T-Motors vrs Axi

[crcr]

I'm looking to build a Droidworx Skyjib lite X4 and trying to decide on the best motors to use.

Most seem to be using the Axi motors 2820/18 that have a KV rating of 670. I'm wondering if anyone has used the T-Motors and how good are they compared to the Axi motors?

Thanks

 

[ovdt]

I'm looking to build a Droidworx Skyjib lite X4 and trying to decide on the best motors to use.

Most seem to be using the Axi motors 2820/18 that have a KV rating of 670. I'm wondering if anyone has used the T-Motors and how good are they compared to the Axi motors?

Thanks

AXi definetely has better quality. I've used Axi 2814/22 on my Hexa and have been super happy about it.

I'm also using Tiger motors extesively, MT2814-10, MT2820 KV830, MT2826 (KV550) and now waiting for some MN series.

MT2814, came with orginal Ezo bearings but I believe they are so sensitive to dust or to any small force applied. Changing them to a better one helps; but this also costs.

MT2820, I had to change my all six MT2820 bearings after a hard landing. When changing the bearings, I noticed that the bearings were no-named. But the replacement bearings sent by Tiger Motor had Ezo brandings on it.

MT2826 has three bearings and quite a powerful motor. I'm happy using this. I would go Tiger MT2826 route with 5S or 6S setup.

 

[crcr]

Thanks for the info.

The 2826 motors are quite a bit heavier than the others, about 440g total over the Tiger 2820 (830kv). What size props would you recommend for the 2826 motor?

Do the Axi motors have 3 bearings?

Thanks

 

[ovdt]

13" or 14" props with 6S will work good on 2826. I don't recommend you to go with Tiger 2820 830KV, it's only suitable for 4S. Too high RPM for 5s or 6s.

 

[crcr]

Just been searching and I see they also do a 2826 760kv, but I can't find specs about weight etc.

What motors did you get in the MN series? for an octo?

 

[ovdt]

Do the Axi motors have 3 bearings?

Thanks

AXI 2820 and 2814 have two bearings. Don't know the AXI 2826.

 

[ovdt]

Just been searching and I see they also do a 2826 760kv, but I can't find specs about weight etc.

What motors did you get in the MN series? for an octo?

I'm getting MN4014 and MT3520. Both of them are KV400. You need 6S for these motors.

What camera will you put on the SkyJib X4? Lets make a ecalc calculation with different motor and prop combos.

 

[Aviator]

I haven`t had any experience with Axi motors but have been using tigers, and can say they are of very good quality and I haven`t had any issues with them...

 

[crcr]

I'm getting MN4014 and MT3520. Both of them are KV400. You need 6S for these motors.

What camera will you put on the SkyJib X4? Lets make a ecalc calculation with different motor and prop combos.

I will be using mainly 550D with sigma 10-20mm (1kg) but also may lift 5D.
AV200 (590g),
Skyjib lite X4 with retracts (not sure of total weight)
and looking at either 5s or 6s setup with DJI.

Thanks

 

[ovdt]

Okay, lets see the options:

These figures are for MT3520 (KV400). This is very similar to MN 4014 400KV in terms of efficiency and performance.

* Weight without components (Only frame, gimbal and camera) is 4400 grams. I'm sure it will be less.

So with 6S and 15x5 props, we will hover around %50 throttle, which is nice. If you have a lighter payload, you can either switch the propeller to 14x4.5 or use 5S Lipo. Changing prop is more reasonable when the costs are considered.

MT2826 can be overpowered with 6S, it's good for 5S if we look at the figures. MN4014 or MT3520 is good to go. Don't forget to buy spare bearings, at least 4 sets.

View attachment 8357

 

[crcr]

Thanks heaps for doing that. What calculator do you use for this?

You don't happen to have a higher res image of the above by any chance do you? its a little hard to read.

You mention the MT3520, are you meaning the MT3515? They have a AT3520 for airplanes.

Thanks
Craig

 

[rsun]

http://www.ecalc.ch/xcoptercalc_e.htm?ecalc

 

[ovdt]

MT3520 is a better motor than the MT3515, it's listed here:

http://www.rctigermotor.com/show.php?contentid=174

On ecalc, just select MT3515 and then manually edit it. And change the internal resistance to 0.03.

Here is the higher resolution:

http://imageshack.us/f/831/screenshot20121220at748.png/

 

[crcr]

Thanks heaps for all your help. Really appreciated.

Do you think ecalc is on the conservative side, or are the flight times pretty close to actual?

Do you know anything about the Tiger ESC's? just thinking maybe it would be best to get their 40amp ESC to go with the motors? I have also been looking at the Plush and Maytech.

Cheers

 

[ovdt]

Yes, pretty close. But should assume the flight time between flight time and hover time. Because you will not with %100 power all the time.

I have no experience with Tiger ESCs. I would go for solid ESCs which are SimonK flashable. Turnigy Plush is also flashable with a similar firmware called BLHeli and users who tried BLHeli claims that the difference is night and day.

You can check out this table:

https://docs.google.com/spreadsheet/ccc?key=0AhR02IDNb7_MdEhfVjk3MkRHVzhKdjU1YzdBQkZZRlE#gid=0

Hobbyking F series supports 16 KHz PWM timing and external oscillator. These are hard to find.

Another problem is, for instance F-40A ESC supports 6S but f-60A doesn't. Be sure to check out their voltage range. ( http://www.hobbyking.com/hobbyking/store/__18966__Hobby_King_40A_ESC_4A_UBEC.html )

Another option is to go with CC ESCs. Theri multirotor firmware is reported to work quite good. CC ESCs have better quality for sure.

I haven't started my tests with MK + I2C converter + SimonK / BLHeli flashed ESCs so I can't say anything more for this matter.

 

[Droider]

CRCR

My SJLX4 weighs in at 5kg witn no batts, 7KG with 2x8000mah 5 cell. carrying 1100g flight time 12 mins, AXI motors as per my thread and 13.6.5 Xoar carbon props, lift off at about 48% throttle. AND if you really give her gas its fooookin scary. Nuff said.

Ecalc is OK if you want to do things not done and with no other reference but I stopped using it an age ago and just rely on my and others experience.

Ill be posting a more in-depth report of my SJLX4 build over the hole but right now it is beating all my expectations after the initial hiccup over batteries I had.

DAve

 

[crcr]

Hey Dave

The SJLX4 is the machine I have in my sights. Basically exactly the same as yours but was wondering if I could get more flight time by going to 6s? which means I can't use the the Axi 2820/18 motors that you are using. This is why I've been looking at the Tiger motors with 14 or 15" props.

I just don't know anyone else at this stage that's running the SJLX4 on 6S.

@ovdt,

I will have a look at that table.

I'm currently using Plush 30 esc's with MK FC and without any flashing and its been working fine for me. But with the new build I'm going to use DJI and not sure about which ESC's work best?

Cheers
Craig

 

[crcr]

@ovdt

Just wondering how you're getting on with you new MN4014 and MT3520 motors?

I'm so close to ordering the 4014 motor but as they are a lower profile I'm not sure if having the top and bottom props closer together with effect to efficiency of the X4?

The Axi 2820/18 motors are 48mm in length and the 4014's are only 34.5mm. So over both motors that's 27mm difference.

Thanks
Craig

 

[Ultra7]

Seems ovdt got his motors and went hiding into the hills... :upset:
Shame, I was looking for some help with those motors too!