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Old Apr 02, 2007, 02:32 PM
Flying motor mount master
fly_boy99's Avatar
San Jose, California, United States
Joined Oct 2004
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Again Steve thanks so much for your support.

Quote:
Originally Posted by sneu
All you need to do is a Google search--you will find that one of the best books is : Brushless Permanent Magnet Motor Design It does cost real money($150)!

Your "tests" will only prove that you can generate heat

Steve
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Old Apr 02, 2007, 04:56 PM
Electric Hippy
Brisbane
Joined Nov 2005
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Quote:
Originally Posted by fly_boy99
For posterity... by the way it's your



p.s. Besides I have no idea why you care if I conduct experiments
at all? You never wrote any books so who are you to talk theory?
Experiments are good. I am glad you are not discouraged.

"There are those that read and quote books and those that write books".
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Old Apr 02, 2007, 05:00 PM
Electric Hippy
Brisbane
Joined Nov 2005
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With experimentation we will soon have outrunners with greater efficiency that inrunners. Inrunners will then be liken to glow motors and we will wonder why we ever persisted with them.
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Old Apr 02, 2007, 05:18 PM
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sneu's Avatar
United States, CA, San Diego
Joined Dec 1999
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Quote:
Originally Posted by Eagleburger
Experiments are good. I am glad you are not discouraged.

"There are those that read and quote books and those that write books".
Fumbling in the dark may be fun--but without some basic book work you will not have much to show for your work. Motor design work is much more than rewinding some stators and sticking magnets a steel ring and running until it flames!. If you think you will discover the perfect motor with that method--dream on!

Just what have you published lately in regards to brushless motors? I suspect very little.

Have you ever actually designed a brushless motor from scratch?

Steve Neu
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Old Apr 02, 2007, 05:19 PM
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United States, CA, San Diego
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Quote:
Originally Posted by Eagleburger
With experimentation we will soon have outrunners with greater efficiency that inrunners. Inrunners will then be liken to glow motors and we will wonder why we ever persisted with them.

Oh really

Steve
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Old Apr 02, 2007, 05:27 PM
Dance the skies...
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United States, MA, Walpole
Joined Dec 2003
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Meanwhile, back at the Scorpion Ranch...

To get this back on topic, I decided to try the Scorpion 2212-26 and see for my self how it compares with my AXI of the same nomenclature. I hope my static tests show decent agreement with those of Dr. Kiwi in the 10 in. prop range.
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Old Apr 02, 2007, 05:41 PM
200 mph club
r/cmark's Avatar
United States, AZ, Fort Mohave
Joined Mar 2005
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Lucien,
I have a 3-D plane 19oz AUW. I have some 1320 3 cell packs. I do not want to go fast. I want lots of pulling power. What Scorpion would you recommend?

Thanks,
Mark
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Old Apr 02, 2007, 08:18 PM
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Chattanooga, Tennessee, United States
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Quote:
Originally Posted by Tom Frank
To get this back on topic, I decided to try the Scorpion 2212-26 and see for my self how it compares with my AXI of the same nomenclature. I hope my static tests show decent agreement with those of Dr. Kiwi in the 10 in. prop range.

So do I, Tom - or else one of us is, or both of us are, wrong!
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Old Apr 02, 2007, 08:47 PM
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unbalanced prop's Avatar
Washington, PA, USA
Joined Aug 2003
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Quote:
Originally Posted by Tom Frank
To get this back on topic, I decided to try the Scorpion 2212-26 and see for my self how it compares with my AXI of the same nomenclature. I hope my static tests show decent agreement with those of Dr. Kiwi in the 10 in. prop range.
I would like to see your results also. Two heads can be better then one!

Doug
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Old Apr 02, 2007, 09:31 PM
Innov8tive's Avatar
Joined Jan 2007
1,715 Posts
Were ae back from the RCX Show!

Hello everyone!

I have been a little out of touch the past couple days since Scarlett & I were exhibiting at the RCX show this past weekend. It was a very good show, and with our booth facing right at the indoor flying area, we got non-stop entertainment the entire weekend!


Time to get back to answering questions in the order that they were received..........

ukpaul,

I must say that I agree with the good Doctor on this one. To get almost 32 ounces of thrust out of an APC 10x4.7 at 6,825 RPM would require operation on a planet where the air was a little thicker than it is here on Earth! On my thrust stand, I got 30.26 ounces of thrust with an APC 10x4.7 turning at 7,375 RPM. To get 32 ounces of thrust requires about 7,500 RPM for that prop.

I am not saying that anyone is lying or misrepresenting their products, sometimes you just get bad readings from your equipment. I know that my test stand is built well, with ball bearing pivots, and I have checked the thrust readings with known weights measured on calibrated scales, so I think my numbers are pretty good.

I just purchased a new Medusa Load Cell to go with my Medusa Power Analyzer, and I will be hooking it up in the next day or two and see how it compares with my current numbers.

To answer your original question, For a 14 ounce plane, if you want true 3D performance with plenty of "Grunt" then you will be looking for 2:1 thrust to weight or more at full throttle. An excellent choice for that plane would be the Scorpion 2215-18 motor turning an APC 10x5E prop. As I have said before, the 10x5E is a MUCH more efficient prop than the 10x4.7 SF prop, and when running on 3 cells, the 10x5E produces 13-14% MORE thrust with 13-14% LESS current draw than the 10x4.7 SF.

With 10.5 volts at the ESC, with the 2215-18 motor turning the 10x5E prop, I measured 16.9 amps, 177 watts, 8,350 RPM, 964 grams or 34 ounces of thrust. That kind of power would make a 14 ounce plane into a rocket ship!


Just to clarify a couple things, on my test stand, I have a 20 volt 70 amp power supply that has remote sensing. I have the remote sense leads connected to a short Male-Female Deans plug adapter that I plug right into the input side of the ESC, then I plug my power supply leads into the other side of the remote sense plug. With my power supply set up this way, I do not have to tweek the power supply each time I run up a prop to compensate for the voltage drop across my power supply leads, the remote sensing does it automatically. In this way, whether I am drawing 1 amp, 10 amps 20 amps or even 50 amps, I always have the exact same voltage right at the input of the ESC.

By testing this way, I get consistant results for all the motor tests. If a Li-Po battery is in good condition, and it is sized properly for the current draw, you will get very close to 10.5 volts under load, so that is why I test at that voltage.

Many other people test their motors with a Li-Po battery instead of using a regulated power supply. While this can give you what could be considered a "Real World" set of values, the data you collect is not repeatable, and as such is not very valid. When using batteries, you need to use a battery that will pull a consistant C value during each test to have the voltages be consistant. So for example, this would mean using an 800mah battery if you are testing an 8 amp motor, and a 1200mah battery if you are testing a 12 amp motor and so on. Not very practical!



Tom Frank,

We received your order, and will process it tonight and ship out tomorrow. On my test stand, with 10.5 volts in, I got 10.04 amps of current draw on an APC 10x5E prop, 105 watts, 7,100 RPM, 642 grams or 22.6 ounces of thrust.





r/cmark,

You did not say what C-Rating your 1320mah batteries were, but let's assume that they are 15C just to be on the safe side. I tend to be a little on the conservative side when it comes to batteries. I NEVER push batteries anywhere near their "Maximum Rating" in actual use. I sell Li-Po batteries, and I will be the first to tell you that 20C battery can be discharged at 20C for a full flight 1 time, and after that the performance will start to diminish. I personally like to size my batteries so that the most I ever pull is 75% of the maximum rated current.

Based on this, for a 1320mah battery pack, if you have a 15C pack, the "Maximum Rating" of the battery is 19.8 amps, and if you have a 20C battery the max would be 26.4 amps. For me, I would not feel comfortable pulling more than 14.8 amps from a 15C pack, or more than 19.8 amps from a 20C pack.

If you want lots of thrust, without much speed, then the motor for that application would be the 2215-22. I like running the GWS HD series props, since they seem to be a little more efficient than the APC SF series. The pitch is also a little flatter than advertised, so a 10x6 is actually more like a 10x5, and an 11x7 is actually closer to an 11x6. On 3 cells, the 2215-22 motor will turn a GWS 10x6 prop at 7,475 RPM, and use 11.02 amps of current for 115 watts. I measured 717 grams or 25.29 ounces of thrust. This is a little less than you are looking for, but makes for a nice long leasurely flight.

Stepping up to a GWS 11x7 prop the current will go up to 14.27 amps for 150 watts of power. The prop will turn at 6,350 RPM and produce 868 grams or 30.6 ounces of thrust. That would pull your 19 ounce plane around pretty good. Not steller 2:1 thrust to weight, but still good enough to hover and have enough left over for a nice pull-out.


Take care everyone, and I will talk to you later!

Lucien
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Old Apr 03, 2007, 08:13 AM
Keep it up, I'm reloading
WACOFlyer's Avatar
In my home
Joined Jan 2006
775 Posts
Lucien,

Is it possible for you let us know what new stuff you will be selling at Toledo right before you leave for the show?
We need to know how much $$$ to bring along.
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Old Apr 03, 2007, 10:16 AM
Innov8tive's Avatar
Joined Jan 2007
1,715 Posts
No Problem!

Of course I can! I have some new stuff coming in this week, so as soon as I am sure of what I have, I will post a list here.

Lucien
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Old Apr 03, 2007, 11:19 AM
Keep it up, I'm reloading
WACOFlyer's Avatar
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Looking forward to it.
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Old Apr 03, 2007, 11:27 AM
Dance the skies...
Tom Frank's Avatar
United States, MA, Walpole
Joined Dec 2003
17,187 Posts
Lucien,

On the 2212 model, can you tell me how far in front and aft of the motor housing the shaft protrudes? And can the set screw on the collar(s) be loosened to slide the shaft fore/aft if desired (is there a flat on the shaft for the set screw?).
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Old Apr 03, 2007, 11:53 AM
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Chattanooga, Tennessee, United States
Joined May 2003
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I haven't checked whether one can alter the shaft position, but on my 2212-26 the shaft protrudes 5.85mm from the boss at front of the bell (10.35mm from the flat face of the bell), and at the rear 7.65mm beyond the collar (12.15mm from the "rear face" with the threaded mounting holes in it).
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