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Other › Motor KV pinon choice questions
12-14-2008 01:52 AM  8 years agoPost 1
Carbon Copter

rrVeteran

USA

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Ok, I was planning on swapping my Scorp -6 in Favor of a Scorp -8 for my rave. I want to run some 340mm Woodies and don't want to go to far over 2400 HS as I am not looking to get hurt. Anyway.

If I can get a 2450 HS with the -6 using a 10T pinion

or 2435 using the -8 and a 12T pinion. Is there any difference due to the different KV Rating? If I keep the -6, will there be any benefit that it is 4400 KV compared to the 3595 KV of the -8? Or will it be inefficient?

Thanks!

~oo~ Stop fogging up my glasses

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12-14-2008 02:15 AM  8 years agoPost 2
Heli 770

rrProfessor

USA.

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HK-2221-8 V2 with the 12T. You could get the head speed both ways, but with the 8 less rpm on the motor.

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12-14-2008 02:17 AM  8 years agoPost 3
what_the_helli

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cookeville, tn USA

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by my math on 11.1 lipo with a 150t main gear you'll get:

10t on 4400 kv 3256 head speed
12t on 4400 kv 3907 head speed

10t on 3595 kv 2660 head speed
12t on 3595 kv 3192 head speed

you'll need to figure in some loss about 10% or so will get you close

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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12-14-2008 02:30 AM  8 years agoPost 4
Heli 770

rrProfessor

USA.

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what the heli
What main gear tooth count did you use.

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12-14-2008 02:48 AM  8 years agoPost 5
what_the_helli

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cookeville, tn USA

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the specs on helidirect said 150, so thats what I used, is that correct? or are there more options?

http://www.helidirect.com/product_i...roducts_id=9050

I put the fun in dysFUNctional :)
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12-14-2008 02:57 AM  8 years agoPost 6
Heli 770

rrProfessor

USA.

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The Rave has a 177T main gear.

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12-14-2008 03:02 AM  8 years agoPost 7
Heli 770

rrProfessor

USA.

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When you use that Calc. you need to change the main gear for the Heli.

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12-14-2008 03:04 AM  8 years agoPost 8
what_the_helli

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cookeville, tn USA

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by my math on 11.1 lipo with a 177t main gear you'll get:

10t on 4400 kv 2759 head speed
12t on 4400 kv 3311 head speed

10t on 3595 kv 2254 head speed
12t on 3595 kv 2705 head speed

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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12-14-2008 03:12 AM  8 years agoPost 9
what_the_helli

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cookeville, tn USA

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the calc I use is this

main gear/ by pinion= gear ratio
volts x kv = rpm

rpm / by gear ratio= head speed

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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12-14-2008 03:13 AM  8 years agoPost 10
what_the_helli

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cookeville, tn USA

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Specifications:

* Length: 692mm
* Height: 254mm
* Main blade length: 325-350mm
* Main rotor diameter: 711-762mm
* Tail rotor diameter: 152mm
* Motor drive gear: 11T/13T
* Main drive gear: 150T
* Drive gear ratio: 1:13.63:4.63/1:13.53:4.63
* Flying weight: 930g
from the link I posted above

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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12-14-2008 03:23 AM  8 years agoPost 11
Heli 770

rrProfessor

USA.

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That 150T is a misprint.

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12-14-2008 03:28 AM  8 years agoPost 12
what_the_helli

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cookeville, tn USA

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thanks for that.
Cause it's hard to give good info to help someone when you find bad specs...

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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12-14-2008 03:34 AM  8 years agoPost 13
Heli 770

rrProfessor

USA.

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I've had it happen to me on other things.

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12-14-2008 03:47 AM  8 years agoPost 14
Carbon Copter

rrVeteran

USA

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For the Rave 177 I get: 2483 with the -6 using a 10T

**I am using the Cal provided on the Redi heli site. http://www.readyheli.com/Online_Hea...ulator_s/81.htm
You could get the head speed both ways, but with the 8 less rpm on the motor.
If it is more RPM, will it make any signifigent difference though? I guess it would be better to have less, but it is just on paper, then I don't care. But if it gets hot, obiously I do not want that.

~oo~ Stop fogging up my glasses

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12-14-2008 04:20 AM  8 years agoPost 15
what_the_helli

rrKey Veteran

cookeville, tn USA

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thats a nice calc with drag co-efficient and motor efficiency thanks for the link. I just made a simple excel spread sheet.

The -8 will be lower
It has the lower kv so you'll have lower HS and a longer flight time to boot.

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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12-14-2008 04:23 AM  8 years agoPost 16
Carbon Copter

rrVeteran

USA

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Sure thing. What exactly is drag co-efficient? I left that to the default setting. I want to run 340mm wood blades, would that affect that drag co-efficeint?

~oo~ Stop fogging up my glasses

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12-14-2008 04:29 AM  8 years agoPost 17
Heli 770

rrProfessor

USA.

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I think you have to Calc. 12.60-11.40 volts and 10-15% for loss. for a 3S pack.

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12-14-2008 05:30 AM  8 years agoPost 18
Carbon Copter

rrVeteran

USA

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Not sure I completely undestand --Can you use the calc on ReadyHeli site and let me know what you come up with for a pinion for these 2 setups Heli? Here is the info:

-8
340MM Wood blades
3595KV
Gear 177
3S pack

-6
340MM Wood blades
4400KV
Gear 177
3s Pack

Woodies rated at 2400 RPM, so trying to stay in that range.

~oo~ Stop fogging up my glasses

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12-14-2008 05:47 AM  8 years agoPost 19
Heli 770

rrProfessor

USA.

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HK-2221-8, 12T 2435rpm.
HK-2221-6, 10T 2483rpm.

At the beginning you will have a higher head speed with both motors and a lower head speed as the pack depletes. Thats why I say you need to Calc., 100% charged 12.60-11.40 80% pack used.

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12-14-2008 05:58 AM  8 years agoPost 20
Carbon Copter

rrVeteran

USA

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Thanks Heli (a lot). So, final verdict, do you think I should sell off the -6 in favor of the -8 or give the -6 a shot first?

~oo~ Stop fogging up my glasses

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