I had a 2kw direct drive working but a custom ESC and custom prop. It’s all about prop design I think. It blew up a lot. Direct drive is hard.
That’s a big prop for a direct drive. Jezza what motor are you going to use?
Yeah it is quite large, I spun it up in a bathtub (outdoors) yesterday and it cleared the water in about 10 seconds. What I really need to do is run it for about 2 minutes and see what the heat dissipation is like. If the prop is to large, I can cut down the diameter on my mill so that’s easy…
Working on the edge , propeller with tongue area off , increase front pitch a bit , hand made no balancing… Will see this evening …
All i want is +400rpm
Good luck!
I think if you reduce the chord of the blades, you must also reduce their thickness evenly over the whole blade, or you change the aerofoil by making it too thick. That may make the blades stall earlier? Compounded because you reduce their reynolds number too.
Another thought might be cut outer most 10mm off, repeat until you get what you need…
thank you, i cut the all tongue area and i reduce the tickness over 2/3 of the blade trying to keep the same angle curve … so yes i guess a change everything and it worked well:
- no numbers (my usb data cable let me down, just order a new one)
- a lot less thrust: less fun but easier to ride when standing up
- speed , not less not more, feel the same
- rpm and amp when a get my cable
i have a few propellers, so now will test by just reducing the diameter
left original, right modified (diameter, thickness, wide…)
it seems that this part of the blade gives the thrust at low rpm:
brentsinger,
Appreciate the math!
How can motor resistance values listed in motor specs be used in initial design calculations? For example, the TP5870 @290kV lists an Rm=0.0426
(Note: corrected TPMotor model number–thanks Alexandre)
I think you meant tp5870 , you can use the tp56 they are the same and less expensive
As i understand you will loose rpm at the end but not that much with the size of motor
The math will be appriciated as well 
Thank you
For the story of this post , all the modified solas propeller worked but i was not able to get higher rpm just less amp
I changed for a smaller high pitch propeller : less thrust , more speed even more amp and always the same rpm
Alexandre,
Yes, TP5870–good eye!
Unless my calculations are incorrect, the TP5870 @290kV would have 60% greater torque than the TP5670 @394kV?
Correct but the 5870 is the same as the 5690 same power same size ( can with for car ) but cheaper
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good job! thanks for your full analysis.