any ideas on a pf pneumatic valve

[Alasdair Ryan]

hi

all do any of you have ideas on making a power function pneumatic valve that goes back to center i have seen sariel or Nico's idea hope to see some good ideas from you

[Jurgen Krooshoop]

Designed by Dmac, Used in Sariel's Volvo excavator. The mechanism on the right is the PF-valve, which returns to centre.

http://www.facebook.com/pages/Sarielpl/243748243695?v=photos#!/photo.php?pid=4385738&id=243748243695

[Alasdair Ryan]

thanks for the help

[dhc6twinotter]

Are there any other pictures of the PF valve? I'm having a hard time seeing how it works.

[DLuders]

Here's a discussion and VIDEO about Dmac's auto-centering Power Functions pneumatic valve: http://technicbricks.blogspot.com/2010/03/tbs-techtips-30-pneumatic-auto-valves.html .

[dhc6twinotter]

Awesome! Thank you!

My current project has PF and pneumatics, but I'm too far along to incorporate any kind of return-to-center function in my project. I'll have to try a return-to-center valve on one of my future models. I never even thought about doing it, so thanks to you all for the idea!

[Burf2000]

There is a even simpler one on this forum somewhere which just uses the torque of the medium motor and no cogs a tall. Its brilliant, I see if I can find it

Arr : I see the link above goes to the exact thing I was referring to

Edited July 12, 2010 by Burf2000

[Remixen]

There is a even simpler one on this forum somewhere which just uses the torque of the medium motor and no cogs a tall. Its brilliant, I see if I can find it

Arr : I see the link above goes to the exact thing I was referring to

On a two-way or three-way valve, turn off all incoming air, disconnect pipe/hose from the work port and plug it. Turn the air back on. If the valve continues to leak it should be removed from service and repaired or replaced.

If the valve is a 4-way or 5-way leave the air on. Whichever work port is exhausted remove hose, pipe or tubing. Determine if the leaking air is coming out of the valve or the ‘work.’ Reinstall piping and cycle valve. Remove the other hose, pipe, or tubing and repeat steps. If the leaking air is coming out of the valve remove the valve from service and repair or replace.

If the leak is coming out from the work (cylinder, actuator, air motor, etc.) the system should be shut down and the work should be serviced or replaced.

[mortenm]

On a two-way or three-way valve, turn off all incoming air, disconnect pipe/hose from the work port and plug it. Turn the air back on. If the valve continues to leak it should be removed from service and repaired or replaced.

If the valve is a 4-way or 5-way leave the air on. Whichever work port is exhausted remove hose, pipe or tubing. Determine if the leaking air is coming out of the valve or the ‘work.’ Reinstall piping and cycle valve. Remove the other hose, pipe, or tubing and repeat steps. If the leaking air is coming out of the valve remove the valve from service and repair or replace.

If the leak is coming out from the work (cylinder, actuator, air motor, etc.) the system should be shut down and the work should be serviced or replaced.

huh??

[Fistach]

CHeck the valve design I used in my snow plow:

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=420812

Edited August 25, 2010 by Fistach

[Milan]

CHeck the valve design I used in my snow plow:

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=420812

This creates terrible damage to the motors according to TB, there are few reported permanent brake downs of the M motors used in this setup.

This is not my experience, just what I red from TB!!!

[Burf2000]

Hi there

I built this and tested it a few times and seem fine, if your only going to give it quick bursts then I cant see the problem

I also built a old 9v motor one and one that uses the hockey player mechanism

Edited August 25, 2010 by Burf2000

[Fistach]

This creates terrible damage to the motors according to TB, there are few reported permanent brake downs of the M motors used in this setup.

This is not my experience, just what I red from TB!!!

Well I used it in snow plow (2 of these), now I'm using it in ARFF truck (4 of these and everything works fine). The user's motor must have been badly damaged and dying. There is no way to destroy the good motor that way (especially with 8887 BB)

[Zerobricks]

Well I used it in snow plow (2 of these), now I'm using it in ARFF truck (4 of these and everything works fine). The user's motor must have been badly damaged and dying. There is no way to destroy the good motor that way (especially with 8887 BB)

I disagree, your idea is really overheating motors, which causes the isolation in the coils to fell apart, killing them.

[Burf2000]

Surely this cant happen with 1 second bursts?

[Zerobricks]

You cant hold valve open with 1 second bursts.... The motor has to be constantly stalled, and pneumatics dont deploy in just a second.

Edited August 25, 2010 by Zblj

[Burf2000]

For what I am doing it does. The pressure is around 30 psi and just a small burst will send the piston from the lowest position to the top

[Fistach]

I disagree, your idea is really overheating motors, which causes the isolation in the coils to fell apart, killing them.

So why I'm using it for few months and have no problems? I also tested the valve before posting it and switched it to left -> right, right-> left for around 500 times stalling the motor randomly. MOREOVER I used it in two mocs (one is not done yet but extreme tests of the arm took a while already) - still NO PROBLEMS with several thousand switches of the valve.

In addition Dmac's and mine autovalves use the same way to return to center - if mine kills the motors then his does it either. His design was used in several MOCs already - and still NO PROBLEMS.

Edited August 26, 2010 by Fistach

[Milan]

So why I'm using it for few months and have no problems? I also tested the valve before posting it and switched it to left -> right, right-> left for around 500 times stalling the motor randomly. MOREOVER I used it in two mocs (one is not done yet but extreme tests of the arm took a while already) - still NO PROBLEMS with several thousand switches of the valve.

In addition Dmac's and mine autovalves use the same way to return to center - if mine kills the motors then his does it either. His design was used in several MOCs already - and still NO PROBLEMS.

How long you keep the motor in stalled position?

[Burf2000]

How long you keep the motor in stalled position?

I had a play with this yesterday and turn it on off a few hundred times and also held it for 5 seconds and seemed fine.

Sadly the compressor did not do so well. so new design to product 32 psi off 7.4v battery

[Fistach]

How long you keep the motor in stalled position?

As I told I had done that randomly. Sometimes for 1 second and sometimes for 20 or more. I have only 2 pumps so to raise the ARFF truck it takes some seconds.

Edited August 26, 2010 by Fistach

[rgbrown]

As I told I had done that randomly. Sometimes for 1 second and sometimes for 20 or more. I have only 2 pumps so to raise the ARFF truck it takes some seconds.

Well we know that the stiff LAs on the 8043 cause M-motors to burn out (many documented cases here), and that's not even a complete stall ... I presume the reason you're not using a clutch gear or similar to prevent the motor from stalling is a lack of space?

[Burf2000]

How would you use a clutch as you rely on the torque to center again.

[rgbrown]

How would you use a clutch as you rely on the torque to center again.

I guess I'm imagining something like this (I don't know how much gear reduction would be required after the clutch)

The torque from the twisting axle will still recenter the valve. (EDIT: actually, not it wouldn't, because it would be trying to backdrive the worm gear. You'd need to use regular gearing down, not a worm gear)

Excuse the crappy picture, I'm supposed to be working

Edited August 26, 2010 by rgbrown