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.
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.
Hi guys i started this thread back in Mar . hoping this would be a promising motor for us but after reading the comments not sure if it is now. I fly a QUAD and was looking for an electric conversion .It takes about 85lbs of thrust to maintain level flight . After some number crunching a came up with the idea to mount 2 M40 motors on the front of the unit so it would be like a twin engine QUAD one on the left side and one on the right. I looked at the efficiency numbers at low throttle settings at about 15% throttle setting they claimed about 11g/w and thought wow this is super efficient at that throttle setting and if i ran 2 motors at the same time i would have about 45 kg of thrust to fly with and only about 50 amp draw for 2 motors. I thought this seemed to be to good to be true and hesitated on purchasing and the Covid came along and i never did purchase the motors. I had my friend convinced and we were going to purchase 4 motors and 4 controllers. I sent MAD an email asking for current draw and thrust data for various props they tested and never got a reply. That would have been a costly very disappointing order.
It seems to me that the receipe to make a cheap ePPG is to take as many components from main stream markets such as ebike, eboat, ecars…
So let’s say:
-M40 motor or equivalent
-More resonable battery pack than 24s (too exotic, a bit dangerous and bring high price when it comes to the BMS and ESC) instead lets say a 16s or 20s like these one
A few things. First, you will need at least 3 of those batteries to handle the current required. that equates to a minimum of $2160 in batteries. There is less than $1300 worth of cells and bms systems in those packs, so if possible just make your own.
Also be really careful with those cheap ESC’s. Most of the time they cant handle weird fluctuations of current in these very large motors.
I must be missing something, according to the previous comments I understand flying an e-ppg takes “around 4.2 to 4.5 kilowatts” (I guess this is peak) so on a 72v battery pack it takes only 62A.
Which one of this kind pump-up ebike battery could handle.
Am I missing something? why would get in the trooubles of sending 200A in M40 motor to achieve 70kg of thurst when 20kg seems enough?
I’m new to e-ppg and only did a couple of flight with combustion ppg, but I built some other electrical stuff like eboat and ebikes and I am an electronic engineer with some spare time. So once I’m up to speed with your knowledge I would like to help to make a really afordable way to fly.
During takeoff and the initial climb most people want somewhere in the range of 100-130lb thrust which equates to something in the range of 12-15kw of real world power usage and they often need to hold it for minutes at a time. Also the cells being used in the battery pack(Panasonic nrc18650ga) don’t handle high currents well for very long without overheating and loosing efficiency. So in my opinion even 3 packs may be pushing it depending on your style of flight, location(elevation and terrain), and wing size.
The thing to realize about flight is that the boundary between the ground and the air is the most critical. Getting off the ground and to a safe height is a very challenging problem and continues to be a limiting factor. It’s a shame to have to spec an entire system around 1% of its operational envelope, but getting that wrong literally means a crash.
The upshot is that you want to climb hard and fast to an altitude at which you have breathing room. Once you’re there you can throttle back and enter cruise mode. But getting there is a slog, and it’s a long enough slog that you can’t assume peak power is different from steady-state power. By the time you’ve run your batteries/ESC/motors for 60-180 seconds, you’ve gotten pretty close to steady-state temps.
Yes I agree this is such a waste to dimension a system for 1/60of its use time! Wait… a very large discharge current is needed for a very short period of time… It sounds like a job for a supercapacitor! The supercapacitor will be used as an energy buffer when you need a current boost, and could be recharged in flight when you are not using the engine at full capacity.
To do a quick approximation:
@Bob27 said that we need full power of 15kW for 1 minute
let’s keep for the demonstration my basic ebike battery that can provide alone 4.5Kw
so the pre-charged supercapacitor needs to provide a boost of 10.5Kw for 1mn. this is J= 1000x10.5x60 = 630 KJ
-A commercial super capacitor can hold 54 kJ/kg (15 Wh/kg https://en.wikipedia.org/wiki/Supercapacitor)
630 KJ / 54KJ/Kg = 11Kg so You will need a 11kg today commercially available supercapacitor to do the job, too heavy but research in supercapacitor are going fast way faster that lipo battery capacity improvement.
But some research talk about energy density of 110 Wh/kg that should in our case be in a near future a super capacitor of about 1kg could help to reduce drastically the size/weight of the battery pack. No wonder why Tesla bought bought Maxwell a supercapacitor company for 218 Millions
Wow that took them a while to post it. I knew about the M50 a long time before even posting the previous comment. The one thing I didn’t know is that there is a 40kv version which should provide more usable rpm for a sub 60 inch prop.