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  #1  
Old 10-01-2014, 06:36 PM
schristo@mac.com's Avatar
schristo@mac.com schristo@mac.com is offline
 
Join Date: Sep 2007
Location: WA
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Default Stop dribbling smoke... add a solenoid valve ;)

I have nice smoke with two injectors and plenty of flow and it looks great... accept for the dribbling and residual puffs that come after the pump is off.

After much poking around I decided to add a simple solenoid to get clean cut off of the smoke stream when the pump is off.

The result is quite nice


Click on the image for the video
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Stephen

RV7 powered by a lycoming thunderbolt IO-390
turning a whirlwind HRT prop

with more hours flying than building... 2,535 on the hobbs!
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  #2  
Old 10-01-2014, 07:30 PM
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Toobuilder Toobuilder is offline
 
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Location: Mojave
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Wouldn't a simple check valve with a few pounds of cracking pressure accomplish the same thing?
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
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1940 Taylorcraft BL-65
1984 L39C
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  #3  
Old 10-01-2014, 10:08 PM
SteinAir SteinAir is offline
 
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Location: Minneapolis
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Way back many years ago when not many folks had these on their planes (decades now) I installed one in our RV6 and used a small solenoid valve like Van's primer valve. Later in years on another RV I used a smoking airplanes kit and I think they did in fact ship it with just such a check valve that Michael references. I know a number of certified installations (and airshow folks) also use a check valve, but I still see solenoid valves once and again, so I think either is probably ok.

Cheers,
Stein
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  #4  
Old 10-01-2014, 10:19 PM
schristo@mac.com's Avatar
schristo@mac.com schristo@mac.com is offline
 
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Location: WA
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Default Residual pressure bleeds through a check valve...

Most every check valve only needs .5 to 2 psi to open and pumps generally put out 30-60 psi... When the pump is shut off there is quit a bit of residual pressure downstream of the pump that will bleed smoke oil in the feed line past any check valve... With added bumps and gees helping to push fluid the result is pretty poor cut off without a solenoid.
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Stephen

RV7 powered by a lycoming thunderbolt IO-390
turning a whirlwind HRT prop

with more hours flying than building... 2,535 on the hobbs!
ORCA Flight
Race 771
margarita!
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  #5  
Old 10-01-2014, 10:23 PM
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RV8iator RV8iator is offline
 
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The dribbling time is directly affected by the length of the line downstream of either check valve or solenoid. I have about 6 inch lines from my solenoid and dribble time is very short, almost not noticeable. When I had 15 or so inch lines smoke would sputter for several seconds.
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  #6  
Old 10-02-2014, 07:20 AM
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Stephen,
Will you share a part number/source and pics of the instillation?
Thank You
Bob
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  #7  
Old 10-02-2014, 07:59 AM
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Quote:
Originally Posted by schristo@mac.com View Post
Most every check valve only needs .5 to 2 psi to open and pumps generally put out 30-60 psi... When the pump is shut off there is quit a bit of residual pressure downstream of the pump that will bleed smoke oil in the feed line past any check valve... With added bumps and gees helping to push fluid the result is pretty poor cut off without a solenoid.
Seems like one could either find a check valve with higher cracking pressure or modify one with a stronger spring. I would think that a valve with say, 5 psi cracking pressure would allow a very clean stop without the hassle of running more wire.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
______________
Harmon Rocket II -SDS EFI
RV-8 - SDS CPI
1940 Taylorcraft BL-65
1984 L39C
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  #8  
Old 10-02-2014, 08:40 AM
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schristo@mac.com schristo@mac.com is offline
 
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Default details...

I used a cheap little valve pulled from amazon that you can get in several NPT sizes and coil choices.

http://www.amazon.com/gp/product/B00...A3A3DZ03XONGGK

With a -6 fitting in from the pump and a -4 out to the two injectors. The body of the solenoid is supported with a -26 adel clamp and -12 to the engine mount.

Power is tied to the pump.

I have around 6-8 feet of 3/8 hose from the pump located on the tank in the baggage area to the firewall... a few inches of 3/8 tube to the valve in the engine compartment... a short run from there with 1/4 tube to a tee then ss flex -4 line to the injectors.

Check valves are rated at opening pressure and don't necessarily close at the same pressure... they reliably prevent reverse flow, and once seated, will only open with pressure that is close to the rated value. Consider that a typical small in-line check valve with .5 psi open pressure only requires about 2 feet of head to open... with a couple of gees, less than a foot is needed. Most any tube routing will end up with some available head to work pressure the valve open in bumps and throw a brief puff out of the system in addition to the slow and fuzzy closure process.

Recently, we flew a 6-ship air show formation routine with 4 smoking that included much practice and filming that highlighted the poor cut off for everyone... 3 with check valves of and one without. They all looked the same at smoke off with lots of trailing and dribbling smoke and included numerous bump / gee induced puffs and spits well after smoke off.

There may be other ways to get clean cut off... I am very pleased with how this is working though. Hopefully the valve will withstand the heat and give good service life. I have it located in a relatively cool area and have a spare I will report back if it fails.

Running a small power wire back to the pump is pretty simple for testing but does require quite a bit of effort for the final run to tuck it away with others in a common run... only time though, and hey it's fun

Here is a photo:
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Stephen

RV7 powered by a lycoming thunderbolt IO-390
turning a whirlwind HRT prop

with more hours flying than building... 2,535 on the hobbs!
ORCA Flight
Race 771
margarita!

Last edited by schristo@mac.com : 10-02-2014 at 08:43 AM.
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  #9  
Old 10-02-2014, 09:46 AM
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Default SOS ??

Stephen....How long before we see morse code ?? :-)
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Last edited by Marc DeGirolamo : 10-02-2014 at 09:49 AM. Reason: wrong name
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  #10  
Old 02-10-2015, 12:50 PM
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RV7A Flyer RV7A Flyer is offline
 
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Default

Quote:
Originally Posted by schristo@mac.com View Post
I used a cheap little valve pulled from amazon that you can get in several NPT sizes and coil choices.

http://www.amazon.com/gp/product/B00...A3A3DZ03XONGGK
So I just got one of these off of Ebay, and yep, it's 1/4" fittings...1/4-19, that is. BSPP, from the looks of the drawing (yeah, I should have checked before spending a whole 10 bucks on it LOL!).

Anybody have a source for BSPP-AN fittings that aren't *each* as expensive as a new solenoid?

Or, in the alternative, a good reliable source for an actual 1/4" NPT solenoid (many of the Ebay ads only say '1/4"'.
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