At issue was one of the four couplers — that little silver fitting you see next to my right shin and above Debbie’s left knee on the top tube of our tandem frame.
For those not familiar with S&S Bicycle Torque Couplings, I did a blog entry about them in November 2012 that you can read HERE. Below is what one looks like before it’s installed.
Invented 23 years ago, these expertly designed and machined mechanical couplings allow bicycle frames to be broken down so they can be packed into checkable suitcases (or, at least what were checkable suitcases before airlines turned baggage into a revenue stream) or into smaller cars, taken on trains, etc. To make them work with the composite tubes on a Calfee, a titanium coupler sleeve has to be used instead of steel to prevent galvanic corrosion, making the couplers for a Calfee a bit more expensive than most. The coupler’s titanium sleeve is pressed into and welded to a longer titanium sleeve that, in turn, gets inserted and bonded to the inside of the composite frame tubes. I should note, after our tandem was built, S&S Machine and Calfee introduced a less-expensive aluminum coupler so aluminum sleeves would logically be used on Calfee travel tandems produced with the aluminum couplers.
I make mention of all this because today I think that weld broke on one of our couplers. Now, before anyone looks at the photo of the coupler sitting next to the top tube gets excited and assumes the coupler or composite tube sheered in half, that’s not what happened. In fact, the small (inner) sleeve you see sticking out from the coupler nut was still fully inserted in the top tube’s outer sleeve. Moreover, the joint where the coupler is located is held in compression when two people are on the bike and riding, which is to say, the front and back-end of the top tube are being pushed together. So, there was no chance the coupler or frame was going to be pulled apart, never mind having a sheer-type failure due to torsional loads. Now, to be sure, there were torsional (twisting) loads at that coupler; however, the rigidity of those sleeves and of the rest of the frame was such that I certainly couldn’t tell the coupler weld joint had failed during our ride.
In fact, I didn’t discover the loose joint until I felt and heard a slight clunk in the frame as I lifted the bike to hang it from the garage ceiling until next weekend. It only became obvious because by lifting the bike I put the top tube under tension, which is to say the opposite ends of the tube were now pulling at the middle of the tube. That was, as I said, when it became obvious I had a problem.
After loosening all four couplers I was able to remove the top tube from the frame so I could more closely inspect the coupler nut. Yes, the tandem had a freaky appearance with the top tube removed. It just looks like the brake cable is holding the whole thing together when, in fact, the very, very slight compression loads from the static weight of the tandem’s front and rear end are trying to push the two saddles towards each other.
It was only after I had the tube out of the frame I was able to slowly extract the coupler with its sleeve attached from the composite frame tube: it was a very tight interface, even after the spirited ride and all of the various loads that were working on that frame joint. Once I had the nut separated from the tube I realized there wasn’t going to be any easy fix I could make to either temporarily or permanently solve the problem.
I shot a note off to our friend and builder Craig Calfee around 3:00pm with a photo of the failed joint and my sad story. He replied to my note a mere 4.5 hours later with instructions to send the frame back to Calfee in LaSelva Beach, California so they can give it a complete going-over. Craig noted this was the first failure of this type he’d seen. There was a similar failure several years ago when a coupler became un-bonded, but this wasn’t a dis-bond: this appears to be a broken weld. Again, the take away was, get the frame to us and we’ll take a look. Can’t ask for much more than that… on a Sunday night no less!
With that guidance from Craig in hand, I knocked down the tandem to just the frame, pulled a box out of the attic that was about the right size. I had the tandem packed by 9:30pm Sunday night and it was in capable hands of FedEx at 9:30am on Monday morning bound for California. It’s a 3-4 day trip by ground, so hopefully it will be at Calfee by Friday.
We’ll learn more about what may have happened after the frame arrives when Craig and/or his technicians are able to give it a closer look. It does no good to speculate at this point but I’m confident that we’ll have her back and she’ll be great.
Now, I would be remiss if I did not note that we have some awesome friends who immediately jumped in to offer up spare tandems for us to use until our Calfee is returned: we are truly blessed with great friends! Now, we used to have a spare road tandem but sold that to some friends down in Florida about 20 months ago. However, unless we hear that the repair and return of the tandem will take more than a couple weeks Debbie and I both have and ride single bikes so we may just give riding side-by-side a shot vs. riding in tandem. I mentioned that we could always hop on the mountain tandem and got a look, but that was followed by a “maybe”. So, there’s a possibility that we’ll be playing in the dirt if it’s dirt and not mud next weekend: our trails close when they’re wet.
Again, more to follow. It’s a bummer that the coupling came loose, but mechanical things do what they do for a reason and that’ll get sorted out. It’s just nice to have relationships with the people like Craig who own the companies and who often times actually put their hands on the bikes during construction or when a post-delivery modification is needed. There’s a reason that all of our frames (sans the two Bianchi’s) were made by people we know: it makes a difference if you plan to hold on to your bikes and put big miles on them.