Custom Power Train - TMotor P80, 80A ESC, 26", 12S

Power System
21

Hello, I recalculated.

With a 26 / 8.5 propeller 2 blade, a speed of around 4200 rpm is necessary in order to be able to fly the paramotor. you need 44 V and about 31 A if the motor efficiency is 90%. The speed at a pitch speed is around 7 kilograms at 54 km / h. (These values apply to a high performance motor.)

That means for an eppg you would need at least 6 such motors to reach at least 42 kg thrust. With a current consumption of 186 A.
The circle diameter is at least 2.2 meters!

That would be the most efficient solution arithmetically without the resistance of the big system and the zero efficiency areas such as propeller midrange and mutual vortices losses.

One can then proceed from about 186 A / 38 kg thrust (losses taken into account) of 4.5 -4.75 g / w.
Therefore not useful and airworthy with big ring 2.2 meters.

If 8 drives are used, of which 2 each are mounted in opposite directions, around 230 A will be necessary for a 50 kg thrust and the diameter would be around 1.8 meters. Whereby there are turbulences in very close together mounted counterflow systems that destroy a lot of power. It would also produce a balance of about 4.4 - 4.6 g / w.

Also not useful and airworthy with 1,8 meters.

You can change the system in different values ​​like more or less pitch or different speeds. However, it would reduce the efficiency of the motor and thus bring no improvement.

All these values ​​are mathematical. The tests were done many years ago and they confirm the calculated values.
Everyone can calculate their degree of efficiency themselves:

Examples: Power requirement 15 kw, thrust 55 kilograms = 3.66 g / w
Power requirement 10 kw, thrust 50 kilograms = 5.0 g / w
Power requirement 16kw, thrust 82 kilograms = 5.12 g / w
Power requirement 17 kw. Thrust 95 kg = 5.58 g / w

(The last example is my current trike with the brand new 150 cm 3 blade propeller.)
Conclusion: it confirms the thousands of times confirmed values in the aviation of ultralight, aircraft, paramotor, e gliders that the approximately 3.5 to max. 6.5 g / w are fact. why can it be the mathematically good g / w values for multikopters such as eg. 19 g / w arise. This is simply explained because these computational values emanate from a very low air acceleration. If a drone rises with an example 10 meters per second, the value is in the direction of 5.0 g / w!

1 Like
22

Ok let’s go best case scenario and work backwards from there. Drone motors in the range of 100kv and 5kg max thrust can operate at 17g/w, and at 10g/w.
This difference can purely be from variancy in motor manufacturers. That is a good indication of what technology can provide us in this day and age.
What’s the stall speed of a good paraglider?
Or should I say slow enough with a decent L/D.
I would work off that, then find a prop around 35".
Coaxial would be nice to avoid because of efficiency reduction, but those numbers I showed you don’t lie.
If you can get a big prop spinning slowly, with low incoming air velocity, your 20 year old data is going to be surprised.

P.S. As I understand it, you can design a prop for the standard cruise speed. I can’t see much difference in performance loss if the incoming air is only 40k/hr.
Not 15 all the way down to 6.5 g/w anyway.

23

i think it is better everybody do what he think ist the best way go flying.