At-Home Engineering Challenge #1

I can see cups in shaggy carpet having a huge advantage here…


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or a long grass

My first attempt came in at ~139


Not quite happy with that, and with 2 hours of nothing else to be doing I started prototyping. after two sets of cups and a couple counterbalance prototypes I came up with this, coming in at 204"
its hard to show that it isn’t touching the carpet, if this isn’t counted then I completely understand. I tried to show by pushing down the carpet underneath to show it doesn’t move when the carpet does.
link to folder of verification


Having completed the challenge - The amount of tension you would need on the floss to get less than a 2 inch drop over that span is pretty staggering, more than the amount of friction you could get from a cup and 10 cotton swabs.

One thing you can do for verification is put a sheet of colored paper (or a file folder) under the middle of the span, and shine a bright light at an angle. You should be able to take a picture similar to the last picture @UnofficialForth took, which shows a gap between the shadow and the floss.

Rule question:

mean that you can’t have an elevation change between the two cups

That’s an interesting question. In my solution, I did not have an elevation change.

I would be interested in seeing how one might accomplish that without introducing another build material. I say go for it :slight_smile:

yay. that solution might not be 100% legal but if it isin’t I won’t use it. (don’t worry I will still post the results)

Materials question
is water allowed?

Also, is photoshop allowed?




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alrighty so

Attempt 1
5m dental floss
2 cups
4 q tips


alright time to crunch the numbers
so lets say that this corner is (0,0)

that puts the cup at the top of the stairs at (-1.5, 108). The cup at the bottom measured from the same point first needs to calculate x, y is 0 because it is on the floor. so the x value (this is the plane on the floor not the plane the two cups make) (161, 66*). so now distance formula for the orange cup gives us its coordinates in the plane between the two cups of about (174.0…, 0). so now distance formula again and we get an approximate distance of 206.1… inches. now I think I can do better. my issue was I have 5 meter spools of dental floss so not it is time for another spool to go in the mix.
*53+13 because the fireplace is sticking out an extra 13 inches and the measure from the fireplace to the cup was 55

Attempt 2
2 cups
4 q tips
10 m floss.
I’m not even going to do the math. these cups are in opposite corners of a room that is 20x19. could I go bigger yes. Am I going to no because I have now run our of floss.


so @efoote868 you said that you were interested in what I was planning on doing so what do you think.

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alright, my first attempt fresh out of the gate, end to end Q-tips. Only finished it to 18" (8 q-tips) long but it looks good and was a fun project

Here is an up close of the connections

Of course my final submission isn’t only 8 Q-tips long, here is my final submission, 170" long and free standing

the tape on the ground was used for nothing more than friction as seen here:

I’ll post a video as a reply that I took sweeping the side profile to show it dosen’t touch


I can’t tell from your photos if the floss dips below the plane of the lower cup, which is definitely part of the rules :wink:
Regardless, I’m impressed.

I’d be interested to see the gap in the shadow at the midpoint. If it checks out, well done!

Hopefully THIS Helps

for the seccond one it does but the first it does not

A still picture with a clear shadow at the middle would be just fine. The beautiful color/texture on the tile is throwing me for a loop!
I put a red file folder (that was handy, sitting out already) under the floss for contrast to better see the shadow. With carpet and other textured surfaces, it’s really hard to tell.

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Can I get a definition of the word span? Asking for a friend