Kevin & Roxi's Tandem

My most epic and advanced bike build yet. This tandem fits into two standard airline suitcases and features a tension-braced design engineered to manage stress better than any other design**.

 

Tandem frames start from $5300. They are constructed using butted tubing which as a Mechanical Engineer, I understand the importance of (it's not to save weight, but to reinforce the weak spots, the joints...). These frames will not have sudden unexpected failures.

 

Constructing these frames using the approach I insist on for durability using these delicate tubes is not an easy task. I install all braze-ons before welding the tubes into the frame because soldering on braze-ons distorts the tubes, and attaching them last would measurably reduce the robustness of the frame.. Frames must be designed to resist premature fatigue failure first and foremost. I go to the trouble of custom butting the base tube since a suitable tube is not available.

 

The frame of this example has 3 pairs of S&S couplers which enables the frame to be disassembled. Priced from $7500   The complete bike pictured was $11,700, or $12,700 with Ortlieb panniers and Tubus racks.

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Kevin and Roxi went for a mega tandem with a long list of features. Six S&S couplers in the frame enable it to be broken down and packed in two cases. Twin belt drive offers supreme lifespan; each belt outlasts 3 to 4 chains and requires no adjustment.
 

Massive 200mm front and 180mm rear disc rotors wipe off speed like nothing else. The tandem-rated fork, 15mm thru axle and White Industries CLD hub keep things under control up front.
 

A Rohloff tandem rear hub has the gear range of a mountainbike triple drivetrain while Paragon rocker dropouts take care of belt tensioning and frame-split duties.

I insist on using butted tubing, even for tandem frames, because the potential for fatigue failure in bicycle frames is known, and no other solution (such as incredibly uniform welds in titanium), addresses that issue nearly as well as butted tubing does. The number of butted tubes suitable for a tandem is limited so that makes these creations all the more special.

The extreme loads of a tandem call for advanced wheel design so I've used here the superior balance of durability and weight of triple butted spokes. DT's Alpine III spokes (one of only two spoke products with this feature), PHR washers and Squorx nipples complete the design. Triple-butted spokes place more material at the hub flange, PHR washers approximately triple the nipple's contact area with the rim and Squorx nipples allow precious extra spoke engagement beyond the nipple head.
 

Tubus racks front and rear with Ortlieb bags are the premium touring setup. My signature triangulation of the rack stays makes this setup many times more rigid than standard.
 

Finally, a thudbuster LT seatpost keeps the stoker happy. Those who've stoker'ed a tandem know.  

** I claim this is the most advanced tandem design because according to a First Principles engineering analysis, a). under hard front braking when hitting a bump, the third lateral tube is redundant (the braking and payload forces counteract each other to a sizeable extent), and b). while in the rear parallelogram, the additional third tube is not nearly as effective when under compression as it is when in tension AND its duties are instead taken up by slightly beefier (and FAR more effective for torsion and load-induced deflection) top and base tubes.  ;)