Carbon fiber props and interference

alokbhargava · Dec 21, 2015

Wibble said:
Ok for people who laugh off theories without keeping an open mind. It is a known problem!

Measuring the Effect of Helicopter Rotors on GPS Reception
Article Abstract

For instance
,
when a GNSS receiver is placed near rotating bodies
,
the signal undergo complex and non-stationary effects
called Rotor Blade Modulation (RBM).

Thank you.

The example you are quoting here is of a single rotor heli with GPS receiver minuted underneath or close to it. It's behavior will be totally different than of multi rotor system as we have in P3. In a single rotor helis the GPS radio signal is affected by metallic blades and effectively a signal is injected whose frequency is related to the rotor speed. The problem in such cases is that the amplitude of this modulating frequency signal is very high and needs special design to filter it out. In case of multi rotor system, the effect of rotating blades is very small if the GPS receiver is mounted in the center as is the case of P3. Also as the rotating blades position is not considerable higher than the GPS receiver, the influence of rotating blades is thus negligible on the main radio frequency signal. Did you notice that GPS receiver is positioned at a relatively higher position?

Secondly, the DJI cf blades are not fully metallic, their influence is further reduced.

SportPilotAviation · Dec 21, 2015

A coat of paint may insulate the highly conductive props from the air and maybe be the cure. Worth a try. Thanks for the heads up!!

alokbhargava · Dec 21, 2015

SportPilotAviation said:
A coat of paint may insulate the highly conductive props from the air and maybe be the cure. Worth a try. Thanks for the heads up!!

No, it won't. But we don't need to do anything. I have been flying with DJI cf props with abs no issue.

SportPilotAviation · Dec 21, 2015

Thanks, I've been wanting to purchase a set. Any make you recommend? Does DJI offer them? I've seen aftermarket CF props On several sites. Thx.

alokbhargava · Dec 21, 2015

SportPilotAviation said:
Thanks, I've been wanting to purchase a set. Any make you recommend? Does DJI offer them? I've seen aftermarket CF props On several sites. Thx.

Use only DJI props

Timritchieblue · Dec 26, 2015

I use 3rd party C.F. props. Had them hanging on the wall for ever, decided to try them out. I like them, more lift, feels more prosaic control. These are the blu, and red top props off of eBay. Work very well.

alokbhargava · Dec 26, 2015

Timritchieblue said:
I use 3rd party C.F. props. Had them hanging on the wall for ever, decided to try them out. I like them, more lift, feels more prosaic control. These are the blu, and red top props off of eBay. Work very well.

Use them on your own risk

TnHwyman · Dec 26, 2015

steves said:
I recently purchased carbon fiber props for my P3P . I took it out this afternoon and noticed it wasn't acting quite right. It seems to over adjust four Wind and it wasn't as responsive as before. I'm not talking about just the attitude from the props I'm talking commands from the remote control. It seemed to have a mind of it's own. I had an extremely hard time landing because it would jump from side to side. Initially I thought it was my IMU calibration. So I took it in recalibrated and tried again with no luck. The only other thing that has changed was the props. So I've put back my old stock props and wouldn't you know it flies like new.

I have only used either the stock or the 9450 carbon reinforced props on my unit. Both have served me well. Could one or more of the props you used be out of balance?

Timritchieblue · Dec 26, 2015

alokbhargava said:
Use them on your own risk

Do you have any personal experance with these? I got 6 full flights oit of them. I think i might lose a minute of run time, but gained 2 mph.

Badfinger · Dec 26, 2015

"I do wish DJI offered the stock material props in black, as well as a black version (faux carbon fiber look) of the P3 (including controller)."

Just remember black props are invisible when spinning and have bitten a lot of fingers!

alokbhargava · Dec 26, 2015

Timritchieblue said:
Do you have any personal experance with these? I got 6 full flights oit of them. I think i might lose a minute of run time, but gained 2 mph.

I do not know which props you are using and have no experience with them. I know one thing that motor-prop torque speed characteristics are very important for it to work optimally with ESCs. It would be a guess in wild that third party propose will work satisfactorily. Choice is yours.

alokbhargava · Dec 26, 2015

Badfinger said:
"I do wish DJI offered the stock material props in black, as well as a black version (faux carbon fiber look) of the P3 (including controller)."

Just remember black props are invisible when spinning and have bitten a lot of fingers!

CF reinforced props by DJI are not true Carbon Fiber props, you can use them if you like black colors. I had heard that they are redesigning them to have better performance.

Meta4 · Dec 26, 2015

alokbhargava said:
It would be a guess in wild that third party propose will work satisfactorily. Choice is yours.

The big issue with third party props (apart from not being what the escs etc are designed for) is that they almost certainly don't have a composite hub designed to deal with the stresses of dynamic braking. Ordinary metal threads are not recommended for P3 props.

Silverwingflinx · Dec 26, 2015

I have used Dji CF props no problems they need to be balanced yes

Keith Lampman · Dec 27, 2015

Use only DJI E305 9450 Carbon Fiber Reinforced Props, they have the composite hub. Do not use the metal hub ones, of course all props need to be balanced........

Timritchieblue · Dec 27, 2015

Does anyone have any PERSONAL bad experiences with 3rd party C.F. props. 9 flights now, and still flys better than stock props. I doubt these are true C.F. as the cost was $9 for a set.

Keith Lampman · Dec 27, 2015

Timritchieblue said:
Does anyone have any PERSONAL bad experiences with 3rd party C.F. props. 9 flights now, and still flys better than stock props. I doubt these are true C.F. as the cost was $9 for a set.

I would worry about the "Hub" Loosening or cracking on 3rd party, but hey, if you like 3rd party I wish you all the luck on your $1000+ machine