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› Ground power for testing with teather, thoughts?
12-24-2008 04:18 PM  8 years agoPost 1
SuperSixTwo

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Virginia City, NV​---USA

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so I have this big converted heli. But need some batteries for it. I was thinking along the lines of 10-12s. Since they want a fortune for the batts, i was thinking of using some lead acid in series and some long wire. Provided i have the right ballast for battery wieght and placement (which is part of this idea of testing it) i dont think it will be a problem.
Jokes aside, this is only for some hover testing, and setup.

Other than the just plain "I think your crazy" what do you guys think? Have any saftey tips? Anyone start flying helis on of the teathered to wall wort deals?

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12-24-2008 06:01 PM  8 years agoPost 2
HeliCSR

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Hesperia, Ca, US

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The problem with that is with the battery voltage as you have selected
would result in 15 to 20 amps, figuring at 50 watts per pound to lift your bird.

The wires from the ground would have to be thick, since there would be long wire leads.

This will affect your being able to hover the heli, you can't use this method for trimming, the current to the motor will be affected by the long tether so when you get batteries the performance will increase.

Not sure if that would be safe, if something goes wrong, say tail gyro locks up, now the heli will drift while spinning, most likely with the wind, big old lead acid battery pack sitting on the ground, teather twisting like taffy, now you got to land and its in the way.

I think you should, if you know what size battery you want and it will fit the heli, just buy it and be on the safe side.

I fly and then I fly some more.
If it don't glitch then I won't crash.

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12-25-2008 04:18 AM  8 years agoPost 3
segman

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Calgary, Alberta​Canada

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+1 to the previous poster. You're not going to be able to trim in any meaningful way tethered to the ground, and if you have one tiny glitch in any number of places, you're going to wind up with the equivalent of a very large, Pi$$ed off circular saw, tied to an anchor on the ground that you probably can't move fast enough to get away from.

If you're gonna fly it, you're gonna have to take the plunge for batteries. do it now, get your set up done right, and enjoy the hobby. I sure wouldn't take the risk of a ground tether power system.

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12-25-2008 05:59 AM  8 years agoPost 4
what_the_helli

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cookeville, tn USA

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you're going to wind up with the equivalent of a very large, Pi$$ed off circular saw, tied to an anchor on the ground that you probably can't move fast enough to get away from.
that's what I was thinking....

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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12-25-2008 05:01 PM  8 years agoPost 5
SuperSixTwo

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Virginia City, NV​---USA

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very large, Pi$$ed off circular saw
I have thought about that. I also considered one of those old school training stands like the whitman, if i could find one to use. I didnt think i could trim it, but rather use battery ballast for balance enough to hover.
The more i think about it, the more i think i am going to buy the batteries. My luck, i would try this in the garage to boot, and have no place to run when the the inevitable happens.

Thanks Guys for keeping me straight!

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12-25-2008 05:49 PM  8 years agoPost 6
HeliCSR

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Hesperia, Ca, US

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No don't do that in a garage.

Open area only even with batteries.

I fly and then I fly some more.
If it don't glitch then I won't crash.

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12-25-2008 06:43 PM  8 years agoPost 7
ch-47c

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san jose, ca

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You could have been famous

Did you want to teather the heli for restraint plus power it with a cable? Not clear on your intent. The battery cable idea isn't a far-featched idea, though I wouldn't bother with it. I'd just fly unrestrained. There was a company back in the mid 80's that sold a battery box with long wire leads to the heli for hovering. It was advertised in RCM (Radio Control Magazine) in a very small 2"x 3" ad. I think it was made in Germany by Ikcarus. Help me here guys I'm getting old. They didn't sell many as everyone back then wanted to get out of hover and into translational lift. I think there may have also been an article about the product as well.
Arthur Young the designer of the Bell 47 studied rotory wing stability and lift with a model powered by an electrical lead from an external source. He designed the stablizer bar or as we call it the flybar. It worked well enough for him to prove his ideas and design. So I would say your idea isn't "crazy". And you could have famous if you were born about 100 years earlier. Good Luck!

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12-25-2008 07:02 PM  8 years agoPost 8
copperclad

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NY

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I think it was made in Germany by Ikcarus
hi
yes , it was Ikcarus , they sold it for the Eco-8 , i learned to hover a Ikcarus Picolo in my front room on a tether , with an RC car battery on the floor , the tether was about 10' of speaker wire attached to the skids at the CG , it worked better than you might think , one of the big problems was getting off the ground without getting snarled in the tether , but once you were airborn it flew well , the rotor disk is very stable and keeps the machine level when you come to the end of the tether , so the machine sets down on its skids , but you are limited to just simple hovering for sure

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12-25-2008 07:35 PM  8 years agoPost 9
SuperSixTwo

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Virginia City, NV​---USA

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No i dont want to tether it for a restraint, rather just power the motor/esc for some true headspeed hover testing. I have some gear ratios to work out, wrung the numbers a bunch but dont know if i want 10 or 12s. I have the gears to do either, but i dont want to buy 2 5s and then decide i need the extra umph.

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12-25-2008 08:19 PM  8 years agoPost 10
HeliCSR

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Hesperia, Ca, US

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Formula

You could use this formula:
Just put in your main gear and pinion tooth count.

(Example)
Main Gear = 138
Motor Pinion = 12

Ratio = 138/12 = 11.5

(Use the battery full charge voltage to calculate 8S battery)
4.2 x 8 = 33.6

%80 ESC 740kv Actro motor

33.6 x 0.8 = 26.88 x 740 = 19891 Motor RPM

19891/11.5 = 1729 Headspeed

In reality I tested this on a 600 heli, and the tach read 1850
to 1900. I was able to move the ESC down to %70 but moved it to %75.

I fly and then I fly some more.
If it don't glitch then I won't crash.

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12-25-2008 08:22 PM  8 years agoPost 11
segman

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Calgary, Alberta​Canada

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doing it in an enclosed space is a REALLY bad idea. years ago, I had a JR VoyagerE on my shop bench, "anchored" or so I thought, to the bench top. I got the bright idea to check tracking with it on the bench, locked doen the way it was.
Vibrasions on spool up are an amazing thing; vibrated itself loose enough from the jig I had it locked down with, and of course, I had to throw some pitch in the blades. broke the anchor point and launched straight up into the flourescent lights over the bench. it was 10 at night, my shop has one small window, and I was in the dark with a 500 sized heli beating itself to death on the bench, heating ducts and walls.
I ducked under the bench and escaped with a few stiches; it could and should have been a lot worse, and I have NEVER mounted a set of blades on a heli indoor ever since. It did scare me that badly

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12-25-2008 09:17 PM  8 years agoPost 12
ch-47c

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san jose, ca

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Super62,
HeliCSR formulas make it easy, but if you want to run it anyway, Ray Hosteteler made a heli runup stand that he used to get power settings right. It was in all his RCM articles and in his book. There were plans for it, but you couls make your own with a tire with a 3" pipe and concrete or a tire and rim with the pipe welded on. They all had about a 12" steel plate welded on top to mount the heli. They never flew off as the stand was heavy, but could be rolled away on the tire.

Ikarus sells thru Hobby-Lobby in Nashville. I'm sure you could fabricate one yourself as long as you don't have too much resistance thru the wire hookup.

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12-25-2008 09:52 PM  8 years agoPost 13
what_the_helli

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cookeville, tn USA

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here are a couple plug and play calc's to make number crunching easy...

http://www.readyheli.com/Online_Hea...ulator_s/81.htm

http://heli.dacsa.net/calculatorv2/Default.aspx

I put the fun in dysFUNctional :)
Team KBDD & Funding by TnPrintMasters.com

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