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Old Dec 05, 2007, 09:03 PM
And You're Not
Timbuktu, Mali (Happy?)
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Things that make you go hmmm..

In This Post, mrm1 does an excellent job of recording a data set for the Scorpion 3014-18.

The 3014-18 (and all Scorpion motors, for that matter) seems to be a great value in performance vs cost. I know they are well thought of here.

The 3014-18 weighs a bit over 4oz, so not a lot of weight for a 600w max motor.

But after looking at the numbers, something didn't seem to add up.

So I thought back on some motors I'd run, specifically on an APC 12x6E. Then I remembered doing a ratio swap on a Lehner 1020/15 in a Cobri, from 6:1 to 5:1 and getting about 8K on that prop (I'd been getting about 6400~6500 RPM on the 12x6SF at 6:1, way over the recommended RPM).

Sure enough, 8000~8050 RPM on the 12X6E, I just checked it on a 3S 2100 ProLite, 5:1 (70/14).

Thing is, the 4oz 3014-18 took 42.26A/423W to get the 8025 RPM. The 1020/15 and Cobri (with collet adapter) weigh just over 3oz.

And it only took 32.5A/335W to get 8025 RPM. 10A and 1oz less. That was surprising, even to me.

Now no doubt about it, the Lehner/Cobri is going to cost a LOT more than the Scorpion, and no way will the 1020/15 EVER do 600W, but still...

25% more amps/watts for the same RPM just made me go Hmmm.

And I'm not in any way dissing the Scorpion. It's as good as any outrunner it appears, a fine value to be sure. It was just the disparity that caught my eye.
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Old Dec 05, 2007, 11:08 PM
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Hastings, Hawkes Bay, New Zealand (Aotearoa)
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Using Rod Badcocks efficency calculator I get ~70% for the Scorpion and ~84 for the Lehner/Cobri combo.

As long as the tests are performed with the same make/model prop then they should form a valid comparison.


Heather
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Old Dec 05, 2007, 11:54 PM
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That's an interesting comparison. And valid, too, as you say, Heather.

What we don't really get from the comparison, however, is a definitive characterization of each power system. We don't know if the point data represents the ultimate potential of each motor.

For example, looking at the prop data on the innov8tive website, I saw that the 3014-18 can swing an APC 11x5.5E at 9K with 330W input at about 79% efficiency. That setup gives the same pitch speed as the Lehner/Cobri with the 12x6E, at the same power input, with only 200g or so less thrust. Efficiency, thrust, p-speed figures from the Badcock calc.

Of course, we don't know the ultimate capabilities of the Lehner either.*

Andrew

*P.S. But there are dyno plots on the Lehner site for some of their motors.
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Old Dec 06, 2007, 09:39 AM
And You're Not
Timbuktu, Mali (Happy?)
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I'm not out to try to best the Scorpion on every prop. To get over 9K RPM would probably require a gear change, I'm not really interested in even doing that (although I have the gears and even the 11x5.5E).

I just remembered breaking 8K on the 12x6E after I swapped pinions last time. B-P-P sold the 1020/15 with a 12T pinion already installed, and you could get at max a 5.83:1 if you filed a little of the Cobri box away. 6:1 was the steepest ratio that was easily obtainable. At 6:1 (or even 5.83:1), the 12x6E only loaded it to about 200~230 watts on 3S lipos I think I recall. Both the 12x6SF and the 14x7E were in the ~6500 RPM/325W range. I didn't like running the relatively large/heavy 14X7E, and that's 1K RPM past the max for a 12X6SF.

So a buddy had a 1020/12 that would spin the 12x6E up in the 325 watt/8K RPM range at 6:1 on 3S, and I installed a 14T pinion to try to get a similar prop kv from the /15. And when I ran it, I remember that it did break 8K RPM, and the watts were back up, but that was a while back and I'd never got around to mounting it on a plane. That's really all this was about, seeing 8K RPM on a 12x6E started me scratching my head.

As for the dyno charts on the Lehner site, they don't really intersect with the way I run these motors. They have just a few winds at a few different voltages for each motor. I'm way off the chart in the way I'm using them, but I have been running a couple others (1020/15) like that (~32A/325W) for a couple of years with no problems.
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Old Dec 06, 2007, 02:43 PM
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Quote:
Originally Posted by Jeffery
I'm not out to try to best the Scorpion on every prop...
Yup. I hear you.

Quote:
...As for the dyno charts on the Lehner site, they don't really intersect with the way I run these motors. They have just a few winds at a few different voltages for each motor...
Yes. I downloaded the file for the 1020-17 at 11V. It shows motor testing to 25A, which is short of the your usage just as you say. And, as you say, Lehner doesn't provide a full slate of charts for their motors.

But then again, having any charts at all goes well beyond the current standard.

It's pretty hard to imagine that established, big name motor makers have not dyno tested their motors. So why aren't they publishing the dyno results? Lehner publishes some. So does Neu. As I recall, Kontronic publishes data from which plots can be drawn. And the rest?

This is something which makes me go hmmm...
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Old Dec 06, 2007, 05:31 PM
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Quote:
Originally Posted by landru
...looking at the prop data on the innov8tive website, I saw that the 3014-18 can swing an APC 11x5.5E at 9K with 330W input at about 79% efficiency.
Hmmm, that doesn't jive with mrm1's data for the Scorpion 3014-18. With the same APC 11x5.5E prop he measured 9k rpm, 388W, for about 67% efficiency (using the Badcock calc).
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Old Dec 06, 2007, 05:57 PM
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Unless I'm mistaken, it's given as 328W on http://innov8tivedesigns.com/Scorpio...18%20Specs.htm .

That's a fairly large difference in input power. Close to 20%. Could altitude be a factor? I haven't looked in detail.
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Old May 30, 2008, 06:26 PM
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Amarillo Intl, Texas, United States
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Quote:
Originally Posted by Jeffery
Now no doubt about it, the Lehner/Cobri is going to cost a LOT more than the Scorpion, and no way will the 1020/15 EVER do 600W, but still...

<snip>.

Hate to drag up such an old (classic) thread, but I BEG to differ. As we both recently witnessed at last month's fun fly (and which you're finely attuned fingers will attest to), the little 1020/15 WILL do 600 watts. Probably getting a bit more than 8K at the prop too. We should've tached it.

Granted it might've been a little warm, but it's still going and going. And performance...well it did have the usual "shock & awe" to it.
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Old May 30, 2008, 06:31 PM
And You're Not
Timbuktu, Mali (Happy?)
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Yep, I can attest to a 60g motor doing 600 watts for quite a flight before the voice of reason stepped in for a temp check Didn't even destroy the motor!

Don't try this at home, kids. Burned fingertips are no laughing matter (unless it's the other guy -me- getting burned, then it seems to be quite hilarious).
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