Sunday, December 12, 2010

Break Time II

After the side load I tested the in plane bending (trying to pull the joint apart in the the plane of the frame).  I used split blocks to support the ends of the tube and a 4' solid steel pry bar to apply the load.

 I applied almost 1/2 my body weight to the joint about 4 feet from the support block.  So, the joint was under 300+ ft-lb of torque.  After alternating this load in opposite direction a few times there was a cracking sound and this small flap of carbon pulled free.  Also, a small crack curved under and along the joint fillet..

One good hard heave (probably over 400 ft-lb) and the joint cracked further.

Eventually if failed completely...


Recumbent Guy said...

Hello Glen,

Beautiful work on these pages! I am building a custom CF recumbent bike and stress testing is a concern for me... does this test show the joint is strong enough under real world circumstances, or did yo have to strengthen it further?


Glen J said...


I did some more joint testing and ended up using more carbon in the joints. Here is a test I did on joint strength in a frame.

Good luck with your build...