davidmull Posted February 3, 2015 (edited) I really do hope the new 1X long cylinder moves nicely and not shoot in and out fast like our current small cylinder. Edited February 3, 2015 by davidmull Share this post Link to post Share on other sites
DrJB Posted February 3, 2015 To regulate the speed, you need either a pressure regulator (speed is a function of pressure) or a slowing-down mechanism such as the sticky silicone they used in the air-shock absorbers. The other option would be to reduce the inner diameter of the inlet/outlet, but I doubt this'll be the case. Most likely the new cylinders have a longer stroke and that's all, I doubt they have a better 'speed control'. Share this post Link to post Share on other sites
arik Posted February 3, 2015 Better control could also be achieved with somehow improved switch design, so that when the lever is pushed, it would open the airflow more gradually (perhaps non-linearly), so that the airflow would be unobstructed only when the lever is at its extreme position. I'm not sure if that's feasible in practice. Share this post Link to post Share on other sites
nicjasno Posted February 3, 2015 The speed is basically regulated by how small the air inlet hole is. The big cylinders have a tiny inlet hole, so that air enters slowly and mimics hydraulics. The small ones have the same size hole, but there's a much smaller volume of air to fill, thus they move much quicker. Also, the seals are smaller and offer less friction. The cylinder on the right is how the stock inlet hole looks like from the inside: Share this post Link to post Share on other sites
Blakbird Posted February 3, 2015 Better control could also be achieved with somehow improved switch design, so that when the lever is pushed, it would open the airflow more gradually (perhaps non-linearly), so that the airflow would be unobstructed only when the lever is at its extreme position. I'm not sure if that's feasible in practice. I find that it is easy enough to control the rate of motion by careful control of the valve. Instead of moving it all the way to one position, I move it very gradually until I hear the air starting to hiss through, then stop. Share this post Link to post Share on other sites
H3NRIK Posted February 3, 2015 i think the LA because the pneumatic hoses would come of the cillinders Check youtobe! Pneumatic is stronger in somw cases! My bet is also that Pneumatics can lift the heavier load.. i'm planning on modding the Arocs, exchanging the LA with 2xPneu. cylinders for the bed. I made a tipper bed on my 8110 with 4 cylinders, 2 on each side, in two separate compressor circuits - 2 large compressor cylinders, 2 valves and all.. The bed easily lifts 1 kg of payload, however, this truck doesn't have the space for 4 cylinders, only two (in the middle) -never saw a hose pop off the inlet, but experienced plenty of LA clutch-grinding when load became too heavy... I find that it is easy enough to control the rate of motion by careful control of the valve. Instead of moving it all the way to one position, I move it very gradually until I hear the air starting to hiss through, then stop. -But what about remote controlling the valve?? not an option to slowly, gradually open the valve.. Anyone tried to remote control a valve using the servo motor?? Share this post Link to post Share on other sites
zux Posted February 3, 2015 Why not to use servo+train controller for smooth pneumatic control. Share this post Link to post Share on other sites
H3NRIK Posted February 3, 2015 Why not to use servo+train controller for smooth pneumatic control. Brilliant idea! thx never tried it, but seem to be a safe bet! Really think that modding that Arocs with pneumatic opening bed will make it the best lego set ever! +remote operated drive+steer :) Share this post Link to post Share on other sites
Blakbird Posted February 3, 2015 Why not to use servo+train controller for smooth pneumatic control. With only 7 stages of movement, I'm not sure you will be able to open the valve to the right "slow" point with the servo, but it would be fun to try. Share this post Link to post Share on other sites
H3NRIK Posted February 3, 2015 (edited) With only 7 stages of movement, I'm not sure you will be able to open the valve to the right "slow" point with the servo, but it would be fun to try. Well, it deserves a chance.. -better than just full throttle on the servo.. Alternatively a wormgear turning a 24 gear, opening the valve.... Edited February 3, 2015 by H3NRIK Share this post Link to post Share on other sites
DrJB Posted February 3, 2015 (edited) What we need really is a 'proportional' valve, where the 'opening' is a function of position. With the current valve (almost digital), there is very little control (precision of positioning the lever), and to complicate this a bit more, there is large friction that makes precise positioning difficult. Yes, you can 'precisely' control the position of the valve by hand, but automating this is bound to be difficult. Lastly, I'm willing to be (pleasantly) surprised. Edited February 3, 2015 by DrJB Share this post Link to post Share on other sites
Blakbird Posted February 3, 2015 A motorized proportional valve would be truly awesome. We've been waiting for that for a long time. Share this post Link to post Share on other sites
Alasdair Ryan Posted February 3, 2015 You could just limit the movement of the handle on the switch,then connect it to sariel's worm gear driven one. Share this post Link to post Share on other sites
H3NRIK Posted February 3, 2015 (edited) You could just limit the movement of the handle on the switch,then connect it to sariel's worm gear driven one. Agreed ! Was actually trying to insert a picture og Sariel's Worm gear, but the picture turnes out in chinese letters in my post.. Edited February 3, 2015 by H3NRIK Share this post Link to post Share on other sites
allanp Posted February 3, 2015 Remember that to properly move a valve using a servo that you should gear it down by about 2:1, 20:12 is close enough, because the valve does not move as far as the servo. This will in effect increase the servo resolution. Alasdair's solution of mechanically limiting the valves movement is probably the best solution if you have room for it. You can limit the valves movement very precisely by using a lever that is adjusted by a 24t gear mated to a worm gear to give you infinite adjustment. Then use a spring as the link between the servo and the valve so that the servo can move to it's full range without being over strained. This works great because you can activate the servo so it opens the valve, allowing the load on the cylinder to drop. Then slowly adjust the worm gear until you here the faint hiss of air that Blakbird was talking about and boom, your heavy load will lower nicely and controlled every time, even with a bang bang remote. Share this post Link to post Share on other sites
Alasdair Ryan Posted February 3, 2015 (edited) Allan if you get a spare hour or so make a MLcad file of an adjustable valve for anyone who needs one. Edited February 3, 2015 by Alasdair Ryan Share this post Link to post Share on other sites
jantjeuh Posted February 3, 2015 You know, I'm still waiting on the first proper MOC that manages to succesfully incorporate remote-controlled pneumatics Share this post Link to post Share on other sites
dhc6twinotter Posted February 3, 2015 (edited) You know, I'm still waiting on the first proper MOC that manages to succesfully incorporate remote-controlled pneumatics RC Mocs with pneumatics have been done by several people on the forum, including myself. My Case Steiger has it, and I'm working on several other MOCs that have RC and pneumatics. Edited February 3, 2015 by dhc6twinotter Share this post Link to post Share on other sites
jantjeuh Posted February 3, 2015 How reliably does it function? It seems it's very hard to do with the current pneumatic parts available. I wonder if things will be improved with the '2.0' system. Share this post Link to post Share on other sites
Blakbird Posted February 3, 2015 How reliably does it function? It seems it's very hard to do with the current pneumatic parts available. I wonder if things will be improved with the '2.0' system. It works very well, but generally requires an M motor and compressor for every valve. Not very cost efficient. Share this post Link to post Share on other sites
Alasdair Ryan Posted February 3, 2015 You know, I'm still waiting on the first proper MOC that manages to succesfully incorporate remote-controlled pneumatics Have a look at my loader too. Share this post Link to post Share on other sites
Brickthus Posted February 4, 2015 What we need really is a 'proportional' valve, where the 'opening' is a function of position. With the current valve (almost digital), there is very little control (precision of positioning the lever), and to complicate this a bit more, there is large friction that makes precise positioning difficult. Yes, you can 'precisely' control the position of the valve by hand, but automating this is bound to be difficult. Lastly, I'm willing to be (pleasantly) surprised. A motorized proportional valve would be truly awesome. We've been waiting for that for a long time. Voila, from 2011: The lower crankshaft dithers the switch valves, which are connected in parallel and offset to sit on the edges of opening in each direction. The air supply is from the grey pipe. I used some non-return valves from BBB to isolate the servos from each other. The output to the cylinder is from the yellow and blue pipes. The feedback of cylinder position is via the flex that adjusts the lever and hence the valve position offset, with long levers to get a suitably small amount. The position of the valves is controlled by a large LA at the moment but I will soon try it with a PF Servo motor, which wold have a quicker and more precise response and can be controlled by IR handset or an NXT with IR link sensor. This servo drives 1 cylinder of my Stewart Platform. I have 2 cylinders on 1 axis working so far, with 4 to replicate. This will mean an NXT could set all 6 servos for the position of the platform, with the pneumatics allowing some position tolerance (compared to 6 LAs which would not). The lower crankshaft will drive all the servos with the same dither frequency so that they all have the same time response. I expect the longer pneumatic cylinders will work with this, perhaps by gearing down the flex return with a lever. The idea is that the length or power of pneumatic movement is far more than the flex return so the system can drive loads far greater than a flex. I contemplated a system where each load might have 4 pneumatic cylinders in parallel yet a single flex for the position feedback. Mark Share this post Link to post Share on other sites
Rishab N Posted February 4, 2015 What is that grey part on the curved blue liftarms? Share this post Link to post Share on other sites
DrJB Posted February 4, 2015 (edited) What is that grey part on the curved blue liftarms? It's part of the flex system 2900 @ Mark Thank you for sharing, and you obviously have done a lot with pneumatics. I must bookmark your brickshelf page and visit often. Edited February 4, 2015 by DrJB Share this post Link to post Share on other sites
Splat Posted February 4, 2015 -But what about remote controlling the valve?? not an option to slowly, gradually open the valve.. Anyone tried to remote control a valve using the servo motor?? Why not to use servo+train controller for smooth pneumatic control. I tried connecting a servo motor to a pneumatic switch (see below). As allanp mentioned, I have the servo geared down using 12 and 24 tooth gears. I made that video about 2 years ago so I'm trying to remember how easy it was to operate. As Blakbird mentioned, it was still difficult to get that sweet spot where the air is just seeping - one step of the servo motor too far, and the switch opens up too much and air rushes into the cylinder. Having a system of course adjustment (with the servo) and fine adjustment (with a worm gear), linked together with a differential is an interesting idea, although I'm not sure how practical it would be to operate, and it would use 2 motors and two remote channels. Watch on YouTube for additional annotations: Share this post Link to post Share on other sites
