fozjared

please dont bite off my head, as i have a very specified case here.. i already searched and posted in the electric forum to no avail (posted 2.5 days ago and have kept a close check for an answer, just never got one)

so i have been building a guillow's piper cherokee kit with a 20" ws so i need to keep it in total, under 6 ounces or so i have been told by several folks! so i need a motor/battery/esc recommendation that will tow this plane around nicely for me, it will be flown using the spektrum dx-7 and the parkflyer rx ar6100 which totals 3.5 grams so i am good there for sure, but i need a lightweight battery that will keep me in the air for around 5min. and a strong enough motor to take off in a reasonably short distance. i am not looking for a hot rod motor, instead, something that will make it fly relatively scale.. keep in mind on the recommendations that i am on a college student budget (about to graduate, thank the Lord!). i would like to keep the motor, battery, and esc below 35$ is that unreasonable?

i also will need a charger as i will most likely not be able to charge this recommended battery with a spektrum wall wart charger so i need help with that also.. i saw a nice hyperion charger that charged lipo, nimh, nicd plus you could select the mah rate you want to charge at, looked very user friendly and like it would last me a long time in this hobby as i am definitely here to stay (this will be my fifth plane over a 9 mo. period, all the others have been .40 size..) i saw the hyperion and liked it but cant remember where i saw it at (online that is) or any other details so if someone knows where to find it at a good price, or knows of a better charger for around 150$ that would be helpful.. thanks in advance for your help, i have been learning fast in this hobby! although i have only been flying for almost 9 months i know a great deal about glow power, radio's, and flight physics among a little bit of knowledge on a few other aspects of this hobby, some of which were learned the hard way.. i promise to continue to learn rapidly and share any knowledge along the way, to help anyone i can and know that someday i will be able to help someone in my shoes today

here are a few pictures of this plane from towards the beginning to now, right before covering, stalled waiting on recommendations for equipment and then the installation of the equipment, then setup and covering and she'll be in the air!!! my first kit build!!

fozjared

the box the kit came in recommended a cox .020 peewee and i thought about it but decided it would put too much strain on such a light weight airframe so i just need an equivalent electric motor i guess.. thanks!

iron eagel

The rule of thumb for electric motor size is 100 watts per pound for sport, 150 watts for aerobatic, and 200watts+ for 3d/high speed.
Given that your finished weight would be 1/3 lb, you are looking at a 33watt/50watt/66watt power as moder power required.
A 33 watt motor would be a motor that draws roughly 3 amps at 11 volts, a 50 watt would be roughly 4.8 amps at 11 volts, and the 66 watt comes in at 6amps at 11 volts, 11.4 is the typical voltage of a li-pol bat which is what you would want to use for the motor.
Here is one that would work Aero-nuts 2204-1470 Outrunner
Input Voltage : 7.4V~11.1V (2~3S Li-po)
KV : 1470RPM/V
Max. efficiency current : 5~9Amps
Current capacity : 11Amps/60Sec
Internal Resistance : 400 mohm
No Load current @ 7V: 0.59A
Dimensions : 27.8mm X 22mm / 1.09in X 0.86in
Shaft diameter : 3.17mm / 0.12in
Weight with cables : 37g / 1.3oz
Number of Magnet : 14pcs
Recomended model weight : 240~280g / 8~10oz

edit to add
http://www.aero-nuts.com

fozjared

thanks man, i found it, its 12.25 plus shipping.. a little higher than expected.. what size prop and how would you attach one to that shaft? i also need an esc correct? how do i select one of those, and where can they be bought cheap? thanks again!

iron eagel

That outfit sells all sorts of esc and charges as does hobby lobby and tower as far as who I have dealt with online. If you look at the bottom of the page you will see the mounts and prop adapters. a 12 to 15 amp esc should be cheap.

As far a twelve dollars ,my average spending for brushless motors is around $100, I just got a 375 watt motor that cost me 30 bucks at the LHs.....
I have also heard of some guys rigging CD rom motors in light weight airplanes

edit to add:
prop size I would say a 4-6 inch max dia. pitch 4-6

fozjared

thanks so much iron eagle, what would be the battery you would chose if you were doing something like this? i dont plan to keep it in the air for long periods or anything just a few minutes, so that should help keep the weight down right?

fozjared

would this be a good battery for this setup?

http://www.aero-nuts.com/product_inf...roducts_id=275

fozjared

http://www.aero-nuts.com/product_inf...roducts_id=381
this is the cheapest esc but it is 25 not 12.. would it work, or am i just adding weight for no reason?

fozjared

with that battery/esc/motor combo i have posted i am overweight, as i was advised to keep the plane under 6oz.. i can see this is going to be difficult..

fozjared

http://www.hobbycity.com/hobbycity/s...idProduct=4852
good price it seems for this combo.. would this be too heavy and too much power though? thanks!

fozjared

that combo with this pack might be nice?
http://www.hobbycity.com/hobbycity/s...idProduct=2050

iron eagel

I think the second battery is fine for what you are looking for. However the second motor is almost twice the weight of the first. You may also want to check out: AXI 2203 Outrunner Brushless it is a 18.5 gram motors for models weighing 3.5 to 9 ounces. Built-in 3 point radial mount and flexible prop adapter with O-ring. Or MJ20204 AC 22/7-60D Outrunner Brushless
Motor from hobby lobby http://www.hobby-lobby.com/brushless-mpjet.htm. Or even MMC1150 LittleScreamers "DeNovo" Micro OUTRUNNER Brushless Motor http://www.hobby-lobby.com/littlescreamers.htm.
Problem is when you try to get special and or light weight it starts to get expensive, I am building a high speed delta the NEU high rpm brushless motor for it is on the order of $300, the ESC $150. Anytime you power a plane with an electric motor trying to keep the weight down is a issue, even more so when you get into the smaller sizes.
have you checked out: http://www.wattflyer.com/forums/

iron eagel

That is fine for an esc for what you looking to do.

iron eagel

You say your plane is a 20 inch wing span what is the cord?
Just as a guess I would say around 5 inches that give you 100 inch wing area or .69sq ft. I would say that you could go as high as 8 oz in weight and still have an airplane that will fly good.

By the way I am building a Herr Eng by SIG Piper Cherokee 42 inch wingspan at this time which is going to be powered by the above mentioned 375 watt motor. This is a nostalgic build for me as I have a many hours flying time in a full scale in a PA-140.

ampeater

My Feedback: (1)

Hey, nice job on your build. How about these:

2S 460 mAh battery - 24.6g - $8.95
http://www.hobbycity.com/hobbycity/s...idProduct=2135

8A ESC - 7.7g - $15.95
http://www.hobbycity.com/hobbycity/s...dProduct=5532#

2100 kV motor propped for 7A - 19g- $7.25
http://www.hobbycity.com/hobbycity/s...idProduct=5431

Total cost - $32.15. Total weight - 51.3g ~ 1.8 oz.

Propped to 7A, would give about 50W, way more than enough power for a 6-8 oz plane.

I've never used any of these brands so I can't speak for any of it, but it suits your needs!

iron eagel

Those are some good options Ampeater!

fozjared I found another light weight motor
http://www.bphobbies.com/view.asp?id...4&pid=B3665241

fozjared

oh thanks so much guys, i will be placing my order today and hopefully have this little booger up in the air within the next 2 weeks! man i am excited now! what do you guys think about this charger?
http://www.maxamps.com/EOS5i.htm
does anyone have this charger? if so will it charge my rx batteries at a selectable mah i have one rx pack 4.8v nimh that says charge at 270mah and one that needs charged at about 100mah.. can i select that with this charger, it doesnt give enough description on that website so i figured i would ask.. would that unit charge individual cells say rechargeable AA batteries or a rechargeable 9v battery? thanks for all the help ironeagel and ampeater!

fozjared

oh and would that charger charge the battery i have listed from hobby city? also how would i connect my rx packs to that unit i have the jr style plugs on them can i put a jr style male plug on that unit? thanks again!

iron eagel

You would put the jr plug onto a lead from that unit.

Keep in mind that you do not need the rx battery when using an ESc with a BEC it supplies power to the rx and servos as well from your main battery.

fozjared

what does bec stand for? thanks for that piece of info though i would have tried to plug in an rx battery as well haha.. so is that charger what i need for the my rx batteries and the battery i just bought.. also will it charge AA and 9v rechargeables? if so i will spend the last of my paycheck getting it haha.. except it is not funny, i only get to work 3 days a week due to college and i only make 50$ a day substitute teaching on those three days.. my wife works so she pays the bills for now and my paycheck is for flying and going taking her out to eat and any other fun stuff she decides we want to do.. so it works out pretty good except that my paycheck is not very big ~500 per month.. anyway i will stop with the sob story.. so i am pretty excited to get this plane in the air and to have a charger that will allow for such.. one last thing i want to know for sure about this charger is, can i select the mah charge rate say 270mah for one battery and 100 for another and 20 for another? thanks guys!

iron eagel

Bec stand for battery elimination circuit it provides power for the servo and rx so you don't have to worry about adding the weight of another battery. The plus side to this is that you can use a bit larger main battery to increase flight time.

As far as the charger I can not say, very little info on the site you listed you would be better asking the guys in the e flight forum or WattFlyer.com

fozjared

thanks iron eagel, i guess i will head on over there.. while we are on the subject look what i found while trying to understand a little more about batteries!

http://electronics.howstuffworks.com/blood-battery.htm