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Pneumatic Retract Question

Old 01-05-2004, 06:30 PM
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SpockF4
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Default Pneumatic Retract Question

Hi,
I am setting up my first set of retracts and I have a question. About how long should the properly installed system hold the pressure charge when you are not actually cycling the gear. If I pump the system up and just let it sit, about how long will the charge last? Are we talking about hours or days? As I said I am new to retracts and pneumatic systems and I want to make sure I set the system up properly. Thanks for the info.
Ken
Old 01-05-2004, 08:49 PM
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Stick Jammer
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Default RE: Pneumatic Retract Question

I can put 100 psi in my system and it's still there a week later (new system). Theoretically, it only needs to hold sufficient pressure for the duration of your intended flight, but if it can't hold it for at least a few hours, you have a leak somewhere, usually O-rings.
Old 01-05-2004, 09:26 PM
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Doug D.
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Default RE: Pneumatic Retract Question

I like to charge the system to the rated capacity, say 100PSI, then see how many cycles that gives you. ( one up and one down=one cycle) Then charge it up again and let it set over night. I you get the same amount of cycles that you got the first time, you should have no problems at the field.
Charging to max capacity will also let you know if anything is going to blow off. [&:]
Old 01-05-2004, 09:58 PM
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SpockF4
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Default RE: Pneumatic Retract Question

Thanks for the info. That is a great idea to count the cycles and then let it sit overnight and try it again. I will give it a try. Thanks again.
Ken
Old 01-06-2004, 02:34 PM
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Kevlar
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Default RE: Pneumatic Retract Question

Good info! I too am new and have a set of Spring-Airs. It only came with a Bike Tube receptacle for charging and my Robart Pump just has the standard nipple to attach line to…do they make a one-way check valve for filling or what should I be looking for…possibly an adaptor to attach to the receptacle? Any help would be appreciated....I’ll cycle my system tonight and re-verify tomorrow.

How many psi? 85-100 ok?
Old 01-06-2004, 03:27 PM
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Default RE: Pneumatic Retract Question

I once had a system that the leak was in the last place you'd expect it, the fitting in the pressure can. Fixed it by pulling a little vaccuum and drawing CA into the gap.
Old 01-06-2004, 10:24 PM
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electricfan
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Default RE: Pneumatic Retract Question

hi. i am also new to pneumatic retracts. i dont have a retract equipped plane, but i want to know how they work in case i want to buy one. so what does a complete package include? how many servos do i need? what do you pump it up with? how do they work in general? and how many times will they go in and out (cycles?)?
thanks
Old 01-07-2004, 10:09 AM
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Doug D.
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Default RE: Pneumatic Retract Question

Well electrifan!
A complete system will include the gear, a actuation valve, air tank, tubing, a fill valve and connectors. You'll need only one servo for operation. A mini servo is adequate.
The number of cycles depends on the size of the air tank installed. CJ will do about 6 to 8 cycles with the tank they supply for there .60 size systems.
As for pumping them up! The ROBART hand punp is junk, the only thing that really works on it is the pressure guage. Most guys use a 12 volt emergency auto air pump that has a built in pressure guage. I've also seen some guys use a bicycle hand pump, they work well also.
Follow the manufacturers installation operating instructions and you should have few problems! Good luck and have fun!!! [&:]
Old 01-07-2004, 04:42 PM
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paladin
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Default RE: Pneumatic Retract Question

How long does it take to get to the tootsie pop center of a tootsie pop?

I've flown air retracts for twenty years and each plane with them needs to be tested prior to the first time out each year and here are the criteria I use.

New:
I pump the gear up and count the cycles I get if I get less than six cycles I either have a leak or need more tank volume. If a leak is suspected I pump the gear up and work them for a good 10-30 minutes to totally circulate the lube. Then before putting it up fully charge the system and leave it. The escaping air will draw the lube to the leak and the lube has a treatment in it to expand neoprene (sorry for the spelling) in the O-ring. So in the morning I'll top off the air, and again in the after noon, but by then the leak should be fixed and no air needed (obviously a pump with a gauge is a must). If in the morning you have not lost air and you did not get six cycles look at adding more tank volume.

As the gear age the hose will age and some begin to leak. No rhyme or reason why some do and some do not it just happens. The test has to be one that can be performed in the shop prior to leaving for the field. So I pump the system to full pressure and count the retracts then refill it and leave it, glance at the clock then go load the car. The last thing to go in is the car is the plane I count the cycles again and look at the clock. If I loose one cycle for every ten minutes that is acceptable for the days flying but the leak will have to be found later.

Care and feeding of pneumatic retracts:
Lube is the same stuff they put in your car's AC sold at most auto part stores.

After a flight on those hot summer days when you have returned your plane to the pits cycle the gear atleast twice to remove some of the pressure for when it is setting on the flight line.

Good Luck

Joe

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