A couple of months ago Steve called me and asked if JBobs could be used for carbon fiber frames. He had been searching for couplings that he could use on his frame but wasn't having any luck with the well known sources until he found the GroupJ website. I told Steve I thought JBobs would work well but that we had not yet done a conversion. But, if he was willing to participate in an experiment, I would be willing to convert his frame in exchange for engineering data on how well the conversion worked. Steve did not hesitate, and within a week or so I had a nice used Scattanti CFR frame delivered via UPS.
The frame has nominally round tubes with the top tube at 31.75mm and the down tube at 39.6mm. There was significant taper in the down tube as it approached the bottom bracket, which dictated the BFC location.
The stainless steel JBobs are joined to the carbon fiber tube (CFT) using high shear 100% solid epoxy and techniques developed in sail boat and motorsports applications. Before cutting Steve's frame in half, we ran some tests to insure that the metal-to-CFT bond was stronger that the parent tube. Test were run on a 26mm diameter CFT bonded to to a -8 STD JBob, subjected to a cantilever bending moment. The test demonstrated that the CFT collapsed under bearing load with the metal-to-CFT bond in tact.
Steve's frame, while not new, was in nice shape so I wanted to demonstrate that JBobs could be installed without damaging the paint and clear coat. A potential advantage to carbon fiber frame conversion is elimination of the need to repaint the frame. A technique was developed to incrementally fit the couplings such that the prepped tube never extended beyond the coupling.
Stay tuned as Steve tests his new travel frame and we learn how well the bonding technique holds up.