If I was looking to launch from between 4,000 - 10,000 and fly up to 12,000 would different props start to be a good idea?
I just tried to figure out how the new 150 KV motors will workā¦
This is the original 180 kv 12s version:
This is the new version 150 kv 14s:
And this is the 150 kv 12s version - looks like they have to use the 22x14 propeller:
There is a possibility that the 150 kv 12s version with the 22x14 props will be more silent and more
effectiveā¦ Maybe we need then really the 100 A ESCās!!!
If you want the higher pitch it would be best to lower the kv even more and stick with 14s. I agree the higher pitch would be more silent because you could use lower RPMs but not sure how that would effect efficiency. Thereās been a lot of talk on hear about using less pitch to improve efficiency but itās all been just talk because nobody has actually tested and reported. Lower RPM would reduce tip vortices but higher pitch would increase them so I donāt know which way the scales would tip here for efficiency.
Found this company they seem to have really nicely built props. I for one would be willing to spend $400 on a nice set of props that will last and be quieter. But i do think we will need new standoffs. This company says they will drill holes to suite the customers requirements for mounting. @Pdwhite
https://shop.mejzlik.eu/detail/propeller-22x74-p-3956
Perhaps we could do bulk order and get the price down, first someone should test a set.
I dont mind going in on a bulk order - - but not until I see some proof of effectiveness ā Say we get them down to 300$ for a bulk order ā I need to see 25% or greater reduction in noise and an increase efficiency to spend that level of money today.
I would suggest they be approached to see about a sample set for someone to do some testing with. I would through my 20$ in for helping someone willing to spend time to help test for the group.
Cheers
Yeah I totally get your point of seeing the improvements first and I agree, a test must be done. The thing to note too is these wood props are very weak, two of my props have nicks it the tips and one came cracked out of the box. They are not good props. If we stick with these we will spend more in replacement props over time.
I do think the developers of openppg should be finding a new solution as they are best to figure out the change in standoffs to work with carbon fibre props. Maybe they are already?!
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)
Iāve 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. Itās not your conventional prop pitch. Itās 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.
Hereās company with some nice small props, iāve emailed to see if they have cw/ccw in 22āā that we can test.
Iām wondering if we used a rubber gasket between standoff and the prop, if that would have enough grip so the prop doesnāt slipā¦
They also have some nice wood props with swooped tips with apparently less noiseā¦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. Iām 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.
Tried it and it didnāt work: Carbon Fiber Prop Bulk Order - #39 by jrsimple
Didnāt see that post shoot okay. Guess we will need new standoffs to use carbon fibre and if there isnāt 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 didnāt hit anything, itās 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 didnāt 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
1 Like
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 saltā¦
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 donāt go over 80% throttle or you burn the ESCās!
Not a lot of room to get less noise and gain more efficiencyā¦
2 Likes
Weāve 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)
2 Likes
I was reading a review from the electric Paracell Simplify with the 130 cm Helix prop and the RPMās
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/hā¦
The test team confirmed they couldnāt hear the electric ppg at 150 meters distance
at level flight and barely at climbing.
2 Likes
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. Itās 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 climbingā¦