the 7,4 inch pitch is even less than of the included 22x10 wooden props.
those propos would need to spin even faster to produce the same amount of trust, they would be even louder!
(mentioning this because of you mentioning the loudness in the other thread)
I’ve seen videos of large quads using props with really wide chords and lots of taper. The taper mimics a high aspect ratio reducing tip vortices while the wide chord pushes more air. Something like that might not need to spin faster even if the pitch is less.
This is what I was thinking also. It’s not your conventional prop pitch. It’s like a hybrid. I would try them if there was a way to mount them but I think we will need new prop stand offs so you can screw in these carbon fibre props.
Here’s company with some nice small props, i’ve emailed to see if they have cw/ccw in 22’’ that we can test.
I’m wondering if we used a rubber gasket between standoff and the prop, if that would have enough grip so the prop doesn’t slip…
They also have some nice wood props with swooped tips with apparently less noise…not sure what the A/C stand for, hopefully cw/ccw. I will buy and test if this is the case.
So desert aircraft is dealer of Xoar props, they sent me link to their props. If you look at the 22x8 propeller specs they tested using 150kv motor and 80amp esc. So pretty close to our setup. I’m really interested in trying this type of prop if can mount. Do you guys think a rubber washer will hold the prop in place on the stand-off?
Interestingly they also have same prop in wood with more pitch options, it looks like they also have a swoop tip design to them.
Didn’t see that post shoot okay. Guess we will need new standoffs to use carbon fibre and if there isn’t much notable difference in performance and sound. What really needs to be done is a bench test setup to test thrust and dB with various props to find the best one. Or have custom prop built for our use.
I might try these wood Xoar props as they look well built with different profile vs the gemfan. Two of my gemfan are already broken at the tips and I didn’t hit anything, it’s like they are self destructing after only 2 flights.
I also had a couple broke right out of the box. I went through 16 props while I was learning to fly and I didn’t have covers to protect them.
I have to thank @etienne for demonstrating how to repair props, I now have 8 repaired ones that work great! Wooden prop repair
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Propeller tip speed is the biggest noise factor - somewhere I picked up that noise pollution is the the lowest when tip speed is under 550 km/h
I made a sheet to see where we are at level flight (36A each motor) and climbing (80A each motor)
Take the numbers with a grain of salt…
22x8 props will be the noisiest and actually will not work for climbing if the batteries are not full!
22x16 props would be theoretically great, but they will have prop stall with this huge pitch and
need a lot of torque power as well!
22x14 with KV180 12S could work if you don’t go over 80% throttle or you burn the ESC’s!
Not a lot of room to get less noise and gain more efficiency…
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We’ve been displaying telemetry data from the ESC which includes amps, RPMs, and volts. Here are some actual RPM values during flight:
36 Amps = 5100 RPM
50 Amps = 5700 RPM
60 Amps = 6000 RPM
80 Amps = 6700 RPM
Tip speed calculates to:
36 Amps = 334 MPH (537 KPH)
50 Amps = 373 MPH (601 KPH)
60 Amps = 393 MPH (632 KPH)
80 Amps = 439 MPH (706 KPH)
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I was reading a review from the electric Paracell Simplify with the 130 cm Helix prop and the RPM’s
are indeed way lower but as I said before the biggest contributor to noise pollution is tip speed:
The tester said under 500 km/h tip speed the noise level is way way lower than any 2 stroke unit.
At level flight he had 1700 RPM = 418 km/h tip speed - almost noiseless
At climbing he had 2700 RPM = 662 km/h tip speed - sure noisy
So I still think to reduce the noise, the tip speed has to be under 550 km/h…
The test team confirmed they couldn’t hear the electric ppg at 150 meters distance
at level flight and barely at climbing.
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I contacted Mejzlik about carbon fibre props. The technician recommended 22x7.4 pitch for our setup for the best efficiency. They have cw and ccw. He said they also have wood spacers available to use for mounting to keep the prop from free spinning on the prop mounts. It’s too expensive for me to try though.
How did he came up with this?
With this pitch they are noisier at level flight then 22x10 at full throttle!
You will lose 20 % flying time!
The thrust is not enough for people over 160 pounds for climbing…
Yes thats what I said, that it will be even louder. Here is what he said about this prop and our specs:
“If the flight speed is only 11 m/s , I you can go for 22x7.4 propellers. You will need at least 3600 RPM for reaching 11.1 m/s ( 40 kmph). And with 160 KV and 47.6V you will be able to reach ~ 5000 RPM loaded.”
You can’t calculate speed without knowing drag. This isn’t a quadcopter… it’s human flight. We need to know thrust values.
But GliderPilot, we DO know speeds already. The wing manufacturers all post the trim speeds of their gliders. Plus or minus a knot here and there due to variations in the loading. Heavy fat pilots through to skinny little blokes in their faired harnesses. A quick check on my phone shows 11m/s is around 21knots. Sounds about right for brakes off trim speed.
I said that wrong… speed doesn’t mean anything without knowing the drag and therefore the thrust required to get that speed. A company that makes drone propellers wouldn’t necessarily know the best prop for PPG without knowing the required thrust.
The very fact that he’s referring to airspeed in choosing props is reassuring IMHO. On a quadcopter, unless it’s acending or descending, there is no airspeed in the plane of thrust. What the guy does know is Available voltage, volume and rate of still air approaching the prop (airspeed) and Motor kV. From this he’s calculated the pitch which will provide the most thrust in the 3500-5000 RPM range. This will not be the quietest though, merely the most efficient.
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I received my Batch4 - accidentally Paul sent me the wrong props. Since I will use the KV150 motors with 12S batteries the 22x10 will not work with my weight. The thrust would be only 100 pounds.
There is a OpenPPG owner in GB (180KV/12S/22x10props) who was on a real PPG thrust stand and they measured just short of 130 pounds thrust. This is pretty good since the Paracel one prop electric with 15KW motor (short time19KW) has as well 130 pounds thrust.
Since I need more thrust I came up with my own custom 23x13 props:
Theoretically they should work out great:
From the wattage use I would be pretty close to a one prop electric PPG. From the prop tip speed it could even be less noisy. Unfortunately I will not fly before end of October - I’m looking forward how it will work out in real life!
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