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Old Sep 02, 2011, 08:46 PM
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United States, IL, Crystal Lake
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Originally Posted by NoMatta View Post
Well gents, I won't try to convince you of what is, is. Can't cram a course of electrical theory into a couple of posts. Won't try to convince anyone of anything. I just know how it works.

On to flying. Finally got the Edge up today, and wouldn't ya know it. Busted my 22-8 on the first flight, then left the wing tube for the eYak at home. Maybe better luck tomorrow.

Later on
Bummer about breaking the prop...I've busted a few 18x10's recently...can't imagine what its like breaking a 22x8 but it can't be good. What happened? Landing speed to slow? Crosswind? Gremlins on the runway?

Better luck tomorrow indeed!
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Old Sep 02, 2011, 09:02 PM
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United States, PA, Bellefonte
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Originally Posted by NoMatta View Post
Well gents, I won't try to convince you of what is, is. Can't cram a course of electrical theory into a couple of posts. Won't try to convince anyone of anything. I just know how it works.

Later on
Wayne and Bob are spot on Nate. I have done a many of re-winds and tested all the different solutions, mag wire sizes, and tested out puts, its great stuff but is hard on the fingers and eyes.

The trick many people over look is getting the most WATTS without voltage drop, there is the sweet spot.
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Old Sep 02, 2011, 09:10 PM
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USA, TX, Springtown
Joined May 2008
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I will try to get an image of all three phases on a brushless motor next week for everyone to see.

Say you have a DC power supply, switch, ammeter, and resistor in series. The power supply is 100V and the resistor is 100 ohms. Throw the switch to on and the ammeter will read 1A (100/100). An ammeter is a voltmeter across a shunt and it shows you the average current across a low value resistor. You don't see the instantaneous changes in the current.

Now if you start toggling the switch rapidly, the average current in the circuit is less than 1A. The on/off sequence tells you that it would not be 1A continuous. Let's say that you can perfectly toggle the switch so that the time on and the time off are exactly equal and it does it pretty fast. This would be a 50% duty cycle, on half the time and off half the time. The ammeter is going to show .5A. If your ammeter was fast enough, it would fluctuate between 0 and 1A. If switching is sufficiently faster than the meter response, you would only see the average value.

Assuming that there are no other components in the curcuit and the power supply is able to deliver 100V @ 1A instantly, then the actual current in the circuit is always V/R. So 1A flows if the switch is on and 0A flows with the switch off. Toggling the switch results in less average current, .5A, with 1A pulses.

I don't know if this is explained too well.
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Old Sep 02, 2011, 09:21 PM
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Portland, Oregon
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You do fine, Wayne. I presume you have either self educated yourself on electrics, or have a background in the subject. I'm an electrician of 45+ years as well as an instructor for 18. I know that sometime it seems we deal in witchcraft, but your on-off switch analogy is dead on for BLDC motors. I think some run into a confusion with brushed motors where speed is voltage (and load) determined, since the commutation is by the brushes, where our brushless motors are electrically commutated and the speed is controlled by the speed of the pulses from the ESC.

Probably won't have a new prop for the Edge tomorrow, so I'll likely fly the eYak and my T150. Go by the hobby shop on the way and pick up the prop, but won't be able to drill it without coming home to the drill press.

Later on
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Old Sep 02, 2011, 09:39 PM
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winston mo
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Originally Posted by mschulz View Post
I thought Kerwin50 was from Missouri ("Show Me")
Yes I am from missouri and I can truly say this, our brushless motors are inductive in nature because of the field winding. So when the fet ( feild effect transistor)1st turns on the feild is going to opose current flow and when the fet turns off you are also going to have counter EMF resitng the stopage of electron flow, There by creating an AC resistance along with your DC resistance there .
Here's the link on the therory of inductance
http://en.wikipedia.org/wiki/Inductance
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Old Sep 02, 2011, 09:41 PM
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Washougal, Washington, United States
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Originally Posted by mt_flyer View Post
... GOT FISH FOR DINNER!!



Nate, I'm with you on this.
I have used meters and seen the readings... I don't see max amps through the complete throttle range......
I put the meters in line between the esc and the battery, and between the motor and esc.
The Wattmeter only displays the AVERAGE amps being used, not the instantaneous amps. It will measure 60 amps for 10% of the time, and zero amps for 90% of the time, and it then displays 10 amps.
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Old Sep 02, 2011, 09:55 PM
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winston mo
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Guys look at my new toy
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Old Sep 02, 2011, 10:00 PM
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United States, PA, Bellefonte
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Originally Posted by kerwin50 View Post
Guys look at my new toy
NICE K50! 3DHS Awesomeness

I got a new one to share to
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Old Sep 02, 2011, 10:02 PM
3d NOOBular
3DNater's Avatar
USA, UT, St George
Joined Aug 2010
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Quote:
Originally Posted by waynemia View Post
I will try to get an image of all three phases on a brushless motor next week for everyone to see.

Say you have a DC power supply, switch, ammeter, and resistor in series. The power supply is 100V and the resistor is 100 ohms. Throw the switch to on and the ammeter will read 1A (100/100). An ammeter is a voltmeter across a shunt and it shows you the average current across a low value resistor. You don't see the instantaneous changes in the current.

Now if you start toggling the switch rapidly, the average current in the circuit is less than 1A. The on/off sequence tells you that it would not be 1A continuous. Let's say that you can perfectly toggle the switch so that the time on and the time off are exactly equal and it does it pretty fast. This would be a 50% duty cycle, on half the time and off half the time. The ammeter is going to show .5A. If your ammeter was fast enough, it would fluctuate between 0 and 1A. If switching is sufficiently faster than the meter response, you would only see the average value.

Assuming that there are no other components in the curcuit and the power supply is able to deliver 100V @ 1A instantly, then the actual current in the circuit is always V/R. So 1A flows if the switch is on and 0A flows with the switch off. Toggling the switch results in less average current, .5A, with 1A pulses.

I don't know if this is explained too well.
So this seems to make it a little more clear. To a lay person who has only a very basic understanding of what is going on it sounds like the amp reading I get from my watt meter is average amps. Is that right? If the amps are averages then I suppose it follows that the watts are averages too? I am guessing that WORK or LOAD is still the driver behind amps. I just don't understand how it all works. Is there a direct ratio between the load at full throttle and the instantaneous current transfer at a lower throttle setting? I know brushless motors have a much more linear torque curve than an engine but is it perfectly linear?

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Originally Posted by NoMatta View Post
You do fine, Wayne. I presume you have either self educated yourself on electrics, or have a background in the subject. I'm an electrician of 45+ years as well as an instructor for 18. I know that sometime it seems we deal in witchcraft, but your on-off switch analogy is dead on for BLDC motors. I think some run into a confusion with brushed motors where speed is voltage (and load) determined, since the commutation is by the brushes, where our brushless motors are electrically commutated and the speed is controlled by the speed of the pulses from the ESC.


Probably won't have a new prop for the Edge tomorrow, so I'll likely fly the eYak and my T150. Go by the hobby shop on the way and pick up the prop, but won't be able to drill it without coming home to the drill press.

Later on
I am really sorry if I offended you or anyone else. I find that my best learning comes from challenging ideas to get to the truth as quickly as I can. I apologize if my tone got confrontational. Mike (mshulz) and I spent a little time researching it. Basically mike shot me a series of links as he came across them. I am not going to pretend to have a deep understanding of it nor am I likely to... I'm more confused now than ever.
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Old Sep 02, 2011, 10:35 PM
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NoMatta's Avatar
Portland, Oregon
Joined Sep 2008
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No offense taken. It's sometimes difficult for me to break things down since I've been in the field for so long. Wayne really does a better job. The whole electric thing can be a bit difficult to wrap your head around. Just to add to the confusion, you work your controller harder at part throttle than a full throttle. Just one more of those magic things. Best plan that I follow when dealing with new stuff is to digest a bit at a time and try not to make expensive mistakes (Not to say that I alway follow my own advice.

Re: the wattmeter, yes it only shows average not instantaneous values. I use mine primarily to make sure that my full throttle values do not exceed the component values, and to watch my battery voltages under load. This usually saves the expensive stuff. I just killed my T40 motor by consistantly running a 4 cell max motor on 5 cells for a couple of years, but I figure the fun was worth the $35.00 I paid for the motor. Just did not like the pancake landing and of course the required repairs (in the typical places). The new motor will be a step up.
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Old Sep 02, 2011, 10:58 PM
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United States, IL, Crystal Lake
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Originally Posted by kerwin50 View Post
Guys look at my new toy
Quote:
Originally Posted by DaOldGuy View Post
NICE K50! 3DHS Awesomeness

I got a new one to share to
Woo hoo!
More 3DHS awesomeness (and addiction)!
Welcome to the addiction, Kerwin!
Ron, this isn't your first 3DHS airframe, is it?
Pic attached of my Vyper since we're all showing off our 3DHS airframes!
Sounds like 3DHS may be back on line very soon...and they have a new EPP Slick coming out as soon as they go back on line!

My lesson about all the electric stuff is to trust Ben & co and go with their recommended components from now on! (but of course, test everything myself [to my limited ability] even so).

-Mike
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Old Sep 02, 2011, 11:06 PM
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Washougal, Washington, United States
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Originally Posted by mschulz View Post
Woo hoo!
More 3DHS awesomeness (and addiction)!
I found out the other day from a guy at our flying field that "3DHS" stands for "3D Hobby Shop" You guys and your acronyms drive me crazy!
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Old Sep 02, 2011, 11:19 PM
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United States, PA, Bellefonte
Joined Dec 2007
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Originally Posted by mschulz View Post
Welcome to the addiction, Kerwin!
Ron, this isn't your first 3DHS airframe, is it?
Pic attached of my Vyper since we're all showing off our 3DHS airframes!
-Mike
I have a 51 AJ Slick <orange> that I am hoping for some stick time this weekend.

Quote:
Originally Posted by balsabuster2004 View Post
I found out the other day from a guy at our flying field that "3DHS" stands for "3D Hobby Shop" You guys and your acronyms drive me crazy!
3DHS stands for Awesomeness.... 3D Hobby Shop is its day job.

I got to see the BIG Awesomeness at Ohio, 126" AJ Slick with a 200cc Fox twin....

Who knew Awesomeness could be that dang big!
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Old Sep 02, 2011, 11:23 PM
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NoMatta's Avatar
Portland, Oregon
Joined Sep 2008
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Now that I like. Always wondered about the Fox gassers. Always loved my glow engines. American made???

Don't think I could get in my Camaro, though
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Old Sep 02, 2011, 11:27 PM
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Prineville Oregon
Joined Jan 2007
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makes sense to me now too. Bob I just figured your just cramped up from planes in your lap and fumes riding around in that Camaro lol
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