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Old Apr 20, 2005, 08:50 PM
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United States, CO, Arvada
Joined Apr 2005
137 Posts
Convert 5LB glow 3D Bipe to Electric-How??

I've found my new plane. It's the OMP Boxer 42" Bipe Profile. Website claims AUW of 4.4--4.7LBS with glow engine in the .46--.53 range.

Here's the plane:
http://ohiomodelplanes.com/42boxxer/

I'm new to electrics. Not flying.

Can someone help me figure out which motor/batt/esc/prop combo to use for this plane?

I'm looking for general slow 3D flying with hovering around 1/2 throttle. Looking for 10--15 minute flights.

Thanks
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Old Apr 20, 2005, 09:11 PM
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Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
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Welcome to RCGroups!

The gang in Power Systems would be the best fit for this question.

mw
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Old Apr 20, 2005, 09:22 PM
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United States, CO, Arvada
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Thanks for putting this in the right forum Mark. I looked around the site for awhile before I posted, but couldn't decide which forum would be the right one.
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Old Apr 20, 2005, 09:56 PM
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everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
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Quote:
Originally Posted by Rcpilet
I've found my new plane. It's the OMP Boxer 42" Bipe Profile. Website claims AUW of 4.4--4.7LBS with glow engine in the .46--.53 range.

Here's the plane:
http://ohiomodelplanes.com/42boxxer/

I'm new to electrics. Not flying.

Can someone help me figure out which motor/batt/esc/prop combo to use for this plane?

I'm looking for general slow 3D flying with hovering around 1/2 throttle. Looking for 10--15 minute flights.

Thanks
Good 3D takes approximately 100 watts per pound. 5 pounds means 500 watts. 4 LiPoly cells in series equals nominal 13 volts under loads which means 38 amps.
Not going to be cheap.
Here is a good place to start looking for motor .

Charles
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Last edited by everydayflyer; Apr 20, 2005 at 10:03 PM.
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Old Apr 20, 2005, 10:09 PM
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Myron's Avatar
United States, TX, Wimberley
Joined Mar 2004
1,915 Posts
Get you an AXI 2826-12... it will fly awesome on a 3 cell pack...

Myron
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Old Apr 20, 2005, 10:47 PM
Southern Pride
everydayflyer's Avatar
Haralson County GA. USA
Joined Oct 2004
34,719 Posts
Quote:
Originally Posted by Myron
Get you an AXI 2826-12... it will fly awesome on a 3 cell pack...

Myron
That's interesting. I looked at the motor chart and with 10 cells(more volts than 3S Lipo) the best thrust I saw was around 50 ounces. 5 pounds equals 80 ounces. My guess is that his 5 pounds model will mostly weight 6 plus pounds converted to electric.
Just trying to fiqure this out.

Charles
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Old Apr 21, 2005, 01:26 AM
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davidleitch's Avatar
Sydney Australia
Joined Feb 2002
5,875 Posts
The sports plane forum has people with a ton of experience with these kind of conversions.

If you are aiming for 3D a geared motor spinning a big prop relatively slowly is regarded as a good way to go.

Something between a Hacker B50 13S - B50 10L with around 4S-5S lipo cells spinning a 17-18 inch prop is typical for 3D planes in this size range, depending on weight. There are many other options but that could be a starting point.

The motor with gearbox weighs around 250 g (say 9oz) and the battery pack will be around 18-20 oz. So add 30 oz to the weight of your plane without the glo engine and fuell tank.
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Old Apr 22, 2005, 07:05 PM
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United States, CO, Arvada
Joined Apr 2005
137 Posts
I've seen some of the bigger brushelss motors with planetary gear drives built on the motor. Would that be the way to go?

Local guy is telling me to get a big outrunner and swing a 12-14" prop on this model.

I've always been of the mindset that RPM=power. So, I'd be more inclined to lean toward a motor turning higher RPM and then gearing it town to get the torque required for my prop.

With that in mind-- then how do you select your reduction ratio? 4.3:1 or 5:1 or 6:1 or 2:1????????????

Relying on a direct drive with an outrunner kinda goes against that theory.

But- then again-- I don't know beans about electrics.

Thanks for the help with this.
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Old Apr 22, 2005, 07:14 PM
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United States, CO, Arvada
Joined Apr 2005
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On the Watts/Pound ratio for my power requirements:

I was told to go MINIMUM 125 watts/pound for decent 3D and that 175--200watts/pound would be the kind of power I needed for 1/2 throttle hovering.

Is 175watts/pound gonna cost me $1000? If so- then I got a .61 glow engine for this thing. It's sitting on the shelf in a box--out in the shop.

I'm willing to spend $300--$600 for this powerplant, but thats even completely nuts when you consider that I have a NIB glow engine for it already. No way I'll spend $1000 for electric power on a $100 Fun Fly plane.
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Old Apr 22, 2005, 07:42 PM
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Well, this thread is a waste of bandwidth.

Just priced the big hackers with gearboxes. They cost between $250--$350.

80amp ESC will run about $125--$150.

And the batteries are gonna run another $200

Forget it. I'm just not that curious about the "cool factor" of an electric 3D plane this size. Sorry to waste everyones time.
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Old Apr 22, 2005, 08:55 PM
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davidleitch's Avatar
Sydney Australia
Joined Feb 2002
5,875 Posts
Either an outrunner or a geared inrunner will do the job. As a general statement in my personal opinion the outrunner will need more amps than the inrunner.

You should aim for 125 watts/lb or more more for hovering power. Again that is just my opinion.

As for price there is no doubt it will cost. I'm in Australia so all I can say whatever it costs you it cost me more because I have to import all my gear.

Just so you don't kid yourself about cost

You need a motor, esc, charger, and batteries. Most people want two batteries to do the job properly.

You can price thunderpower batteries at www.tppacks.com, and geared motors and esc at www.aircraft-world amongst vendors that I use personally.
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Old Apr 24, 2005, 02:45 PM
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cloudhopper's Avatar
Mississippi
Joined Jul 2000
755 Posts
Quote:
Originally Posted by Myron
Get you an AXI 2826-12... it will fly awesome on a 3 cell pack...

Myron
I think you ment a 4S pack I've got this motor on a 3S and it flys a 4lb. Tiger Moth scale but nothing more.4S is needed to get the motor close to its potential

Rcpilet
If you change your mind check out Espritmodels.com they have lots of nice mounting options.FWIW minus the cost of the plane it cost me around $550 to get a 4lb. glow model converted to electric...well worth it to me anyway

steve
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Old Apr 24, 2005, 06:16 PM
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vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,703 Posts
Quote:
Originally Posted by Rcpilet
Well, this thread is a waste of bandwidth.

Just priced the big hackers with gearboxes. They cost between $250--$350.

80amp ESC will run about $125--$150.

And the batteries are gonna run another $200

Forget it. I'm just not that curious about the "cool factor" of an electric 3D plane this size. Sorry to waste everyones time.

Yup. It can be done but not cheaply.

You don't need to spend that much in te motors, but ESC and batteries are in the ballpark, sadly.
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