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Old May 05, 2007, 11:01 PM
Innov8tive's Avatar
Joined Jan 2007
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turbojoe,

Scorpion is coming out with a series of High Kv 22mm motors specifically for helicopters, and there will be one for the T-Rex 450 size heli's. There will be 4 different size motors, a 2208, 2213, 2216 and 2221, and each of these motors will be available in 3 different Kv styles with Kv's of approximately 2500, 3000 and 3500 so you can find one to match the gearing of your particular helicopter.

The new HK series motors should be available by the end of May, so all of the helicopter flyers will soon be able to fly with Scorpion power too!

Lucien
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Old May 06, 2007, 02:58 AM
ramovan's Avatar
United States, NV, Pahrump
Joined Aug 2004
851 Posts
Thanks everyone!

Thank you all! This gives me a lot more information to help me decide on a power system.

Lucien, I knew I could count on you to provide a ton of greatly detailed information. I'm glad you voted for the 3014 motor. I was thinking about going this large, but I wasn't sure if I was insane for even thinking it. I almost feel normal now.

I'm building a really HOT sport and 3D plane here so I think I want insane performance; therefore I am going to choose either the 3008-28 or the 3014-18 motor. With the 3014 the plane will have ridiculous amounts of power available, but will be heavier and require a 20C battery. The 3008 would save a little weight and I could use a 15C 2200 battery or a 20C 1800mah to save even more weight.

Like I said before, I like to over-power my airplanes. Building this airplane with the 3014 would be totally pushing the envelope and thats pretty attractive. It could be a little harder to pull it off, but it would be incredible to fly.

I'm going to think about it for the next couple days as I wait for the rest of the components to arrive. I've decided to use 4 Waypoint 6g/BB servos, a Hitec 05S receiver, and a Scorpion 35A ESC. I'll let everyone know the final decision on the power system and post a link to the build log for those that are interested in following the progress.

If anyone else has some thoughts on this please share more.

Randy Van Moody
Ramovan
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Old May 06, 2007, 06:19 AM
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Lucien,

Do have any recommendations for prop size for the Scorpion 3008-28? Maybe expected thrust as well?

I'll be using a 35amp Scorpion ESC, Berg4L and 3 cell 20C 2100mah lipos.
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Old May 06, 2007, 07:06 AM
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United States, WA, Kapowsin
Joined Jun 2004
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WACOFlyer: Iam Using the Scorpion 3008-28 With a 11X5.5 As Recommended By Lucien. The Specs Are: 35.4 Amps @ 371 Watts @ Full Throttle, & 52oz's Of Thrust With a Prop Speed Of 45 MPH. Hope This Helps You. Cheers:JP
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Old May 06, 2007, 10:11 AM
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Joined Apr 2004
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flux ring ?

You refer to the outer casing as a flux ring.
What is it made of ?
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Old May 06, 2007, 10:33 AM
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Quote:
Originally Posted by Yardbee
WACOFlyer: Iam Using the Scorpion 3008-28 With a 11X5.5 As Recommended By Lucien. The Specs Are: 35.4 Amps @ 371 Watts @ Full Throttle, & 52oz's Of Thrust With a Prop Speed Of 45 MPH. Hope This Helps You. Cheers:JP

Thanks, Yardbee.
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Old May 06, 2007, 01:41 PM
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Chattanooga, Tennessee, United States
Joined May 2003
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Quote:
Originally Posted by Yardbee
WACOFlyer: Iam Using the Scorpion 3008-28 With a 11X5.5 As Recommended By Lucien. The Specs Are: 35.4 Amps @ 371 Watts @ Full Throttle, & 52oz's Of Thrust With a Prop Speed Of 45 MPH. Hope This Helps You. Cheers:JP
That doesn't seem very efficient - that comes out at only ~3.98g/W - is that too much prop for that motor?

10.5v, 35.4A, 371W, 8650rpm, 45mph, 1476g, 52oz, 3.98g/W

I know this is a ridiculous comparison (apples to cucumbers or something) but I happen to have just run an 11x5.5 on a LightFlight 2T Long - geared 2.29:1 getting similar rpm figures.

Not really valid comparison since the LightFlight with TM 2800 is 130g, and the Scorpion is only 85g.

But the LightFlight got this:
10.5v, 28.7A, 300W, 8850rpm, 46.1mph, 1600g, 56.34oz, 5.33g/W

That's 2% higher rpm (neither here nor there) but, from 20% less input power.
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Old May 06, 2007, 02:21 PM
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near Nijmegen, Netherlands
Joined Feb 2001
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Quote:
Originally Posted by AirWolfRC
You refer to the outer casing as a flux ring.
What is it made of ?
Has to be made of iron (not stainless steel).

Vriendelijke groeten Ron
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Old May 06, 2007, 03:05 PM
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Fourdan's Avatar
Antony (France)
Joined Sep 2003
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Quote:
Originally Posted by Dr Kiwi
That doesn't seem very efficient - that comes out at only ~3.98g/W - is that too much prop for that motor?

10.5v, 35.4A, 371W, 8650rpm, 45mph, 1476g, 52oz, 3.98g/W

I know this is a ridiculous comparison (apples to cucumbers or something) but I happen to have just run an 11x5.5 on a LightFlight 2T Long - geared 2.29:1 getting similar rpm figures.

Not really valid comparison since the LightFlight with TM 2800 is 130g, and the Scorpion is only 85g.

But the LightFlight got this:
10.5v, 28.7A, 300W, 8850rpm, 46.1mph, 1600g, 56.34oz, 5.33g/W

That's 2% higher rpm (neither here nor there) but, from 20% less input power.
Hi guys
If you take one prop (for example a 11x5.5) turned by 2 motors A and B
* If A weight is 85 g and overloaded relatively to its peak eff% (83%) you have an operating point could be at 72%
* If B weight is 130 g and selected to get its peak eff for the same prop (could be 81%)
The scientific comparison shows that B with 81% is better than A with 72%
It is not a proof that B is intrinsically better than A.

As a retired radar expert and specialist of DSP we have a word in this technical community that is:
"A matched filter is better when considering S/N ratio"
Louis
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Old May 06, 2007, 03:43 PM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
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I agree absolutely, Louis. I was interested in making the comparison, simply because of the coincidence in timing of my testing of the LightFlight with the posted numbers for the Scorpion.
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Old May 06, 2007, 04:18 PM
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manuel v's Avatar
Mexico, BC, Mexicali
Joined Aug 2004
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I think that a S3008-32 is better and more efficient this to propeller APC 11x5.5 and serious far better with a KV. slightly lower. A Kit of the S.3008 winded to kv. of 920-950 serious ideal for this prop. and the 12 x6. for applications of 3d. in 23-30 oz airplanes.

Manuel V.
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Old May 07, 2007, 07:52 AM
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Frojd's Avatar
Sweden, Västra Götaland, Goteborg
Joined Aug 2005
718 Posts
Hi Lucien!

My dad's got a Supra Star 25, which he never finished building. Today we're building with depron but I think it would be awesome to finnish this fantastic balsa kit. As we're only flying electric an electric-conversion is what I want to do.

According to the box (IIRC) the measurments are ~1,2m ws and 1,05m lenght. AUW should be 1400-1600g. The plane is designed for a .25 engine i think, but i've read that it flew better with a bit bigger.

Anyway, I played round in the scorpion calc and found some different combinations. Due to the landing gear i think a 9" prop is max, maybe 10" if i'm lucky. A graupner 9x6 gas prop or something like that is included in the box.

Lightest weight:
Scorpion 3008-28, 3s Lipo, 9x6 APC E: 26A, 1200g, 57mph
Scorpion 3008-28, 3s Lipo, 9x7.5 APC E: 30A, 1100g, 67mph

Light:
Scorpion 3008-28, 4s Lipo, 8x6 APC E: 33A, 1500g, 76mph
Scorpion 3008-28, 4s Lipo, 9x4.5 APC E: 34A, 1700g, 56mph

Scorpion 3008-32, 4s Lipo, 9x6 APC E: 28,5A, 1500g, 63mph
Scorpion 3008-32, 4s Lipo, 9x7.5 APC E: 32A, 1350g, 73mph

Heavy:
Scorpion 3014-16, 3s Lipo, 9x6 APC E: 30A, 1400g, 61mph
Scorpion 3014-16, 3s Lipo, 9x7.5 APC E: 36A, 1350g, 73mph

Heaviest:
Scorpion 3014-16, 4s Lipo, 9x4.5 APC E: 39A, 2050g, 61mph
Scorpion 3014-16, 4s Lipo, 8x6 APC E: 37,5A, 1800g, 82mph

Scorpion 3014-18, 4s Lipo, 9x6 APC E: 36A, 1950g, 72mph
Scorpion 3014-18, 4s Lipo, 9x7.5 APC E: 43A, 1875g, 87mph

That's about it, not going into anything bigger than 9". The problem is that i'm not sure how to decide which option to use. This plane is a sport/pattern plane and i guess it would need more than 1:1 to be happy. I've never built or flown any plane this big so I have nothing to compare it to. Also, my dad's built most of the fuse already and he often tend to build fairly heavy (too much glue ). Just guessing I would say that i can probably finnish the whole structure under 700g (24oz) but I really have no idea.

Also, the numbers in red are for when the motors exceed maximum A rating according to the website, how hard is this limit?

I hope Lucien or someone else here can answer this question, if not i guess I can ask a bit more about the plane in the appropiate forum.

Thanks,
Fredrik
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Old May 07, 2007, 08:48 AM
Innov8tive's Avatar
Joined Jan 2007
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Frojd,

I will get back with you with some information later tonight after I have some time to look over your numbers that you have listed above.

Lucien
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Old May 07, 2007, 10:21 AM
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Frojd's Avatar
Sweden, Västra Götaland, Goteborg
Joined Aug 2005
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Thank you for taking the time, I'm not in a hurry!
It's not too many companies who offer this kind of advice the same day for sure,
Keep it up!

Fredrik
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Old May 08, 2007, 07:55 PM
ramovan's Avatar
United States, NV, Pahrump
Joined Aug 2004
851 Posts
Decision made?

I think I have to decide on the Scorpion 3008 series for the Hyperion Yak-55. After checking the motor fit I discovered that it's going to be difficult to install even the 3008 motor without some creative cutting inside the airplane's mount. Either that or I would have to cut the excess shaft on what is going to be the back of the motor. Once the motor is in, there will be plently of room for it but Hyperion didn't leave enough room for installing it. I hate to do any chopping but there may not be any other way. I even took the motor apart to try fitting it in that way.... it was like a rubic's cube and I couldn't solve it.
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