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e-MS Composit Hornet > Motor Analysis with Power System Comparison Spreadsheet
 
 
JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		I've been using a spreadsheet posted by K.C. on e-zone called the Power System Comparison spreadsheet. It really does a good job of taking into account the main contributing factors when analyzing a given battery/ESC/motor/gearing combination. Several folks have commented on how closely this spreadsheet comes to estimating the performance of a certain setup; so, its results are believed to be pretty decent.

Using the spreadsheet with the following parameters...
Average Power: 40 W (this is rotor power after all other system losses)
Peak Power: 100 W (this is rotor power after all other system losses)
Minimum Headspeed: 2000 RPM
Wiring Resistance: 10 mOhm
Main Gear: 180 teeth
Gear Stages: 1 Stage
Gear Loss: 3 %
Heli Weight: 12 oz (heli without ESC, motor, or battery) (Am I close???)
CC PH-10
E-tec 3S 1200 battery

I get these results...

Code 

Motor              Pinion  40W RPM/Eff%  100W RPM Drop/Eff%  Weight  Price



Astro 010 8-turn     10     2475   78.8      386       72.0    32     75



Hacker B20 22S       11     2672   77.5      443       70.5    40     99



Razor Micro Heli V2  10     2548   80.1      457       70.2    27     85



Himax 2015-4100      10     2497   72.0      545       63.7    48     52



Astro 010 10-turn    12     2505   79.2      565       65.5    32     75


Ahh... From those results it would appear that the Astro 010 8-turn motor is actually the BEST of these five motors because it has the lowest headspeed drop under load. It also has the lowest peak current at 100 W.

Comments? Please suggest any changes I should make to the parameters such as target headspeed, heli weight, etc.

Thank you,
John
12-29-2003 Over year old.
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jeff1
Senior Heliman
Location: Ottawa, Ontario, Canada

My Posts This: Topic  Forum		Where did you see a Razor for $125? If it was zebrahobby.ca, it is in canadian funds. Razor is actually about $85US. This changes order as follows:

Astro 010 8-turn, 386 RPM, $75
Razor Micro Heli V2, 457 RPM, $85
Hacker B20-22S, 443 RPM, $100
Himax 2015-4100, 545 RPM, $52
Astro 010 10-turn, 565 RPM, $75

For $10 extra, I'd get the Razor.
12-29-2003 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		> Where did you see a Razor for $125? If it was zebrahobby.ca ...

Oops. Thanks jeff1. Changing the price doesn't change the order from lowest to highest bog under load.

> For $10 extra, I'd get the Razor.

Why would you buy the motor which sags/bogs more under load? And costs more?

I did notice that on the Astroflight site they quote the 010 10-turn as 85 W max power and the 010 8-turn as 75 W max. Does anyone know the manufacturers stated max power output for these other motors? Does anyone have Whattmeter readings from their Hornet II to know just how much these things are pulling?

Thanks,
John
12-29-2003 Over year old.
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hornet dave
Key Veteran
Location: Pittsburgh PA USA

My Posts This: Topic  Forum		Cool, we're somewhat on the same page with respect to power loads. I was using 45 and 80 watts, you're using 40 and 100. That's close enough for me.

Could you also list the efficiencies at 40/100 watts for each of those motors? Efficiency has a snowball effect, as higher efficiency means lower current which means either smaller lipos may be used and/or the batteries will last for more cycles, etc. I was getting about 71% effy with the himax vs 78% for the razor/hacker, which meant a difference of about 2 minutes of flight time.
12-29-2003 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		hornet dave,
I will update my first post to this thread tonight with more numbers from the spreadsheet. I wouldn't call 2 minutes less off of the about 18 min predicted flight times much of a sacrifice for more power.

- John
12-29-2003 Over year old.
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hornet dave
Key Veteran
Location: Pittsburgh PA USA

My Posts This: Topic  Forum		You know, playing with the spreadsheet, it almost seems that an astroflight 9 turn 010 motor would be perfect. Too bad it doesnt exist.
12-30-2003 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		I updated my original post with more data for each motor. It seems very clear to me that the Astro 010 8-turn motor would be a great motor for our application. I have e-mailed AstroFlight to ask if there is any way to get this motor with a 2 mm shaft. It is currently only available with an 1/8" shaft.

I'm also not sure why everyone is clamoring for the Razor motor when better motors exist.

hornet dave,
Why not just go with the 8-turn?

- John
12-30-2003 Over year old.
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hornet dave
Key Veteran
Location: Pittsburgh PA USA

My Posts This: Topic  Forum		The 8 turn is sure intriguing, the only thing I dont like about it is that you cant slip on a smaller pinion to de-tune the headspeed. If I'm looking at the spreadsheet correctly, it looks to be in a useful efficiency range and should be a good high-power 3d choice.

The spreadsheet shows that the hacker, razor, and astro 8 turn have similar efficiencies at the 40 and 100 watt levels, the astro and razor being quite a bit lighter and cheaper than the hacker. The advantage of the razor, other than 4 or 5 grams of weight, is that you do not need to custom order one. Of course, they're never in stock anywhere, so that's not much of an advantage. If the 010 8 turn was readily available with a 2mm shaft, perhaps it would be the motor of choice. I am not aware of anyone who's tried one yet on a hornet. Let us know what kind of response you get from Astro.

I am not convinced that the RPM drop under load is a very important variable, as long as you can get the power you want at the headspeed you want. If you run your speed control in non-governed mode at 100% throttle, then I guess the RPM drop under load would be a little more important, but that's not how I set up my heli. A governor or throttle curves make it all a non-issue I would think. Perhaps I'm just not seeing something.

Oh, the razor MH needs an 11 tooth pinin to get the headspeed shown in your chart, I'm sure that's just a typo. That is, in fact, the combination I use, with the headspeed governed to 2400 RPM, on a Hornet I. It bogs just a little with full collective, just as the spreadsheet predicts. It's been a nice combination for my lightweight hornet (260 grams or so).

Playing with that spreadsheet sure is fun, isnt it?
12-30-2003 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		> Oh, the razor MH needs an 11 tooth pinin to get the headspeed
> shown in your chart, I'm sure that's just a typo.

Nope, the spreadsheet is showing that headspeed, 2548 RPM at 40 W, with the a 10-tooth pinion. Did you use kV = 4300 rpm/V, Io = 0.4 A, and Rm = 120 mOhm? CC PH-10 and 3S Etec 1200? Without all those being the same, we would, of course, get slightly different numbers.

> If you run your speed control in non-governed mode at 100% throttle, > then I guess the RPM drop under load would be a little more
> important

The most efficient setup is to be as close to or at 100% throttle as much as possible. This has been verified in real life tests. Doing so minimizes heating and lengthens flight times. Proper gearing should be used to get the headspeed correct. I can explain more if you would like.

Maybe it isn't as important with these little helis, but guys doing serious testing of Logo 10 and larger helis are finding that the RPM drop under load is an important indicator of how the heli will perform. The best performing setups are those running at or near 100% throttle with a motor/battery/gearing setup which drops very little under full load.

> Let us know what kind of response you get from Astro.

Certainly will. Nothing yet. Of course, I just wrote them near the end of the word day today.

> Playing with that spreadsheet sure is fun, isnt it?

Yes, it really is. The neat thing about it is that it seems to be doing well when compared to real life tests!

- John
12-30-2003 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		Here is a quick example of why partial throttle is "bad."

Assume a given heli hovers at 100 W rotor power. Further, assume that the no load battery voltage is 20 V and the system losses are 20 W due solely to I^2R losses. So, 120 W / 20 V would imply a current of 6 A and a system "R" of 0.555 Ohm.

Now, reduce the throttle to 80 % and assume that means 80 % average input voltage or 16 V. Since the heli still requires 100 W rotor power to hover, the average current is now found by solving 16 I - 0.555 I^2 = 100 or I = 9.17 A and system losses are now 9.17^2 * 0.555 or 46.7 W.

Thus, reducing the throttle to 80% more than doubled the system losses and those losses are directly expressed as heat in the battery, ESC, and motor as well as reduced flight times.

Does that make sense?

- John
12-30-2003 Over year old.
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hornet dave
Key Veteran
Location: Pittsburgh PA USA

My Posts This: Topic  Forum		Yeah, I've been following some of the threads on the larger e-helis, I agree that part throttle is something best used in moderation. I know the guys with bigger e-helis burn up controllers when they throttle back, but my personal preference is a governor, mostly because too much speed causes havoc with my tail rotor. The Phoenix 10 handles it without so much as a hiccup.

I see the error in my version of the spreadsheet - it looks like the included motor data uses the original razor micro-heli motor, not the V2 version. Good catch John.

Now that I've got my new canopy finished, I think I'll fly out a couple batteries tomorrow if it isnt snowing. I'm hoping to not crash, so I can get some endurance figures for my Irate 850 batteries.
12-30-2003 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		Well, it looks like AstroFlight is going to be less than helpful in my mission to get an 010 8-turn in a micro-heli. Here are their responses to my inquiry. Unedited.

> the best motor for the hornet is our heli motor
> made especially for the hornet.
> 801H

Too which I responded that I had asked about the 8-turn with a 2 mm shaft not about which motor they think is better. That got me this.

> we do not make that version of the motor

I was very nice in my e-mails and even gave them a link to this thread and the analysis. Oh well.

Now I will find out how guys who have had motor shafts turned down did it. There are guys turning 5 mm shafts down to 1/8" in order to fit smaller pinions when using high voltage LiPo setups.

- John
12-31-2003 Over year old.
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Buzzsaw46
Veteran
Location: Spring Valley, MN.

My Posts This: Topic  Forum		I turned a 3.2mm mega shaft down to 2.3mm by clamping the motor in a vice with esc connected a receiver and my tx I was able to spin the motor and grind the shaft down with a dremel and a fiber cutoff disk. not ideal method but if you take your time and dont heat the shaft up too much as you turn it down it is possible.
12-31-2003 Over year old.
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hornet dave
Key Veteran
Location: Pittsburgh PA USA

My Posts This: Topic  Forum		That's too bad about Astro. It was worth a try, though. And this is one more scenario where I really wish I still worked in a machine shop.
12-31-2003 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		Good News!

Good news! A 12-tooth pinion can succesfully be drilled out to 1/8". I had a friend with access to a machine shop at work take in the Astro 010 8-turn and a stainless steel 12-tooth pinion and have the pinion drilled for a nice tight press fit. It came back perfect!

One of these days here soon I'll get my H2 done and get to test it out. I now have a Razor Micro Heli V2 and a Himax 2015-4100 to compare it to. I may even send it to Eric Larson and let him test it out.

- John
01-16-2004 Over year old.
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bgotori
Heliman
Location: Los Angeles, Ca.

My Posts This: Topic  Forum		Hey JKos

I thought you said in another Post AstroFlight can make an 8 turn 010 with a 2mm shaft???

Also where do you download the Program""spreadsheet posted by K.C. on e-zone called the Power System Comparison"" Looked all over and can't seem to find it???

Thanks for all the work you've done so far really helps a lot of us!!!


Thanks!!!

Brad Gotori
bgotori@hotmail.com
01-16-2004 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		> I thought you said in another Post AstroFlight can make an 8 turn 010
> with a 2mm shaft???

Only if someone orders a large enough custom batch or we can convince them to start making them as a standard item.

> Also where do you download the Program "spreadsheet posted by
> K.C. on e-zone called the Power System Comparison"

Here is a link to the thread about it: http://www.rcgroups.com/forums/show...threadid=163662

A link to the Excel spreadsheet is in the first post. Another thread was also started about it because the first got so long: http://www.rcgroups.com/forums/show...threadid=180339

Hope that helps.

- John
01-16-2004 Over year old.
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wedge
Elite Veteran
Location: Victoria BC, Canada

My Posts This: Topic  Forum		I want to get the himax 2015-4100 will this be ok to use on a 2cell lipoly.

Thanks

Wedge
01-16-2004 Over year old.
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wedge
Elite Veteran
Location: Victoria BC, Canada

My Posts This: Topic  Forum		What about an Razor RZ 300, will it have good power on a 2cell lipoly.

Thanks again.

Wedge
01-16-2004 Over year old.
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JKos
Elite Veteran
Location: Soon to be Los Angeles

My Posts This: Topic  Forum		Wedge,
Neither motor looks very promising on 2S LiPos. These brushless motors work much better on 3S. The problem is that the required current levels are too high at the 2S voltage levels.

It takes the same power to hover and fly the helicopter around with 2S as it does on 3S except for the small weight difference. Since the voltage of the 2S is lower, more current must be drawn to achieve those power levels.

- John
01-16-2004 Over year old.
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e-MS Composit Hornet > Motor Analysis with Power System Comparison Spreadsheet
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