Calfee Tandem Headed For A Check-Up After Coupler Loosens Up…

20150823_125739After our tandem ride on Sunday I made an interesting discovery as I lifted our Calfee tandem to put it back into storage until next weekend.

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.

ti coupler

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.

20150823_135106I 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.

20150823_135052

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.

20150823_203155 20150823_214300

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.

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About TG

I've been around a bit and done a few things, have a couple kids and a few grandkids. I tend to be curmudgeonly, matter-of-fact and not predisposed to self-serving chit-chat. Thankfully, my wife's as nice as can be otherwise we'd have no friends. My interests are somewhat eclectic, but whose aren't?
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10 Responses to Calfee Tandem Headed For A Check-Up After Coupler Loosens Up…

  1. Dave Walker says:

    Hi, Mark,
    Sorry to hear about your (temporarily) out-of-commission bike. This description has me puzzled:
    “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 or aluminum sleeve that, in turn, get inserted and bonded to the inside of the composite frame tubes.”
    I understand the galvanic corrosion issue, but here are my questions:
    1) Does Calfee sometimes use Al sleeves rather than Ti? Ti can be welded to Ti, but not Ti-to-Al. Some other bonding method would be needed in that case.
    2) Why not just make the whole thing in titanium and eliminate the sleeve? This would have the dual advantages of less complexity and no possibility of the sleeve coming loose.

    • TG says:

      It was a case of poor writing and no proofreading on my part. S&S and Calfee introduced the aluminum couplings after our tandem was built, or earlier Calfee tandems have titanium couplings and sleeves like ours, whereas the newer Calfee tandems have the aluminum couplers and sleeves. I’ve re-written that part of my blog to clarify, so thanks for pointing out my error. Also, as noted, I’m describing what I discovered as I pulled the loose coupling off the top tube. I can’t speak to the design intent: it was purely a discovery process to me.

      • Bryan Boldt says:

        Actually, the current method Calfee uses with all Aluminum S&S couplers & carbon frames involves a fiberglass sleeve. This sleeve acts as an insulator between the AL and carbon tubing to prevent corrosion.

  2. Dave Walker says:

    Hi, Mark,

    Can you put a link to the follow-up report on the frame?

    Also, following up on Bryan Boldt’s post, I’m interested in understanding exactly how the fiberglass sleeve is bonded on both sides–to the carbon on the frame side and the Al on the coupling side. Maybe you (or Calfee) can describe the advantages of using Al couplings with a fiberglass sleeve vs. an all-Ti coupling that doesn’t (presumably–correct me if I’m wrong) require a sleeve? Yes, Al is lighter, but my question is whether the additional complexity involved with the Al-fiberglass-carbon system is worth it for the small weight savings.

    Thanks, and happy holidays!

    Dave

  3. TG says:

    Follow-Up Report.

    https://tandemgeek.wordpress.com/2015/09/26/our-calfee-tandem-returns-home-is-now-ready-to-ride/

    You’d probably need to ask Craig to provide his rationale. Back when we were having our Calfee built in ’07 we talked about the then stalled S&S aluminum coupling project and the big driver for getting the project restarted was the cost of the Titanium couplers. Case in point, the additional cost of the four Ti couplers we needed for our $3,999 Tetra frame was $2,850. If memory serves, the aluminum couplers at that time would have been about $1,800.

  4. Dave Walker says:

    Current price for adding Al/Ti (aluminum for the toothed tube stubs in the frame; Ti for the nuts) on Paketa frames is the same: $1250 for two-coupling design or $2500 for four-coupling model. The Paketa couplings are custom for the frame tube sizes used, and are the most aesthetic of any S&S-coupled bike. This works nicely because the relative strength of the Al/Ti coupling pairs very well with magnesium tubes in the sizes used. I’d be happy to talk about the coupling design (a collaboration between S an S Machine and Paketa) if people are interested.

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