If you hang out on Facebook and have “Liked” Calfee’s FB page, or are a regular on BikeForum.net’s tandem subforums then you’ve probably seen the two over-the-top tandems Calfee took to this past weekend’s North American Handmade Bike Show in Colorado: one was a time-trial special whereas the other was an off-road hardtail 29er with a Lefty carbon fork that will be used in this year’s Leadville 100. Mind you, these are customer bikes, not one-off show bikes built on speculation to showcase builder’s talents and artistic vision.
Here is the Calfee Dragonfly Custom Time Trial Tandem; from Calfee’s FB Page:
**BREAKING NEWS: The Calfee Dragonfly TT selected Best Tandem at NAHBS.
This Calfee Dragonfly Custom Time Trial Tandem features S&S couplers, sculpted joints (inspired by our Dragonfly single frames), full carbon Aero BarStems, Ultegra Di2 with our Internal Battery and Wiring System and a host of highly covetable components. The custom geometry allows both the Captain and the Stoker to ride/race in positions optimized for aerodynamics and power transmission. The Captain required a 52.5cm top tube while the Stoker required a span of 89 cm; compare to our 72cm stock stoker TT length. Critically, we laminated a faux-steerer in the middle of the stoker compartment, between the S&S Machine couplers, where the custom Aero BarStem will be fitted. Our Dragonfly tandem uses a high modulus carbon fiber (66 msi) co-mingled with Boron fiber to build the lightest possible tandem bicycle frame without sacrificing stiffness, durability and ride quality. Our Dragonfly tandem frame, size Large/Medium, weighs only 2900 grams or 6.25 pounds. Compare to our Tetra frame, built with an intermediate modulus carbon (42 and 55 msi) at 3160 grams or 6.8 pounds in a Large/Medium. Notably, there is no weight limit on either our Dragonfly or Tetra tandem frames; certain tandem teams might benefit from enhanced frame stiffness, an option on all Calfee single and tandem frames. S&S machine couplers add only 2.8 pounds to our tandem frames, allowing the frame to separate and pack for easy transportation. Couplers were a thoughtful addition to this tandem, owing to the extra-long wheelbase. Similarly, this tandem benefits from electronic shifting as the very long mechanical cable runs would have compromised shifting performance. Our tandem frames, as light as the very lightest aluminum, titanium and hybrid-carbon frames from our competitors, set a new standard for comfort, durability, beauty, lateral-stiffness and power transmission. We are doing for the tandem world in 2011 what we did for the single world in 1987; building a lighter, stronger, stiffer more absorbent frame that is faster and more fun to ride.
You can view the full 22 image photo set at Calfee’s FB page by clicking HERE.
J. Price’s Tiemeyer TT Tandem
As for my comments, I’m pretty much speechless on this one. About the only thing that I’d like to see is wind tunnel data and video of smoke flow visualization around the down tube in comparison to say John Price’s Tiemeyer TT tandem that we featured in a piece back on November 11th that you can find HERE. My gut tells me that our beloved Calfee tandems may not have the most aerodynamically efficient down tube design and such a comparison would be great to see. Now, frankly… that ain’t gonna happen, but that’s my only “wish I could see” on this fabulous-looking Calfee. The paint scheme is right up my alley, as are the sculpted lugs and Lord knows.. we like long stoker compartments. However, at 35″ this even makes Debbie’s 30.5″ stoker compartment on our Calfee look short!!!
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Next up is the Team Westcott 29er; again, from Calfee’s FB page:
Team Westcott took delivery of their Dragonfly road tandem months ago; to support their off-road riding/racing effort, they commissioned us to build this very special 29er. This tandem is highly personalized; custom Cdale cranks, decals, component refinishing, and more. This tandem tips the scale at only 31 pounds, with pedals, as pictured.
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Beautiful bikes. I wish that my “Calfee Tandem” savings account would grow a little faster. I notice that both of these bikes have timing chains rather than the gates carbon belt, which seemed to be really taking off on performance tandems. Have there been any issues with the carbon belts?
In addressing your last question first, the only early concern about the Gates system was the realization by teams who used them in demanding conditions that the sprocket/pulleys would wear out before the belts at around 10k-12k miles, necessitating a new pair of sprockets and belt. At that time, that was not an inexpensive proposition and it somewhat undermined the cost advantage the belt system might have over a chain driven sync drive. However, the cost of the replacement sprockets & belts have since then dropped dramatically, putting the belts back into a cost model that makes them a wash with lightweight chains. For the average tandem team that doesn’t log big miles every year, the belt will likely last the life of their tandem. As for failures, there were a few folks who had belts slip under load when they weren’t tensioned high enough, there were a few that broke after the belt had been damaged during installation or removal (i.e., accidentally rolled-on or off, which is a no-no) which was exacerbated by the 1st gen 70t sprockets making for a tight fit; 69t is now the spec. Typical teething pains for the most part. There is now a new belt & sprocket design on the market called CenterTrack that is just now reaching the market which addresses some of the teething pains of the original CarbonDrive system so we’ll see how those fair. Personally, I have yet to see a big enough advantage or disadvantage from the belts to make them a game changer over chain drive, aside from the obvious: a cost neutral option that offers less maintenance & longer service life as well as potential weight savings over a sync chain. The limitations are dimensional at this point, as a frame needs to have either a BB-to-BB CTC length of 27.75″ (74t sprocket spec) or 28.5″ (69t sprocket spec) for the existing belt length and the lack of a ready field-repair unless a spare belt is carried, although I’m sure someone will come up with something at some point.
As to the first part of your question / observations, both of these Calfee tandems had unique specifications that put them outside the size / application range of the Gates Carbon Drive, i.e., 28.5″ CTC BB-to-BB in the case of the Dragonfly TT tandem with its 35″ CTC BB-to-BB / stoker compartment dimension and the need for low-profile timing rings / high ground clearance on the off-road 29er. I’m also not sure how well the sync belt will fare on an off-road tandem, as we’ve kicked up several branches into our chain drive with interesting & mixed results. Sometime the chain/sprockets simply sheer the branch in half, but we’ve also had the chain derail and in one instance get knocked several teeth out of phase. Carbon re-inforced belts don’t take kindly to being “stretched” and break shortly thereafter if that happens. So, again… not sure if any teams have been running a belt in technical single track, which is what that Calfee 29er was designed for. Gravel grinding… no issues as best as we can tell.
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