Hi all!

Having received news of the next LEGO Fan Weekend, my interest in my mothballed electropneumatic robot project has reawakened... and one of its main problems is getting a good RCX-controlled pneumatic valve.

I searched everywhere for autovalve designs, but couldn't find any that told me "I'm ideal for you, build me". Here's what I sketched up, based on Sariel's design and adding a suggestion JAMS gave me at TechnicBRICKs. The motor isn't well braced (a PF M-motor would fit better and be more compact, but I need to use old 9V motors) but in this case I don't think it's very important. I also couldn't find yet a way (but didn't try very hard) to properly fixate the small pump (the 6L version is out of question for me at the moment).

So, is there any design you guys recommend?

I have done one also based on Sariels but I turned mine up side down. I found it more reliable

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=463575

Ldraw file

http://www.brickshelf.com/gallery/phantom59/Bridge-Layer/bridge_layer__pneumatic_auto_valve.ldr

Edited December 29, 201113 yr by Phantom59

I too have used sariels design but i geared mine up so it runs faster.

Edited December 29, 201113 yr by Alasdair Ryan

When i tried using sariel's switch with an automatic compressor i would find that the switch would take a few seconds to turn in the opposite direction so excess air went into the switch which pumped the cylinder more before the switch even switched directions. does that make sense?

tim

I have done one also based on Sariels but I turned mine up side down. I found it more reliable

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=463575

Ldraw file

http://www.brickshelf.com/gallery/phantom59/Bridge-Layer/bridge_layer__pneumatic_auto_valve.ldr

Thanks for the tip, placing the pump horizontally does make it that much easier to be at a proper distance! As for placing the assembly upside down, at least on theory I don't see what advantage it could have, but since I didn't try it on real ABS, I can't be sure.

does that make sense?

Yes. That happens because, when you reverse direction, first the worm has to slide to the other 12T gear, and then must rotate it enough for the attached 2L liftarms to move the switch.

You can try using 8T gears instead of 12T and having the worm in a more confined space to speed up both actions, like in the image below. It has the advantage of being studless and therefore easier to integrate in different directions, but potentially ruins the delicate positioning required for the pneumatic valve.

I like your solution but i have used a different autovalve instead.

tim

This is how I did the auto valves on my Case Steiger tractor:

Sorry those pictures aren't very clear. I used clutch gears to keep the motors from stalling. The black and tan gears are used for some extra gear reduction between the clutch gears and valves. This works well, but I did notice that some of the valves I bought on BL were too stiff and didn't work as well (I think they sat in the store for a while). The stiffer valves would have worked with more gear reduction though, but I just used some of my less stiff valves. There is no auto-centering feature. I have yet to figure out how to build an auto valve that is both non-stalling and auto-centering. The new servo motors would solve all this.

My current moc that I'm working on has auto valves based on this also, but I used a white clutch gear and worm gear instead for each of the 4 valves. The remaining valve I have to install will probably use the same setup as my tractor.

Edited December 30, 201113 yr by dhc6twinotter

Does this new moc have returning to center valves?

I tried a different approach and tried to make a valve into a gearbox,but this still needs work.

Does this new moc have returning to center valves?

I tried a different approach and tried to make a valve into a gearbox,but this still needs work.

My new moc? Unfortunately, it won't have return to center valves. I will be building it into a gearbox as well, but to be honest, I haven't tested it yet. I don't see why it wouldn't work though, since it has more gear reduction than the version I used on my tractor. Hopefully I'll get the valves and gearbox finished this weekend or next, but this project is kicking my butt, so who knows, I may not even finish it.