Master Airscrew props/Vibration

[RadioFlyerMan]

I am experiencing what I consider unnessary and excessive vibration from the Master Airscrew props. This is in reference to a Mavic Pro Platinum with landing leg extensions.

This all started when I noticed the left landing leg was cracked at the base. I was dumbfounded as to how this happened! I have flown over 350 flights with absolutely no crashes and bad landings. And I know I have never banged into the door on the way out. I am obsessively careful with my Mavic. The only thing that changed was I had switched to the Master Airscrew props during the last 30 flights or so.

After fixing my cracked leg with cyanoacrylate glue, it crack again on the next flight with MAS props. So I fixed it again and then switched back to the DJI 8331 props. No more cracking after my latest 10 flights. So yesterday, I switched back to the Master Airscrew props to see what would happen. It cracked again after one flight. Ah Ha!

So I did a little experiment (should have done this earlier). I have included a link to my YouTube video with my observations.

Your mileage may vary, but my observations are:
1) Master Airscrew props exhibit a greater vibration than the DJI 8331 props. Visually and by touch.
2) With leg extensions, the Master props MAY cause structural cracks in the legs. Without leg extensions, probably not.
3) The reason for the difference in vibration level may be many things... imbalanced prop... different architecture... bad batch? I do not have the right instruments to balance a prop. However, I shouldn't have to.

Bottom line, the Master Airscrew props will probably be OK for most drone configurations. For me, I'm going back to DJI 8331's. Try the touch test yourself and make your own determination.

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[Former Member]

I have a bunch of Master Airscrews I need to test. Thanks for posting this.

 

[Thomas B]

Great info. Is there a way to identify the lot#, manufacture date,etc. so the end user can identify and test other batches similarly to discover if this is true of “all” or just a few / one batch?

 

[RadioFlyerMan]

Great info. Is there a way to identify the lot#, manufacture date,etc. so the end user can identify and test other batches similarly to discover if this is true of “all” or just a few / one batch?

Most excellent question...

Here’s what I have. Maybe it will help.

 

[RadioFlyerMan]

I have a bunch of Master Airscrews I need to test. Thanks for posting this.

I sure would like to know what your findings are.

 

[iowahill]

Did I miss something here? I see no connection between a prop imbalance and a cracked leg extension unless there's a sympathetic vibration issue, in which case I'd be looking at the legs being the weak link.

 

[FoxhallGH]

I am experiencing what I consider unnessary and excessive vibration from the Master Airscrew props. This is in reference to a Mavic Pro Platinum with landing leg extensions.

This all started when I noticed the left landing leg was cracked at the base. I was dumbfounded as to how this happened! I have flown over 350 flights with absolutely no crashes and bad landings. And I know I have never banged into the door on the way out. I am obsessively careful with my Mavic. The only thing that changed was I had switched to the Master Airscrew props during the last 30 flights or so.

After fixing my cracked leg with cyanoacrylate glue, it crack again on the next flight with MAS props. So I fixed it again and then switched back to the DJI 8331 props. No more cracking after my latest 10 flights. So yesterday, I switched back to the Master Airscrew props to see what would happen. It cracked again after one flight. Ah Ha!

So I did a little experiment (should have done this earlier). I have included a link to my YouTube video with my observations.

Your mileage may vary, but my observations are:
1) Master Airscrew props exhibit a greater vibration than the DJI 8331 props. Visually and by touch.
2) With leg extensions, the Master props MAY cause structural cracks in the legs. Without leg extensions, probably not.
3) The reason for the difference in vibration level may be many things... imbalanced prop... different architecture... bad batch? I do not have the right instruments to balance a prop. However, I shouldn't have to.

Bottom line, the Master Airscrew props will probably be OK for most drone configurations. For me, I'm going back to DJI 8331's. Try the touch test yourself and make your own determination.

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I'm wondering about sympathetic and/or harmonic vibration too ... There is a condition where putting 8331 'quiet' prop's on a Mavic Pro, can cause gimbal shake. I'm wondering if the MA prop's are causing feedback sensitivity problems and oscillation due to them being a bit less forgiving than the DJI 8331's ... It's usually the gimbal that you see the shake occurring in - but - in this case, the leg-extensions are showing it. Also - it's interesting that the prop's are relatively steady in regard to rpm with the DJI 8331's on (you can see this is the strobed view of the prop' disks), but with the MA prop's - the motors are continually changing rpm.
I'd suggest that you use that same camera, on the same fps settings and take some more film of the drone from underneath with the MA prop's on i.e. from an angle wher you can see all four prop' disks. It would be interesting to see if it is one motor, a pair, or all - that's constantly doing the speed changes.
I'm using the MA (orange) prop's on my Mavic Pro Platinum, and it's the opposite. It's steadier than with the 8331 prop's on it - with no vibration that can be seen or felt. I've been using them in place of the 8331's for some time now.

 

[Mossiback]

I had to adjust my gain settings when I used the MPP props on my MP because of the gimbal shake error the MPP props caused. Perhaps this vibration is caused by the Mavic overcompensating for the more responsive props than a balance issue and can be fixed with a gain adjustment.

 

[RadioFlyerMan]

Did I miss something here? I see no connection between a prop imbalance and a cracked leg extension unless there's a sympathetic vibration issue, in which case I'd be looking at the legs being the weak link.

I am convinced the resonance frequency of the MAS props caused the failure of the leg. At hover, MAS runs about 300 rpms less than the 8331. And I believe that without the leg extension, the leg would not have cracked since its net resonance frequency would be significantly higher than the oscillations of the prop at around 4500 rpm. The moment arm of the leg with the extension is significant compared to just the leg alone.

I can’t prove it, but I don’t think it’s an imbalance. The molding of the components is as precise as an investment casting. Rather it’s due to the different pitch at the root of the MAS blade, combined with the prop wash over the arm.

Notwithstanding my speculations and theories, the amount of vibration just by feeling it is proof enough for me. Try it.

 

[FoxhallGH]

I had to adjust my gain settings when I used the MPP props on my MP because of the gimbal shake error the MPP props caused. Perhaps this vibration is caused by the Mavic overcompensating for the more responsive props than a balance issue and can be fixed with a gain adjustment.

That was my thought too ... There is a good (long but GOOD) video here that explains the cause and adjustment, and may be worth a try in this case ...

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[FoxhallGH]

I am convinced the resonance frequency of the MAS props caused the failure of the leg. At hover, MAS runs about 300 rpms less than the 8331. And I believe that without the leg extension, the leg would not have cracked since its net resonance frequency would be significantly higher than the oscillations of the prop at around 4500 rpm. The moment arm of the leg with the extension is significant compared to just the leg alone.

I can’t prove it, but I don’t think it’s an imbalance. The molding of the components is as precise as an investment casting. Rather it’s due to the different pitch at the root of the MAS blade, combined with the prop wash over the arm.

Notwithstanding my speculations and theories, the amount of vibration just by feeling it is proof enough for me. Try it.

You'll probably find that if you put a short toothpick through the centre hole of each opened-up MA prop' it will be perfectly balanced ... The problem you are seeing, may be due to the prop's being stiffer and more efficient than the DJI 8331's. The Mavic Pro is inherantly unstable and uses a feedback loop to make it stable. That feedback loop is very sensitive, but is tunable (as described in the video in my post #10 above). If the 'Gain' settings on the stability circuits aren't right, you can get a condition where the Mavic oscillates [minutely] back & forth due to each motor input being slightly more than needed to reach the stable point. This leaves the Mavic 'shaking' imperceptably, but at a frequency that has sub-harmonics that will make the gimbal shake in sympathy. It could be that the leg-extensions also have a sub-harmonic that puts them into oscillation due to the same sort of effect.
Just like with the standard Mavic Pro flying 'Quiet' 8331 prop's ... it's strange how most are OK, but some just don't like it!

 

[iowahill]

You'll probably find that if you put a short toothpick through the centre hole of each opened-up MA prop' it will be perfectly balanced ... The problem you are seeing, may be due to the prop's being stiffer and more efficient than the DJI 8331's. The Mavic Pro is inherantly unstable and uses a feedback loop to make it stable. That feedback loop is very sensitive, but is tunable (as described in the video in my post #10 above). If the 'Gain' settings on the stability circuits aren't right, you can get a condition where the Mavic oscillates [minutely] back & forth due to each motor input being slightly more than needed to reach the stable point. This leaves the Mavic 'shaking' imperceptably, but at a frequency that has sub-harmonics that will make the gimbal shake in sympathy. It could be that the leg-extensions also have a sub-harmonic that puts them into oscillation due to the same sort of effect.
Just like with the standard Mavic Pro flying 'Quiet' 8331 prop's ... it's strange how most are OK, but some just don't like it!

Very well explained! Guess I'm one of the many who hasn't experienced any issues in using two MAS sets. And only two because an earlier autonomous flight had a mishap and damaged two of the blades.

 

[RadioFlyerMan]

You'll probably find that if you put a short toothpick through the centre hole of each opened-up MA prop' it will be perfectly balanced ... The problem you are seeing, may be due to the prop's being stiffer and more efficient than the DJI 8331's. The Mavic Pro is inherantly unstable and uses a feedback loop to make it stable. That feedback loop is very sensitive, but is tunable (as described in the video in my post #10 above). If the 'Gain' settings on the stability circuits aren't right, you can get a condition where the Mavic oscillates [minutely] back & forth due to each motor input being slightly more than needed to reach the stable point. This leaves the Mavic 'shaking' imperceptably, but at a frequency that has sub-harmonics that will make the gimbal shake in sympathy. It could be that the leg-extensions also have a sub-harmonic that puts them into oscillation due to the same sort of effect.
Just like with the standard Mavic Pro flying 'Quiet' 8331 prop's ... it's strange how most are OK, but some just don't like it!

Brilliant! Makes sense. Thanks for that.
I’m a little challenged when it comes to the inner logic of Mavic control systems. Got a lot to learn.

 

[RadioFlyerMan]

So I can learn more about this effect, specifically what are the changes in the gain settings to be made to offset this control oscillation? I’ve never played with mine as I don’t know what their effects are on control.

 

[iowahill]

So I can learn more about this effect, specifically what are the changes in the gain settings to be made to offset this control oscillation? I’ve never played with mine as I don’t know what their effects are on control.

Watch the video that FoxhallGH linked up a few posts. That will explain how to find your optimal gain settings.

 

[RadioFlyerMan]

Watch the video that FoxhallGH linked up a few posts. That will explain how to find your optimal gain settings.

I was too quick to respond. I’ll watch it now.

 

[BossOlive]

I am experiencing what I consider unnessary and excessive vibration from the Master Airscrew props. This is in reference to a Mavic Pro Platinum with landing leg extensions.

This all started when I noticed the left landing leg was cracked at the base. I was dumbfounded as to how this happened! I have flown over 350 flights with absolutely no crashes and bad landings. And I know I have never banged into the door on the way out. I am obsessively careful with my Mavic. The only thing that changed was I had switched to the Master Airscrew props during the last 30 flights or so.

After fixing my cracked leg with cyanoacrylate glue, it crack again on the next flight with MAS props. So I fixed it again and then switched back to the DJI 8331 props. No more cracking after my latest 10 flights. So yesterday, I switched back to the Master Airscrew props to see what would happen. It cracked again after one flight. Ah Ha!

So I did a little experiment (should have done this earlier). I have included a link to my YouTube video with my observations.

Your mileage may vary, but my observations are:
1) Master Airscrew props exhibit a greater vibration than the DJI 8331 props. Visually and by touch.
2) With leg extensions, the Master props MAY cause structural cracks in the legs. Without leg extensions, probably not.
3) The reason for the difference in vibration level may be many things... imbalanced prop... different architecture... bad batch? I do not have the right instruments to balance a prop. However, I shouldn't have to.

Bottom line, the Master Airscrew props will probably be OK for most drone configurations. For me, I'm going back to DJI 8331's. Try the touch test yourself and make your own determination.

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I sent email and they responded.
They’re sending me a new set. Awesome service. Send them an email.

 

[RadioFlyerMan]

I sent email and they responded.
They’re sending me a new set. Awesome service. Send them an email.

Good to know and thanks for the info. However, I have come around to the opinions of the previous posts that it’s not a balance issue, and can only be corrected with changes in gain.

And notwithstanding all the science of gain, oscillations, etc. to smooth things out, I am giving up on MAS props as I see no overwhelming qualitative difference in flight characteristics that affect my ability to shoot videos. Lastly, I have a pile of brand new 8331 props that need to used up.

 

[FoxhallGH]

Good to know and thanks for the info. However, I have come around to the opinions of the previous posts that it’s not a balance issue, and can only be corrected with changes in gain.

And notwithstanding all the science of gain, oscillations, etc. to smooth things out, I am giving up on MAS props as I see no overwhelming qualitative difference in flight characteristics that affect my ability to shoot videos. Lastly, I have a pile of brand new 8331 props that need to used up.

Interesting - one of the reasons that I use the MA 'Stealth' prop's on my Mav' Pro Platinum, is that the hover is more stable with them on - as compared to the DJI 8331 quiet prop's. That must be helping the camera in that it will keep it steadier without the gimbal having to work. I did a flight duration test with 8331's and MA prop's one-after-the-other, and just watching the Mavic hover in my garden, with a cross-hatched trellis behind it - made it easy to see that the Mavic was compensating for a gusty cross-wind a lot easier with the MA prop's than with the DJI 8331's.

 

[NITEWULF]

Basically, as I understand it is the gain works like an amplifier for the IMU. The higher the gain is set the more sensitive it becomes. What goes against the conventional wisdom is that 100 is not the perfect setting. Lower the gain to 80-85 with the MAS props. The pitch is different than the one that DJI uses therefore you have to adjust the sensitivity for vibration and pitching.