• Support PF! Buy your school textbooks, materials and every day products Here!

Building a crumple zone

  • #1
For a school project I have to build a device made of only toothpicks and glue gun glue that will hold an egg. The device will be dropped 5 meters and the egg must not break, so the idea is to build a device with a good crumple zone. I have a few ideas about how to build it but its pretty hard to find advice on how they are made, I can only find info on how they work. Oh yea it has to have a mass of 50 g or less, thats a lot of toothpicks.

If someone could comment on my ideas, or suggest different variations it would be great. Here are my ideas.

1. Build a crumple zone where the base is made of squares each connected to a square above them by 4 toothpicks.

2. Same idea as above but use only 2 toothpicks to connect squares (therefore its weaker, which means I can have a longer crumple zone right?)

3. Make the base triangles that are connected to above triangles with 2 toothpicks.

4. Attempt to make it a shape sort of like a blimp? I have my doubts on this one.
 

Answers and Replies

  • #3
lightgrav
Homework Helper
1,248
30
I expect that if the toothpicks are vertical they will not flex or break;
the Energy absorbed will only be in the glue coming undone.

It might be good to connect vertical toothpick posts
to the center of horizontal toothpick beams, so the beams will break.

If the posts are not vertical, but all slanted one direction,
you might be able to change vertical motion into rotational motion.
 
  • #4
Hmm well with the vertical thing Ive tried it a few times and it seems that the sticks do break. I dont really understand what you mean about rotational motion though, if you think it will help for my project please explain.

I was thinking that I need the structure to be very long and have the impact part break very easily over a long distance right? In this I am trying to create the longest stopping distance with equal force at all moments on the egg I think. So the best way to do this would b to have it reasonably weak but for as long of a time possible. Anyone have ideas how i would do this? or what shape would be the best to use that will break easily?
 
  • #5
pervect
Staff Emeritus
Science Advisor
Insights Author
9,737
960
I rather like Buckminister Fuller's "Octet truss" consisting of tetrahedrons and octahedrons. You should be able to find diagrams if you look on the WWW. I have never actually seen this applied to egg drops, I don't have any emperical data on how well it works.
 
  • #6
pervect
Staff Emeritus
Science Advisor
Insights Author
9,737
960
Some more feedback, after a little bit of fooling around with real toothpicks. The octet truss will probably theoretically be a very strong design, but it will be very hard to build correctly because of the joints.

If you put the joints of your toothpicks together haphazardly, the structure will not be very strong, defeating the purpose of the structure. You have to imagine that you are building on a larger scale, and use good joints.

The joint structre for a octet truss design can have up to 12 beams (toothpicks) meeting at a point, making it a difficult build. I think the best practical approach will be to engineer the structure for the simplest possible joint configuration.
 

Related Threads on Building a crumple zone

  • Last Post
Replies
0
Views
9K
Replies
1
Views
26K
Replies
1
Views
2K
  • Last Post
Replies
5
Views
10K
Replies
8
Views
4K
Replies
1
Views
3K
Replies
10
Views
743
  • Last Post
Replies
15
Views
659
Replies
3
Views
2K
Top