ScottP107

Hello all, I'm trying to plan my next plane out and am looking for some input on the power system. This is all in my head at the moment, but hopefully before too long it'll actually be in the air. Everything I have done to now has been RTF, so please bear with me.

I'm thinking about going with the DW Foamies 38 in YAK 54. The purpose of this plane will be to get me used to flying a more agile plane and thus I'm trying to keep the components as inexpensive as possible for the inevitable crash and so I can keep saving for a nice balsa model of some sort. Anyway, these are the components for the power system I am contemplating:

ESC
http://www.hobbycity.com/hobbycity/s...eed_Controller

battery
http://www.hobbycity.com/hobbycity/s...00mAh_3S1P_25C

The part I am having the hardest part with is the motor since hobby city seems to never list all the specs or even the same specs from motor to motor. This is what I have my eye on

http://www.hobbycity.com/hobbycity/s...less_Outrunner

Please if you have a minute just take a look at it and leave some feedback. I know ultimately I will need to put a watt meter on it to see exactly what is going on, but I'm just trying to see if I'm in the ballpark. I have read a lot on the forums and have a basic understanding of electricity, but putting it into practice is a whole different story.

Dr Kiwi

It seems that as long as you don't get ridiculous, with a prop which draws in excess of 15A on 3s, you should be fine - an 8x4 GWS HD seems to be the ticket.

CHELLIE

this will work even better for you, with a 8x4 prop

http://www.hobbycity.com/hobbycity/s...less_Outrunner

http://www.hobbycity.com/hobbycity/s...eed_Controller

its always best to over kill the ESC a little, so it does not get hot and quit on you. if the motor says it requires a 18 amp esc, go to the next size bigger, its just cheap insurance

http://www.hobbycity.com/hobbycity/s...Ah_3S1P_15-25C

or

http://www.hobbycity.com/hobbycity/s...5C_Lipoly_Pack

for more flight time use a 1300mah 3 cell lipo, hope that helps, Chellie

ScottP107

Thanks for the reply, I definitely do see your point about getting a bigger esc than necessary. In regards to the motors, are there any notable differences between the one you reccomended and the one I posted except for yours spinning a little faster? Still trying to wrap my brain around all of this

CHELLIE

both motors will work great for you the 1350KV motor will allow you to turn a little bigger prop, up to a 9x3.8

Great motor!!!! Greg Jackson |

This is the best value in out runners out there!! I use this motor on my formosa 1 and I have ulimited vertical and great run times!! I use a 9x3.8 prop with a 2100 30c 3cell lopo it only pulls 12.5 amps at full power!! and I get about 15 mins of flight no problem. This is one Great Motor for the money! I plan to by more!! Greg

The 1650kv motor will give you more speed, with a 8x4 or a 7x6 prop on 3 cells.

TR 28-26 1650Kv - great Stephen Taylor |

Fantastic little out-runner Static performace: 2S running a 7x6 9.5A and 80W 3S running a 7x6 17A and 170W Perfect for my 400mm EPP Combat Delta

The 2 motors are somewhat close to one another, the 1350kv will give you a little more power, and the 1650kv will give you a little more speed, its up to you what you want more power or speed, both will work fine, hope that helps, Chellie

ScottP107

is there any advantage to spinning a smaller prop faster vs a larger prop slower?

CHELLIE

spinning a smaller prop faster = speed - go fast
spinning a larger prop slower = thrust- more pulling power

here is a little example from Heads up rc
http://www.headsuprc.com/servlet/the...lectric/Detail

Propeller test data for the 2826-14 with a 3 cell Lipo battery:
It's a good idea to balance all propellers with a Propeller Balancer before using them on this motor. TP propellers are available in our store, and are nearly identical in performance to APC props. Rotating propellers are dangerous. Please stay clear of prop and wear eye protection.
GWS EP8040:26 ounces of thrust at 15 amps with a pitch speed of 47 mph. Excellent choice for maximum performance, but be sure to provide good airflow over the motor.
I do not recommend using any other 8 inch prop with this motor.
GWS EP7035:16 ounces of thrust at 8.5 amps with a pitch speed of 49 mph
TP 7 x 6E: 22 oz thrust at 16 amps with a pitch speed of 69 mph. Avoid constant wide open throttle.
GWS EP6030:13 ounces of thrust at 7 amps with a pitch speed of 49 mph
APC 6 x 4 speed 400: 14.5 ounces of thrust at 9 amps with a pitch speed of 58mph
APC 6 x 5.5E: 15 ounces of thrust at 11.5 amps with a pitch speed of 74 mph

CHELLIE

notice the speed of the 6x5.5 prop 74 mph with 15 oz of thrust

notice the speed of the 8x4 prop 47 mph with 26 oz of thrust

you get one or the other

ScottP107

Hmm...those specs are interesting

I hope you don't mind me picking your brain, i always have tons of questions when i'm getting into something new.

On the 1650 motor you linked to, it says "power: 140w" yet the guy in the comments running the 7x6 says he is pulling 170w. is he risking burning up the motor at that point?

ScottP107

I saw that, and that's what doesnt really make sense to me. it seems to me with more thrust, you would get more speed

CHELLIE

it all depends on the limitations of your power system, a power system with certain motor will produce x amount of speed or x amount of thrust depending on the prop used and the number of lipo cells, Volts/Amps used and the KV of the motor, hope that helps, Chellie

CHELLIE

you can push these motors a little, its called burst for a few seconds and not hurt them, i push a 150 watt motor to 200 watts burst and it does not hurt them

CHELLIE

If you want to have some real fun, try one of these motors, its a 1800kv motor, these sell out fast, so when they are in stock, grab one fast, only $6.95 I push these motors to 200 Watts plus, and they can take that abuse all day, they have very thick windings in them, it will take a 8x4 7x4 7x5 and 7x6 apc prop on a 3 cell lipo, its rated for about 120 Watts, but i take them to 220 watts, and they dont even get hot, they love the abuse i give them use a 25 AMP esc or bigger, Take care, Chellie

http://www.hobbycity.com/hobbycity/s...ss_Micro_Motor

my friend Kosh has this motor in his X41 here is a video of it, not bad for a $6.95 motor huh

http://www.youtube.com/watch?v=MgV17GlLMlI

ministeve2003

for the 38" juka's and Yak's you'll want around 200watts and a light battery like a 1000mah -1300mah 3cell pack,

I liked this motor on my 38" Juka... try apc 10x3.8sf prop
http://www.hobbycity.com/hobbycity/s..._23A_Outrunner

30amp turnigy esc...
http://www.hobbycity.com/hobbycity/s...eed_Controller

hst900 servo's... Cheap and reliable...
http://www.hobbycity.com/hobbycity/s...ec_Micro_Servo

SK

ministeve2003

Here's an old video of my 38" juka... it had the 15amp red turnigy motor on it in this video, however it always seemed underpowered untill I put the bigger motor on it... (I know it might not look that way though..)

all the wing-rock you see in the video was due to me not balanceing the plane latterally, (side to side)

[media]http://www.vimeo.com/1738843[/media]

SK

CHELLIE

This will work even better yet, Thanks Steve for Chiming in, Steve is in our RC Club, and is a Master of RC Flight Take care, Chellie

ScottP107

Thanks for all the input everyone. With all this talk about it, I pushed my plans up a bit and went ahead and ordered the plane and some parts. I ordered the ESC/motor/battery setup that Chellie first mentioned. I think it will be ok if it is a little under powered for now, i'm not the best pilot in the world (yet...), so i think some margin for error will be good. Plus, with the hobby city stuff so inexpensive I figure its not too much of an investment if I feel I need more motor at some point.

Just one last question, does anyone know of a chart of some sort that shows comparable props of different sizes? Example what pitches of other diameters would provide similar thrust/draw similar watts as a given prop?