Paul,
You had mentioned that the SP140 was flexible for different configurations to choose quietness vs power. I quite value the quiet aspect. At one point you did a video where the prototype was extremely quiet. I am assuming you had a larger prop like a 150 on there.
Can you please tell me what prop and any other configurations that would be needed to get that quiet configuration?
Thanks.
Have you checked if a 150cm Prop would fit in the cage at all?
As far as I know there is no 150cm high pitch Prop from E-Props specific for the SP140, but other Props like the 150cm 2-Blade Prop for the AirConception Tornado should give you similar results (although the pitch is slightly different).
I doubt that 150cm will be significantly more silent, because engine noise should not be the major part for E-PPG in contrast to ICE engines at higher RPM.
If you do run test and create measurements then please share your results!
The frame used in that video what a different frame that was designed for a 150cm prop. Also the motor was running at a different rpm then the current motor so the prop used before wouldn’t be very good.
I thought this was as all (rpm) to be configurable with the ESC (sans the frame). Did that turn out to not be the case?
Not sure what your saying but there is still a max rpm for the motor with a given voltage.
the frame is different also.
Perhaps I misunderstood. That was a completely different motor for that version?
I was actually wondering about a shorter blade prop, 130 or 135. Are they available and how would that change things?
Heh, its not too much to ask to get some sp-130’s and sp-150’s right? 
So what kind of static thrust could be expected from that 150cm prop, and at what rpm? People do say that most of an electric paramotor’s noise comes from blade tips approaching mach threshold, and so the longer the blades are, the more noise you can expect.
Just curious - is there any link to that video of the 150cm prop? Would just be interested in seeing it.
At a given rpm, the 150cm prop would probably be louder due to the higher tip speed. On the other hand, at a given thrust level, a 150cm prop could be quieter because you may not need as high of an rpm for the given thrust level.
basically correct that more blade length has more tip speed and is theoretically louder. but since less pitch is necessary, the air is less “shredded” 2 that means the efficiency increases overall with eppg as long as you don’t want to fly much faster. if you want to fly faster with a small reflex wing, a 150 cm propeller is too big at foot launch because the eta curve goes down again. 140 cm is often the maximum and the best choice when starting from the foot.
What kind of rpm would 150cm have compared to 140cm, if you want to reduce noise?
page 21: https://elib.dlr.de/109278/1/Hepperle%20-%20Elektrisches%20Fliegen%20-%20Stuttgart%202015.pdf
Anyone try a 150cm tri blade prop? EProps made a few 150cm tri blade props that will fit.