Pneumatics General Discussion

[9v system]

This topic is for pneumatic tips and tricks, how to use pneumatics and mocs including pneumatics or just general things about pneumatics.

Ps mods if you feel this topic is not required feel free to remove. I just made this seeing there was no general discussion on pneumatics.

Edited July 10, 2015 by 9v system

[sm1995]

I'll start off, is there anyway to make the retraction of a pneumatically actuated arm/ crane more controllable? In my experience, the weight of the crane arm( or whatever) always makes it drop down too fast when the valve is opened. You could make it controllable by adding another cylinder on the opposite side of the hinge, but is there any other way to overcome this problem?

[9v system]

I'll start off, is there anyway to make the retraction of a pneumatically actuated arm/ crane more controllable? In my experience, the weight of the crane arm( or whatever) always makes it drop down too fast when the valve is opened. You could make it controllable by adding another cylinder on the opposite side of the hinge, but is there any other way to overcome this problem?

well you could try to slowly open the pneumatic valve so that only a small amount of air comes out

[jorgeopesi]

Interesting, I have to learn more about pneumatics because I want to build lots of RC machines with the new ones.

[Nazgarot]

I'll start off, is there anyway to make the retraction of a pneumatically actuated arm/ crane more controllable? In my experience, the weight of the crane arm( or whatever) always makes it drop down too fast when the valve is opened. You could make it controllable by adding another cylinder on the opposite side of the hinge, but is there any other way to overcome this problem?

You can spring load the cylinder to make it more in balance with the weight. This way, if done correctly, the cylinder needs to apply a small force to move the arm either way. You can use the standard lego shock absorber springs of different hardness, and test with the whole shock absorber assembly to find the right spring strength.

I did this to make a pressure switch a few day ago: Link.

-ED-

[Corvette3]

I have to ask, how does one combine RC with pneumatics? they always seemed a little mutually exclusive, unless you used motors to control the switches or something.

[allanp]

letting the air out slowly via the valve is the best way. You can do that by hand or by making an adjustable limit stop which mechanically limits how far the valves lever can move in the down direction.

You can control the valves using servo motors and have a compressor that turns on whenever the pressure drops below a certain threshold.

Edited July 10, 2015 by allanp

[TheItalianBrick]

to increase the precision you also would need a longer lever to control the switch! the valve itself has a short lever...but if you make it longer than it completely change the accuracy and smoothness of movements!

[thomol]

I'll start off, is there anyway to make the retraction of a pneumatically actuated arm/ crane more controllable? In my experience, the weight of the crane arm( or whatever) always makes it drop down too fast when the valve is opened. You could make it controllable by adding another cylinder on the opposite side of the hinge, but is there any other way to overcome this problem?

If you can rely solely on gravity to retract the cylinder (like on a crane arm, for example 8421) there is an easy trick.

Connect the cylinder's (extraction) inlet to the center inlet of the valve and the pump to one of the valve's outlets. Then connect a hose to the other valve outlet and plug it with an antenna or something alike. Punch a hole in the plugged hose with a needle. Now, when you flip the switch to lower the crane arm the air will slowly seep out through the needle hole and the arm will slowly descent to it's low position.

[allanp]

If you can rely solely on gravity to retract the cylinder (like on a crane arm, for example 8421) there is an easy trick.

Connect the cylinder's (extraction) inlet to the center inlet of the valve and the pump to one of the valve's outlets. Then connect a hose to the other valve outlet and plug it with an antenna or something alike. Punch a hole in the plugged hose with a needle. Now, when you flip the switch to lower the crane arm the air will slowly seep out through the needle hole and the arm will slowly descent to it's low position.

Or instead of punching a hole, you could sent it to another valve which you leave in a finely adjusted place. You could connect the valves lever to a 24t gear which is then adjusted by a worm gear.

[dr_spock]

Would using a linear actuator allow for fine movement of the valve?

[9v system]

seeing this is now a general discussion should it be added to the index?

[OzShan]

I'll start off, is there anyway to make the retraction of a pneumatically actuated arm/ crane more controllable? In my experience, the weight of the crane arm( or whatever) always makes it drop down too fast when the valve is opened. You could make it controllable by adding another cylinder on the opposite side of the hinge, but is there any other way to overcome this problem?

Battled with this one for a while. I've tried NXT and power function approaches. None were as compact as I wanted, only one of my attempts so far has been reliable. Lengthening the pneumatic arm is a great way to improve sensitivity, but the trade-off is speed.

I'll share a few of my attempts, I'm not afraid to point out where they went wrong :)

The single valve approach suffered from reliability issues returning to center. Both NXT and PF servo motors struggled to return without any deadband that left the valve a open a fraction.

My preference is two valves. This one was based on Sariel's autovalve but uses 4 valves for one function. It is designed to have separate central pump and tank supplying it. All it does is allow small amounts of air into or out of the cylinder depending on motor direction

The next iteration used only two valves but with the addition of its own pump and was a little more bulky. Drive the motor forward and the cylinder extends, run in reverse and it retracts by indexing through the two valves in series. Only one valve is open at a time though so there is no issue with valves sticking open and draining too much. It worked OK and the 4 piece linkage working the valve is kinda fun to watch but the spring return meant that the mechanism had to overcome the spring and the valve resistance making it work more than 2x as hard.

Final iteration is similar but it doesn't need the spring return and runs a lot smoother.

If someone does have something that is compact and provides a controlled release from the cylinder I'd be keen to see it.

I like the ideas ^ using a restrictor to limit how fast the air can escape. You could also restrict the flow by weaving/wrapping the hose between pins or axle and bushes to crush it a little. Then you wouldn't have to keep track of that one hose you put the pinprick in 6 months ago

[Bricktrain]

This is the RC compressor/valve module for my rough terrain crane, in the third pic you can see the 1/2 pin which limits the opening of the valve to allow the slow luff down for the boom.

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=486169

[Jim]

This topic is for pneumatic tips and tricks, how to use pneumatics and mocs including pneumatics or just general things about pneumatics.

Ps mods if you feel this topic is not required feel free to remove. I just made this seeing there was no general discussion on pneumatics.

This can definitely be an interesting topic, but since you created the topic, why didn't you start by showing some tips and tricks?! You haven't contributed anything to your own topic. There's lots of stuff to find on EB, Youtube, Bricklink (parts), so you could have easily taken 5 minutes to come up with some content.

[Milan]

I'll start off, is there anyway to make the retraction of a pneumatically actuated arm/ crane more controllable? In my experience, the weight of the crane arm( or whatever) always makes it drop down too fast when the valve is opened. You could make it controllable by adding another cylinder on the opposite side of the hinge, but is there any other way to overcome this problem?

Maybe you could take a look at this:

http://www.brickshelf.com/cgi-bin/gallery.cgi?f=405269

[9v system]

Ok so looking on YouTube I found some videos that would fit this topic quite well.

The difference between LAs and pneumatics

Edited July 11, 2015 by 9v system

[skaah]

Maybe you could take a look at this:

http://www.brickshel...ry.cgi?f=405269

The 8851 used some rubber bands to make lowering the digging arm more, euhm, say graceful.

[Epic Technic]

I hope this is the correct topic.

So I might build a compact v6 lpe with a custom crankshaft and I was wondering what would the best crankshaft configuration. It will be a 90 degree v6.

I was thinking of using a crankshaft like this:

http://www.reddit.com/r/formula1/comments/1xnck0/f1_engine_regulations_question/[\img]

But I'm not sure if there is a better crankshaft design

And why does it say this " An error occurred You are not allowed to use that image extension on this community." when I use the image extensions? I have changed the slashes to backwards ones.

Edited July 12, 2015 by Epic Technic

[nerdsforprez]

well you could try to slowly open the pneumatic valve so that only a small amount of air comes out

Yup......I worked on a project about a year ago where I opened the valves with actuators and it variably controlled my LPE quite nicely.

More at

http://mocpages.com/moc.php/393479

Edited July 12, 2015 by nerdsforprez

[Captainowie]

I hope this is the correct topic.

So I might build a compact v6 lpe with a custom crankshaft and I was wondering what would the best crankshaft configuration. It will be a 90 degree v6.

I was thinking of using a crankshaft like this:

http://www.autozine....ine/smooth3.htm[\img]

http://www.reddit.co...tions_question/[\img]

But I'm not sure if there is a better crankshaft design

And why does it say this " An error occurred You are not allowed to use that image extension on this community." when I use the image extensions? I have changed the slashes to backwards ones.

My guess is that you've put image tags around a couple of webpages (rather than directly linking to the image you're interested in)

Owen.

[Alasdair Ryan]

I have not been very active on the building front lately but here is a idea I had for a compact yet reliable / easy to control pneumatic valve.

Connecting a servo motor to the red axle joiner will move the rack and in turn operate the valve.

It's smooth movement will also allow the valve to return to the centre.

In terms of mounting and connecting you can connect straight to the red joiner or directly to the 12 tooth gear,since it is a double bevel gear you can also connect too

it at a 90 degree angle which can take up less room.

Instructions can be made on request but it it should be easy enough to get the idea on how it works (great for beginners).

Edited July 22, 2015 by Alasdair Ryan

[9v system]

good job! but should this be in the general discussion?

[Jim]

Instructions can be made on request but it it should be easy enough to get the idea on how it works (great for beginners).

Instructions are probably not needed, but the pictures could be better. It's all a bit dark en black now. Hard to distinguish the parts.

[slopemodified]

I'm having trouble with some of my pneumatic parts. I got them from an old set, 8862 Backhoe, and I'm trying to use them in a garage MOC as a car lift, and I've positioned the cylinders upright. Pumping down works just fine, but going up doesn't always work - sometimes it works, sometimes it doesn't. I have to pull them up and push them down by hand, and then it will work for a while.

Some backstory: When I first brought out the set after many years in storage, I found it was hard to disconnect the rubber tubes from some of the nozzles as they had somehow become stuck. I thought the plastic had degraded from being wrapped in a rubber tube for so long. When I was using them yesterday, I cleaned out some plastic stuck inside the tube, and I thought I had removed a blockage.

I will be trying to see if one of the tubes has a leak or change out the switch to test. Can anyone advise me on how to troubleshoot this issue?