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Century Radikal E640 - Swift 16 NX
› a123 configuration on the Swift - what is the​ultimate?!?!
03-17-2009 06:55 PM  8 years agoPost 1
wrathofkhan

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LA, CA - US

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hello

i have flying my swift 16, with 10s a123 with 550mm blades and z30 (800kv) for some time now. it has quite a bit of power, but not much flight time (around 4.5-5 minutes). my head speed now is around 2000 (since i am back to plastic grips & metal center block). when i had metal grips, i used to turn at around 2200 HS - way too much power for my level of flying,

anyhow, in my last crash i destroyed a battery pack (partially). most likely two of the cells are not performing like the other 8. i am contemplating on trying out other configuration. my motor can handle (and maintain similar HS with the correct pinion).

what do you all think of 8s? it will be a bit lighter of course, but will the power go down and/or flight time will be lesser? has anyone tried out 8s setup on the swift? i am curious about the trade off, lesser voltage vs. weight savings of lesser cell count. is 10s the best, or is lighter better?

look forward to your feedback ... cheers, khan

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03-17-2009 07:49 PM  8 years agoPost 2
imnxtc

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BC.Canada

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If you go 8S, and gear for the same rotor head speed, you will end up with less flight time. The best way to gain flight time is to gear for slower head speeds.

This will result in less aggressive cyclic and collective pop, but I have successfully flown 3D at 1650, using 4S/3700 Flitght Power 20C lipos, that gave 6 minute flights. Of course it is not as "flitty" or have as much "pop", but with proper collective/cyclic management it was still very capable - much like a 30 nitro with an OS32 engine.

And I have also flown with the same packs, set for a slow 1500 head speed, and got almost 8 minute flights, that provided more softer responses that was great for scale type flying.

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03-17-2009 08:09 PM  8 years agoPost 3
wrathofkhan

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LA, CA - US

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when i first started flying the swift, i had actually started with 4s lipo (3700 mah FP packs). used to get around 6 minutes too, as far as i can recall.

the a123s are a bit different since they weigh quite a bit more - but i guess the same principle applies (as you mention, less cells, less flight time, maybe lesser pop).

khan

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03-18-2009 12:30 AM  8 years agoPost 4
born2rc

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Rolla, Missouri

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Have you thought of running 2p5s (a123s), with different motor/kv ofcourse.

You might get the power and extend flight time at the same time. Haven't done the math, but that is my $0.02.

Bob

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03-18-2009 01:00 AM  8 years agoPost 5
imnxtc

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BC.Canada

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the a123s are a bit different since they weigh quite a bit more
Not only do they weigh a lot more, but in this type of application they do not deliver their nominal 3.3V/cell, but only 2.7 - 2.8V per cell, while a good Lipo will give 3.65V/cell from its nominal 3.7.

And your 4S/3700 Lipo had a 3700mah capacity, while your A123's only have at best a 2300 capacity, and at 2000, their voltage will have dropped off below what would be required to fly the heli - so they are really only a 2000mah capacity in this application.

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03-18-2009 09:19 AM  8 years agoPost 6
wrathofkhan

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LA, CA - US

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for power to weight ratio (in our current technological state), lipos are better than a123s

but, i use a123s mainly for its durability, safety, fast charging ability. i also have a trex450 on a 3s a123 setup. for smaller packs, the voltage really dips as more amps are drawn. i checked it with elogger

anyhow, i have over 500 flights on the trex, with lots of fast charging, some zip charging even - can't tell much degradation of power (recently i flew a brand new 3s a123 pack for comparison).

it is true that the voltage under load drops quite a bit for a123s, but i gear it accordingly (also buy the right kv rated motor). for example, on my trex 450 i use the scorpion 2221-6 which is 4400 kv motor, while most people flying trex using 3s lipo us 2221-8 (i think the kv on that is around 3400). instead of calculating target HS at 3.65v/cell, i just use 2.8v/cell

cheers, khan

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10-08-2009 08:00 AM  8 years agoPost 7
wrathofkhan

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LA, CA - US

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going back to this topic

has anyone tried 5s2p a123 setup yet. i did some rough math, and it seems like it is possible.

what would be the downside with this config? i am thinking with the correct gearing/motor/high amp esc - it should get longer flight time, am i wrong?

cheers, khan

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10-08-2009 05:52 PM  8 years agoPost 8
oldfart

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Vancouver, Canada

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The problem with a 5S A123 configuration is the resultant low Voltage.

Under load they will only deliver about 2.8 volts (optimistically) for a total of 14.0. That is less then a 4S Lipo pack. SO it would give you even less power then a 4S/5000 lipo and weigh a lot more.

For low rotor speed application (1400 to 1500 or so) it will work and give you about an 7 to 8 minute flight.

Why bother considering the relative low cost of good 5S/4000 or 6S/4000 plus packs today?

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10-09-2009 02:34 AM  8 years agoPost 9
wrathofkhan

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LA, CA - US

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i would consider going lipo in a heart beat, power to weight ratio is hard to beat

my issue with lipo is safety. i have a hyper active 2 and a half year old

i have been using 3s a123 on my trex450 with close to 1000 cycles. i don't think the power is there, but i am not at that level yet to appreciate lipo. i have banged them up lots of time, one time i noticed vibration while in a inverted hover. as i was flipping it over, the pack came off and the blades got them. it must have flung that pack at least couple hundred feet ... sure there was damage to one of the cell (casing), but i still used them for at least a hundred more flights. eventually, there was some corrosion and i decided to stop tempting fate

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10-11-2009 09:00 PM  8 years agoPost 10
CompyMike

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sacramento, ca

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Are any guys going from Swift A123 10s to Swift 8s Lipo since the lipo prices are coming down? I've flown my Swift A123 10s for a while now and I want to lighten it up some. I'm starting to notice the heavier 10s A123 packs. Want more float. Been flying the heck out of a Trex 250 getting low and flipping and inverted FF flight.

What would be some solid lipo choices if someone wanted to go from 10s a123 to Lipo. I know that 8s lipo would be a similar voltage

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10-11-2009 09:06 PM  8 years agoPost 11
wrathofkhan

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LA, CA - US

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i think voltage wise, 8s lipo is similar to 10s a123

BUT, since 10s a123 weigh quite a bit ... i think as far as performance is concerned, 10s a123 would actually have similar performance to 6s lipo pack (4000mah)

8s a123, i never tried it ... but i do not think it would have the duration or the punch of a 10s a123

khan

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10-11-2009 09:55 PM  8 years agoPost 12
CompyMike

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sacramento, ca

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I don't want to run s a123. I was thinking 8s lipo

really like the Hyperion G3's

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10-12-2009 01:14 AM  8 years agoPost 13
CompyMike

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sacramento, ca

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Looks like I could use 2 2500mah 4s or 3500 mah 4s hyperion G3's. The 3500's wouldn't be much if a weight savings though

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10-12-2009 06:23 AM  8 years agoPost 14
oldfart

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Vancouver, Canada

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A lot depends on your motor's KV, and the gearing for what head speed.

Even in potentail power to weight ratio etc., a 6S/3700
lipo would be similar in voltage output nder hese type of loads (22.2 for the lipo and 23,2 for the A123, but the 2300 mah A123's will not give the same flight times when geared for the same rotor speeds and would also weigh about 30% more then the 6S lipo pack.

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10-12-2009 07:22 AM  8 years agoPost 15
CompyMike

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sacramento, ca

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I'm running the Scorpion 4025-740 with a 10T pinion.

So your saying my 10s A123 pack has about the same voltage as a 6s Lipo pack? I think you and I have been down this road before so I don't really want to get into it with you.

Under a 30 amp load a A123 packs voltage is around 2.95 volts.

I have not measured it but I'm probably outputting 29 volts under load. A good 6s pack would be outputting 21 volts.

I would love to be able to run a 6s pack. But I can't. And if I did a 12T pinion would not even give me a 1700 headspeed.

I do most of my flying around 1850 with the swift right now.

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10-12-2009 09:12 PM  8 years agoPost 16
oldfart

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Vancouver, Canada

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My voltage figures are based on the Eagle Tree computer readings we took a number of years ago, when we first started testing different battery combinations for use on the Swift, while geared for 1800 or more rotor speeds.

We also discovered during those tests, that the relative load, on any battery pack, was much more related to rotor speeds then to most any other factors. It was surprising to see the difference in wattage required to turn the same rotor at 1500, compared to that required for turning it at 2100 (from 425 watts to 825 in the hover if memory serves).

We also found that some batteries, with C ratings that were supposed to be high enough for the amprage demands of flying these size of helis, dropped substantially in voltage in flight, compared to some of their competitors. But non of the 3.7V lipos tested dropped anywhere near as much from their nominal voltage ratings as did the 3.3V A123's.

Of interest to some, is that recent testing we have done on some of the current versions of the lipo technology, actually show they delivered more then the nominal 3.7V/cell under 3D flight loads and rotor speeds!!

The next interesting finding, was the difference in the wattage requuirement to hover using different blades.

My conclusions from all these tests were that the A123's were fine under loading that were in keeping with what they were designed for - for use under relative lower current demands. But for the higher current demands and weight considerations of the more demanding area of 3D, where a high power to weight requirement is much preferred, they where not our favorite choice.

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10-12-2009 09:27 PM  8 years agoPost 17
oldfart

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Vancouver, Canada

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I would love to be able to run a 6s pack. But I can't. And if I did a 12T pinion would not even give me a 1700 headspeed.
If your motor runs at an honest 90% efficiency, then using a DECENT 6S/3700 pack on a 740KV motor and 12T pinion should easily give you an 1850 rotor speed.

Using a 13T pinion would deliver a 2000 rotor speed.

An older technology 6S/3700/20C Flight Power lipo on my old (now discontinued) Century 600/800KV motor back in 2005/2006 gave me a 2000 head speed using the 12T pinion.

All the above being said. If anyone wants to fly their Swift using one combo and find it flies it as well as they wish, and if others want to use a different combo and find it flies their Swift as they wish, then all is GOOD.

As the Swift is such a versatile heli, it can easily put a smile on all our faces.

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10-13-2009 12:51 AM  8 years agoPost 18
CompyMike

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sacramento, ca

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WOW!

Thanks OFart. Going back to the drawing board... and yes your right a 6s pack is very do-able. And much lighter than my A123 pack.
Very tempting. I could save 200 grams (7 ounces) going from a 10s A123 pack to a 4000 mah 6s pack. That should make a difference.
Heck that is almost half a pound!

The only bad thing I could think of is that my motor is designed for 10s lipo. But I don't think it would be hurt running on 6s. And I think my CC85HV ESC should work fine.

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10-13-2009 07:26 AM  8 years agoPost 19
oldfart

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Vancouver, Canada

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I assume your motor uses a 5mm shaft. Century offers pinion gears for 5mm shafts from 9T to 14T. So you should easily be able to match your motor to a head speed you want using a 12T or 13T or 14T pinion.

As for your ESC it should have no problem with the 6S packs.

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12-12-2009 04:51 PM  7 years agoPost 20
just4fun2

rrApprentice

torrance

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I don't see any point in switchng from 10s A123 to 8S a123 Wrathman, hardly any weight loss from removing 2 cells. the lesser voltage is adjusted for by pinion gearing o motor kv, your only going to increase the amp draw on the pack and on your electronics most likely you will increase watts consumed to make up for the lower voltage. this will put more heat into your battery pack and increase internal resistance over time. if you go lipo, you'll be standing around forever just waiting to charge up. The grass is always greener, huh? I like the 10s a123 best, it's hard to beat even with lipo cells.

My 12 lbs AP swift is a pig, and only draws 20 amps in hover while using the reliable 2s10p setup.

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Century Radikal E640 - Swift 16 NX
› a123 configuration on the Swift - what is the​ultimate?!?!
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