Cylindrical thumb ring from black pool ball No 8 or Plastic

jsachers · Post by **jsachers** » Fri Nov 20, 2009 1:11 pm

Indeed polycarbonates and ABS are used in motorcycle helmets. Their purpose is to spread as much impact energy as possible over a large surface. So they are not easily deformed, but (quite) easily broken. Plus without layers and layers of finish they are very sensitive for scratches. UV rays make some of the additives evaporate so that the material becomes even more brittle with the years (helmets last app. 5-7 years).
I don't think these are desired characteristics in a thumb ring.
Being a motorcyclist myself, I could however provide you with lots of old helmets if anyone wishes to give it a try ?

orange · Post by **orange** » Sun Nov 22, 2009 3:16 pm

Yes, purpose of helmet is to break on certain force, otherwise you neck be seriously harm even when head will not.

Anyway, if I will try Acrylic Plexiglas, I can try additive free Polycarbonate like Lexan too.

I will check tomorrow it them have so usable thickens on stock.

Daniel T. · Post by **Daniel T.** » Mon Nov 23, 2009 6:13 am

I don't know how you reached your conclusions, but I know that the fracture toughness of ABS is easily twice that of plexiglas. As orange already pointed out, it depends alot on the specific brand. In the case of ABS it depends strongly on the rubber content. Plexiglas you can buy e.g. in hardware stores could also contain a fraction of rubber to make it less brittle.

Fortunately a colleague at work is currently working with ABS and I will ask him for suitably sized scrap pieces. Then I can try a ring according to the instructions given here.

Joomong · Post by **Joomong** » Sun Sep 28, 2014 5:14 am

I have seen wood thumb rings made for Korean archers. The maker uses very strong wood, carve it, and makes amkkajee or sukkajee.