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Zoom › The Point of Diminishing Returns
11-30-2005 01:18 AM  12 years agoPost 1
Rimas

rrNovice

Adelaide, South Australia

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Hello,

I'm just wondering if anyone has managed to put any large capacity (above 2500mAh) into their zap/zoom?

Is there a point where going up in power offsets the weight gain?

I'm thinking I would like to modify the frame to accept a bigger battery for longer flight times, but I guess I should know where that cutoff point is before I go to crazy with my Dremel...

Thanks,

Rimas

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11-30-2005 01:39 AM  12 years agoPost 2
Helimon

rrApprentice

Washington

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There is a threshold for flight time vs weight. I know a couple of people who fly with 1600-1800 mAh packs that get 14-17 minutes. Not sure what a 4000mAh would do, but for the price it seems that 2 or 3 1800's could be swaped out on the charger and you can keep flying. One of the more popular packs is the 2100mAh. This one seems to be a favorite with Foamy flyers. I plan to use 2100's on both my Heli's and Foamys. The price of a 4000mAh seems to be the deciding factor.

Helimon

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11-30-2005 05:25 AM  12 years agoPost 3
turboomni

rrProfessor

East of the Equator

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Is there a point where going up in power offsets the weight gain?
That depends on what YOU want the heli to do.
Scale stuff? Long Duration Hovering? What are your goals for your setup?

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11-30-2005 08:18 AM  12 years agoPost 4
Rob_T

rrElite Veteran

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To answer your question, yes there is a point of diminshing returns. I haven't stopped to do the math on it but I would guess that its when the battery is half of the total flying weight (ie the battery weighs as much as the rest of the system). (I'm guessing that's the optimum, based on the observation that many similar optimizations are when 2 components are equal, eg maximum efficiency from a motor is when the iron and copper losses are equal, maximum power from a battery is when you load it down to half its unloaded voltage etc).

There is also a lot that can be done to improve duration by lowering the head speed, making sure the gearing is optimal and running the foamy blades. (Despite their tracking issues I have not found a more efficient blade on the Shogun).

Like turbooni said, it does depend on what you're trying to do.

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11-30-2005 08:45 PM  12 years agoPost 5
Rimas

rrNovice

Adelaide, South Australia

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Forgive me for being thick, but how, when all other aspects are equal, does what you are trying to do with the heli affect the power/weight/time issue?

Maybe I didn't make myself very clear. I just want the thing in the air for as long as possible - from hovering to gentle flying about.

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12-01-2005 12:31 AM  12 years agoPost 6
Rob_T

rrElite Veteran

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You're forgiven

Tuning for maximum duration in hover and gentle flying around will mean sacrificing peak power and power/weight ratio meaning you lose the ability to do 3D. Knowing what you want to still be able to do helps with knowing just how far you can push towards endurance (and away from performance).

If you want much more duration, start thinking about assymetric rotor blades for more lifting efficiency and lower headspeeds too.

I can see a fun challenge here- maximize the flight time using the stock frame and rotor diameter (blade substitutions OK if the length remains fixed). Any motor/pinion and lipo size (but no other battery technology). (For fun we could add a subclass for models still able to loop- must be documented on video. That should give some great videos of overweight models drilling into the ground from great heights!)

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12-01-2005 04:19 AM  12 years agoPost 7
turboomni

rrProfessor

East of the Equator

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Interesting, For the lightest airframe ,I hope you have a V1 Shogun.
For all out duration you could go with longer blades and a longer boom at lower rpm's. Are you going to fly this indoors with no wind?
I would maximise run times first with a 2100 Lipo first as it is a proven power/weight source and go from there. That way you have a baseline time to work from. You could make your own design blades that exploit efficiency, never mind all the brushless motor/pinion possibilities.
I would think the mechanics and electronics could be further searched to find the sweet spot first and then add higher Mah,heavier Lipo's and go from there. Light electronics and lightening the frame could also be explored. Perfect alignment of blades and flybar paddles comes to mind and gear mesh and bearings working perfectly smooth.
Instead of blowing money on a big expensive lipo I would work up to it with the mechanics and electronics and proven power supplies first to maximize what you already have to it's fullest. This could open a BIG can of worms!! I like worms!
Just a thought

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