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Saturday 7/7/18

2018-07-07, 21:07 by Gary M Jones

I was at the field today between 14:00 & 15:00 all on my own , good flying too. There is a dead sheep along the fence line towards the gate from the pits, I saw the farmer so reported this to her. I hope no one had plans for a BBQ Smile .

Farmer …

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Post by Stubbsy on 2011-02-10, 18:37

Need to run 2x 8g micro servo's and a spectrum orange box receiver run from any of the following:

1) 4.8v 120mah NIMH pack
2) 4.8v 210mah NIMH pack
3) 6v 210mah NIMH pack
4) 6v 400mah NIMH pack

This is a "how longs a piece of string" type question, but can anyone please suggest roughly estimated flight times for each of the above packs? - also, am I right in saying that the servo speed would be quicker with the 6v packs compared to the 4.8v packs? - would it be a noticable difference between the two voltages?
Cheers all..............
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Post by Guest on 2011-02-10, 18:45

It will work faster - on the servo spec you will see 2 speeds - for 4.8 and 6V
How long ? Depends on what model you gonna use it Wink - my 2xhs-81 in a sloper are powered by 450 mah - 4.8V - works for an hour at least never flew longer and never checked how much left :/

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Post by Andy Sayle on 2011-02-10, 18:56

It is a case of how long is a piece of string..... I'm assuming that this is going in your little iwng that you are building?

If so, then build it up, cover it, and then figure how much nose weight you need to get the balance point right. Size the battery pack based on that, so you don't have useless lead in there, but have a battery that will work for its living.

The 4.8/6v thing is simple. Think of voltage as the driving force, the more of it, the more current that is pushed through things like servos, and the more gusto things like servos have. The downside is that at the higher voltage, the current flow is greater too, resulting in a need for a higher capacity battery pack.

with some servos, you wont notice the difference. With others, the speed increase is noticeable. In flight, unless it is a super sensitive model, you won't normally notice the difference. That little wing though, will be mega sensitive on the elevator (unless you have a CG quite a bit forward), so you might be able to notice the difference. You;ll also find that the amount of elevator travel needed is minimal, so having a decent servo will make it much nicer to trim/fly Smile

Andy

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Post by Mark Barnes on 2011-02-10, 19:02

As the guys have said no way of knowing untill you try but only running 2 servos you should fly all day on any.

As Andy rightly says, I normaly spec batterys by how much weight i need for COG, no point carrying pointless weight!

M

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Post by Stubbsy on 2011-02-10, 19:17

Cheers chaps!
Suppose its all academic really - I will be on the sticks so no doubt it will be buried within 5 mins anyway! Rolling Eyes
Build nearly over - only control surfaces and covering left so will wait and see what weight I have left to play with! - Glider is only 150 - 180g all up anyway so will be looking for really small battery packs - this is the range avalable from component shop in what I am guessing will be within the sort of weight range im looking at!
Cheers for your help again! Wink
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Post by Allan Patrick on 2011-02-10, 20:55

With 2.4 GHz gear I would definitely use 6v packs. 4.8v is fine on warm days but in cold weather the voltage can drop quite significantly and this can be fatal. Especially with small capacity packs

For a couple of small servos on a sloper not under too much load, I would guess that you could safely fly for at least an hour on the 210mA pack and pretty much all day on the 400mAh pack. But I would a) check to see how much was left in the pack when I got home and modify my idea of max flying time accordingly. And b) beware of reduced capacity and ability of the pack to supply high currents in cold weather if its a nimh pack. This can catch one out! Personally, for what it costs, I would fit a battery monitor. It weighs very little and the cost is much less than replacing the airframe
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Post by Stubbsy on 2011-02-11, 10:59

Cheers fore the advice Allan - I didnt know they made battery monitors for NIMH packs though - I thought they were for Lipo's only? scratch
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Post by Allan Patrick on 2011-02-11, 11:18

This is the sort of battery checker I had in mind.. http://www.brchobbies.com/?page=shop&action=additem&item=86 And £3 each

If there's not a suitable location for it then I would use something like this before flying or as the day wore on or as one felt the need http://www.brchobbies.com/?page=shop&action=additem&item=17

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Post by Stubbsy on 2011-02-11, 11:44

Right - Know what you mean now!
The model is a small l'alysee flying wing - 70cm x 30cm - open wing ribs with covered battery compartment in the nose of about 7x10cm - might have been able to bury a little audible buzzer in there somewhere but think an LED strip would probably spoil the overall look of the glider - especially as it is so small anyway!
Basically im just worried about having ridiculously short flight times with it - about 3 minutes flight then watching my little model disappear into the distance - never to be seen again!
Someone give me a rough guess please? E010
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Post by Allan Patrick on 2011-02-11, 13:04

If you are covering it with a translucent film then the battery monitor could be inside the structure but made visible. Or just check it with the tester before flying

If it was me, for such a model I'd use a 6v 210 mAh pack unless one needs any extra nose weight, in which case, as Andy observed, might as well use a bigger battery. Either pack would (should!) last a lot longer than a few mins

Good luck

Very Happy
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Post by Andy Sayle on 2011-02-11, 16:52

As a guide Ben, I fly my Elf DLG on a single cell lipo device that has a capacity of 240mAh. This is stepped up to 5v, so the real capacity is about 175mAh neglecting any inefficiencies in the conversion electronics.

I'm powering a receiver and two SD100 servos off this, and I get flight times of around 2-2.5 hours, depending on whether the flights are mainly floaty floaty thermal flights, or stick banging loopy loopy flights.

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Post by Stubbsy on 2011-02-11, 17:12

Thats put my mind at rest thanks Andy!
I will see what weight I have left to play with and get the highest capacity I can for the weight allowance left over!
Im wouldnt be looking to fly for 2 hours anyway - maybe half an hour at a time tops!
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