GroundskeeperWillie

23: 10 36: 6 12: 4 1: 3 16: 2 20: 1 Great contest. Thanks everybody!

I like the BuWizz because it fixes these things. More power than the regular boxes and rechargeable. But sadly it is not available just yet.

It looks really good. Good thing you had time to fix the rainbow colors. I with you about the hand pump - it gets tiresome real fast. Good luck - you have my vote.

I've added my entry to the entry topic. The video is here:

24. Useless Box Pneumatic functions: 4-step sequencer (5 valves, 2 x 2x11 cylinders) Up/Down (2x6 cylinder) Push/pull (1x11 cylinder) Motorized pump (2 x 1x6 small pump and 1 PF L motor) Regulator (2x6 cylinder) Manual pump input (1 valve) Other functions: Golden Ratio-sized box (31x19x12 studs) Openable door for power on/off Openable door for manual pump input Video: Photos: Discussion topic: http://www.eurobricks.com/forum/index.php?/forums/topic/139463-tc-10-useless-box/

What a beautiful thing!

It looks cool Can't wait to see the final video.

Glad I could help. I also had a real hard time figuring out how to reason about pneumatic circuits and still do - but at least I got far enough to do what I needed. Feel free to use the idea, it's hardly mine anyway. I don't think @Mark Bellis has done this particular design, but make sure to browse his work at http://www.brickshelf.com/cgi-bin/gallery.cgi?f=141478. Some of it is massively complex and helped inspire me to keep looking for a "simple" solution to my concrete problem. Thanks Mark! I hope you make your entry work. It could be the pneumatically most complex entry and a joy to watch

Thanks! The question makes perfect sense. As I'm working with the video, I've been wondering how to explain/show this in a simple way. I haven't found such a way just yet so here goes ... As you notice, the problem with "just swapping hoses" is that you likely get pressure on both ports of a cylinder. The simplest way to avoid that is to have a dedicated control valve X for the up/down cylinder and another valve Y for the push/retract cylinder. This turns out to be a good start. The sequencer itself has two cylinders and two valves V1 and V2. The sequence then has the following steps or "truth table": Step 1: V1 off V2 off Step 2: V1 on V2 off Step 3: V1 on V2 on Step 4: V1 off V2 on What we want to happen is: Step 1: Up Step 2: Push Step 3: Retract Step 4: Down The thing to notice is that Up/Down should only change when V1 is off and Push/Retract should only change when V1 is on. Also, Up/Down only changes when V2 changes and Push/Retract only changes when V2 changes (but in opposite positions of V1). So, by adding an extra control valve Z that is controlled by the sequencer to have the same position as V1 we're almost there. The next thing is to attach X and Y to be controlled by the sequencer to have the same position as V2 and using the outputs of Z as inputs of X and Y, we have all the motions covered. The only thing remaining is to set up the main on/off switch to block the air flow to one port of V1 so that it can only move from step 4 back to step 1 when the switch is on. As I said, I hope I can come up with a visual way to show this Sequencer and control: 2 x 2x11 cylinders and 5 valves Lift: 1 x 2x6 cylinder Push/pull: 1 x 1x11 cylinder Regulator: 1 x 2x6 cylinder Motor pump: 2 x 1x6 small pump and 1 PF L motor Main ON/OFF switch: 1 valve and 1 light sabre Manual pump input: 1 valve So, a total of 7 valves, 5 cylinders, 2 pumps and 1 motor. And I'm not going to count the hoses

It's time for another update. I managed to just squeeze a small battery box in there so was able to complete my entry A note of warning to future sequence builders: Be careful when lubricating cylinders. While the dynamic friction was greatly reduced, increased static friction caused all kinds of problems in a sequencer. I ended up using non-lubricated cylinders, except for the 1x11. Here's a couple of shots of the final box: A manual pump option is hidden behind a door. And a few inner details:

That's a great machine. Well done!

I have run into the same issues. The higher pressure on the sequencer, the faster it runs. So you'll just have to have enough work air to get the job done in time. If there are regulators in play, this complicates matters, because this will cause pressure to vary over time. Eventually I settled on using 2x11 cylinders for the sequencer because I found that runs most consistently and also not too fast. Another option is to use multiple cylinders, maybe only for the steps that need most time. An example of this from Mark Bellis who seems to be the go-to-guy for sequencers:

Ok, thanks Jim. You're right! I'm getting lazy for no good reason.

I have a question about a possible illegal build technique. I've found that the following work really well as a rubber foot for my entry, but I'm concerned that it may not be entirely legal: Replacing the friction pin with a would obviously be legal but it doesn't work well since it would just be resting directly on the pin. Is this a problem?

Looks like a great idea. It's related to my Useless Box, except it has slightly more purpose ;-) It sure looks like it could work. While pneumatically very similar to my model, yours has significantly more complexity (four state cylinders vs my two) so you might run into some of the issues I've struggled with. For example, seemingly out of the blue, it stopped working properly - like the timing was suddenly off on some of the transitions. Since you completely separate work/logic pressure your model may be less prone to these issues but still, it only takes a little more friction or air loss somewhere and suddenly your loosing your hair over what broke. One question - when you separate the logic/work pressure, do you intend to have separate pressure controllers and/or air tanks for both? That's what put me off because I have very limited space.

Everything is working now and I'm getting really pleased with it. I just need to steal some gray panels off of my 42043 to complete the box. Here it is in action: There are a few things I'd like to improve though: The first two times the speed is ok and I guess I could live with that. But the third time I leave it off long enough for the regulator to turn off the motor. And then when the machine is turned on, it quickly runs out of pressure and is really slow until the motor starts again. There are a few options but they all take up more space and I'll need to go shopping for more pumps and/or air tanks. The battery box doesn't currently fit inside the box. If I'm really lucky there may be space for a small battery box but I don't think so. Any ideas besides making a bigger box?

Yes, good suggestion. The 1x11 has a larger extension so that's certainly possible. I also wonder whether it could shift two valves in one go as that might enable a certain "stretch goal" feature ;-)

Marvelous undertaking! What I don't quite understand is how you manage the states. You have four states for each leg, but does that translate into four main states as well? Or something vastly more complex?

Yes, there are a couple things. In the video I'm using a hand pump and the PF pump provides a little more air so that will be slightly little faster. Then there's my latest regulator that provides more pressure but I'm not sure how far that will last using a single air tank before the pump kicks in. Finally I might try a 1x11 cylinder for the switch. This should be faster but I'm not sure whether its up for the job. Oh, and that would in fact free up another medium cylinder so I could try using two of those for the feed-back loop, which would also make the loop faster. So many things to try...

I've settled on the design and have started building the actual box. Here's a video of the lift and the switch working together:

Great idea, looks good. I'm wondering what kind of speed you can out of it.

Wow, that really looks great. Love the colors.

An overdue update. While my previous feed-back loop idea had promise, it was not consistent enough. This was due to one state change that had to flip two valves as well as a main cylinder. Just too many ways that can fail. So I went back to Mark Bellis' design (1) and tried to extend that instead. I have found it really hard to reason about complex pneumatic designs, but looking over the "truth table" of (1) over and over, I came up with a solution that I'm really happy with, just by adding three secondary valves to it. This means that control pressure is not mixed with "work pressure" so state transitions are always consistent, as in (1). So the only thing that can go wrong is a cylinder not extending/retracting far enough in its "time slot". I made a small video that demonstrates it with a mock-up box. The box needs a lot of mechanical work - i had to help it as you can see. But the pneumatics work great now I'll present the pneumatic design in detail in a later post.

I'll be looking forward to seeing your version

After some experiments using a feedback loop, I've come up with this that kinda works. There are some timing problems that can make things go out of sequence but with just the right amount of rubber bands it seems to be working consistently. Though I had more "technical" ideas in mind with levers and mechanical switches, I think this is the way to go for me. Good to hear and sorry for my mistake. Thanks - good luck to you too.