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Electric Stunt => Gettin all AMP'ed up! => Topic started by: RC Storick on December 26, 2013, 04:30:54 PM

Title: Cobra 3515/18
Post by: RC Storick on December 26, 2013, 04:30:54 PM
I just got my bigger motor. I want to be able to swing a 13 inch prop and I have been told the small frame motors should not run a prop that large. The motor is 740 KV and .10 lighter than the AXI 2826/12.

The front bearing appears to be around 1/2 inch. I will report how this motor performs when the MC73 is done.
Title: Re: Cobra 3515/18
Post by: Dean Pappas on December 26, 2013, 07:32:50 PM
Happy New Year, Sparky
I don't see why this motor won't do nicely on a 13 inbch prop with a 5S battery.
Granted, you'd probably over-dissipate the motor on a 72 ounce airframe ... but I know there ain't a snowball's chance you'll show up with one of those!

later,
 Dean P.
Title: Re: Cobra 3515/18
Post by: Avaiojet on December 27, 2013, 05:22:24 PM
I just got my bigger motor. I want to be able to swing a 13 inch prop and I have been told the small frame motors should not run a prop that large. The motor is 740 KV and .10 lighter than the AXI 2826/12.

The front bearing appears to be around 1/2 inch. I will report how this motor performs when the MC73 is done.

Are you sure you made the correct choice?

RPM? Thrust?

Charles
Title: Re: Cobra 3515/18
Post by: Allan Perret on December 28, 2013, 09:07:14 AM
Happy New Year, Sparky
I don't see why this motor won't do nicely on a 13 inbch prop with a 5S battery.
Granted, you'd probably over-dissipate the motor on a 72 ounce airframe ... but I know there ain't a snowball's chance you'll show up with one of those!

later,
 Dean P.
"over-dissipate"    ???
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 02, 2014, 11:58:11 AM
How heavy is your model Robert?

Saving .1 oz.

You can trim a full once with choices like the following AXI:

2820/14
2820/12

And, if you dial down to a tad smaller prop, you can save weight there also.

I read someplace where it all adds up.

Charles
Title: Re: Cobra 3515/18
Post by: RC Storick on January 03, 2014, 08:00:58 PM
I do not design around the motor I design around the King battery. I use a 5 cell because its the lightest (10 OZ) so I need to choose a motor with the correct KV rating. Not choose a motor and then the battery and get stuck using a 4 cell 14 ounce battery.
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 03, 2014, 09:06:02 PM
I do not design around the motor I design around the King battery. I use a 5 cell because its the lightest (10 OZ) so I need to choose a motor with the correct KV rating. Not choose a motor and then the battery and get stuck using a 4 cell 14 ounce battery.

I understand.  What does your battery pack measure and who sells it?

Charles
Title: Re: Cobra 3515/18
Post by: RC Storick on January 03, 2014, 09:37:01 PM
I understand.  What does your battery pack measure and who sells it?

Charles

Google Thunderpower 5S 2700 they are pricey at 99.00 each
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 04, 2014, 07:01:04 AM
Google Thunderpower 5S 2700 they are pricey at 99.00 each

Thank you Robert.

Charles
Title: Re: Cobra 3515/18
Post by: Darkstar1 on January 04, 2014, 07:46:27 AM
Google Thunderpower 5S 2700 they are pricey at 99.00 each

Sparky,
I assume you are talking about the latest gen of the batteries. If U go to Thunderpower's site directly
U can get the previous gen batteries 5s 2700 30c for 43.99. I have four on the way now.
Title: Re: Cobra 3515/18
Post by: RC Storick on January 04, 2014, 07:59:54 AM
Sparky,
I assume you are talking about the latest gen of the batteries. If U go to Thunderpower's site directly
U can get the previous gen batteries 5s 2700 30c for 43.99. I have four on the way now.


5S 25C 2700 not the 30C. If you have a link to a 10 ounce 2700 MAH 25 C battery for 43.00 dollars please post it. I have 5 batteries now but could use more at 43.00 dollars.

This is the battery I use from their site. http://www.thunderpowerrc.com/Specials?search=5s+2700+25c
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 04, 2014, 08:09:40 AM

5S 25C 2700 not the 30C. If you have a link to a 10 ounce 2700 MAH 25 C battery for 43.00 dollars please post it. I have 5 batteries now but could use more at 43.00 dollars.

This is the battery I use from their site. http://www.thunderpowerrc.com/Specials?search=5s+2700+25c

Robert, I went all through the Thunder Power site.

This is what I came up with:

2700mAh 5-Cell/5S 18.5V G8 Pro Lite+ 25C LiPo

Measures:  40 x 34 x 102

Weighs:  290g  -  10.23 oz.

Is this the battery of your choice?

Thanks

Charles


Title: Re: Cobra 3515/18
Post by: RC Storick on January 04, 2014, 08:12:27 AM
Robert, I went all through the Thunder Power site.

This is what I came up with:

2700mAh 5-Cell/5S 18.5V G8 Pro Lite+ 25C LiPo

Measures:  40 x 34 x 102

Weighs:  290g  -  10.23 oz.

Is this the battery of your choice?

Thanks

Charles




that's it. I choose this only because of its weight. Battery first ,motor second, design plane around that. IMHO

I do not espire to the design plane choose drive train and add weight to balance theory. It helps tp know your fixed weights first.
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 04, 2014, 08:22:33 AM
Sparky,
I assume you are talking about the latest gen of the batteries. If U go to Thunderpower's site directly
U can get the previous gen batteries 5s 2700 30c for 43.99. I have four on the way now.

Darkstar1,

Don't underestimate the power of the Force.

I believe the 5S 30c pack, you are referring to, weighs 335g. That's 11.83 onces. A considerable difference than what Robert is using.

My personal interest would be the lighter battery pack.

Charles
 
Title: Re: Cobra 3515/18
Post by: Zuriel Armstrong on January 04, 2014, 10:10:08 AM
Robert,

I'm interested in how your 3515-18's perform. I bought two of them while they were on sale. I bought one from Monto RC for $29.95.

Zuriel
Title: Re: Cobra 3515/18
Post by: Darkstar1 on January 04, 2014, 12:38:03 PM
Sparky,
Thanks for clarifying for me. But for me those 5s 30c batteries are a bit lighter as the latest gen 6s 2700 25c batteries. I can use two different motors (720 & 640 kv)  in a Infinity airframe and the plane will weigh about the same. (around 60-61 oz.) When I bought them before they were more than twice the price and was only 25c before.
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 04, 2014, 02:18:23 PM
Sparky,
Thanks for clarifying for me. But for me those 5s 30c batteries are a bit lighter as the latest gen 6s 2700 25c batteries. I can use two different motors (720 & 640 kv)  in a Infinity airframe and the plane will weigh about the same. (around 60-61 oz.) When I bought them before they were more than twice the price and was only 25c before.

Darkstar1,

Turning a larger prop? What motors would that be?

Charles
Title: Re: Cobra 3515/18
Post by: Crist Rigotti on January 04, 2014, 03:56:21 PM
Sparky,
I assume you are talking about the latest gen of the batteries. If U go to Thunderpower's site directly
U can get the previous gen batteries 5s 2700 30c for 43.99. I have four on the way now.

Can you provide a link?  I've looked at their website and can't find them.  Thanks.
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 04, 2014, 04:14:04 PM
Can you provide a link?  I've looked at their website and can't find them.  Thanks.

Christ,

No photo, bottom left, you'll see the text.

http://www.thunderpowerrc.com/2700-mAh

Charles
Title: Re: Cobra 3515/18
Post by: Darkstar1 on January 04, 2014, 06:34:07 PM
Darkstar1,

Turning a larger prop? What motors would that be?



Charles,
Still turning APC 13 x 4.5 F2B. The motors are the Pletty 20-16 & 25-14
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 04, 2014, 09:08:27 PM
Quote
Charles,
Still turning APC 13 x 4.5 F2B. The motors are the Pletty 20-16 & 25-14

Darkstar!,

I figured that. Bet your turning it clockwise.

That's my goal, to spin a 13 x 4 prop. Clockwise also.

Are there many guys spinning a prop that size?

Charles
Title: Re: Cobra 3515/18
Post by: RC Storick on January 05, 2014, 12:32:16 AM
Specs on the 30C

2700mAh 5-CELL/5S 18.5V PRO POWER 30C LIPO
Specifications:
Max Charge: 5C
Max Charge Current: 13.5A
Max Cont. Discharge: 30C
Max Cont. Current: 81A
Max Burst: 60C
Max Burst Current: 162A
Weight (g): 335
Dimensions (mm): 38 x 39 x 116

Price $44.17

Specs on the 25C
Product Description

2700mAh 5-Cell/5S 18.5V G8 Pro Lite+ 25C LiPo

Specifications:

Max Charge: 5C
Max Charge Current: 13.5A
Max Cont. Discharge: 25C
Max Cont. Current: 67.5A
Max Burst: 50C
Max Burst Current: 135A
Weight (g): 290
Dimensions (mm): 40 x 34 x 102
 Price: $98.99
 
Title: Re: Cobra 3515/18
Post by: Darkstar1 on January 05, 2014, 04:30:30 AM
Charles,
The APC 13 x 4.5 F2B pusher is used by several fliers out there. I tried several props all two blade so far and the APC
for me seems to be the leader in the clubhouse. Of course that depends on what you are flying.
Title: Re: Cobra 3515/18
Post by: Allan Perret on January 05, 2014, 09:13:55 PM
Specs on the 30C

2700mAh 5-CELL/5S 18.5V PRO POWER 30C LIPO
Specifications:
Max Charge: 5C
Max Charge Current: 13.5A
Max Cont. Discharge: 30C
Max Cont. Current: 81A
Max Burst: 60C
Max Burst Current: 162A
Weight (g): 335
Dimensions (mm): 38 x 39 x 116

Price $44.17

Specs on the 25C
Product Description

2700mAh 5-Cell/5S 18.5V G8 Pro Lite+ 25C LiPo

Specifications:

Max Charge: 5C
Max Charge Current: 13.5A
Max Cont. Discharge: 25C
Max Cont. Current: 67.5A
Max Burst: 50C
Max Burst Current: 135A
Weight (g): 290
Dimensions (mm): 40 x 34 x 102
 Price: $98.99
 

Why the big difference in price ?
Title: Re: Cobra 3515/18
Post by: RC Storick on January 05, 2014, 10:14:19 PM
Beats me? I think cause they know I want them. LOL
Title: Re: Cobra 3515/18
Post by: Avaiojet on January 06, 2014, 05:28:35 AM
Why the big difference in price ?

Size and weight.
Title: Re: Cobra 3515/18
Post by: Alan Resinger on January 06, 2014, 12:17:24 PM
The reason they are cheaper is that they are Generation 4 batteries as opposed to the improved chemistry Generation 8 batteries.  They are "close outs".
Alan
Title: Re: Cobra 3515/18
Post by: Zuriel Armstrong on January 19, 2014, 09:11:21 AM
Robert,

Did you ever get any time on this motor?  As stated, I bought two of them and would love some feedback....hopefully positive.

Zuriel
Title: Re: Cobra 3515/18
Post by: Allan Perret on June 29, 2014, 01:05:39 PM
Have you flown the Cobra 3515/18 yet ?
Title: Re: Cobra 3515/18
Post by: RC Storick on June 29, 2014, 03:46:03 PM
Have you flown the Cobra 3515/18 yet ?

Yes it works great!