[Balloon-makers] FW: micro-solenoid valve

[Noah Forden]

Hello Kyle-
 
I developed RC hot air balloons and their burners 20 years ago (Balloon
Life, June 1990) and determined early on that solenoid valves were not the
way to go because of their large current draw and the associated heavy
battery that was required. I have always been disappointed that the
manufacturers of RC balloons used a brute force approach using solenoid
valves and heavy batteries. Instead, I experimented with various ball and
plug valves from Nupro, Whitey, and others which were actuated with
low-power standard RC servos, and which had the added benefit of not drawing
any power when they are on - unlike solenoid valves, which draw a lot of
current all the time they are on.  This seemed like a much more elegant
solution than a solenoid valve.  Standard small lightweight RC battery packs
were plenty big for 3 or 4 hours of flight time.  After a lot of playing
with a lot of valves, I ultimately settled on a toggle-actuated valve
manufactured by Hoke: 
www.
<http://www.hoke.com/products/instrumentation/1500/1500-series_2007-12_lo.pd
f> hoke.com/products/instrumentation/1500/1500-series_2007-12_lo.pdf
 
During initial tests, the valve would sometimes shut off and not flow, even
though the valve was in the open position.  This was very perplexing.  After
a while, it would start working again.  I would open the valve, and things
would look fine. I would put it back together and it would work fine.  Then
every once in a while, it would stop flowing again.  I was really beating my
head against a wall.  One time I took it apart I noticed that the rubber
seat on the valve stem was inflating because liquid propane had gotten under
the seal and flashed, inflating the seat and closing off flow.  After
discovering this failure mode, I drilled a hole in the middle of the rubber
seat to allow any propane that got around the edges of the rubber to exit
through the hole.  After this, I never had any problems.  
 
Aerostar uses this valve in their liquid pilot lights with some modification
to minimize downstream volume so that the pilot shuts off in less than 3
seconds.  This size valve is plenty big for a burner of about 1 million
BTU/hr.  This is about a 6 ft. flame, should be plenty big enough for a
small blimp.
 
Unfortunately, there are very few homebuilders out there who experiment with
burner design.  It is a lot of fun but you will probably lose your eyebrows
a couple of times and you will use a lot of propane in your experiments.  Be
careful, good luck, and let us know how you make out.   
 
Highest Regards,
 
Noah Forden
Rhode Island


  _____  

From: balloon-makers-bounces at taleos.com
[mailto:balloon-makers-bounces at taleos.com] On Behalf Of Kyle Kepley
Sent: Friday, December 26, 2008 9:55 PM
To: balloon-makers at taleos.com
Subject: [Balloon-makers] micro-solenoid valve


I'm working on a 1/6 scale hot air blimp project and need a pair of small
solenoid valves for the burners. I've searched relentlessly for these things
and it seems like all retailers mainly just carry the ASCO brand.  ASCO only
has one model of low voltage mini valves (ideally 6v DC, or 12v max), and
the only vendor I can find that even sells them takes six weeks to deliver.
Has anyone built an RC balloon using small solenoid valves for the burner?
If so, where did you buy them?

-Kyle 
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