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Air Line Restrictors

Old 12-02-2020, 11:57 AM
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redtail
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Default Air Line Restrictors

Hey Guys, already committed to pneumatic retracts/doors, however, I have one lurking problem. The lightning fast retracting of the gear and the shockingly fast closure of the gear door, are not very satisfying. Is there any problem with inserting the "Air Line Restrictors" in an attempt to SLOW DOWN the closure rates? Seems much more realistic then hearing the usual "SLAM" when they close. Thanks. Chic
Old 12-02-2020, 12:15 PM
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FlyJ
 
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https://www.dreamworksrc.com/rc-air-...ne-restrictors
Old 12-02-2020, 12:32 PM
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Have you flown the model yet ? The gear banging up, and doors slamming shut on the ground doesn’t always carry over in the air, especially after takeoff.

Some more information about model type or U/C & doors might help others chip in.
Old 12-02-2020, 12:38 PM
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CARS II
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You could try adjusting the speed on the way up with a wheel collar screw, what you want is a big screw to compress the tubing to restrict the flow of air without cutting into the tube, replace the hex screw with a longer screw so it travels all the way down.
Old 12-02-2020, 02:15 PM
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tp777fo
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Put restrictors on the "down" line. It will slow down both up & down. Been doing it this way for years.
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Old 12-02-2020, 07:25 PM
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redtail
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Thanks Guys. Will follow leads given. Chic
Old 12-02-2020, 10:02 PM
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Have you considered using an variable rate control valve, that's what I use.

https://robart.com/products/variable...trol-valve-red
Old 12-03-2020, 04:52 AM
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redtail
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Boomerang, already committed to a MAP valve (gear/doors). However, I did use your idea on my TBF Avenger's torpedo doors. TP777FO - do you put more than one air restrictor in your system or just a single restrictor? Again, good thoughts guys, appreciate it. Chic
Old 12-03-2020, 05:23 AM
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grbaker
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I usually put a restrictor in each airline an inch or two from the retract. If that is not slow enough, I add another one at the retract valve. I used to use a small plastic restrictor by Bob Dively and it only took one of them in each line, but the Robarts aren't as restrictive so it takes more to get the speed I want.

I also use a restrictor in my wheel brake airlines.
Old 12-03-2020, 07:39 AM
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tp777fo
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Ive done it both ways. Small light gear 1 at the retract valve. Heavier gear 1 at each retract. My Fouga has 1 at each retract down line about 1" from retract
Old 12-03-2020, 01:40 PM
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redtail
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Many thanks everyone. A previous fellow as what airframe I am questioning for this post. I am building an all wood Kerry Sterner Design De Havilland Sea Vixen. I am using Sierra L/Gear. Will insert restrictors on the down line near each retract. Many thanks to you all. Chic
Old 12-03-2020, 05:04 PM
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Auburn02
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I still can't wrap my head around the benefit or need to add 3 restrictors (one at each cylinder) compared to just one at the output from the valve and before any tees which would restrict all 3 simultaneously (I think). But I wasn't a fluid dynamics major either, so I'm sure the science of it just escapes me.

I'd like to experiment with this on my CARF MiG-15 though, I have no restrictors anywhere and that gear and doors have AUTHORITY! Maybe a little too much authority.
Old 12-03-2020, 05:31 PM
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redtail
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My point exactly - way tooooo much authority. I guess having one restrictor at each gear allows the full blast of air to run its course trom the air tank to each gear and then have to slow down due to the restrictor before activating the retract mechanism. I'm a JD with an MBA. No fluid science for me either. Ha, Ha. Chic
Old 12-03-2020, 07:28 PM
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I've always put the restrictors on the exhaust side of the retracts I wanted to slow down, thus controlling the pressure coming in by the restriction going out. Usually gear slamming down is more of a problem than slamming up, with exceptions, so I put the restrictor on the up (exhaust ) line.
I tried it both ways years ago and this worked the best in my applications so is something to consider.
Old 12-04-2020, 05:24 AM
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tp777fo
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​​​​​Philip Avonds taught me years ago to place the restrictors on the down (exhaust) side. When you go gear down the restrictor causes pressure on the down side to fight the air coming in thus slowing the gear extension. You will still get the full pressure it just takes longer. Air retracts need volume as much as pressure. If you put a restrictor at the valve you reduce the volume of air to the entire system. Our bigger heavy gear need the volume to work. Gear such as spring air with wire struts are much lighter and require less volume to work. Dont believe the volume theory just remove 3 of your 4air tanks and see how they work. Bottom line its Ford v Chevy. Try it both ways and see which one works best for you
Old 12-04-2020, 06:24 AM
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Originally Posted by tp777fo View Post
​​​​​Philip Avonds taught me years ago to place the restrictors on the down (exhaust) side. When you go gear down the restrictor causes pressure on the down side to fight the air coming in thus slowing the gear extension. You will still get the full pressure it just takes longer. Air retracts need volume as much as pressure. If you put a restrictor at the valve you reduce the volume of air to the entire system. Our bigger heavy gear need the volume to work. Gear such as spring air with wire struts are much lighter and require less volume to work. Dont believe the volume theory just remove 3 of your 4air tanks and see how they work. Bottom line its Ford v Chevy. Try it both ways and see which one works best for you
+1
Old 12-04-2020, 06:34 AM
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Not trying to make this more of a debate than it needs to be, but two things still escape me:

1) if you still only install one restrictor at the valve but install it on the down line (return/exhaust side of the up circuit), you would still get the full volume of air to the cylinders on gear up just the same as you would if each cylinder had it's own restrictor on the exhaust side of it, right?

2) no matter what, and assuming a successful flight, each line is an "exhaust" line exactly half of the time. So if the retracts need volume and that's why you put the restrictor on the exhaust side, then when you flip the switch the other way aren't you fighting the exact battle you just mitigated by restricting the volume for the reverse operation? So your gear might come up nice and slow and smooth, but then will they struggle to come down because you've now restricted the volume on that side of the cylinder?

Again I'm not claiming to know any better, just trying to understand a little more. Probably just overcomplicating it, I tend to do that. I know lots of pilots have had lots of success and I need to just start hacking open lines and experimenting (boy I wish I had festo push connects throughout my planes instead of barbed connectors).
Old 12-04-2020, 06:53 AM
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tp777fo
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Like I said. Ford v Chevy. I drive Chevys. With the restrictor on the exhaust side there is no resistance when you retract the gear other side of the cylinder (no restrictor)

Last edited by tp777fo; 12-04-2020 at 06:57 AM.
Old 12-04-2020, 10:39 AM
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Ford here! :P

https://www.clippard.com/part/MNV-2K
Old 12-04-2020, 03:41 PM
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Redtail if you are using MAP U.P2, 3 or 8 they have speed controls on them and there is no need to us inline restrictors. You can turn them in to the point were they will stop, these speed controls control the vent air from the cylinder. If you add a restrictor to a U.P2 or 3 it will mess with the door timing. It would work on one end of the cylinder but not the other, I can not tell you off the top my head which end it is as I would have to go an look at the schematics. If you need any help fell free to call me and I will be happy to help you out.

John

MAP
Old 12-04-2020, 06:15 PM
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Originally Posted by tp777fo View Post
​​​​​If you put a restrictor at the valve you reduce the volume of air to the entire system.
Ah, what?

The volume of the air has nothing to do with restrictors anywhere, likewise they have nothing to do with pressure in the overall system.
All restrictors do is effect the speed of air going from one part of the system to the other or the atmosphere.


Last edited by Boomerang1; 12-04-2020 at 06:19 PM.
Old 12-05-2020, 05:54 AM
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redtail
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John, thanks for opening up my eyes. I knew there was a very good reason why I purchased your product. Will certainly call if I have any problems. Is your number on your website? My email address is [email protected] Many thanks for your response. Chic


Old 04-15-2021, 04:07 AM
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Default Avond f16 pneumatic to electro

Originally Posted by tp777fo View Post
​​​​​Philip Avonds taught me years ago to place the restrictors on the down (exhaust) side. When you go gear down the restrictor causes pressure on the down side to fight the air coming in thus slowing the gear extension. You will still get the full pressure it just takes longer. Air retracts need volume as much as pressure. If you put a restrictor at the valve you reduce the volume of air to the entire system. Our bigger heavy gear need the volume to work. Gear such as spring air with wire struts are much lighter and require less volume to work. Dont believe the volume theory just remove 3 of your 4air tanks and see how they work. Bottom line its Ford v Chevy. Try it both ways and see which one works best for you
Can be Avonds F16 landing gear mechanic upgraded to Electric one? Also wheel brakes? Is tout there any kit exist to upgrade it ?
Old 04-15-2021, 05:04 AM
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tp777fo
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I would guess a Robart conversion or down and Locke conversion would work.

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