The tube ID turned out nicely. The fine groove from turning on the lathe was clearly reproduced as well. It will need more layers to be an effective BB shell tube. This process may even work for custom layup frame tubes as well.
Thursday, October 07, 2010
Here is the finished tube (test) for a Press30 BB. I need to adjust the mandrel OD to account for the thermal expansion of the UHMW but other than that, the process worked as planned. I might even be able to use 90deg fibers and not have it stick to the mandrel.
I tried unsuccessfully to lay up a head tube on a turned polished aluminum mandrel. Even with 3 layers of high temp release wax, post cure the carbon would NOT come off the mandrel. Back to the drawing board. Next I conducted a test using UHMW as a mandrel. It has a higher coefficient of thermal expansion than aluminum and nothing sticks to it (at least not epoxy). It turns up in the lathe nice and smooth and the 250F cure temp has no lasting effect on it.