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Old Jan 09, 2011, 08:17 AM
Vertical Unlimited
Straight Up's Avatar
Mandurah, Western Australia
Joined Mar 2007
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Quote:
Originally Posted by hugofly View Post
If you follow the 80% rule, you should use a 35 amp ESC if you're pulling 28 amp static. Just saying.
I agree with your approach. I don't use any formal "rule", except that I ensure the ESC is rated to take more than the maximum possible current, whether that occurs on the ground or in the air. If the person asking the question has a 30A ESC, use it. No sense buying a 25A ESC when it potentially puts you close to the edge, saves negligible weight and incurs unnecessary cost (assuming the 30A ESC).
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Old Jan 09, 2011, 10:00 AM
Registered User
Wallington, New Jersey, USA
Joined Apr 2010
236 Posts
The 80% rule says that you should, if you can, load any piece of electronics to a max of 80% of its rating. So if an ESC is rated for 100amp continuous, you should only load it to 80amp static at the most. This is for longevity. Yes, a 100amp rated ESC can probably be loaded to 120amp, 140amp or even more, but the risk gets higher and higher the more you load it. If you load a 100amp to 80amp, you can be 99.9999999% sure that you won't overload the ESC.

That's all. I used to not follow the 80% rule either and never had a problem, but it's just a matter of lowering the risk of an ESC failure and then have an 80mph rifle hit whatever happens to be in it's path while the ESC fails.

The glow engine rule of running it a few clicks richer is because in the air the engine leans out a bit.

I'm not saying that you all have to change your ESC now, but if somebody asks me if a 30amp ESC is fine, then I say yes, if your static full throttle amp draw is not more than 24amp. Safety margin, margin of error, etc., even if you're using a high quality ESC. If you're using a cheap Chinese ESC, it's even more important to leave some head room.
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Old Jan 09, 2011, 12:53 PM
Tim Lampe; Hobbico R&D
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Champaign, IL
Joined Dec 2009
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That sounds good. I wonder how they came up with 80%? I wonder why you wouldn't go with like a 50% rule or maybe a 75% rule? I guess it comes down to some statistical data in a study someone somewhere must have done where you get into the law of diminishing returns. Something to keep in mind though.
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Old Jan 09, 2011, 02:29 PM
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Wallington, New Jersey, USA
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Quote:
Originally Posted by KRProton View Post
That sounds good. I wonder how they came up with 80%? I wonder why you wouldn't go with like a 50% rule or maybe a 75% rule? I guess it comes down to some statistical data in a study someone somewhere must have done where you get into the law of diminishing returns. Something to keep in mind though.
I guess it's a rule of thumb. Just like the 80% rule of LiPos, where you're supposed to discharge it to about 20% (e.g. you should discharge a 1000mAh LiPo down to 200mAh and not lower), that's also a give-or-take kind of rule.

It all comes down to how long you want your equipment to last.
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Old Jan 09, 2011, 02:48 PM
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Joined Sep 2008
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My Rifle is coming on tusday and I'm planning to use a 4.75 x 4.75 prop, 1800 lipo 25c (3s) battery, ammo 24 33 3180 motor. I have the option to go with an eflite 25 amp (heat sink) ESC 2 years old or the volcano series 30 amps from hobby partz. Eflite weights 32g and the volcano 25g.
I'm trying to save weight also, so thats why I was asking for an advice with the ESC.
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Old Jan 09, 2011, 03:10 PM
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USA, FL,
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has the wing been reinforced on the new rifle?
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Old Jan 09, 2011, 03:17 PM
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I am just curious, has anyone tried launching their Rifle using the same bungee launch system that comes with the Evader.
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Old Jan 09, 2011, 03:37 PM
Dream Build Fly Scale
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Philadelphia, PA
Joined Oct 2004
2,865 Posts
Guys, some time back I picked up an ARC 28-37-2 for a rifle, but they seem like they are forever on backorder. Back in the beginning of 2005 I scratchbuilt a Microjet2 from MAN plans with an enya .09 in it. Flys great. I've been converting over to electric the past year or so and am curious about doing the same with the microjet2.

Do you think it's too much motor for the microjet?

Here's some video and pics of the model.

micro jet (1 min 51 sec)


Hope it's not deemed off topic for this thread...but I was shooting to get a rifle....or something 'spirited'...
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Old Jan 09, 2011, 04:22 PM
WATTSUP.SE
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Sweden
Joined Dec 2001
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I maiden my Rifle the other day, considering the battery used and outside temp it had about 700-750watt power.

With a 2150 50C pack, i am up to 850watts, and yes its fast

Pletti Moskito 3
CC ICE 50
5,2x5,2" prop Graupner CAM
Futaba 3114 and 3115 servos.

My friends will be using Mega 16/EDF, we messured one with a good 3s 30C 2200 packs to 74Amps using a 5,2x4,5" prop.
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Old Jan 10, 2011, 05:45 AM
Tim Lampe; Hobbico R&D
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Champaign, IL
Joined Dec 2009
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Quote:
Originally Posted by Jocke View Post
I maiden my Rifle the other day, considering the battery used and outside temp it had about 700-750watt power.

With a 2150 50C pack, i am up to 850watts, and yes its fast

Pletti Moskito 3
CC ICE 50
5,2x5,2" prop Graupner CAM
Futaba 3114 and 3115 servos.

My friends will be using Mega 16/EDF, we messured one with a good 3s 30C 2200 packs to 74Amps using a 5,2x4,5" prop.
WOW! And congratulations Jocke. You bested my hottest Rifle setup (610W--MEGA 16/15/2, Hyperion 3S 1800mAh 35C, 4.1 x 4.1) by about 250 Watts! That's incredible. And just a 50A ESC.

How long do you go full-throttle? Do you throttle back at any time during the flight--as in the turnarounds?

How did you reinforce your wing?

I love the colors you used. Very classy. Nice job!
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Old Jan 10, 2011, 05:51 AM
Tim Lampe; Hobbico R&D
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Champaign, IL
Joined Dec 2009
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Quote:
Originally Posted by robertbrol View Post
My Rifle is coming on tusday and I'm planning to use a 4.75 x 4.75 prop, 1800 lipo 25c (3s) battery, ammo 24 33 3180 motor. I have the option to go with an eflite 25 amp (heat sink) ESC 2 years old or the volcano series 30 amps from hobby partz. Eflite weights 32g and the volcano 25g.
I'm trying to save weight also, so thats why I was asking for an advice with the ESC.
Well robertbrol, we just went through a little discussion about your very question. Have you read the previous posts? But now that I read your question a little more carefully I think the answer is obvious--the Volcano is both lighter and higher Amp, so that's the one I'd go with.

We have used the 25A ESC time and again with the same Ammo and prop you are using, but with a 1500mAh battery. As you are using a slightly larger battery I would go with the 30A ESC.

Tim
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Old Jan 10, 2011, 06:14 AM
WATTSUP.SE
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Sweden
Joined Dec 2001
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Quote:
Originally Posted by KRProton View Post
WOW! And congratulations Jocke. You bested my hottest Rifle setup (610W--MEGA 16/15/2, Hyperion 3S 1800mAh 35C, 4.1 x 4.1) by about 250 Watts! That's incredible. And just a 50A ESC.

How long do you go full-throttle? Do you throttle back at any time during the flight--as in the turnarounds?

How did you reinforce your wing?

I love the colors you used. Very classy. Nice job!
I have 2 flights now, and i would guess full power has been in a few sec bursts, and will fly like that for a while to see have everything performs. I have used same setup in FunJet, and flight time at WOT is just under 3min. Castle ESC is modifyed some, and current limit disabled. This is the "new" version, so i havent done any extra reinforcements to the wing.

Colours done by a friend who is a car painter.
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Old Jan 10, 2011, 06:19 AM
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Sweden
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Some paint jobbs on my friends Rifles.
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Old Jan 10, 2011, 08:43 AM
Tim Lampe; Hobbico R&D
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Champaign, IL
Joined Dec 2009
3,644 Posts
Jocke, I am impressed with your creativity and flying your Rifle at 700W - 850W, but please remember the limit specified in the instructions is 300W. You may get away with this power if using it only in bursts when flying straight-and-level, but if you use too much power in the turns you may apply too much stress to the wings. Please reinforce the wing, or use extreme care when turning.
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Old Jan 10, 2011, 08:53 AM
WATTSUP.SE
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Sweden
Joined Dec 2001
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No problem, im well aware that its designed for 300watts, and i might reinforce the wing in the future. Its not the first plane i overpower
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