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Mar 28, 2014, 02:16 PM
3D Printer Owner
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Question

Determining a new power system for this 3D printed tricopter frame.


Hello all,

I recently designed this awesome tricopter frame, and for the power system I just pulled everything off my old scratch quadcopter. The frame alone only weighs about 220g to 230g and measures about 660mm between each motor shaft. You can check it out here: http://www.thingiverse.com/thing:275915

The current power system includes the following:

With the 9x4.7 props I get about 15mins (12mins safe) of flight time, something I would like to keep. It also hovers at around 55%-60% throttle and struggles to catch a moderate fall, this is something I would like to change.

Preferably, I would like to keep my current battery, and upgrade whatever else I can to improve performance.

Instead of picking a few new motor/esc choices at random and asking if they'd work, I'd like to ask you what you would use for this frame.

Any thoughts or suggestions would help.
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Mar 28, 2014, 04:25 PM
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Mortimer's Avatar
Present AUW?
Mar 28, 2014, 05:38 PM
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Quote:
Originally Posted by Mortimer
Present AUW?
All up weight? I'm really not sure. I just know the frame without any electronics weighs 230g. I had to give a copy of the frame away to get that number.

A quick tally using Hobby King's product pages and some other known gives me a maximum, with everything (battery, FPV, GoPro H3, etc), of roughly 1240g. I doubt there is very much accuracy at all in this number. Take it as you will.
Mar 28, 2014, 06:01 PM
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Mortimer's Avatar
Quote:
Originally Posted by Physics_Dude
I recently designed this awesome tricopter frame, I'd like to ask you what you would use for this frame.
roughly 1240g. I doubt there is very much accuracy at all in this number. Take it as you will.
So, you need combos giving around 450g thrust at 50% throttle. Look at eCalc.
Mar 28, 2014, 08:12 PM
3D Printer Owner
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Quote:
Originally Posted by Mortimer
Look at eCalc.
Alright, I finally bought the full version of eCalc and spent a couple hours testing various setups. Here is what I came up with.

First, here is my current setup:
http://imgur.com/11ujm6V.jpg
I can confirm that the motors get quite hot, however my flight times are slightly greater then eCalc suggests.

Here is what Turnigy Aerodrive SK3 - 3530-1340kv motors will get me:
http://imgur.com/oFdgLkt.jpg
These will require new 25/35A ESCs

Finally, my top choice, NTM 28-36 1200kv / 530W motors:
http://imgur.com/JnQ3mSK.jpg
eCalc didn't have these motors listed, so I used my best judgment under the "custom" selection.

The more I look at it, the more I want these NTM motors. What do you think? Do the numbers look good?
Apr 01, 2014, 01:17 PM
3D Printer Owner
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Since running these NTM 28-36 1200kv motors at their max would stress my current 18-22A ESCs (according to eCalc), I was also planning on getting some 25-35A ESCs to boot.

However, HobbyKing suggests 30-40A ESCs on their product page. I'd assume this suggestion assumes you are using a 4s setup and 25-35A ESCs will work just fine on a 3s setup like my own.

Can I get a second opinion on this newly proposed power system?
Apr 02, 2014, 06:11 PM
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Mortimer's Avatar
What prop do you intend to use?
APC 10x4.7 SF?
Apr 02, 2014, 08:02 PM
3D Printer Owner
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Quote:
Originally Posted by Mortimer
What prop do you intend to use?
APC 10x4.7 SF?
Yes, those and generic 10x4.5SF. I have more generic HK 10x4.5SF props than anything else right now, but the difference seems negligible according to eCalc.
Apr 03, 2014, 11:55 PM
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It seems that every time I visit Hobby Kind I find new stuff.
I'm also reconsidering motors again...

I realized how sensitive eCalc is to a motor's resistance. So an "educated guess" may not have been the best idea for filling out a custom motor in eCalc. The NTM motors I want unfortunately don't list resistance data.

On top of my previous best choice, the NTM 28-36 1200kv / 530W motors, I also found and tested NTM 28-30 1200kv / 400w motors as well. The results are pretty much identical, but I'm leaning toward the 400w ones a bit more due to their size.

Ideally, it would be nice to get a proper resistance value for these NTM motors. Anywhere from 0.12 ohm to 0.01 ohm would prove ideal.
Apr 07, 2014, 01:52 AM
Hamburger
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For increase of efficiency = flighttime :
Aim for lower kv and larger props.
Apr 07, 2014, 08:09 AM
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Quote:
Originally Posted by hamburger
For increase of efficiency = flighttime :
Aim for lower kv and larger props.
So you would probably go with something like the NTM 35-36A 910Kv / 350W and 12x4.5SFs? Here are eCalc's results for that combo:
http://i.imgur.com/2KKCHej.png
I have to say, they preform pretty well (11x4.5SFs will work nicely too). If I can't find any resistance values for the previous choices, then I might just have to go with these.
Apr 07, 2014, 11:15 AM
Registered User
manuel v's Avatar
Quote:
Originally Posted by hamburger
For increase of efficiency = flighttime :
Aim for lower kv and larger props.
Yes.

Maybe this motors:
https://www.rcgroups.com/forums/show....php?t=2093749

Manuel V.
Apr 07, 2014, 12:24 PM
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Quote:
Originally Posted by manuel v
Although that does seem like a good deal (props + motor for < $15), those motors are unfortunately too small for my size tricopter. eCalc says I will need to apply 73% throttle just to hover.
Additionally, 12x4.5sf props will cause this motor to run quite hot.

I'm still in favor of my previous choice(s).
Last edited by Physics_Dude; Apr 07, 2014 at 01:13 PM.
Apr 13, 2014, 07:42 PM
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Alright, Hobby King Live Chat support was able to sway my decision over to the Multistar lineup. Of all of them, I found the Turnigy Multistar 3525-850Kv 14Pole Multi-Rotor Outrunner with 12x4.5SFs or 12x4.7SFs to be my best option.

Here are those results: http://i.imgur.com/DaXxGyO.png Pretty awesome I say.

I'm probably going to stay with Plush Bulletproof ESCs since they have proven themselves to me so far. Technically, I could stay with my current 18A/22A, but having only a mere 2 amps of head room would be pushing it. I'll likely go for the 25A/35A Plush model.

Any second opinions would still be appreciated.

Edit: On second thought, is there any word on how well bottomless Multistar motors handle cooling? 55C-60C is a bit high for my standards. Granted I left eCalc's "motor cooling" to medium. Should this be set to good or even excellent for my style mount?
PLA plastic motor mounts can get a bit soft at temperatures any higher then this. I would have to switch to ABS if these figures are true.
Last edited by Physics_Dude; Apr 13, 2014 at 10:31 PM.
Apr 29, 2014, 05:21 PM
3D Printer Owner
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Wile I wait for Hobby King to replenish their stock on a few things, I figured I'd bump my previous message to get a final-final word.

(i.e. 12x4.5SF, Plush 25A, and Multistar 3525-850Kv.)
(eCalc results)


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