Dec 10, 2004, 06:40 PM Registered User Portland OR Joined Jan 2003 86 Posts Not to worry ChuckD. Here's the formula: Power = current X voltage Power is measured in Watts Current is measured in Amps And of course votage is measured in volts If you know any two of the three you can figure the third. Also keep in mind Voltage = current X resistance Resistance is measured in ohms It's been about 25 years since my last physics class so if this isn't right, please somebody set me straight. npm
 Dec 10, 2004, 06:41 PM Suspended Account USA Joined Jun 2002 2,340 Posts Lol I love parkzone. espicaly there Stryker.
 Dec 10, 2004, 06:59 PM Cancelled Account Joined Oct 2004 738 Posts NPM, Thanks a bunch...so my Mega CAN handle the power with a gearbox and prop! Now I am in business... Again, for your help, I thank you; no end! Spence....if it flies, I will buy one.... --Chuck
Dec 10, 2004, 08:02 PM
Counter agent of B.S.
United States, IN
Joined Aug 2003
224 Posts
Quote:
 Originally Posted by ChuckD So that is how much it can take? 480 watts? Is that correct (sorry for the 'needing to have it beaten across my forehead' approach)...but I am still new to all of this. My best, --C
Watts = Volts x Amps

A fully charged 4S1P LiPo pack will have a reading of 16.8 volts fresh off the charger (a bit less a few minutes later). Sooo, take 16.8(volts) x 25(amps)=420 watts.

But why the sudden interest in watts? Mega's specs & LiPo specs deal only in amps & volts.

Best you get an Astro Flight Watt-Meter & CHECK your setup for yourself!

Jim
Dec 10, 2004, 11:55 PM
If it floats....sail it!
Elk Grove, CA
Joined Sep 2002
4,611 Posts
Quote:
 Originally Posted by a1pcfixer But why the sudden interest in watts? Mega's specs & LiPo specs deal only in amps & volts. Best you get an Astro Flight Watt-Meter & CHECK your setup for yourself! Jim

npm:
As a former HS Physics teacher, I can confirm you are correct!

fixer:
The reason Chuck is interested in watts is that is really what matters in working with motors. In fact, it is really the energy lost to heat that matters, since that is what heats up the motor and too much heat will either demagnetize the permanent magnets or melt the insulation on the windings, shorting it out. Programs like MotoCalc come in handy when selecting the correct propeller since they can show the watts lost to heat. The programs get you close, but real world testing (via current and voltage meters or an integrated meter like the Astro Whattmeter) is necessary, particularly if you are using expensive and current sensitive lipo packs.

The motor manufacturers give the limits in interesting ways; they specify the voltage limit since that is proportional to the rpm and if the motor spins too fast it will throw a magnet damaging the motor; then they specify the current limit since the wire is a fixed diameter and if you try to run more current through the wire it will heat up and melt the insulation, and then assuming you are running less than the max voltage and max current, they tell you the max wattage because that is all the heat the motor can dissipate (you check your own current x voltage).

These are all just approximations anyway. Depending upon how much air flow you have over the motor, and the ambient air temperature, you can push the motor past the specs without any trouble. The Stryker flown on a 50F day is great with motor out in the open and lots of cold air flowing over it. Put the same motor inside a Tiger Moth 400 with a fully enclosed cowl and you will cook it.

FoamCrusher
 Dec 11, 2004, 12:05 AM Tied to the whipping post Warm-Sunny-no-Wind, Az. Joined Dec 2003 2,483 Posts ChuckD Remember, when it comes to wives (who we love very much), its much easier to get forgiveness than permission especially when it comes to R/C planes. I was LOL at your earlier description of talking about justifying the expense of the hobby to your wife. Rgds, Mike
 Dec 11, 2004, 05:17 AM Cancelled Account Joined Oct 2004 738 Posts Thanks Jim, and again, Foam... Although becoming an avid pilot over the past few months, there are always the questions that humble me. My concerns with WATTS are driven simply from a guy who does not know better; and after three decades of 'just trying it' and then leaving 'it' in a box after I screwed it up...I now ask the proverbial experts before I jump. With age comes wisdom; and mine is the wisdom of inquiry...don't try to do plumbing, dont try to fix a microwave, and for the love of my mother...DONT HOOK UP A 4s LIPO to a 300 dollar power system and then toss it into the air if all you are going to do is make a flying ball of fiery styrofoam. (hey, it only took 30 years, right?) I still slip sometimes, though...like buying the wring gearbox for a mega motor...(see my post in 'power systems') Thanks for being my mentaurs in this new hobby...and I will have MORE questions. I do have a MEDUSA power meter...bet have not assembled all of the equipment yet...motocalc says my setup is good....I just want a 'human' opinion before I jump. ...gotta go get my parachute! Thanks a million, Chuck
Dec 11, 2004, 06:01 AM
Counter agent of B.S.
United States, IN
Joined Aug 2003
224 Posts
Quote:
 Originally Posted by FoamCrusher fixer: The reason Chuck is interested in watts is that is really what matters in working with motors. FoamCrusher
I'll grant you that watts is a part of the entire equation, but overall has little value to us in these particular situations. Both mfg's of these brushless motors & LiPo's are primarily concerned with MAX amp draw. The brushless motor's rating include cell count based on 1.2volt NiCd/NiMh style batteries, for voltage limitations.
Nice to know the wattage information, but we only need concern ourselves with amps & volts.

Jim
Dec 11, 2004, 06:14 AM
Counter agent of B.S.
United States, IN
Joined Aug 2003
224 Posts
Quote:
 Originally Posted by ChuckD Thanks Jim, and again, Foam... My concerns with WATTS are driven simply from a guy who does not know better; and after three decades of 'just trying it' and then leaving 'it' in a box after I screwed it up...I now ask the proverbial experts before I jump. (hey, it only took 30 years, right?) Chuck

Hey, we're ALL still learning, if not you're dead.

I've been checking my F-27 Styker brushless/LiPo setup for flight enduance times. WOT for most of a flight & I get around 9 minutes. Conservative flying, some motor off/gliding, and I've gone 16 minutes.

That's with a Mega 16/15/4, CC-25, Kokam 2000/15C-3S1P, and MAS 6X4 prop.

Quote:
 Originally Posted by ChuckD Thanks for being my mentaurs in this new hobby...and I will have MORE questions. I do have a MEDUSA power meter...bet have not assembled all of the equipment yet... Thanks a million, Chuck
Hmmmm, haven't yet heard anything about a Medusa power meter. Is that the one like AF's Super Whattmeter, but can connect to your PC?

Jim
 Dec 11, 2004, 06:17 AM Counter agent of B.S. United States, IN Joined Aug 2003 224 Posts All, Looking to order another Mega brushless motor & a Berg receiver for my second F-27 Stryker. Where online, did you get yours? Prices? Does anyone carry both items? Jim
 Dec 11, 2004, 08:27 AM Cancelled Account Joined Oct 2004 738 Posts ...I put all my stuff together from LHS, Hobby-Lobby (motor), and Bishop Power Products (ESC).... --C
Dec 11, 2004, 08:43 AM
If it floats....sail it!
Elk Grove, CA
Joined Sep 2002
4,611 Posts
Quote:
 Originally Posted by ChuckD ...I put all my stuff together from LHS, Hobby-Lobby (motor), and Bishop Power Products (ESC).... --C
AirCraft World in Japan - quick shipping (only \$2.50 world wide) and no sales tax. I get items here on the left coast within 5 days.

When looking for the best deal, the added tax and shipping make a difference when the total of all of the items starts getting up there. I can usually get another item for what I save buying from Dave.

Bishop PP, eDogFight, and e-Flightline are my other favorite places, but the CA sales tax is a price killer for me on big purchases.
 Dec 11, 2004, 10:22 AM "Marcy" VF-A Marysville, WA Joined Jul 2004 200 Posts I just saw an ad in the for sale section here. Hobbys and beyond are running specials until the end of the year. I haven't dealt with them yet, but may place an order. "combo deal= Mega 16/15/4 and CC Phoenix 25 =\$135.00 " They are offering free shipping too. Best price I've seen yet. Tim
Dec 11, 2004, 11:58 AM
Counter agent of B.S.
United States, IN
Joined Aug 2003
224 Posts
Quote:
 Originally Posted by FoamCrusher AirCraft World in Japan - quick shipping (only \$2.50 world wide) and no sales tax. I get items here on the left coast within 5 days.

Well, I just made my first order from them. Getting a Berg 4*DSPII MICRO STAMP Rx 72Mhz with FREE CRYSTAL, 2 micro servo's, a Mega 16/25/3, and connectors.

This being the weekend, I'll fathom a guess at sometime around Dec 21-23rd to get to me in N.W. Ind.

Thanks ALL for your input on dealers!

Aircraft World

Jim
Dec 11, 2004, 03:23 PM
Registered User
shawnee, ks
Joined Apr 2004
898 Posts
Quote:
 Originally Posted by wekenav8r I just saw an ad in the for sale section here. Hobbys and beyond are running specials until the end of the year. I haven't dealt with them yet, but may place an order. "combo deal= Mega 16/15/4 and CC Phoenix 25 =\$135.00 " They are offering free shipping too. Best price I've seen yet. Tim
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