Alasdair Ryan Posted July 9, 2010 Posted July 9, 2010 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 Quote
Jurgen Krooshoop Posted July 9, 2010 Posted July 9, 2010 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 Quote
dhc6twinotter Posted July 10, 2010 Posted July 10, 2010 Are there any other pictures of the PF valve? I'm having a hard time seeing how it works. Quote
DLuders Posted July 10, 2010 Posted July 10, 2010 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 . Quote
dhc6twinotter Posted July 10, 2010 Posted July 10, 2010 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! Quote
Burf2000 Posted July 12, 2010 Posted July 12, 2010 (edited) 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 Quote
Remixen Posted August 25, 2010 Posted August 25, 2010 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. Quote
mortenm Posted August 25, 2010 Posted August 25, 2010 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?? Quote
Fistach Posted August 25, 2010 Posted August 25, 2010 (edited) 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 Quote
Milan Posted August 25, 2010 Posted August 25, 2010 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!!! Quote
Burf2000 Posted August 25, 2010 Posted August 25, 2010 (edited) 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 Quote
Fistach Posted August 25, 2010 Posted August 25, 2010 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) Quote
Zerobricks Posted August 25, 2010 Posted August 25, 2010 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. Quote
Burf2000 Posted August 25, 2010 Posted August 25, 2010 Surely this cant happen with 1 second bursts? Quote
Zerobricks Posted August 25, 2010 Posted August 25, 2010 (edited) 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 Quote
Burf2000 Posted August 25, 2010 Posted August 25, 2010 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 Quote
Fistach Posted August 26, 2010 Posted August 26, 2010 (edited) 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 Quote
Milan Posted August 26, 2010 Posted August 26, 2010 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? Quote
Burf2000 Posted August 26, 2010 Posted August 26, 2010 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 Quote
Fistach Posted August 26, 2010 Posted August 26, 2010 (edited) 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 Quote
rgbrown Posted August 26, 2010 Posted August 26, 2010 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? Quote
Burf2000 Posted August 26, 2010 Posted August 26, 2010 How would you use a clutch as you rely on the torque to center again. Quote
rgbrown Posted August 26, 2010 Posted August 26, 2010 (edited) 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 Quote
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