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Old Dec 04, 2012, 10:20 AM
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Beeler19's Avatar
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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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Old Dec 04, 2012, 10:33 AM
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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.
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Old Dec 04, 2012, 10:44 AM
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Quote:
Originally Posted by Dr Kiwi View Post
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?
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Old Dec 04, 2012, 10:55 AM
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Orleans, MA
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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.
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Old Dec 04, 2012, 11:15 AM
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Quote:
Originally Posted by whitecrest View Post
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 =/
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Old Dec 04, 2012, 11:37 AM
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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.
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Old Dec 04, 2012, 12:58 PM
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Originally Posted by whitecrest View Post
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
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Old Dec 04, 2012, 03:47 PM
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Beaumont tx
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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 ;}>>
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Old Dec 04, 2012, 05:22 PM
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Quote:
Originally Posted by Beeler19 View Post
I mainly build scratch builds so idk how many kvs or motor watts I should choose?
Wow, that tells the story doesn't it.
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Old Dec 04, 2012, 05:50 PM
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Quote:
Originally Posted by gwinhh View Post
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.
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Old Dec 05, 2012, 11:02 AM
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Beaumont tx
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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
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Old Dec 05, 2012, 12:08 PM
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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.
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Old Dec 05, 2012, 04:43 PM
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And a Seniorita has operating parameters outside a range of plausibility?????

howell
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Old Dec 05, 2012, 06:01 PM
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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.
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Old Dec 05, 2012, 06:32 PM
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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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