Co-axial 8/ flat 8 stability problem

[Bartman]

i'm not sure why I'm being excluded from the conversation here.....

a 15 lb heli on six motors and 15" props sounds like a marginal arrangement to me. would it be possible to get answers to the questions asked above?

 

[DucktileMedia]

@BART.....Does this imply that there is a limitation for weight based on number of motors? I was wondering if you could make a heavy lift Y6. Given you have 120 deg of spacing you could attach some seriously large motors/props. From what I have read/learned it seems the bigger issue is the heli's ability to compensate in real time with fixed pitch props. The larger the mass of the prop, the less responsive it is. Even if your motor has the torque to accelerate quickly, it doesnt want to slow down quickly. We've seen tests of variable pitch helis react instantly in comparison to fixed pitch. So in making an ultra large quad or hex, why is it any different having fewer larger motors than more smaller motors? I'm guessing the mass of the entire object acts to help stabilize things as well. but I am no aero engineer so I dont know where these factors balance each other out.

 

[SleepyC]

i'm not sure why I'm being excluded from the conversation here.....

a 15 lb heli on six motors and 15" props sounds like a marginal arrangement to me. would it be possible to get answers to the questions asked above?

Dude, my Hex has 15/5 T-Motor props and Avroto 3520’s and can fly all day at 25 lbs. (which is 13 lbs payload) At 21lbs for the review the motors were pulling 58-62% according to the blackbox readings.

 

[Bartman]

i think your 3520's are a very different motor from the MN motors he's running. what KV are your 3520's?

yuri, there's a limitation based on what the motors/props can produce. when the motors are maxed out then there's nothing left for the flight control to use for control. wobbles, yaw deviations, delayed control response are the symptoms of being maxed out.

 

[DucktileMedia]

That doesnt really address what I was asking. thats a whole other aspect of being weighed down. I'm saying you have motors that are more than capable of lifting the weight but are in fewer numbers versus the same lift capacity with more motors.

 

[SleepyC]

400KV.. designed for lifting. And yea, I agree his motors may be taxed a bit.

 

[nickwad]

i'm not sure why I'm being excluded from the conversation here.....

a 15 lb heli on six motors and 15" props sounds like a marginal arrangement to me. would it be possible to get answers to the questions asked above?

Sorry for late response , the DJI S 800 running dual batteries , Zenmuse Z15, Sony Nex 5/7 with downlink iosd etc is over 7kgs and it flies !

 

[nickwad]

If it flies it vibrates and there is only so much you can do. You need to be holistic about this and if you have done all you can do to reduce vibes then there is nothing wrong in changing the mounting pad- look at all solutions. Changing pads in not necessarily a band aid approach at all although IrisAerial does have a point if you have not looked at every other issue. Some pads work well at some frequencies, and other pads at other frequencies or at least this has been my experience with flybarless sensors on my SRs. I have used bog standard double sided 2mm tape and anti vibe pads from Spartan who make Vortex Flybarless controllers. If one of these isn't good the other always has been for me.

I agree with this statement as vibration is all about harmonics and frequency so changing the firmness of a mounting pad could help , I will try that next on the X 8 which is the machine I have the stability problem with not the S 800 Evo.