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Old Dec 15, 2012, 03:39 PM
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Choosing motor

Im about to order stuff for a hexacopterbuild. I am getting a ATG 750-X6 frame
http://www.omgfly.com/index.php?main...tfnbev61pk5cg6

Not sure what the total weight will be but I will be using a 3S 5000 lipo, 10x4.7 GWS props and it will carry a Nex 5 camera.
Im looking at motors. Does anyone have experience with the motor below?

http://www.hobbyking.com/hobbyking/s...00kv_380w.html

I wonder if that would be a good motor or if I should look at something else?
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Old Dec 15, 2012, 04:17 PM
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You must rethink the setup.
The total AUW must be about 1900 grams to hover at 50% throttle with this setup.
Removing motors, ESC, battery and other known weight items from the total, you remain with the 600 grams for the frame that must include the NEX camera too ! Mission impossible !

What should be the right approach:
- you should plan to use the biggest prop you can on this frame. For a 750 hexa they are 13"
- with this prop size in mind, you should search the a good 28 sized motor, these 35 class are too much, why you need 380W motors, when the power drawn by each in hover is under 50W ? Also, you gain at least 100 grams from a better chosen motors. What exactly is the search criteria: the optimal RPM for the required trust, and lowest idle current you can find. btw, based on last criteria, the 1.5A idle current of the NTM is an offense to global warming power waste galore...
- well. right RPM... crunching some numbers, we found that the best combination would be a 750kv / 13" prop or 850kv / 12" prop, both offering you the luxury of 1200 grams weight for empty frame and NEX together. This could be any 2830/2836 motor from rctimer or other manufacturer, and the total AUW will be a bit over 2kg.

The efficiency difference is spectacular too: 12 minutes hover from you intended lipo, versus 6 minutes for initial setup.

Also, as a sidenote, the gws props could break at this load, consider something more resistant.
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Old Dec 15, 2012, 04:27 PM
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Originally Posted by RENATOA View Post
You must rethink the setup.
The total AUW must be about 1900 grams to hover at 50% throttle with this setup.
Removing motors, ESC, battery and other known weight items from the total, you remain with the 600 grams for the frame that must include the NEX camera too ! Mission impossible !

What should be the right approach:
- you should plan to use the biggest prop you can on this frame. For a 750 hexa they are 13"
- with this prop size in mind, you should search the a good 28 sized motor, these 35 class are too much, why you need 380W motors, when the power drawn by each in hover is under 50W ? Also, you gain at least 100 grams from a better chosen motors. What exactly is the search criteria: the optimal RPM for the required trust, and lowest idle current you can find. btw, based on last criteria, the 1.5A idle current of the NTM is an offense to global warming power waste galore...
- well. right RPM... crunching some numbers, we found that the best combination would be a 750kv / 13" prop or 850kv / 12" prop, both offering you the luxury of 1200 grams weight for empty frame and NEX together. This could be any 2830/2836 motor from rctimer or other manufacturer, and the total AUW will be a bit over 2kg.

The efficiency difference is spectacular too: 12 minutes hover from you intended lipo, versus 6 minutes for initial setup.

Also, as a sidenote, the gws props could break at this load, consider something more resistant.
Thank you very much for taking the time to answer my question. Much appreciated.
Is there any partcular motor/brand you would recommend for my hexa? A link would be very nice
Can you recommend a good reliable propeller too?
Finally a question I have been trying to find the answer to for some time. What does the numbers stand for regarding motors. For example 2030, 2836?
Im sure I have read somewhere here on rcgroups but I cant find it again.

Thanks
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Old Dec 15, 2012, 05:01 PM
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What is budget ?

The numbers means usually a diameter and a length, two digits each.
What exactly measure these numbers is different from manufacturer to other. Some designates the external diameter of motor, other the diameter of stator, internal, must disassemble motor to measure it.
The length is more unified though, the stator / magnets / bell, are all the same or close.
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Old Dec 15, 2012, 07:19 PM
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Hi Renatoa,

I have been searching to get a better understanding of motors/propellers setup and avoid big mistakes for when I'm finally ready to go for a more expensive equipment. But ecalc seems pretty generic and sometimes is hard to find the motor/propellers combination I want to check. Specially when considering all the new pancake motors that have been realeased lately and most used props for AV.

Do you have any method for doing that manually?

I've been looking at motors manufacturer charts for best motor/propeller combo eficiency (g/w) at 40%-50% throtlle and trying to match that lift multipling it by the number of motors to make it equal to the total weight of the multirotor ready to fly.
Is this a good method?
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Old Dec 16, 2012, 04:31 AM
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Originally Posted by Velociraptor73 View Post
...But ecalc seems pretty generic

Aren't all physics laws "pretty generic" ?

...and sometimes is hard to find the motor/propellers combination I want to check.

Yeah, my friends call me Mr.Google... it's curious how I find relevant stuff others are unable to find using a search engine

...Specially when considering all the new pancake motors that have been released lately and most used props for AV.

About the prop is simple, each has a constant, labeled "Prop Const." , 1.11 for APC slow fly. Thrust is directly proportional with constant.
You can switch to custom prop, and play with that constant as you feel right.
If you check the several 6-7 props listed in the eCalc database, you will see this constant varies only slightly, between 1.09 to 1.18, excepting some exotic props. Also an exception would be GWS for me, they are too weak and limited to 8000 RPM mostly.

The new pancake motors... well there is no change formulas are the same.
Not the form is the major difference, but the magnets / pole count. This increased 24/28 number versus the standard 12/14 means you can obtain the same thrust at lower RPM/kv. But for the thrust what is important is the RPM, not how is obtained.


Do you have any method for doing that manually?

When I have motor data, I switch to Custom motor and input values. If not, I try an estimation with closest motor I can find.

I've been looking at motors manufacturer charts for best motor/propeller combo eficiency (g/w) at 40%-50% throtlle and trying to match that lift multipling it by the number of motors to make it equal to the total weight of the multirotor ready to fly.
Is this a good method?
If your final result will be close to mfr data, yes. But practical result not always match the mfr numbers. My current motor is very good for $23, at 11g/W, but I wasn't been able to match the mfr data of 13g/w. The setup was different than mfr, though. eCalc itself has a warn about the 15% precision of results, nothing is absolute in this field.
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Old Dec 16, 2012, 07:10 AM
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Thanks a lot Renatoa!

If I can get 11g/w I will celebrate! If I get that with $23 I not even know what I would do, apart of flying more, of course!
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Old Dec 16, 2012, 07:15 AM
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uh, forgot to specify which motor AX2810Q 750kv (because there are available 900kv too)
9A in hover from 3S, 1150 grams quad, 12" props.
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Old Dec 16, 2012, 07:32 AM
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The Hobbyking AX2810Q?!
I was curious about it as someone was asking about them on FY680 thread!
Are they well balanced from factory and with good bearings?

Another doubt I usually have is regarding results in flight and hover time. Just did a calc and got under 5mins for flight time but over 32 for hover! Would be the ideal the closer i can get them or just worry for fligh time data?
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Old Dec 16, 2012, 08:03 AM
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Not THAT AX2810... I buy almost all from different sources than HK.
That price is fake and is an attempt of HK to do his dirty business, as described in a rant here.
I got mine from bevrc, free shipping because order was more than $200.
Can be found at HiModel too. Different prices than HK, but real, they sell, unlike HK, who will not get other batch from manufacturer, he was been warned.
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Old Dec 16, 2012, 04:25 PM
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Originally Posted by renatoa View Post
What is budget ?

The numbers means usually a diameter and a length, two digits each.
What exactly measure these numbers is different from manufacturer to other. Some designates the external diameter of motor, other the diameter of stator, internal, must disassemble motor to measure it.
The length is more unified though, the stator / magnets / bell, are all the same or close.
I would prefer to not pay more than around $30/motor. Reading through your replies above, would you recommend this for my build?
http://www.bevrc.com/ax2810q-kv750-h...otor_p413.html

I also looked at HK. Would these two also work do you think?
http://www.hobbyking.com/hobbyking/s...50kv_140w.html

http://www.hobbyking.com/hobbyking/s...50KV_265W.html

I would also be really glad if you or any one else could recommend a good brand of propellers instead of using the intended GWS.

Thank you
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Old Dec 16, 2012, 07:06 PM
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Goofy68, as renatoa just told us, stick to AX2810Q on 3S with 12x6 and you should be very well set. I wish I had this tip before.
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Old Dec 17, 2012, 04:07 AM
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Yeah especially not NTM... I seen a set of four breaking bearing next minute after first takeoff. And their idle current is awful.

If you want cheaper, check the rctimer 2836 880kv, sold at HK as D2836 950kv. $12-13 both sources, free shipping at rctimer, and spare bearings available.
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Old Dec 17, 2012, 11:51 AM
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Originally Posted by renatoa View Post
Yeah especially not NTM... I seen a set of four breaking bearing next minute after first takeoff. And their idle current is awful.

If you want cheaper, check the rctimer 2836 880kv, sold at HK as D2836 950kv. $12-13 both sources, free shipping at rctimer, and spare bearings available.
Ok, thanks for your help
Now on to look for propellers
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Old Mar 30, 2014, 06:20 AM
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I want to upgrade ax2810

Hi everyone,

I have tarot fy680 hexa.
I want to upgrade my ax2810Q-750KV motors, what kind of motors should I buy ? sunny sky , turnigy, ect.

I use it with Gopro and tarot 2d gimbal. I want to be able to fly with Canon 7D in the future. is it possible by upgrading motors?


Any suggestions?

thanks

Tarot FY680 Hexa
ax-2810Q-750KV motors
hobby wing flyfun 30A ESC
11x4.7 CF props
DJI Naza M V2 GPS
zippy compact 5800 x2 4s
FPV
Gopro hero 3 with tarot 2d gimbal
auw 3,5 kg
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