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How strong HDPE is?


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Old 07-17-2017, 05:47 AM   #1
Luis_zeas
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Default How strong HDPE is?

I'm curious of how strong HDPE can be, how much weight can a 1/4 inch thick fork can hold, share your experience with this material and any accidents(fork hits, bending, breaking)you got.


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Old 07-18-2017, 07:33 AM   #2
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Hey Luis,

HDPE has an E-module of around 1.000N (1k), which is 1 kN/mm² - that of constructional steel is 215 kN/mm².

This means that steel is incredibly strong, but also that a "rod" of HDPE with a cross section of 1 x 1mm can withstand
a force of 1 thousand Newtons - which is 98kg here, equaling almost 220lb.

I dare to say you won´t find any negative reports on HDPE..

When it comes to homogenity of self-made HDPE (or LDPE, LLDPE) air bubbles in the material can make a difference (for the worse) - If you manage to get some at least HDPE700 (weighing 700 grams per liter), most likely even a 6mm sheet would suffice to build a decent and safe slingshot.


Hope this is usefull to you!


kind regards,

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Old 07-18-2017, 10:12 AM   #3
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Quote:
Originally Posted by BeMahoney View Post
Hope this is usefull to you!
Nope, sry your calcs are far from reality! No way a 1mm² surface area can hold 98kg. Do the same with steel! It will break instant if you apply a force of around 22000kN!

The Young's modulus only decribes the linear elastic behavior of material regarding to force per surface and strain. It has nothing to do with the strength of a material!

Anyway I can say that the strength of HDPE is high enough to build high power slingshots with it!
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Old 07-18-2017, 11:15 AM   #4
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Quote:
Anyway I can say that the strength of HDPE is high enough to build high power slingshots with it!
If you dont make mistakes building it!

Also you guys are nards
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Old 07-18-2017, 03:14 PM   #5
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Quote:
Originally Posted by wursthunter View Post
Nope, sry your calcs are far from reality! No way a 1mm² surface area can hold 98kg. Do the same with steel! It will break instant if you apply a force of around 22000kN!

The Young's modulus only decribes the linear elastic behavior of material regarding to force per surface and strain. It has nothing to do with the strength of a material!

Anyway I can say that the strength of HDPE is high enough to build high power slingshots with it!
Dang! I knew I messed it up again!

I though that the E-Modul describes the range within materials "work" elastic -
exceeding that given value would then result in irreversible change of form.

This being "real", in "my world" steel would withstand a force of 215 kN/mm² - versus 1 kN/mm² of the HDPE.



But you are pretty darn right! 22.000kN - which could easily be
22 MEGA!Newtons - That´s around twentytwo million Newtons..
Or 2158 tons - which will certainly crush one square millimeter of steel.


And I learned something, thank you for that!:


Next time I´ll try to be helpful and explain something to someone,
I´ll get my numbers straight! - Like everybody should make clear who´s
boat he gets on - it might be sinking surprisingly..
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Old 07-18-2017, 03:18 PM   #6
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The Young's modulus .. has nothing to do with the strength of a material!
Wow! This to me almost sounds like "far from reality"..

I will have to scrutinise.
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Old 07-18-2017, 07:52 PM   #7
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Yeah I shouldn't ride a canoe, you shouldn't mess with strength calculation But together we are a dreamteam!
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Old 07-18-2017, 08:17 PM   #8
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So far i have built slingshots from 20mm HDPE 500 as boardcuts.
They seem pretty unbeakable. At least with any bandset that i can pull.
As you can see from the pictrue, my HDPE skills are very bad... my router sucks and cutting and sanding HDPE is a bitch.
but its a very cool material


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