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Comment by martin-adams | Hacker News Reader

After 4 days 6 hours it did 36,720 iterations. After 10 days it failed on 37,112 iterations.

It takes 10 seconds per iteration. My calculations say it would have failed after 4 days and 7 hours. I wonder what happened to the other 5 and a half days.

Very cool experiment. It's this type of testing that makes me feel reassured in mechanical engineering. It's about reassuring that a car air bag will work after years of inactivity, or a car seat belt buckle will not break under pressure in a collision. The only way to know is to test, test, test.

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I'm the guy that built it: During the tests, I had to guess the current count based on the estimate that one full iteration was about 10 seconds. This was not a good estimate and it made me overshot the actual number. When the test was finally over I was able to see on the SD-card the final 'real' total of 37,112. I'm making a new video explaining some of this.

Honest question: do you think it matters that the bricks are attached with a radial motion rather than linear? From my personal usage, I tend to press all areas down at the same time rather than one side fully contacting before the other. I would imagine the wear is different between these two cases.

You're right and this is why I intend to build a better rig. More answers in this new vid I just uploaded: http://www.youtube.com/watch?v=VLt8HkIOAuY

Do you think you could perhaps make it faster by doing computer vision and making the mechanism go up-down only and not waiting for the sensor, and then checking the photo while it moves?

The sensor was not the slowest element, it was the servos combined with the design. For the next build I plan to use a big step-motor rotating in continuous mode and transfer the rotation motion into a linear one like steam powered machines do.

I like your plan of testing LEGO bricks[1] from different eras, but I would recommend you use the same rotary mechanism for all the tests. If you change the mechanism to a linear one, you won't be able to compare with confidence the first (rotary) test with any follow-on linear actuator tests.

OTOH, if you repeat the (rotary) 70's era test with the linear actuator, that would be interesting estimate of whether a rotary actuation is better or worse for the brick longevity. Of course, you will still have a sample size of one, so your confidence interval will be meaningless. I can see this turning into a lifelong obsession... ;-)

[1] http://aboutus.lego.com/en-us/legal-notice/fair-play/

Once I have a new test machine that his much faster I will indeed retest all the eras (with multiple tests per era). Of course this time I plan to build a real sound proofing system around it. This last machine was really annoying.

Ooh, good question!

Congratulations, sir. I just about lost my shit laughing when I saw the arduino in the first picture. Good work, it's really cool seeing people doing interesting projects like this. The maximum number of lego presses is something I might never have thought of (I'm a k'nex person!), but I'm really happy to now know.

I think the 10 day figure included the time it took to build the machine.

After 4 days 6 hours it did 36,720 iterations. After 10 days it failed on 37,112 iterations.

I noticed that inconsistency as well.

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