RC India

Hi,

I have seen availability of 2 types of GWS props

1. EP8040
2. HD8060
3. EP9050
10.EP1060

I am planning to use a 1200kV / 18A outrunner brushless motor.

Now i have a question which is basic. Due to non high speed characteristics of some props,  Can i use a 11.1 safely on all 4 of the above or i have to move to APC type

Thanks in anticipation.

I doubt any of the below are SF/RD (Slow fly / Reduce Drive) props.
for a 1220kv/18A BL, 8x6 would be ideal, and max you can try 9x5 with care. 10x6 would be a over kill at 1200kv/18A.

And i suppose by 11.1, you mean 3S LiPo !
Get a Watts meter if you plan to be in the hobby for long. its a good investment to save from a Dead stick  due to a burnt ESC/Motor.

if for this motor a 8*4 propellor is recomended
1. what propellor should we use?
there are
APC 8*4E
GWS DD 8*4
GWS RD 8043
TGS Sport 8x4E Precision propeller
with same dimentions

2. does direct drive and and reduced drive will have large differences in
current draw

3.  does sport precision propeller mean that it is used for nitro plane
  
    


 

i based my prop selection based on a simmilar 1250kv suppo motor with almost identical Amps

The difference in these props are about weight, amps draw and max supported rpm.  I believe the (increasing) order is reduced drive, APC slo-flyer and APC E (not 100% sure about this).

A wattmeter would give you full confidence on your setup.  Digging for data-sheets (and other people's reviews/tests) would really help with purchase decisions.

Anwarbhai,
Does that means that a prop's pitch does not fully state whether its a Sports or a SlowFly???
eg. a 10x6 can be slowfly as well as a Sports?? and the difference being not in the Pitch but the Weight of the prop??

On other line why will one require to use "reduced Gear' (as in for GWS RD 8043) for a prop of size 80x4?? can not one simply use a slower (lower RPM) motor for it??

Pitch and "type" of prop are distinct issues. The difference is in the construction... material used, thickness, flexibility (do they bend easily), shape of each blade, shape of the blade edge etc.  And these differences in physical characteristics translate into performance (including amps drawn).

Someone.. ???
very basic- I see RPM is lowered by using gears in some planes (mostly Indoors). Why so? wont mounting the prop on the motor directly will give larger RPM and hence larger thrust ??? One can then use smaller propeller or smaller battery. Or does it harm the flight characteristics in some way??

Sorry for asking such a basic question, but somehow the fact that everyone wants to get max thrust with a motor and prop at lesser power rating and still with gear reduction we kill it, i couldnt understand the funda!

You are missing a crucial ingredient... "torque" :)  Basically gear reduction allows the rpm of high rpm motors to be reduced to match the rpm of lower rpm props (and typically these props have higher torque).

As a crude example, if you had a higher rpm (usually a high KV) motor that is used in pushers and delta jets, and you want to do 3D (or slow) type of flying, a gear reduction system will allow you to swing a larger dia but smaller pitch prop which is more suitable for 3D.

Anwar, torque is purely a characteristic of the motor/engine and nothing to do with the prop, per se. Higher torque will allow you to swing larger (diameter and/or pitch) props. The ability to use a more efficient prop for the particular style of flying comes from the motor design and not vice versa.

While what you said is true, that is not the point of discussion here, right ?

My point was about the impact of using reduction gears.  A simplistic view of their impact is that these reduction gears act as torque enhancers, which allow larger props to be swung by higher rpm motors which would not be able to do so if the props were directly connected.

May be torque (as a property of any given motor) is not the word for this in a puritan sense, but what would you call the angular momentum required to swing a prop ? :)

Great information,
Does this means that if i have reduction gear of 3.1
1. then i can use my 3500kv outrunner motor with a 10" or a 9" prop maybe 11"
2. If my motor is having 17A power capacity then the prop can take almost 2 X 17 A = 34A
3. Where can i buy reduction gear for outrunner motor for testing

1.  I would assume yes, if you can find the right reduction gears.  BE SURE to watch out for the amps drawn.

2.  I am not sure I understood this.  Why is the multiplication by 2 done ?

3.  I am not sure what is available locally.  Here is a sample of how it would look like :

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXAGC8&P=ML
http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXHUV9&P=ML

No, the power transferred to the prop will also be the same - 17 Amps ideally (assuming no loses in motor/gear systems for example). though the prop size is increasing, the RPM is reducing, so no difference. not X 2.