Need help picking power system... - RC Groups
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Dec 04, 2012, 11:20 AM
Registered User
Beeler19's Avatar
Help!

Need help picking power system...


Alright so ive been doing research about what kind of motor/bat/esc i need for good flight but they are based on manufactured airplanes with manufacture recomendations. I know the formulas... well 3 any ways
*Motor watts/ Batt volts = motor amps
*Battery mah* Crate/1000= amps
*ESC has to be between the two...

But like I said I mainly build scratch builds so idk how many kvs or motor watts I should choose? Ive been trying to use ESC 15-25amps with a 1050kv 90gram motor? and 2-3 cell 700mah-2200mah batteries... The only luck ive had with these combos is a GEObat uav I made flew good, even with a payload.

Ok so most of my planes are 1-4lbs, 36"-55" wingspans and I usually fly gentall pipercub style flight just flying around is fun enough for me. Im working on a scratch made REDBULL plane (contradiction of my flight style) but I may rig my uav brain in there and teach my self on it.

please let me know if you can help.
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Dec 04, 2012, 11:33 AM
Registered User
Dr Kiwi's Avatar
One useful rule of thumb is watts/lb... for your gentle flyers you'll not need much more than 50W-75W/lb. Decide what size prop will fit best, determine whether you want 2s or 3s, then choose a motor of suitable Kv to spin that prop at somewhat less than max.amps for motor and pack, yet give you the 'watts" you need.... larger diameter prop = greater thrust....but keep in mind that pitch speed is an important factor....you won't need a particularly high pitch speed if you are flying Cub-like planes.
Dec 04, 2012, 11:44 AM
Registered User
Beeler19's Avatar
Quote:
Originally Posted by Dr Kiwi
One useful rule of thumb is watts/lb... for your gentle flyers you'll not need much more than 50W-75W/lb. Decide what size prop will fit best, determine whether you want 2s or 3s, then choose a motor of suitable Kv to spin that prop at somewhat less than max.amps for motor and pack, yet give you the 'watts" you need.... larger diameter prop = greater thrust....but keep in mind that pitch speed is an important factor....you won't need a particularly high pitch speed if you are flying Cub-like planes.
The planes them selfs are not cub like, my flights are simular to their slow/ easy going just flying around, not the 90mph, 400ft climbs, hovering 3d moves lol in comparasion. And props are recomended by motor manufactures so till i know what motor i need im kinda dead in the water... =/
I want to stay in the 9"-12" prop range idk bout pitches, stay in the 11.1v bat range too

Im thinking about getting a Gens Ace 30Amp or 45Amp ESC/Motor combo?
Dec 04, 2012, 11:55 AM
Frequent Flyer
whitecrest's Avatar
Try WeboCalc. After entering a plane's wingspan, wing area, weight and desired flying style in the short form, the program will calculate power required and suggest a list of props for direct drive or with an appropriate gearbox. This information will help you select the right battery, ESC and motor/prop. Click the "Help" command for a tutorial.
Dec 04, 2012, 12:15 PM
Registered User
Beeler19's Avatar
Quote:
Originally Posted by whitecrest
Try WeboCalc. After entering a plane's wingspan, wing area, weight and desired flying style in the short form, the program will calculate power required and suggest a list of props for direct drive or with an appropriate gearbox. This information will help you select the right battery, ESC and motor/prop. Click the "Help" command for a tutorial.
Im getting about 108Watts/pound?
Its rated for medium/mild aerobatics with 60degrees of climb
flies like a lead sled?
Dosent list a good prop for direct drive though just geared =/
Dec 04, 2012, 12:37 PM
Frequent Flyer
whitecrest's Avatar
It's hard to comment without seeing the data you entered. Look at the program tutorial ("Help") for a good explanation. A good exercise is to enter data from published model specifications and observe the calculated results.
Dec 04, 2012, 01:58 PM
Registered User
Beeler19's Avatar
Quote:
Originally Posted by whitecrest
It's hard to comment without seeing the data you entered. Look at the program tutorial ("Help") for a good explanation. A good exercise is to enter data from published model specifications and observe the calculated results.
heres what i got
Dec 04, 2012, 04:47 PM
Registered User
Whitecrest, I entered the data for a seniorita which is close to a large foam Cub I have. It kept telling me to change the parameters instead of answering the question. Reminds me of some of my students ;}>>
Dec 04, 2012, 06:22 PM
Night Flying
Ron H's Avatar
Quote:
Originally Posted by Beeler19
I mainly build scratch builds so idk how many kvs or motor watts I should choose?
Wow, that tells the story doesn't it.
Dec 04, 2012, 06:50 PM
Frequent Flyer
whitecrest's Avatar
Quote:
Originally Posted by gwinhh
Whitecrest, I entered the data for a seniorita which is close to a large foam Cub I have. It kept telling me to change the parameters instead of answering the question. Reminds me of some of my students ;}>>
Here's a WeboCalc run for the Kadet Seniorita published data. I used the suggestion commands and wizards and didn't get any refusals.
Dec 05, 2012, 12:02 PM
Registered User
With a 22" prop and 4S LIPO? There's bound to be a set up which doesn't include an impossibly large prop and 4S lipos.

howell
Dec 05, 2012, 01:08 PM
Frequent Flyer
whitecrest's Avatar
Of course, the program will question entered data if airframe or operating parameters are much outside a range of plausibility, and it is certainly more likely if working with an unproven design. Sometimes, it's fun to enter extreme data just to see what will happen.
Dec 05, 2012, 05:43 PM
Registered User
And a Seniorita has operating parameters outside a range of plausibility?????

howell
Dec 05, 2012, 07:01 PM
Frequent Flyer
whitecrest's Avatar
No. The Kadet Seniorita described by the published data (wingspan, area and weight) and flown in the manner generally intended and marketed is well within its design expectations.
Dec 05, 2012, 07:32 PM
Registered User
Beeler19's Avatar
yall are loosing me lol and is the term "Lead Sled" bad?
when i hear that I think its gonna fly sloppy but, wind shouldnt phase it? LOL


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