# Force - extension experiments for Theraband Gold



## StraightShoot (Apr 16, 2015)

Hi,

I was trying to work out how changing the length of my straight cut bands would affect the draw weight of my bands, and I couldn't find any meaningful qualitative data for the resistance of theraband Gold, so I decided to do some tests myself.










And these are the results I got. This is a typical rubber force - extension graph, where it is harder to stretch at first and gradually starts stretching further for a given change in force. It then starts 'stacking' at around 450%, where the force starts increasing rapidly. To estimate the pull weight of your straight cut therabands, calculate the extension of your bands at your draw,

= 100 * (draw length - band length) / band length.

Then approximate what the tension force in a 1cm strip of rubber at that extension would be, and multiply that force by the total width of your bands in cm. This will give a relatively accurate draw weight estimation.

Also, I'd like to add that the length of the bands is arbitrary, as long as draw length is changed by the same factor. To put the in context, if one shooter uses 10" long, 1" wide bands at a 30"draw, and another shooter uses 20" long, 1" wide bands at a 60" draw, they will both have the same draw weight.

Cheers,

Jack


----------



## Lee Silva (Feb 9, 2013)

Facts.... Me like em, facts. ..

Hi Jack.

Me blacksmith...Hammer no good for math...

So blacksmith like em, and thank em straight shootin Jack for sharing straight shootin math....

Thank you, Jack, for taking the time to share the fruit of your efforts.....

Lee


----------



## JohnKrakatoa (Nov 28, 2013)

thanks for the data man !


----------

