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technical questions: want to convert heli to antenna support


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pa5bw
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Joined: 20 Oct 2013
Posts: 2
Location: the netherlands

PostPosted: Sun Oct 20, 2013 3:36 am
PostPost subject: technical questions: want to convert heli to antenna support
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Dear all,

I have a quite non-standard project, but need your specific electric RC helicopter knowledge as I'm pretty new to this stuff.

I have a Double Horse (coaxial rotor) toy helicopter that is hardly fit to fly with. I want to convert it to keep an 80 meter long wire vertical in the air. I am a (licensed) radio amateur and want to use the helicopter as a "sky hook".

I want to feed the helicopter through that same wire, so that it can stay up for a long time. I will give it a vertical tail fin so that it will keep it's nose in the wind and I'll put the tail rotator up front to compensate for the wind if the wire is not vertical. So battery and radio control can be omitted.

Technical questions:
(1) Are the motors in these cheap Double Horse helicopters all brush types? Does that mean that I control motor speed by changing the DC level?
(2) The Double Horse has two motors for the stacked (coaxial) rotors. While hovering and not navigating, do both motors get the same voltage and hence the same speed?
(3) For brushless motors, are they controled by varying their AC frequency/ If so, around what frequency do they operate typically?
(4) My motors make a lot of noise. Are there affordable low noise motors? If so what types are recommended?

Kindest regards,
Ben

(The Netherlands)
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pa5bw
Charging
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Joined: 20 Oct 2013
Posts: 2
Location: the netherlands

PostPosted: Sun Oct 20, 2013 3:38 am
PostPost subject: Mod. Double Hors as Sky Hook for antenna
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Dear all,

I have a quite non-standard project, but need your specific electric RC helicopter knowledge as I'm pretty new to this stuff.

I have a Double Horse (coaxial rotor) toy helicopter that is hardly fit to fly with. I want to convert it to keep an 80 meter long wire vertical in the air. I am a (licensed) radio amateur and want to use the helicopter as a "sky hook".

I want to feed the helicopter through that same wire, so that it can stay up for a long time. I will give it a vertical tail fin so that it will keep it's nose in the wind and I'll put the tail rotator up front to compensate for the wind if the wire is not vertical. So battery and radio control can be omitted.

Technical questions:
(1) Are the motors in these cheap Double Horse helicopters all brush types? Does that mean that I control motor speed by changing the DC level?
(2) The Double Horse has two motors for the stacked (coaxial) rotors. While hovering and not navigating, do both motors get the same voltage and hence the same speed?
(3) For brushless motors, are they controled by varying their AC frequency/ If so, around what frequency do they operate typically?
(4) My motors make a lot of noise. Are there affordable low noise motors? If so what types are recommended?

Kindest regards,
Ben

(The Netherlands)
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tombo242
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Joined: 04 Nov 2008
Posts: 4718
Location: Santo Estêvão, East Algarve, Portugal. Now 82, but still feels 22.

PostPosted: Sun Oct 20, 2013 5:46 am
PostPost subject: Re: Mod. Double Hors as Sky Hook for antenna
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Welcome Ben,

Motor speed in this heli is controlled by the level of the DC power.

Brushless average AC frequencies are varied acording to the motor poles and windings we need to know what motor you are refering to.

In hover the lower rotor will have slighly more power than the upper as it is working in the uppers wash and will need slightly higher revs to produce the same torque and hold the nose straight.

In the few single motor coaxials this is accomplished by gearing or pitch.

Problems:

1. I doubt that this heli has the power to lift 80m of wire.

2. The best upgrade for it would be ball bearing motors and high lift blades. Without a battery it might just lift the wires (you need +ve & -ve).

3. The motors are unlikely to last more than 15 mins continuous running without seizing up.

4. Even with a front prop your coaxial will not cope with more than an 8kmh wind, the additional drag of the wire(s) will increase the wind effect.

5. The ball bearing motors are quieter than the others but not much, most of the noise comes from the blades.

Sorry to be so negative,

Tom.
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Burgess
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Joined: 27 Mar 2012
Posts: 1092
Location: Wales

PostPosted: Sun Oct 20, 2013 12:39 pm
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Welcome to the forum Ben,

That's an interesting idea but, as Tom has explained a Double Horse coaxial toy helicopter is going to be problematic and short-lived.

However, the concept may work better using a powerful multi rotor six or eight rotor craft with GPS capabilities, to keep it autonomously on station.

Or may be a shorter on-board areal on the multi rotor with 2.4ghz down link to you base station. That would provide longer airborne period.

Burgess
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solentlife
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Joined: 30 Dec 2010
Posts: 927
Location: Latvia / UK

PostPosted: Mon Oct 21, 2013 1:59 pm
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Years ago MFA produced a Heli that ran of an umbilical cord ... it was crap. Would lift to about 2ft and that was it.

Second - don't underestimate the windage of that 80m cable ... even if the heli could lift it .. which I doubt very much ... it would never stay in one place even in a slight breeze...

Nigel
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Burgess
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Joined: 27 Mar 2012
Posts: 1092
Location: Wales

PostPosted: Sat Oct 26, 2013 6:56 am
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Here's some larger multi roto machines
http://www.heliguy.com/article/SkyJib-8-for-Cinematography-/

Here's two alternatives batteries not included or needed

160 Meter Balloon Antenna

Link


Kite antenna for 160-10m - Oceania DX Contest 2010

Link



Burgess
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