings won’t even do that with a free flight harness. A 6:1 or 5:1 L/D is more realistic for a PPG setup. Obviously this is all theoretical, but if you design your motor setup assuming you’re going to get an 8:1 L/D in flight you are going to end up disappointed.
That would be with a very large and high glide ratio wing to keep you minimize drag from the frame. With a realistic size wing you won’t get an 8:1. Even if you did go with a 6:1 glide ratio your still looking at only 37.5lb thrust needed. I do believe many modern wings have a glide ratio over 12:1 so with a VERY large and low speed wing you could even see higher than 8:1. It entirely depends on your frame and wing.
Here is some of the older specs on one of the 2010 ish paracell paramotors.
It says that it uses equal power to basically 22kg static thrust to maintain altitude. Moving at 20mph it would be about half that thrust at that throttle level. If you also look at the thrust table you have above, they are maintaining altitude with only about 2,850 watts power. I would never expected to achieve those numbers. Honestly they would have needed to use thermals or had a VERY light person flying it.
If you go through and look through every current high end paramotor on the market, the current trend is that you will get an hour of flight with as low a 3.7kw up to about 4.3kw used power with a big wing. It entirely depends on the power system, weight, pilot, wing, humidity, altitude, temperature, and dozens of other factors. Don’t take me wrong. The chance of getting that low of a power consumption is very small and requires everything to be perfect. The point I’m trying to show is that it doesn’t require that much power to fly.
this is an old video from 2018. here i had a standard propeller (e props 751) and needed around 3.4 kw for the level flight. 85 kg pilot, wing 26 m2. (total mass 120 kg) the static thrust is 3.4 kilowatts at around 21 kilograms. today i fly with my impress 3 setup with around 3 to 3.1 klilowatt in the level which is then around 18 kg static thrust. With standard e-ppg around 4.2 to 4.5 kilowatts are necessary. all the values apply to optimized concepts (esc + motor) for 14 - 15 s batteries. many think a high-performance wing would bring much more performance. yes, that’s only true in one point. you have more kilometers because you can fly faster with the same electrical performance. the sink is pretty much the same whether EN-B or EN-C. you just fly about 10 to 15% more kilometers in the route. the more power you use when climbing, the more inefficient the whole thing becomes. A paraglider loses performance due to the angle of attack as a braking effect is created. therefore glide and performance calculations of normal aircraft are not correct here with e-ppg.
From minute 19 onwards you can see how consumption is with a standard e-ppg concept. here it is a rotex motor Rex 30/4
Be extremely careful with that table. According to the full table from https://mad-motor.com/product/mad-torq-m40-c30-pro-kv43/, they have invented a perpetual motion machine. The output power (
rpm * (2*pi/60) * torque) is greater than the input power (
V*A). This shows that something is terribly off.
The motor looks interesting, but we need a damned good explanation of why they fabricated data.
Well, it looks worse than just fabricated test data. Check out a teardown at Electric PPG - ONE motor project -.
I was interested so I ran the math myself.
Hp = RPM x torque / 5252
48.61Nm ~ 35.9 foot pounds
3710rpm x 35.9ftlb / 5252 = 25.36hp
25.36hp = 18,918 Watts
18,918watts / 18,884watts x 100
My first thought is that the torque measuring device is inaccurate. Whatever sensor is inaccurate, its only about 5% off.
I know that Open PPG has worked almost exclusively to get there motors from MAD components and I believe that the open ppg motors are fairly high quality. Also everything I have heard about them points to them being a fairly reputable company.
That’s a good data point. It can lead to a restoration of confidence, supposing there’s a good explanation.
The devil’s in the details when it comes to high-power, high-efficiency motors. Heat is a huge killer, and a few percentage points of efficiency can represent thousands of watts of waste heat. That’s the difference between full power for 180s and full power for only 30s, which itself is the difference between being high enough off the ground for safety and, well, not.
Thermal issues arising from motor losses can lead to having to spend tens of thousands of dollars, or even a failed project (ask me how I know). So it’s not a non-trivial hand-wavey thing for them to get wrong.
There are many ways to have arrived at the wrong numbers, however all the published values are off by basically the same margin. This points away from miscalibrated test equipment and toward someone consciously manipulating numbers, possibly by using measured test data to calculate the rest. So maybe they got RPM, Voltage, and Current-- all very easy to measure-- and backed out torque from that.
And this is such a terrible mistake it’s hard not to argue that it burns a reputation for forever. This isn’t their only webpage where this is happening. You don’t publish fraudulent-- or even overly optimistic-- numbers when you’re at this cost and power level. These things aren’t toys, these are part of safety critical systems. People can get really badly hurt or development projects can be sunk. In the best of cases, you buy the motor and you wind up being burned and disappointed (like @ITGlider).
Not saying they deserve to fail as a company, but I would say that without an incredibly good explanation (careless intern, fired employee, previous management, etc…) that I could never trust them in the future. Otherwise, you’re left wondering what else they didn’t come clean on. Bearing life? Bolt strength? Demagnetization temperature? Winding insulation thickness, consistency, and melting point? All those things are not academic when it’s our silly butts on the line (and hopefully not on fire)!
On the motor tear down, I would like to know a few more things. I am no professional on these modern large scale motors as the only brushless motors over 15kw in power I have dealt with are around 10 years old.
First of all how old was the motor? He said he was on of the first to buy one in Europe. I do believe that the 80kv M40 model is one of their oldest models that hasn’t been redesigned and because of that its not even on their website.
There are some things that I am really concerned about. the main thing being how they balanced the motor. I feel like there should be a better way to do it. On that size of motor bearings could also be a concern but when it was built for large scale drones that use very light weight propellers I am not too concerned.
I would like to point out the price. If you are comparing it to say Hacker, Rotex or Geiger the quality may be lower but the price is also a ton less. You get what you pay for.
MAD components does have some better motors for paramotor use such as the 50kv and 43kv M40 motors. Both of the motors are physically bigger than the 80kv model and can handle a lot more power and torque. Also both of those new motors have bigger bearings.
I have recently ordered one of these bigger MAD M40 motors and it is too late to cancel the order. I will be interested to take it a part and look at it myself and probably post some pictures to the form. I know that the mad M10 motors have performed well on the Open PPG X4 and I believe that the prototype MAD M50 motor has also done well on the SP140, so I will keep my fingers crossed that it will be a better motor that what @ITGlider ended up with.
Agreed, and if it weren’t for manned flight then maybe I could look the other way. After all, I never believed any of the motor stats I got for drone motors. Somedays it feels like everybody in that field is lying or overstressing stuff. Like “25A” ESCs that look like they’d melt down on a spring day in the sun, or “100C” batteries that sag at 10C.
But when the price includes my life, I’m a lot stingier to pay. Suddenly an extra $500 for a Rotex doesn’t look so expensive.
I’m excited to hear how your MAD M40 works out. Just because they’re overselling doesn’t meant they’re not making quality products. It only means that we can’t trust their word. If testing shows the efficiency and performance is there, then that’s what really counts.
What I most want is to do a long term test and efficiency test. I am confident I can get the thrust I want out of it, but will it hold up?
For those of you with an Open PPG unit- Has anyone had a motor issue or know anyone who has?
My MAD motor came in the mail less than 30 minutes ago. So these are all initial impressions.
Everything but the shaft looks very nicely machined. Just looking at the top of the shaft, the star shape is just a little bit off. I don’t think it will impact anything, it just could look nicer. The winding is nice and uniform, the wires have nice protective covers, and it has a really cool way to get rid of the heat.
As for the company itself it has responded to all my questions quickly before and after I payed for the motor and the shipping from China took about a week and a half from the time I ordered it.
Could you go into more detail on this? I’m really keen to know if it can dump all its heat all full-power. That’s challenging but not out of reach.
That’s really great! I had reached out to them via Skype last week, but so far have had no response. I suspect that their Skype account isn’t continuously monitored. How did you communicate with them?
What does it weigh? Is this the 2.8kg “lightened” version done by “Cedar Anderson form electricparamotoring of Australia” (a name I could only find on MAD’s website)?
I contacted them through Alibaba. Most of the time they respond anywhere from a few minutes to a few hours. The longest it ever took for them to respond was less than 24 hours.
I tried to show a picture of the internal cooling but it’s not very good. Basically imagine a brushless inrunner RC car motor with a heat sink on it. Then you flip it instead out. So the center of the motor has cooling fins which you can sort of see in the image. Then air is pulled through the internal heat sink and blown out these vents which are shown below. It wouldn’t surprise me if there are other motors with it, but I have never seen it.
I got the model that weighs 3.5kg. I chose that model because it is more efficient, it has bigger bearings, and I believe it also has a third bearing as apposed to the 2.8kg motor which has 2 bearings.
I also figured the larger size would help it keep cooler during flight.
Thanks for the clear description, it sounds like a great solution. Is it basically relying on a centrifugal fan to draw air up from the base and expel it from the holes in the ring at the top?
With such a system, it sounds like if you needed extra cooling you could have a small mister with just a few mL of water. Water’s latent heat of evaporation is enormous-- 500 times higher than its specific heat-- so a very fine aerosol mist (like from a ultrasonic humidifier) could have a possibly decisive cooling potential. If you had the motor running at 100C and needed to cool it down urgently, 1g @25C would suck up
(.001 * 4186 * 75) = 314J +
(.001 * 2256000 = 2256J) =
2570J. So if the motor is 90% efficient, and you’re running a full 15kW, you have 1500J/s of waste heat. That’s a little more than half a gram per second of water cooling.
With batteries running at 10C for max power, that’s only 360 seconds of runtime. The upshot is that 180g of water would theoretically supply all cooling needs for an entire flight.
Did you get efficiency numbers beyond the ones published on the above-linked pages?
I was thinking of limiting full throttle to around 130-140 lb thrust. Under optimal conditions I think I can get 130lb thrust with 16ish kw power using a 51 inch 3 blade. Under that full throttle load if I can keep the cells cool, I think I will get around 3.1kw from the battery I will build. So with all that in mind, I think I could get around 12 minutes full throttle.
This whole thing is an experiment so it will be interesting to see what I can actually get.