Charpy impact testing angle measurement suggestions

[Coleslawnicks]

I am designing my own Charpy impact testing machine and I am unsure what would be the best as well as relatively simple and affordable method I can use to accurately measure the angle the pendulum travels after it has broke the sample. I would also appreciate any complex and more expensive ideas too that I can consider, accuracy and reliability are the most important things.

I have thought of some methods but a lot of them will cause friction against the pendulum which could overcomplicate the final calculations.

Thanks.

 

[Q_Goest]

There are pressure gages that have needles that float freely on the same axis the pressure indicating needle such as the one shown here:
http://www.globalw.com/products/pg150.html

The black needle is the 'normal' one that follows the pressure. The red needle is pushed higher by the black one but doesn't track it when the black needle falls back down, so the red needle is left in position where the black needle max'ed out.

Something similar to that should work for you.

 

[Coleslawnicks]

Thanks you Q_Goest, Do you know of any instruments that are like this gage but I could use for the Charpy? Also do you know how the mechanism in this gage works?

I have thought of the idea that the pendulum rod would extrude past the pivot and this extruded part would push a pointer (much like the gage). My only concern is that to get an accurate reading the pointer would need to stop simultaneously with the pendulum rod. To do this I would need to tighten the pointer fitting but in turn this would create a reasonable force that the pendulum would have to overcome which could be quite hard to compensate for in the final impact calculations.