Hi,

Here is my progress so far on my attempted entry for the pneumatic challenge:

I am trying to build an AT-AT walker, but is proving to be very, very challenging ...

The mess of tubes inside the structure are part of the pneumatic sequencer that control the legs. For each leg four phases are defined:

1) Whole leg backwards

2) Bend knee to lift lower leg

3) Move leg forward & straighten knee

4) Move straight leg backwards

The four legs are kept out of phase with each other to keep at east two legs straight at all times (either forward or backwards). In fact the sequence is not ideal, since 2 out of the 4 phases have a leg in the air (2+3), while idealy only one phase should have a leg in the air because then there are always 3 legs supporting the weight.

What definitely not helps is the hopelessly high center of gravity combined with a ridiculous small base for the feet.

With a manual pump I can make the whole assembly walk to some degree (well, walk, let's call it stumbling forward), but after a few steps it usually topples over sideways. When I add the batterybox and a small pump it doesn't even move the legs when I lift the model in the air. Apparently one small pump does not build up enough pressure...

So, decision time...

Option 1) Continue with the model (I do have some cool ideas for the head still including a simple return to center mechanism for rotating the head ). Solve the pressure issue with either more small pumps or by going manual (saves weight as well)

Option 2) Abandon project and go for a six-legged walker (AT-TE) which is much less of a challenge, but has therefor also a much higher chance of actually working in the end.

What would be your advice?

Jeroen

Nice progress! This is very cool. There is still a lot of time left in the contest, so I think you should restart with an AT-TE.

This seems to be an amazing project!

By what you say,I would go with a AT-TE, partially because I like it more

Edited September 13, 20168 yr by LXF

The AT-AT would be a difficult build because of the high COG, even an AT-TE is rather complex, as I have attempted to build a proper leg structure a couple times, and there is a lot of intricate joints in the legs, and the middle legs are sort of difficult to work with because of the angle on them. An AT-OT would be probably the easiest to build, as it has 8 legs of the same size.

here's an AT-OT

Edited September 13, 20168 yr by Tommy Styrvoky

Never give up, go for option 1 maybe you can't finish it on time but we all win watching a pneumatic walking AT-AT.

AT-TE for 100%. This would be incredible, but it's scary close to impossible I think :)

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?

This is an incredible undertaking. I think that no matter which one you decide to do it will be unique in a brilliant way. I recommend going for option 2 that you know you can do in the time frame then set yourself the challenge for option 1 after the comp and take your time to perfect it.

This is an impressive undertaking. I say stick to the AT-AT - you've already proven your outstanding technical and creative skills, so the best thing to do is seize the opportunity to push yourself and take up the greater challenge.

I say keep working on the AT-AT. It is pretty complete, and there is still a lot of time to finish it. Challenge yourself with this one.

I would say keep working on AT-AT, it is too good to abandon it. And it might have a wow effect when voting starts just because of the name and how it looks!

I totally agree with Milan! There are many ways of solving the pressure issue.

^ He may solve the pressure but not the stability issues :/ Trying to make this work peoperly can end up in frustrating battle against laws of physics. I mean, are there any really functional walking AT-AT models out there? Besides the lego set one, which wobbly performance wasn't really great, still being incredible that it even balances. Jeroen's model may look complete but from his post I understand that he already tried a lot and the walking functionality is still crippled. I don't think he should abandon the project completely - if he sees any chance to the eventual success. But making the six legged, much more stability friendly walker seems like a logical option. Still huge challenge but with better odds to success.

i think 6 legs provides much better stability than 4 legs, but of course it makes everything much more complicated and it will be even bigger.

That's a real challenge but one we are all looking forward to seeing completed.

I like the look of it so far.

H

Thanks everybody for all the encouragement

I'll stick with the AT-AT for a while longer. GroundskeeperWillie made me think about the sequencer. At this moment I use only 4 states for the whole machine. However it is quite easy to get 8 states without even adding extra cilinders & valves. (each upperleg has 2 states, so I can make each leg movement trigger only one other leg to move). As a consequence there will always be at least 3 legs on the ground. That should help with the stability.

I could even add 2 more cilinders & valves and increase the number of states to 12. Then the raising of the lower leg can become a separate state (in the current 8 state version I have on paper a lowerleg will lift while one of the other upperlegs moves forward or backwards (note to myself: tinker some more in the statemachine to only combine lifting a lowerleg with moving an upperleg backwards)).

So thanks for helping me over/through my builder's block I'll keep you posted on the progress

Whatever option you eventually enter for the competition, it's build is going to be facinating to watch.

Looking good so far, I personally have been working on an at-st but haven't posted about it yet.