The 2017 NEAT Fair, Downsville NY Sept-14 thru 17 - Page 24 - RC Groups
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Sep 24, 2017, 06:53 AM
Dr. Toggle
You are off by decimal points 960/8.5= 112.94 watts per pound which should be more that enough.
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Sep 24, 2017, 08:31 AM
Just Plane Crazy
datazman's Avatar

Some more math


Ldm:

I have an advantage over most new electric fliers being a Certified Electronics Technician knowing the mathematical formulas for various factors involved in Electric flight.

Now that you know and understand Watts Per Pound from us old timers one very important component calculation needs to be in your tool box.

WATTS / VOLTAGE = AMPS or CURRANT.

I have seen suggested specs for speed controllers wrong on some sites.
In this case 960 WATTS divided by 14.8 VOLTS = 64.87 AMPS.
Now you know why Tower changed the suggested speed control from 40 to 90.

Till the next time.

Paul
Sep 24, 2017, 08:47 AM
Ldm
Ldm
Registered User
Ldm's Avatar
Harold , yes I do have a watt meter and agree it's been a very effective tool however,,,,, its infective when making the initial motor selection.
In fact when motors were being suggested by the "much more experienced reps" in the A26 thread I asked the very same question "have you put the 32s on a watt meter" ?
Unfortunitly when you are experienced enough to work in the hobby industry you don't need to use a watt meter they base theire results on feel at first then check temps and battery useage after each flight.
Will definitely PM you and thank you for allowing me to ask some questions.

Thanks Paul but ,,,, so you know Tower did not change the specs on there own, they changed the specs based on the questions we generated in the A26 thread and there again is why I was skeptical on the 32s rimfires.
Seems like at 112 it should be ok but I have to make a decision if I want to go up in power and simple manage throttle.
All these choice are so easy for me in a fighter. Almost always I go up in power because the planes need weight in the front end.
IN most cases I have been able to achieve CG by increasing power + larger battery's = funcational weight , super easy decision for me in a fighter.
This being a bomber , and apparently very little weight needed to achieve CG, I dont need to go up in weight for CG , it would only be for added security in the event there was a problem.
Sep 24, 2017, 08:59 AM
No ! Your other left !
aramsdell's Avatar
It gets more complicated. You know your target w/lb. Now what size prop looks right on the plane? Motors have a watt rating and voltage rating often in # of lipo cells. Often they also have a recomended prop range say. 11x6. To 13x8. The small # goes with the max # of cells, the larger with the low cell #. Ex: 11x6 6 cells,
13x8 4 cells.

LDM. It takes me a little juggling of motors/props/cell count/esc size to get it comfortable in my head. Notice I didn't say "get it right"
I brought a good size Lavochkin 7 to NEAT.
WAY overpowered.
Box called for .46 size nitro. I used a .46 sized Suppo motor and 5 cell with 3 bladescale looking prop. Motor good for 4-6 cells and max power just over 1500 watts.
Plane is 8-9 lbs. Straight up till the moon.

Confused now?
If an ARF calls out a nitro motor I would seriously consider using the next standard size LOWER electric. IE: .46 or .40 nitro use a .32 electric and prop for max power.
Sep 24, 2017, 09:24 AM
Ldm
Ldm
Registered User
Ldm's Avatar
Some of the guys tried this combo .
https://static.rcgroups.net/forums/a...28%2014.06.jpg
Sep 24, 2017, 10:05 AM
Kit Manufacturer
coreman's Avatar
Quote:
Originally Posted by aramsdell
It gets more complicated. You know your target w/lb. Now what size prop looks right on the plane? Motors have a watt rating and voltage rating often in # of lipo cells. Often they also have a recomended prop range say. 11x6. To 13x8. The small # goes with the max # of cells, the larger with the low cell #. Ex: 11x6 6 cells,
13x8 4 cells.

LDM. It takes me a little juggling of motors/props/cell count/esc size to get it comfortable in my head. Notice I didn't say "get it right"
I brought a good size Lavochkin 7 to NEAT.
WAY overpowered.
Box called for .46 size nitro. I used a .46 sized Suppo motor and 5 cell with 3 bladescale looking prop. Motor good for 4-6 cells and max power just over 1500 watts.
Plane is 8-9 lbs. Straight up till the moon.

Confused now?
If an ARF calls out a nitro motor I would seriously consider using the next standard size LOWER electric. IE: .46 or .40 nitro use a .32 electric and prop for max power.
let me throw more gasoline on the fire, we haven't talked about the KV rating of the motors which directly effects the prop size. Many motors come available in various windings which give various KV values. I have one motor I have used that is available in 1050, 1300 and 1550KV. As the KV goes up the prop diameter typically goes down to maintain the wattage output and keep the amps into the motor in the rated range. This can help when you need a smaller propeller to "look right"

There are several motorcalc applications that can help with sizing the motors and some suppliers like HeadsUpRC have extensive prop data available to help as well. The prop is an important factor in all this as well
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Sep 24, 2017, 10:46 AM
Registered User
Now you know a big reason I like to design my own models -- I have power system combos I know work, so I design around them.

CD
Sep 24, 2017, 10:53 AM
AMA 1242

motor


Quote:
Originally Posted by Ldm
Harold , yes I do have a watt meter and agree it's been a very effective tool however,,,,, its infective when making the initial motor selection.
In fact when motors were being suggested by the "much more experienced reps" in the A26 thread I asked the very same question "have you put the 32s on a watt meter" ?
Unfortunitly when you are experienced enough to work in the hobby industry you don't need to use a watt meter they base theire results on feel at first then check temps and battery useage after each flight.
Will definitely PM you and thank you for allowing me to ask some questions.

Thanks Paul but ,,,, so you know Tower did not change the specs on there own, they changed the specs based on the questions we generated in the A26 thread and there again is why I was skeptical on the 32s rimfires.
Seems like at 112 it should be ok but I have to make a decision if I want to go up in power and simple manage throttle.
All these choice are so easy for me in a fighter. Almost always I go up in power because the planes need weight in the front end.
IN most cases I have been able to achieve CG by increasing power + larger battery's = funcational weight , super easy decision for me in a fighter.
This being a bomber , and apparently very little weight needed to achieve CG, I dont need to go up in weight for CG , it would only be for added security in the event there was a problem.
Well we will see my flying buddy is redoing a old BERKLY A-26 witch we hope to have up next year !! About twice the sze of Towers . Bouth 2 1100 kv. hellie motors for it, should be more than enough power.
Sep 24, 2017, 06:53 PM
RC Junkie!
The Slayer's Avatar
I just got done upgrading a Dynam ME-262 I got in trade at NEAT this year. It WAS a 4s plane, it's now a 6s. A pair of 2500kv outrunners with 5 bladed rotors and a big 'ole 5300 6s 35c. 2180 watts at 97amps. Unfortunately I don't have a scale large enough to get an AUW.
Sep 25, 2017, 01:40 PM
Registered User
Alan W's Avatar
Quote:
Originally Posted by datazman

or CURRANT.

Paul
We talking airplanes or jelly ? I think they're mostly mutually exclusive

Pete's wife has the formula for currants

sorry .. just being obtuse
Last edited by Alan W; Sep 25, 2017 at 01:45 PM.
Sep 25, 2017, 03:28 PM
AMA 1242

jet


Quote:
Originally Posted by The Slayer
I just got done upgrading a Dynam ME-262 I got in trade at NEAT this year. It WAS a 4s plane, it's now a 6s. A pair of 2500kv outrunners with 5 bladed rotors and a big 'ole 5300 6s 35c. 2180 watts at 97amps. Unfortunately I don't have a scale large enough to get an AUW.
Is that my 262 ? If so let me know how it goes . Fury flies neice.
Sep 25, 2017, 06:01 PM
RC Junkie!
The Slayer's Avatar
Quote:
Originally Posted by jerseyhank
Is that my 262 ? If so let me know how it goes . Fury flies neice.
Yes sir!! The Furyis an excellent flyer, and with the gyro on the rudder, you never have to worry about wavey takeoffs! Lol The 262 should go good, I've seen them fly in both 4 and 6s, they fly with alittle more authority using 6s. Hey if all goes well, you'll see her at NEAT next year!! Lol
Sep 29, 2017, 07:40 AM
AMA 1242

fun/fly


Quote:
Originally Posted by The Slayer
Yes sir!! The Furyis an excellent flyer, and with the gyro on the rudder, you never have to worry about wavey takeoffs! Lol The 262 should go good, I've seen them fly in both 4 and 6s, they fly with alittle more authority using 6s. Hey if all goes well, you'll see her at NEAT next year!! Lol
P/M sent


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