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Raising the stakes, long range idea.

PostPosted: Wed Mar 27, 2013 3:47 pm
by Crowstooth
Hi all,
I tried Bruce's idea for longer range FPV by taping my receiver to a long pole, but I found I was forced to stand alongside the pole and almost on tiptoe (allowing for exaggeration). While watching someone on youtube flying from inside a car, I saw they were using an extension cable for their video antenna. This seemed the answer to my problem so I looked up SMA extension leads on ebay and found the 3 metre length I wanted. However, I also saw a 10 metre lead which gave me an idea. A helium balloon to raise the antenna to a great height (i.e. 10 metres). The only problem I could see was the cost as the helium would be a total loss each time. I have a 12volt tyre pump which pumps up to 200 PSI and it occured to me that if I used a plastic bag type balloon there would be no pressure as in a rubber balloon and I could either run a tube to the air inlet of the pump or place the pump inside the bag and pump the helium back into the bottle.
I wonder if I could use a similar lead to raise my radio antenna? This would give me a great range increase.
If you're reading this perhaps you can tell me if this is a pipedream or a real possibility for the video and/or the radio?

John.

P.S. a cubic foot of helium can lift 28.4 grammes which is 1 ounce.

J.

Re: Raising the stakes, long range idea.

PostPosted: Wed Mar 27, 2013 5:52 pm
by BillGriffiths100
You can easily get fishing poles and flag poles to 10 meters:
for instance on this site
http://www.windcreations.co.uk/shop/cat ... tAodMxwABw
Just google poles fishing poles etc in your area, it will work out much cheaper than balloons.

Re: Raising the stakes, long range idea.

PostPosted: Wed Mar 27, 2013 7:10 pm
by Crowstooth
BillGriffiths100 wrote:You can easily get fishing poles and flag poles to 10 meters:
for instance on this site
http://www.windcreations.co.uk/shop/cat ... tAodMxwABw
Just google poles fishing poles etc in your area, it will work out much cheaper than balloons.


The object is not to save money, but to enjoy this fascinating hobby. I ride a bicycle to and from the flying field so a flag pole is not an option and using a fishing rod is much less interesting than a helium balloon.
I don't see how it would be cheaper if the plan to replace the helium back into the gas bottle works.

John.

Re: Raising the stakes, long range idea.

PostPosted: Wed Mar 27, 2013 9:50 pm
by Keith
Sounds like it should work. Not sure if you could recover the gas again.

I have a vision of you flying into the mooring line and watching your Rx floating away...

Re: Raising the stakes, long range idea.

PostPosted: Wed Mar 27, 2013 10:42 pm
by BillGriffiths100
So a battery a pump the gas cylinder and the tubing and the balloon would be easier to carry on a bicycle than a collapsed telescopic pole along with all the fpv gear and plane.
What kind of bicycle is that? :?
if the plan to replace the helium back into the gas bottle works

It won't! The tyre pump will leak helium like nobodys business it won't have the capacity to back pump more than a few cc a minute at 200 psi and the heat generated will soon make the pumping even more inefficient

Re: Raising the stakes, long range idea.

PostPosted: Thu Mar 28, 2013 12:06 am
by cynr100
Recovery of the gas will be problematic, for your bike. Boiling point of Helium is -269C at 25MPa so you are going to need a bigger recovery pump and a cooling system to liquify the Helium and get the genie back in the bottle.(re: Low Temp Gas Liquefaction/Quantum mechanics)
It may be cheaper to run a relay Tx/Rx in a small foamy, set up with RTL and auto pilot, then you will get more than your 10m.
Or you could stand on a hill............. :!: .........sorry, no disrespect I couldn't help myself.

Re: Raising the stakes, long range idea.

PostPosted: Thu Mar 28, 2013 7:58 am
by Keith
I picked up an aluminium tripod stand for stage lighting at the local recycle tip for $5 the other week. Stands about 4 meters atm but can add as much ally tube as I want...

Re: Raising the stakes, long range idea.

PostPosted: Thu Mar 28, 2013 9:23 am
by Crowstooth
A large gas bottle costs about £17 or $20 so I could try to get the genie back in the bottle but the liquification issue sounds like it might present a problem. I'm hoping that the helium will liquify under pressure. I don't know about quantum mechanics as I'm just an ordinary mechanic and I've never worked on a quantum. I know the pump is very slow but I don't think it will leak as it holds air at high pressure.
I plan to use a Sodastream bottle to get the helium to the flying site if I can get enough helium into it.
I don't know how much helium it would take to lift the antenna and cable but I think it would be fun to try out the principle using a black plastic bag. The pump would be powered by a 3s LiPo or two, I know that works as I've tested it.
A hill would require earth moving equipment and might upset other flyers.
I like the idea of a little foamie circling overhead but a second RTH setup might be a bit pricey.
Thanks for your input.

John.

Re: Raising the stakes, long range idea.

PostPosted: Thu Mar 28, 2013 10:33 am
by BillGriffiths100
I don't think it will leak as it holds air at high pressure.

There is a huge difference in the size of a helium atom and nitrogen, oxygen and co2 atoms found in air, helium will pass through an ordinary plastic bag as though it wasn't there, the helium atom will squeeze through the gap between the cylinder and piston with equal ease.
That's why modern helium balloons are made of metallised foil and plastic the dense structure resists the passage of helium.
An ordinary rubber balloon goes down in only a very few hours as many disappointed children of the past found out.
Your plastic bag probably only a few minutes.
You will need a balloon containing a minimum of 17 cubic feet to lift the receiver and the wire if it comes in at around 500 gm (most of the weight will be the cable) the higher you want to go the more the cable will weigh.
The balloon will have to be approximately 3.2-4 ft diameter to contain that much gas, that's a big balloon that will have to be custom made.

Re: Raising the stakes, long range idea.

PostPosted: Thu Mar 28, 2013 12:23 pm
by Keith
You could use an 'Air Swimmer'... Maybe.



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