How to do this physics project.

[ed21x]

if you want good structural rigidity, cut toothpicks in half and proceed to use half sized toothpicks.

 

[drinkmorejava]

Originally posted by: ed21x
if you want good structural rigidity, cut toothpicks in half and proceed to use half sized toothpicks.

Err, I suppose that works. It would probably be better to just properly support each vertical beam with diagonal members. Breaking them in half will just lead to more stress concentration points == more chances for something to break.

Either way decreases the effective length.

 

[Jeff7]

Originally posted by: drinkmorejava
Missed a few commas, but now you're confusing me.
FLUENT

Ah, and a few capitalizations.

I'm afraid I've never heard of Fluent (FLUENT?) until just now.

Originally posted by: drinkmorejava

Originally posted by: ed21x
if you want good structural rigidity, cut toothpicks in half and proceed to use half sized toothpicks.

Err, I suppose that works. It would probably be better to just properly support each vertical beam with diagonal members. Breaking them in half will just lead to more stress concentration points == more chances for something to break.

Either way decreases the effective length.

Ah, but more points also means more supports, and better load distribution.

 

[ural]

Your best bet is simple rectangular trusses. Triangles are best when you are building a truss that spans between supports (think bridges) and those diagonal members do carry critical loads. In your project the weight of the book will be carried entirely by vertical members (think of columns supporting the roof), however you will need diagonal members for stability.

If you have something like this "|_|" and put a weight on top, it could go like this "/_/"
So better build something like this "|\|/|\|". Just pick a simple pattern and repeat it in all directions.

 

[Howard]

Originally posted by: Jeff7

Originally posted by: drinkmorejava
err, how high off of the ground does it have to be? Just make a flat plate of toothpicks. If that doesn't work, I'd be happy to show you how to do a stress analysis for truss members

Ugh, my class got to that stuff in ANSYS just a week or two ago. Old ANSYS makes babies cry. Workbench is soooo much nicer. Granted, it's not quite as capable as the old ANSYS, but I don't think that'll last more than a few years.


Cheaper option: Pontifex demo.

Surprisingly, there are some videos of big bridges on Youtube.

Fuck old ANSYS. Shitty interface, random-ass saves (where did my file go?) and NO UNDO WTFFFFF

EDIT: How are you supposed to use the structure to hold up the blocks? Are you building a bridge upon which the weight rests?

 

[drinkmorejava]

Originally posted by: Jeff7

Originally posted by: drinkmorejava
Missed a few commas, but now you're confusing me.
FLUENT

Ah, and a few capitalizations.

I'm afraid I've never heard of Fluent (FLUENT?) until just now.

Originally posted by: drinkmorejava

Originally posted by: ed21x
if you want good structural rigidity, cut toothpicks in half and proceed to use half sized toothpicks.

Err, I suppose that works. It would probably be better to just properly support each vertical beam with diagonal members. Breaking them in half will just lead to more stress concentration points == more chances for something to break.

Either way decreases the effective length.

Ah, but more points also means more supports, and better load distribution.

Doesn't necessarily mean more supports. There?d be the same number of supports, just broken up into smaller sections. He'd essentially be gluing them back together anyway. I suppose he could offset each level.

I think we should define his needs first. Maybe, how much time does he want to spend?

 

[ural]

yeh, no kidding, ANSYS is just plain weird and... sooooooo frustrating!

 

[Jeff7]

Originally posted by: Howard
Fuck old ANSYS. Shitty interface, random-ass saves (where did my file go?) and NO UNDO WTFFFFF

:laugh:
I like your style.


We had to build a small bridge recently entirely by commands.

But, unfortunately, there are some things that can only be done in old ANSYS.

Originally posted by: drinkmorejava
Doesn't necessarily mean more supports. There?d be the same number of supports, just broken up into smaller sections. He'd essentially be gluing them back together anyway. I suppose he could offset each level.

I think we should define his needs first. Maybe, how much time does he want to spend?

Also how much time he wants to spend.

 

[Epic Fail]

I think the OP is missing the weight requirement, without it, the whole exercise is pointless as pointed out by the box of glue comment.

Anyway, these projects aren't good simulation of full size models, the joints will fail much faster. Your model will be more efficient if you don't do any design and pack the toothpicks close to each other to minimize glue failure.

 

[drinkmorejava]

Originally posted by: Jeff7
Also how much time he wants to spend.

lol, if you're going to keep fixing my grammar, I'll just go to sleep, and you'll be all by yourself.

 

[Jeff7]

Originally posted by: drinkmorejava

Originally posted by: Jeff7
Also how much time he wants to spend.

lol, if you're going to keep fixing my grammar, I'll just go to sleep, and you'll be all by yourself.

*Sigh*
Maybe I should go to bed.
That was actually my bad. I didn't see the word "time" there when you said it. I thought you were talking about monetary costs, so I mentioned time.
Yay me.

 

[ural]

And for the size - since in "|\|" the longest member is the diagonal one, I would set the diagonal equal to the length of one toothpick and go from there.
And given average toothpick is about 2" long, you are looking into 3 levels of simple rectangular trusses. Just make sure your diagonals "meet" in the same corners, like this:
|\|/|\|/|\|
|/|\|/|\|/|
|\|/|\|/|\|

*Note that horizontal members are missing since I just can't fit 2 characters in one space.
This thread turned out to be fun... I look at my own post and realize it looks like something from "Big Bang Theory"...

 

[DrPizza]

If there's a limit on the toothpicks, but not a limit on the hot glue, then go the shoebox route: fill it half full with hot glue, insert 1 toothpick, fill it the rest of the way.

 

[DrPizza]

Alternative idea that should win for creativity: Nothing is glued together. Use hotglue sticks as truss members & rivet them together with toothpicks. (Bore out pilot holes with a dremel). Act incredulous when you say "this isn't what you meant??"

 

[CrazyLazy]

block of wood and glue works very well, you just have to make sure you give it time to dry.

 

[TallBill]

Originally posted by: DrPizza
Alternative idea that should win for creativity: Nothing is glued together. Use hotglue sticks as truss members & rivet them together with toothpicks. (Bore out pilot holes with a dremel). Act incredulous when you say "this isn't what you meant??"

I like this one better.

 

[bonkers325]

how will the structure be loaded? in junior high we built bridges out of toothpicks and elmers glue and they were loaded with weights and books from a hanger in the middle.

you can just build an i-beam out of toothpicks and glue (mostly glue)

 

[SirStev0]

How bout you uses a plastic cup as a mold and grease it up.

Then add a layer of glue (like 1.5 inches of glue per layer) and use the toothpicks as rebar. Wait till it dries. Add another layer that will cover the toothpicks. Add more toothpicks as rebar for this layer. Let it dry. Add another half inch to cover those toothpicks. Put in some more toothpicks. Wait till it drys and add more. Continue until you fill the mold. Cut the mold off and you should have a solid pedestal of glue with toothpick rebar holding the layers together. Could easily put 50 pounds of weight on it and it should hold nicely .