HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jun 24, 2006, 12:59 PM
Registered User
Joined Oct 2003
56 Posts
Discussion
4 cell or 3 cell for small 3d. (30-40oz)

wondering if anyone can help me first

i have a kontronik gb25, 5.2/1 ratio. which way would you guys go? 3 cells and look for something in the high 3000kv range, or go 4 cells and look for something in the high 2000kv range. i think the 4 cell would be more effecient. but im not sure if there are any good models out there for that size.

im fiarly content with 20-30oz models. and there seems to be alot. but i cant find many 40oz 3d type models out there for electric, and i presume this would be the weight id be looking for if using 4 cell with a say 2800kv 400 size bl motor with that GB. if anyone has any insight. if be more than gratefull, as im sort of confused.

thanks
painly is offline Find More Posts by painly
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 24, 2006, 05:04 PM
Electric Hippy
Brisbane
Joined Nov 2005
2,360 Posts
With a 5.2/1 I would be looking at least 3000kv and 4S.

I have a mega 16/15/3, 3000 kv , geared ~4.3/1 swinging APC 13x6.5 on 4S at 30-25amps. I cant remember the exact ratio. This combo puts out 60+oz of thrust and propels my 27oz pitts vertical like the space shuttle.

I would definately go 4S if you dont already have batteries. At that size I would not use the BEC on the ESC, so you might as well gain some watts and effiency.
Eagleburger is offline Find More Posts by Eagleburger
Reply With Quote
Old Jun 25, 2006, 09:32 AM
Straight up is all I ask
Fairfield Ct USA
Joined Apr 2002
2,317 Posts
Yea I'm of the 4s ilk It is a fantastic way to slip a bunch of extra power into a model without adding much weight Mega 3 turn is a good choice also a littlte hotter like medusa 28 32 3400 will work with a high ratio like you have . The kontrinik 5.2 is the smoothest gearbox I ever had by far Dont forget to put loctite on the threads on final assembly(like I did) an expensive mistake . As for planes , Stevens Aero edge 540 , Formosa 2 , a smallish hotliner . Some planes from NE sail ,samba ....well a lot of sp600 size planes will work cause you will be making 400 whatts of power . The only problem I've had with lightweight power systems is balance , those bigger planes are looking for more weight in the nose . Whats a little lead between friends?
jmolwitz is offline Find More Posts by jmolwitz
Reply With Quote
Old Jun 26, 2006, 12:34 PM
Registered User
Joined Oct 2003
56 Posts
thanks for the great advice. the only battery i have is an 1100mah 3cells persuading me to stay 3 cells, but i could always just grab another 1100 and wire it in to make a ghetto 4 pack and then buy some nice four packs. i gues the 16/15/2 would work with 3 cells pretty good.

. i keep debating selling the gearbox but i havent used it yet, and really, with all the awsome feedback ive heard, i just want to hear and experience this little gem! i dont care if its cheaper to go with an outrunner!

should i maybe go with a 480 if 4 cell? or does that step things up, and kond of ask for a 4s2p rather than 1p? i remeber my 480 twist in my heli needed the 2p

barrett
painly is offline Find More Posts by painly
Last edited by painly; Jun 26, 2006 at 12:49 PM.
Reply With Quote
Old Jun 27, 2006, 02:15 PM
Where's your CofG?
Gibby's Avatar
San Diego
Joined Apr 2004
777 Posts
Barrett,
You will likely need to get a larger battery pack to power a 30oz model. Even if your pack is true 20C your looking at pulling a max of 22 amps. The 16/15/3 adn /2 will both pull more than that unless you're really under utilizing them by proping way down. For a 30oz 3D plane a Mega 16/15/3 geared 3:1, APC 10x4.7 SF, Thunder Power 3s 2100 Pro-Lite. If you really want rediculous power you can bump up to the 4s. YOu could also look at the Neu 1105/3.5y in that set up. My 2 cents.

Gibby
Gibby is offline Find More Posts by Gibby
Reply With Quote
Old Jun 28, 2006, 01:44 PM
Registered User
Joined Oct 2003
56 Posts
you mention a 3.1 gb, i got a 5.2 so just change at the prop end, something larger? 11x6?

and as for motors, im thinking either a 16/15/2 and 3cells or /3 and 4 cells. what size are those motors anyways, 40mm?

thanks
painly is offline Find More Posts by painly
Reply With Quote
Old Jun 28, 2006, 09:28 PM
ProBro Spaz
spastic's Avatar
Buffalo, NY
Joined Aug 2004
1,013 Posts
I suggest, first pick a plane then buy the motor and battery to go with it otherwise your'e wasting time.. there are thousands of combos and people will sit here and tell you all of them and that will never end..............
why did you start with a gearbox? just wondering
spaz
spastic is offline Find More Posts by spastic
Reply With Quote
Old Jun 28, 2006, 09:38 PM
phillyphly
e-guru's Avatar
United States, PA, Philadelphia
Joined Sep 2005
1,223 Posts
Mega 16/15/x motors are 28mm

The KPG gearboxes are fantastic units and worthy of building a system around

To get the same prop speed you either use high kv and high ratio or lower kv with lower ratio... I think you're right on if you have 5.2 ratio and already have 3S packs. The 4600kv 16/15/2 will match well.


No matter what, you'll want larger capacity batteries for duration and higher C discharge
e-guru is offline Find More Posts by e-guru
Reply With Quote
Old Jun 29, 2006, 03:01 PM
Registered User
Joined Oct 2003
56 Posts
i agree with picking a plane, yet i want a versatile system. - i am building it around a gearbox cause i have this buet sitting here and i really want to use it! and for what i want i think it will work.

i think i am going to try the formosa 2.
two ways of going
4s/16/15/3
or 3s and a 15/2 or high 4000kv 40mm motor.

for this plane, is it doable to run an inrunner and would a 3s system be enough for unlimited vertical? i like the fact with 3s i dont need to run ext bec, and its cheaper.
painly is offline Find More Posts by painly
Reply With Quote
Old Jun 30, 2006, 04:28 AM
Registered User
vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,693 Posts
Quote:
Originally Posted by painly
i agree with picking a plane, yet i want a versatile system. - i am building it around a gearbox cause i have this buet sitting here and i really want to use it! and for what i want i think it will work.

i think i am going to try the formosa 2.
two ways of going
4s/16/15/3
or 3s and a 15/2 or high 4000kv 40mm motor.

for this plane, is it doable to run an inrunner and would a 3s system be enough for unlimited vertical? i like the fact with 3s i dont need to run ext bec, and its cheaper.
I think you will fnd that teh 16/15/3 is likely to not be as efficient - especailly at reduced throttle - on 4s as on 3s.


You want to get a 3000mAh 3s pack and run that motor up towards 30A with the box.

It will be screamigly powerful for a formosa. The oroginal is desugned to fly on about 40W out..you will be putting out getting on for 250W...
vintage1 is offline Find More Posts by vintage1
Reply With Quote
Old Jun 30, 2006, 07:13 AM
Straight up is all I ask
Fairfield Ct USA
Joined Apr 2002
2,317 Posts
Vintage the formosa 2 is a fairly big plane almost the size of the sky cat .
jmolwitz is offline Find More Posts by jmolwitz
Reply With Quote
Old Jun 30, 2006, 01:14 PM
Registered User
Joined Oct 2003
56 Posts
so your saying either go with 3s on the 15/3 or 15/2 , im leaning towards 3s 2100's on the 15/2
painly is offline Find More Posts by painly
Reply With Quote
Old Jun 30, 2006, 02:20 PM
Where's your CofG?
Gibby's Avatar
San Diego
Joined Apr 2004
777 Posts
Barrett,
The 15/2 sucks some serious amps so make sure you run your set up through p-calc or similar before you move forward to make sure you're not going to kill your TP 2100.

Gibby
Gibby is offline Find More Posts by Gibby
Reply With Quote
Old Jun 30, 2006, 03:15 PM
AMA 754
BobRCnut's Avatar
Phoenix area
Joined Apr 2004
1,613 Posts
The Formosa II needs a fairly heavy motor, weight-wise, something in the 300 watt range to perform at its best.
BobRCnut is offline Find More Posts by BobRCnut
Reply With Quote
Old Jun 30, 2006, 03:36 PM
LJH
Moths do not fly inverted
LJH's Avatar
Greenwich CT.
Joined Sep 2000
4,191 Posts
I have to say I am totally happy with my 16/15/3 geared 3.28:1 with a 13X8 in my 35oz Stevens Edge. I am pulling around 37A for 385 watts and it launches my edge like a Saturn V rocket. The 3 turn will prove to be more versitile motor for anything from a geared set-up to direct drive to a EDF, with teh 2 turn you are really limited in where you can use it.

just my $0.02

Cheers,
Jim
LJH is offline Find More Posts by LJH
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
2 cell or 3 cell for twin? morphideous Batteries and Chargers 4 Oct 18, 2005 09:12 AM
TM400 - 2 cell or 3 cell etc etc Rob_P GWS (Grand Wing Servo) 1 Aug 14, 2005 10:04 PM
2-cell or 3-cell rc-guy Batteries and Chargers 2 Jun 29, 2005 06:14 PM
lipo for space scooter 2 cell or 3 cell? paul747 Parkflyers 6 Feb 06, 2005 02:47 PM
2 cell or 3 cell? av8n Batteries and Chargers 5 Dec 19, 2003 08:58 PM