[MOC] Lissajous Machine (but failed)

[Carsten Svendsen]

Hello everyone

I haven't posted a new MOC in a long time, mainly because I haven't had the interest lately.

This thing has been with me for years now, trying to get it to work, and it is one of those projects that causes so many headaches and will never work properly, no matter what you do.

So this video is the result of straight up agony, and I do not think I'll be revisiting this again. I haven't disassembled it because I hadn't got the time before putting all my LEGO in storage for a few years.

So "enjoy" my failure 

See a few photos here

But maybe let me tell a bit about this contraption as if it had worked alright:

 

The first challenge was to figure out a soutable gear ratio. I chose to make the 2nd fastest (orange) the 1:1 gearing from the motor as then the slowest was still able to spin somewhat comfortably.

The size of the circles and spacings are all a function of the LEGO brick arches and discs. To get the arms in the right location, I had to offset them by 0.5 studs, which was easy enough with some 4-pin connectors with axle hole.

Then the challenging bit - designing the gear ratios to also fit inside the box. It looked like there was a lot of room, but I had to use many more gears than what I thought, so this wasn't so easy either. Also here, I had to space them by 0.5 studs.

I had initially only planned to power the red (the fast) ends which would be 3 motors, but there was just no power at the slow end when I did this, so back to the drawing board.

I then decided to power each side from either end, which meant I had to add gearing in the small corners - 1:1 for one end, and 1:5 on the other, in some cases. The slow end was the hardest to figure out and need quite a few more gears.

 

Now for the fun part, to see if it works! Turn on the motors and yup, everything is running at a different speed, as I expected. This is not good, as the axles will keep twisting more and more, or gears will skip. So I had to figure out a solution to sync them up. I went with Power Up, and no matter what I did, there was no way to sync them up in software. I had to write my own code, and I'm not good enough for that. It would work sometimes, but mostly just with 3 motors for some reason.

So in the very end, I decided to link them up physically, but this was a challenge in itself. They are long distances, what's the best way? I ended up with the ol' steam engine solution and just multiplied that by 4. And it works great! As long as nothing is stalled anywhere, because then gears will tick over and over.

In the video, you can hear this, and it's probably because those gears already need a replacement. But it is so darn hard to do.

 

Lastly, decoration - this was already decided on well before I was halfway through with the project. It had to bricks, because of the arches. Building the long panels was easy, but building the corners took some more skill. Not too much it turns out - I looked for help here in Eurobricks and no one would help. What seems simple to you, may not be simple for me. 

Anyway, I ended up with some lightsabers underneath and some clips to hold the corners in place. They aren't perfect, but I guess nothing in life ever is.

Also the large panels move around all the time, I think the tolerances on those arches aren't actually perfectly round, they seem kind of oval.

 

What went wrong with the demonstration though, was that a CV joint on the backside had popped out, and so the whole left side of it wasn't spinning to begin with, thus being the source of most of the issues shown.

And then I also only bought a pack of 24 marker pens, when I needed 25, luckily I had one extra lying around that fit the 1x1 LEGO dimensions.

And acrylic is not cheap! 2 sheets of 0.3mm each. But I guess that's nothing compared to all of the black panels, liftarms and plates and bricks that I had to buy.

 

Failure all around. If anything it was a good learning experience.

Edited July 10, 2023 by Carsten Svendsen

[Good old Lego builder]

What an amazing machine. Never seen it before. You have comenvery far, there must be somebody here that can help you out. 
You speak of failure, but just by coming so far you have achieved something. The proces is often more  important then the end result. I applaud you!

[Berthil]

Kudos for trying and sharing the result even if not satisfactory! The machine itself looks very good but unfortunately only works in your head, I know the feeling from creating intrinsic GBCs and also experienced failure after many attempts.

Have you tried spraying the whole thing with PTFE (dry Teflon)? Because it seems the main obstacle is friction and synchronizing everything on one motor (like in GBC). PTFE helps for me to keep friction lower.
Also some gear combinations work with less friction when using the new straight tooth gears instead of the bevelled gears.

[howitzer]

Wow, this is an ambitious project, the sort that would be amazing if it worked out but understandably is very hard to get to work, if at all possible (with Lego anyway).

Still, respect for trying and sharing your results with us!

[Davidz90]

Very interesting project!

I think that it could work much better if the wheels holding the bars on both ends were doubled. That could solve the issue of the bars not being parallel.

[TinkerBrick]

1 hour ago, Davidz90 said:

Very interesting project!

I think that it could work much better if the wheels holding the bars on both ends were doubled. That could solve the issue of the bars not being parallel.

That was my first thought as well. A 2nd set of wheels on either side with the same gear ratio, size and driving pin position would force the coupling rods to stay in parallel. Basically like the setup of a steam locomotive where you have that second pair of wheels on the other side of the axles res. frame.

 

Anyway, thanks for sharing this usual machinery and your MOC. Quite inspiring.

[ord]

I think you are so close to making it work, and it would be so cool if you did.

If you do decide to revisit it, I strongly suggest you watch this video (from 6:37 particularly). The principle shown in this video is almost fundamental to many of my creations now. 

If you built such axles into the main drivetrain of your machine, I think you'd be halfway to making it work. Then maybe some better pen holding method would be the finishing touch. 

If you leave it be, that's understandable. Either way, thank you for sharing such an interesting project despite it not being finished.

[Carsten Svendsen]

20 hours ago, Berthil said:

Have you tried spraying the whole thing with PTFE (dry Teflon)? Because it seems the main obstacle is friction and synchronizing everything on one motor (like in GBC). PTFE helps for me to keep friction lower.
Also some gear combinations work with less friction when using the new straight tooth gears instead of the bevelled gears.

I bought some White lithium grease for this very purpose, however I decided not to use it, as the problem was not friction after all. The rotating parts are getting caught on the brick arches on the long black plate, and also getting caught between the rotating disc part and the liftarms going across. The tolerances are simply too small. 

 

8 hours ago, Davidz90 said:

Very interesting project!

I think that it could work much better if the wheels holding the bars on both ends were doubled. That could solve the issue of the bars not being parallel.

That is a good point, but would however, destroy the looks of the creation.

 

7 hours ago, ord said:

I think you are so close to making it work, and it would be so cool if you did.

If you do decide to revisit it, I strongly suggest you watch this video (from 6:37 particularly). The principle shown in this video is almost fundamental to many of my creations now. 

If you built such axles into the main drivetrain of your machine, I think you'd be halfway to making it work. Then maybe some better pen holding method would be the finishing touch. 

If you leave it be, that's understandable. Either way, thank you for sharing such an interesting project despite it not being finished.

I think you should be able to see in the video on the backside, that there are no gears going the whole long way. Everything is geared down continously as you go from the fast end to the slow end. So there's a lot of gear slipping as well.

I do remember seing this video though, thanks for bringing it back to my attention :)

[Bluehose]

You can Also use the mechanism used in this video (at 1'55 ) on both the sides of your horizontal and vertical beams. 

 

Edited July 11, 2023 by Bluehose

[Carsten Svendsen]

1 hour ago, Bluehose said:

You can Also use the mechanism used in this video (at 1'55 ) on both the sides of your horizontal and vertical beams. 

Ah. I see now. This is so much better. It could actually work. Okay, so maybe I haven't given up all hope yet. I'd still have to change out all of the gears that have slipped from rounded edges though. It's quite an operation.

By the time I get back to my LEGO and this creation, I think I'll try it out. For now though, I am currently doing some scuba diving for an unknown period of time. At least 3 months, hopefully a year.

[Thierry-GearsManiac]

The mechanism in the video is one possible implementation of a circular translation movement.
I'm not sure that this is what will help the most (not counting that the 2nd Z8 idler pinion in parallel doesn't correctly align its teeth with its adjacent gears, building stress and friction).

However, why not build the output cranks by the help of Z56 or Z60 turntables ? The "axle" of rotation is therefore very sturdy, with low backlash, and the torque at the pinion driving the gear part of the turntable will be lower (and the crank and gear won't be heard "suffering").

Two drawbacks : your driving gear train will have to spin faster because of the speed reduction caused by the pinions+turntables (at worst 1:7 with Z8+Z56), and I don't know where you'll have room for the aesthetics (colored background plate).

Edited July 28, 2023 by Thierry-GearsManiac
mistyping Z9 ==> Z8