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Author Topic: Cobra 3520/10 vs Brodak 3520  (Read 1315 times)

Offline John Rist

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Cobra 3520/10 vs Brodak 3520
« on: November 15, 2018, 02:42:08 PM »
I am leaning toward buying Brodak's Electric SV11.  Brodak recommends a Brodak 3520 motor with a KV of 950.  Is the Cobra 3520/10 an equivalent motor?  Cobra 3520/10 has a KV of 980 and is rated at 890 W (on 4C battery).  It appears to have the same mounting bolt circle as Brodak at 25 mm.  I need to stay with a 4C setup.  (lots of 4C batters on hand)

 ???   #^
« Last Edit: November 15, 2018, 03:56:09 PM by John Rist »
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Offline Mike Alimov

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Re: Cobra 3520/10 vs Brodak 3520
« Reply #1 on: November 17, 2018, 09:16:31 PM »
John,
I just got an SV-11 myself, and like the build quality.  All parts minus the powertrain total ~ 40 oz, so it might be possible to build it at ~ 63 oz if configured properly.
Unfortunately, I think the restriction to use 4S battery puts you at a disadvantage here...  It forces you into relatively high kV motors, which means higher current -> heat losses, and also a high-RPM low-pitch setup, which is not energy efficient. 
Last year I tested a Top Flite Score ARF (680 sq in, 65 oz) with a Cobra 2826-12 (760 kV) and a 5S 2700 mAh battery.  Average power required to haul that plane on 68' lines at 5.1" lap was about 650-700 Watts.  I tested a APC 12-6 prop at 9000 RPM and APC 13-4.5 prop at 11000 RPM.  Both flew fine, but the lower pitch prop required quit a bit more current, and ended up using up the battery faster than I liked.

But if you want to stay with the two choices you named... I'd go for the Cobra over Arrowind.  (Just spent two days researching and testing motors, including those two brands).

Offline John Rist

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Re: Cobra 3520/10 vs Brodak 3520
« Reply #2 on: November 17, 2018, 10:00:48 PM »
John,
I just got an SV-11 myself, and like the build quality.  All parts minus the powertrain total ~ 40 oz, so it might be possible to build it at ~ 63 oz if configured properly.
Unfortunately, I think the restriction to use 4S battery puts you at a disadvantage here...  It forces you into relatively high kV motors, which means higher current -> heat losses, and also a high-RPM low-pitch setup, which is not energy efficient. 
Last year I tested a Top Flite Score ARF (680 sq in, 65 oz) with a Cobra 2826-12 (760 kV) and a 5S 2700 mAh battery.  Average power required to haul that plane on 68' lines at 5.1" lap was about 650-700 Watts.  I tested a APC 12-6 prop at 9000 RPM and APC 13-4.5 prop at 11000 RPM.  Both flew fine, but the lower pitch prop required quit a bit more current, and ended up using up the battery faster than I liked.

But if you want to stay with the two choices you named... I'd go for the Cobra over Arrowind.  (Just spent two days researching and testing motors, including those two brands).

Thanks for the info. I am still learning the beginner's pattern.  So I only need 4 minutes run time.  I am planning to use a APC 12-6 EP set at 9000 RPM.  According to the Cobra prop chart the 3520/10 should be able to do this.  If and when I go to the full pattern, and if the SV-11 is still in one piece I will probably go with a 5 cell setup and a Cobra 3520/12 at 820 KV.  By the way I use A KR timer to set RPM.
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Offline TDM

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Re: Cobra 3520/10 vs Brodak 3520
« Reply #3 on: November 18, 2018, 01:43:40 PM »
XOAR 12x6 even better. The electric prop.
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline John Rist

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Re: Cobra 3520/10 vs Brodak 3520
« Reply #4 on: November 18, 2018, 05:47:59 PM »
XOAR 12x6 even better. The electric prop.

But does it come in pusher electric.  The APC F2B 12x6-EP Pusher Control Line Prop is a lot thinner than the stander APC EP prop.  Seams to work very good.  All of my setups are pusher.  At $6 price is right.
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Offline TDM

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Re: Cobra 3520/10 vs Brodak 3520
« Reply #5 on: November 19, 2018, 09:05:15 AM »
If the Brodak motor breaks even in weight compared to the cobra I would go in the Brodak direction. Why because it has more diameter more torque hence power you are actually comparing a 3520 to a 4250. Anyone has the specs on the Brodak motors?

Sorry I was looking at stator dimensions instead of overall. JENIOUS ME
« Last Edit: November 19, 2018, 01:12:06 PM by TDM »
Each goal you meet is a moment of happiness
Happiness is the harmony between what you think and what you do. Mahatma Gandhi

Offline John Rist

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Re: Cobra 3520/10 vs Brodak 3520
« Reply #6 on: November 19, 2018, 12:04:13 PM »
If the Brodak motor breaks even in weight compared to the cobra I would go in the Brodak direction. Why because it has more diameter more torque hence power you are actually comparing a 3520 to a 4250. Anyone has the specs on the Brodak motors?

Both motor have the same P/N ie 3520

Both motors are about the same size.  According to the Brodak web sight "The new 3520 is built in a 42mm x 50mm motor shell and has a 4 x 25mm mounting bolt circle".   Per the Cobra data sheet the Cobra 3520/12 has length of 46mm and a diameter of 43mm.   It also has a 25 mm bolt circle.  Brodak KV = 950.  Cobra KV = 980.
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