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Old Apr 07, 2009, 12:55 PM
ZAGI man!!!
Leeds, UK
Joined Feb 2009
31 Posts
Question
What powered LIPO will I need...?

Hi there,
I just bought my dad a basic high wing trainer from she bay.
Its a balsa model, standard stuff, 1700g model.

Here's the fun bit.

The motor Ive never heard of and cant find anything on Google...
Its a richmoto R42a-1...
and thats all the info thats on it...

So my question is this, for the following model:

RICH MODEL ELECTRIC TRAINER,

1400mm WING SPAN,

3 X FUTABA FP-S148 SERO FITTED,

60AMP ESC,

RICH R42A-1 BRUSHLESS OUT RUNNER,

What Lipo? - I suggested 3s 3000mah and the local model shop said nononononoooh...any suggestions anyone?
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Old Apr 07, 2009, 01:03 PM
Air, Ground & Water
freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
23,636 Posts
what size prop?
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Old Apr 07, 2009, 01:08 PM
ZAGI man!!!
Leeds, UK
Joined Feb 2009
31 Posts
Good question - Ill call my dad and find out...
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Old Apr 07, 2009, 01:20 PM
ZAGI man!!!
Leeds, UK
Joined Feb 2009
31 Posts
OK theres nothing stamped on the prop but it's 11" x about 1" at its widest point - does that help? Originally it was a .40 trainer obviously but has been converted to electric...
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Old Apr 07, 2009, 01:21 PM
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Houston, Tx
Joined Oct 2006
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This is the motor info.
http://www.avia-richmodel.com/Produc...ss-Motors.html
And the plane.
http://www.avia-richmodel.com/Produc...In-Stock).html
It seems to be a large motor for a trainer. 520 watts on a 3 3/4 pound plane. Seems like a lot to me. Some one else can jump in with the motocalc numbers. I can never get it to work well.
The 3s lipo might not be a bad idea if you can get the right prop.

John
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Old Apr 07, 2009, 01:45 PM
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Chattanooga, Tennessee, United States
Joined May 2003
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You are going to need a hefty battery to supply the 40A-50A this might draw with say an 11x7 - a 20C 3s 4000mAh might be okay. You might be better off going with 4s to keep the amp draw down a bit, yet still get you the 400W+ you may need.
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Old Apr 07, 2009, 01:58 PM
ZAGI man!!!
Leeds, UK
Joined Feb 2009
31 Posts
Hmmm thanks guys - it's a bit of a minefield but youve managed to unravel it a fair bit! I really dont understand prop sizes.
I know the first figure is the length, the second figure I dont understand, or how this impacts the strain on the motor. Can anybody explain simply?
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Old Apr 07, 2009, 02:01 PM
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Houston, Tx
Joined Oct 2006
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Quote:
Originally Posted by Dr Kiwi
You are going to need a hefty battery to supply the 40A-50A this might draw with say an 11x7 - a 20C 3s 4000mAh might be okay. You might be better off going with 4s to keep the amp draw down a bit, yet still get you the 400W+ you may need.
Dr. Kiwi,

Please help me with my ignorance. I have always thought you wanted less than a 100 watts per pound for a first plane trainer. Is this another rule that needs to be pounded into the right configuration for the specific problem being considered?

John
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Old Apr 07, 2009, 02:04 PM
ZAGI man!!!
Leeds, UK
Joined Feb 2009
31 Posts
Guys...help..battery and prop...?...???
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Old Apr 07, 2009, 02:20 PM
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United States, CA, Garden Grove
Joined Oct 2000
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I use a GWS 11x7 direct drive prop on my smaller low KV Scorpion 3008-32 outrunner with 2200mah 3S ( 3-Cell) 20C rated Lipo to fly a 40" wingspan 2.5lb scale model P26 Peashooter giving me about 8 minutes cruise time . Your trainer has about 5 foot wingspan and weighs 3 lbs, I would guess that you'd want at least a 3000-4000 mah rated 3s 20C rated lipo. You will need a quality lipo charger capable of charging 3S packs and probably a power supply of around 10 amp rating if charger has no built in power . You will need to obtain a charging cord with a connector to fit your brand of lipo pack supply. If you are serious about staying in the hobby, you should invest in a charger with built-in lipo cell balancing feature or a separate cell balancing device like the Astro Flight "Blinky". You will probably need an adapter for the balancer to battery connection. Find some electric flyers and get advice, maybe deals on stuff they are upgading from.
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Old Apr 07, 2009, 02:25 PM
ZAGI man!!!
Leeds, UK
Joined Feb 2009
31 Posts
No problems - I already have a sigma EQ charger - Im just getting my dad started in the game with this plane so I know a little about chargers. My main issue is just what Lipo (and now it would appear, prop) to get for his plane!
Given that the motor is 520w, 15-48A current operating range with a plane that weighs 3 3/4lb plane...?
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Old Apr 07, 2009, 02:39 PM
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Xpress..'s Avatar
Joined Oct 2007
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You should be fine running a 3200-4000 mah 3 cell lipo with either an 11x6 or 11x7 E prop.

You can get lipos inexpensively from Hobby City. Rhino and Zippy lipos seem to be the best, and a lot of people are very happy with them.
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Old Apr 07, 2009, 02:53 PM
ZAGI man!!!
Leeds, UK
Joined Feb 2009
31 Posts
OK - I have a good lipo supplier locally.
Whats the difference between an 11x6 vs an 11x7 prop?
Like I said I dont understand prop sizes!!!
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Old Apr 07, 2009, 03:10 PM
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11 = the props diameter. 6 or 7 = the pitch forward, say at 1000rpms the prop will theoretically move 7" forward (iff 11x7 prop).

The more pitch you have the higher the speed will be, and the less instant acceleration you will get. However there are also SF or Slow Flyer props that the 3D guys use (including me) as well as parkflyers. The SF means they won't have a very high speed, but do to the blades being wide they grab a lot of air for a more instant acceleration, but a lower top speed. The bigger the prop size is, the more amps you're going to draw. Same goes for pitch.

The difference between the 11x6 prop and the 11x7 prop is really nothing huge, toher than the 11x7 will draw more amps than the 11x6 will, but the 11x7 will give you a higher top speed, as well as more thrust. Get both and see which one you (or him) like.
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Old Apr 07, 2009, 03:15 PM
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Houston, Tx
Joined Oct 2006
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The first number is the diameter of the prop. Generally the larger the diameter, the more thrust. The second number is the pitch of the prop. For one revolution, the prop will move the plane forward that distance in inches, ideally speaking of course. So an 11x7 prop is 11 inches in diameter and has a pitch speed of 6 inched. So for 1 revolution of the prop, the plane will move forward 6 inches. These are somewhat generalized rules of thumb and you may or may not get these results.
You will need some kind of meter to measure amp draw to be able to find the correct setup. To roughly maintain equal amp draw, but more thrust or more top speed, as one number increases, decrease the other number the same amount. Again, this is a very generalized rule of thumb. Put a prop on the motor and increase throttle, noting the amp draw. If the amp draw is too large, then prop down, if too small, prop up. The number of cells in the battery will also affect amp draw. A higher number of cells with increase amp draw with the same prop than a battery with fewer cells. Number of cells indicates voltage. 2s lipo = 7.2v, 3s lipo = 10.8v, and 4s lipo = 14.2v. As the voltage increase, the motor tries to spin the prop faster, meaning higher amp draw on the same prop.

John
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Last edited by GD5015; Apr 07, 2009 at 03:50 PM.
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