Replies to This Discussion

Permalink Reply by Andke on April 28, 2012 at 6:53am

do yo know a place to find suggested prop/motor combination for 4 cell use ?

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Permalink Reply by Todd Hill on March 7, 2012 at 8:41am

@jani, the iBM4006Q looks very promising.  I have been working with larger diameter motors for the last year on my builds.  They are simply more efficient and produce less noise/vibration.  They are much more versatile than motors that have smaller diameter, but longer stators.  I have had no issue with over heating ESCs' or motors.  I am turning 14"APC slow fly props on my MT3506 motors on 3 cells.  Wind is an issue though with this setup, but it can be easily alleviated by switching to 12" APC slow fly props and 4 cell pack (only small adjustment in PIDs').  If you start stocking the iFlight motors I will surely buy some to give them a try.  The thrust to weight ratio for these motors are hard to beat given their current draw. 

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DeveloperPermalink Reply by R_Lefebvre on March 12, 2012 at 3:07pm

One potential negative point to these motors, don't they have significantly higher inertia, and thus slower response, which leads to a reduction in stability?

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Permalink Reply by Todd Hill on March 12, 2012 at 4:45pm

These type of motors simply have a higher thrust to weight ratio, plus it takes them less force to produce it.  As far as stability goes that depends in large part to the motors resolution and the ability of the flight controller.   Because of the higher number of stators and magnets these types of motors generally have a higher resolution .  From what i have experienced the APM is fully capable.  

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Permalink Reply by Ron Curry on April 6, 2012 at 8:08am

Hi Todd,

I have similar results with larger props and larger diameter higher torque motors. Makes a significant difference in noise, efficiency, and stability. As you found I predicted they would be a bit less stable in high wind because I saw the same thing with traditional single main rotor helicopters when I decreased the RPM and increased the rotor diameter. Everything is a tradeoff of course. For quick maneuverability you want small rotors turning fast for flight endurance and efficiency you want big and slow.

Anyhow, I just built an Octo with the MT3506's and I'm having an issue related to the motors starting and loosing sync. Reading through RCGroups I'm finding that a lot of people are having the same problem. I found that with simonk ESC firmware they have a hard time starting and severe sync problems and with stock ESC firmware they are better when I choose "High" timing but still fall out of sync on rapid RPM changes (like in turbulence) so they are unusable. What ESC's are you using and have you experienced the sync problem at all?

BTW, to add to your answer to Rob, larger diameter motors trade off RPM for torque because they have more torque they compensate for the small amount of higher inertia and have no penalty in terms of reaction time. THe only real penalty is when using larger props because there is a larger disc area for the wind to push on which is why they are more sensitive to the wind that's why the 12" props work better in that respect but then you have to go to 4s to make up for the lift reduction..

Thx,

Ron

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Permalink Reply by Todd Hill on April 29, 2012 at 11:34am

Hi Ron,  You don't need the Simonk firmware or special ESCs' to get the most out of the MT3506.  I have used several different ESCs' on these motors.  For me the best have been the turnigy AE 20A ESCs' and the Blue Series 30A ESCs'.   I always leave my ESC timing on Auto or low timing due to the low kV ratings of the motors I use.  How many ESCs' have you tested on this motor?  

Same results here with the prop and battery findings.  12*3.8 SF props and 4 cell lipo are best match for all around stability and performance with these motors.  

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Permalink Reply by Victor Brewer on April 1, 2012 at 1:25pm

actually it's now up to 88 min flight time check the website

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ModeratorPermalink Reply by Hai Tran on April 28, 2012 at 9:44am

That don't impress me much.

If you don't carry a 500g gimbal and 1kg camera, that's 1.5 kg of extra battery that can be carried that will extend flight times.

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