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.

I recently attended the Handmade Bike and Beer Festival in Portland Oregon, hosted by the Hopworks Urban Brewery  (HUB) on October 5-6, 2015.    What a great event; somewhere in the neighborhood of 30 local bicycle frame builders and suppliers and excellent craft brewed beer.  The frame builders had some very interesting custom bikes on offer from Titanium 29ers to grocery haulers to aluminum tandems.  The workmanship on the custom bikes is remarkable and it was so inspiring and educational to introduce JBobs to this group of elite craftsmen and craftswomen.  The majority of the builders are using Chrome moly tubing.  Lug brazing is still dominant among the CrMo builders but a lot of builders are using TIG.  There were also a good many aluminum and titanium builders.  If there were custom carbon builders there I missed them.
 
I went to the show with a handful of JBobs (Standard, Full Torque, P Option) and a stack of business cards.  My objective was to get some direct feedback on the JBob design from the builders and to understand what they wanted to see in a BFC.  Most builders were familiar with the current BFC offerings from other vendors, and many of them had used these couplings in their custom bikes.  All were very receptive and gave some great feedback:

• The fit and finish of the JBobs were immediately appreciated – They really liked that JBobs came fully polished, saving them a lot of hand labor
• They liked that JBobs were available in alternate materials of CrMo and Ti as well as the default 304SS
• The Ritchey clamp was recognized as a tried-and-true coupling mechanism
• The Full Torque BFC was by far of the most interest to the builders – they just felt more comfortable with the torque carrying capability.  While they recognized that the standard BFCs were probably adequate, they wanted top line equipment on their products.  (All of their bikes were to-die-for gorgeous)
• The most common request from builders was for a “sleeker” coupling – particularly for the top tube.  Bulges or protrusions beyond the tube diameter were seen as negatives.  The down-tube coupling, which is surrounded by “protrusions” was seen to be not as much of a “sleek” issue.
• Couplings for larger tube diameters were desired.  Builders now use 1.25 in. (31.75mm) and larger tubes, all the way up to 2.0 in. (50.8mm)
• They would be most interested in engineering data on the strength of the coupled JBobs

​At GroupJ Engineering we took all of this to heart and are at work on each of the above attributes of the “perfect” BFC.  Our first effort was to expand our line of BFCs to cover the tube diameter range from 1.0 to 1.5 in. (25.4 to 39.6 mm).  We do this with the two Ritchey clamps  (31.8 and 34.9 mm).   The larger diameter JBobs are also a bit “sleeker” as the clamp diameter is smaller than the tube OD. 

​Keep your eye on this space for further BFC features and products.