sportflyer-RCU

My Feedback: (35)

I would like to use wheel collars for restricting the airflow to slow down the retracts . However I am sure the collar grub screw will make a hole in the retract tubing over time. What kind of barriers are you folks using between the grub screw and the tubing to to prevent this?

tks

RGN01

I use electrical terminal blocks - you get some that have a metal plate between the screws and the wires.



The pipes may eventually crack anyway but they'll last longer than using screws directly onto them.

Richard

YAT-28E

Try one of the line restrictors from Spring Air or I think Robart has a Brass one.

TLH101

My Feedback: (90)

I have been messing with retracts for a lot of years, and I have completely given up on using line restrictors. I use adjustable valves now.
The problem with using line restrictors, lies in the fact that when you do, you restrict the air going in, as well as out of the retract. It causes erratic action, and will even change the action with air temperature. The adjustable valves only restrict exhaust air leaving the system, so you still have full pressure to raise your gear, or release any locking device. I have seen many systems, that would not come come down because the restricted air would not release the lock mechanism.
If you still want to use wheel collars, slip a piece of brass tubing over the air line, and then tighten the collar on the brass tubing. The brass will prevent the screw from piercing the tubing.

sportflyer-RCU

My Feedback: (35)

Thanks for the inputs.

huggins

Let me start by saying that I know next to nothing about retracts. I have never even had a plane with them. However, I am very well versed in pneumatic systems, which is what a Robart system is. THL101 is correct that line restriction is a poor way to control speed in a pneumatic actuator for the reason that he states. Typically, speed of an acutator is controlled with a "flow control" which provides a restriction in one direction only, and free flow in the other. They are installed so that air coming out of the actuator is restricted and the air going in is non-restricted (refered to as "meterred out" ). I have not investigated availablity of devices for hobby use, but they are a staple in industrial applications. This will work with "double acting" cylinders (two lines) only and not on spring return type cylinder. This is probably how the adjustable valves that THL101 mentioned work, but that is just a guess. This now concludes Fluid Power lesson #1, which is probably more than anyone wanted.

Mike

Edwin

My Feedback: (2)

Uhhh! I would like to sign up for lesson #2 <g> I use the spring down retracts mostly. The spring-air valve does not give the option to control the exhaust air. Just recently I bought some robart spring down retracts and their valve does have what looks like to be the air exhaust adjustable restricter. I wasnt going to use it at first because of space requirements but after reading this I think I'll find a way to make it work.
Edwin

TLH101

My Feedback: (90)

Spring Airs actually just come down when the air is exhausted. Pressure hols them up. The speed can be controlled by using a valve built by UPI, espcially for Spring Airs. Works well, and somehow controls up and down speed.[&:]

sportflyer-RCU

My Feedback: (35)

I am using a retract system that uses air actuation for up and for down. So it looks like need to use metered system for reliablilty. Tks

YAT-28E

I used the restrictors for my Spring Airs on a trike gear and some guys asked how I got a scale looking movement with them!

I was sticking my chest out , as these are the 1st retracts I ever used and was impressed with the timing of both up and down!

But I am sure the next time I will spend the $$ to get a better valve!

huggins

I guess I need to clarify something I said in my earlier post. I may have lead some to believe that controlling spring return cylinders is not possible with flow controls....which really is not quite true. It depends on how it is used, how it is hooked up and the design of the cylinder. It sounds like the Sping Air just bleeds the exhaust air using the spring pressure. The speed would then be controlled by restricting that flow. Sorry if I mislead anyone. See.....I told you that I don't know anything about retracts[X(]. Maybe some day I'll go there.

Mike

dhal22

i was just going to start looking into how i could slow my spring air retracts down and the thread is already started. where can i get the UPI valve mentioned several posts up?

TLH101

My Feedback: (90)

Here's a link to Ultra Precision, but it appears the S/A valve is no longer available. It is "UP5".
http://www.up-1.com/valves.html

fw190a8

The UP5 is not available per the last post.

I just spoke to the gentleman at spring air and they have an air restricter part number 131 that will restrict the air for gear up (gear moving into the plane).
I'm going to pick this up and give it a try unless anyone has a better solution.