Tandem Cycling - Aluminum couplers

Anybody have any input on the S&S aluminum couplers used by Santana. I'm ordering a new bike and am concerned about the durability of the aluminum threads.

It is my understanding that the couplers are steel, actually stainless steel. I personally do not own a coupled tandem but have met and known many who have them and have never heard of any complaints regarding durability of the couplers. Some people feel that the disassembly/reassembly is too complicated for their taste but many travel extensively with these without problems.

The design of S&S Couplers is pretty robust. I can't imagine ever having a problem with them unless you rode with them loose or didn't lube them every so often.

BTW the Couplers on the Aluminum Santanas are Aluminum-can't weld steel to aluminum.

It is my understanding that the couplers are steel, actually stainless steel.

While the original (aka, classic) S&S Machine Bicycle Torque Couplings (BTCs) were machined from stainless steel, titanium models were developed for use on titanium & carbon tubing, a lower-cost chromoly model was developed for the OEM market (e.g., Burley, etc..), and an aluminum model was developed in cooperation with Santana for use with their Easton aluminum framesets.

However, with regard to the "material", it's only the coupler lugs (that parts that are inserted into the tubeset) that is 17-4 stainless, 6AL/4V titanium, chromoly or aluminum with 17-4 stainless coupler nuts used on all models. The latter has in the past created some confusion when folks with the VERY expensive titanium couplers were surprised to find magnets would be attracted to what they assumed would be titanium coupler nuts. The aluminum couplers were also being looked at by Calfee & Steve at S&S Machine as a possible lower-cost / lightweight alternative to the light but expensive titanium couplers and the not-as-light but more affordable stainless steel couplers. Alas, they had not progressed to the "available now" state when we commissioned our Calfee.

Regardless, and getting back to the aluminum couplers, while they are available for use by any builder in talking with various frame builders they are simply reluctant to build travel tandems using aluminum tubesets for the usual reasons: it's not as durable / dent and ding resistant as steel, titanium, or even carbon and if a frameset does get dinged, repairs are far more complex and expensive to execute. As for the weight savings, stiffness, etc., once again most of the builders I've spoken to simply won't use aluminum for a travel tandem. In talking with Santana, their take is: give the customers what they want and do so in a prudent manner. In addition to making a commitment to help develop and buy the couplers from S&S in sufficient quantities to make it worth their while, Santana also had already addressed the "damaged in transit" risk by developing their safe-case with shadow-box, foam tray system which makes packing Santana's S&S equipped tandems a no-brainer that ensures tubing won't be damaged inside the case by other tubing or components. This 'in-transit' damage caused by improper packing is probably far-and-away the highest risk to most travel tandems vs. all other causes based on what we've seen and heard over the years.

Anyway, getting back to your original question, hopefully someone with a Sovereign Stow-Away will chime-in; however, in the interim I can say that I've never heard of anyone stripping or otherwise damaging an S&S coupler lug or nut because the tolerances are just too tight. They only go together one way and so long as you use the recommended Dupont Teflon bearing grease and snug them down, there's not much that can go wrong. Now watch, someone will prove me wrong on this last point.

Wow, those things are expensive.

It looks like you get the double boom tubes on aluminum bikes (unless you're buying Scandium). http://santanatandem.com/Techno/CouplerSpecs07.html

I find the double tubes to be classier looking than the oval, though they are a little more difficult to tighten. Also (at least on my bike): If you ever drop the chain (off the inner chain ring), getting it back on requires removal of a crank--or at least loosening of a crank.

A little bit off-topic since this doesn't apply to the Santana couplers. I looked into using aluminum couplers on my Calfee late Spring of this year. At that time, S&S sent me an email saying that their new aluminum couplers that they were developing (for non-Santana tandems) did not pass their tests and they did not know when they would be available. I don't know why they did not pass their tests or how they differ from the Santana couplers. (Size? Not oval?)

I will be using the aluminum couplers as part of a new Calfee build. Apparently the new aluminum design has passed whatever testing S&S puts them to. I stopped by Calfee today and personally inspected several sets; I am not an engineer or metallurgist so I will put my faith in Calfee and S&S. I have a Calfee dragonfly single and a Serotta titanium retrofitted by Bilinkey with couplers no problems with either bike. In the past Calfee has reworked titanium S&S couplers to meet the requirements of bonding to carbon now all the machine work on the new aluminum couplers will be done by S&S. Titanium couplers will not be available.

I will be using the aluminum couplers as part of a new Calfee build. Apparently the new aluminum design has passed whatever testing S&S puts them to.

Steve at S&S is very rigorous in his testing so if the couplers have passed muster with him I have every confidence they will be as durable and reliable as all of the other BTCs he has offered.

BTW: For anyone in the market for a coupled Calfee, this change from Titanium to Aluminum couplers has lowered the cost of the S&S option for Tetra Tandem by 30%, as the Ti couplers carried a $2,895 price tag compared to Aluminum at $1,999.

Relative to the time-line for this new design change, some may recall we discussed the possibility of using the Aluminum couplers last year about this time with Calfee and S&S. However, at the time it was still only in the discussion stage pending some open machine time for development work at S&S... noting the BTC product line is more-or-less a hobby-like sideline for Steve's machine shop. We're happy with our Ti couplers; however, I would have much rather had the $1k in my pocket.

I will be using the aluminum couplers as part of a new Calfee build.

Any idea how Craig will be dealing with some of the issues described here, in section on "Interfacing Carbon With Metal Parts"?

http://www.calfeedesign.com/whitepaper8.htm

Thermal expansion, corrosion, etc.? I guess they should be a little lighter than titanium?

Great news. I wish it were 5 months earlier though. l guess the nut will still be stainless though? Otherwise it would be hard to tighten.

Any idea how Craig will be dealing with some of the issues [of] "Interfacing Carbon With Metal Parts"?


Probably by using the same techniques successfully employed by Trek and other makers for many years. Meticulous bond prep combined with fiberglass interface layers or glass "microspheres" in the adhesive (to force a small bond gap) has made bonding CF composites to aluminum and steel quite routine in the bicycle industry. Contrary to Craig's somewhat dated "whitepaper," it is no longer rocket science.

Any idea how Craig will be dealing with....Thermal expansion, corrosion, etc.?

As bikeriderdave notes, there are several ways to deal with bonding the materials to mitigate both galvanic corrosion and what, if any, issues pertaining to thermal expansion could be experienced in even the extremes of normal ambient temperature ranges, e.g., -30 to +150. Moreover, it's not only aluminum couplers that Calfee has had to address, but the aluminum insert used in their redesigned eccentric shell.



I guess they should be a little lighter than titanium?

1,500 grams, per the Calfee website... which sounds about right given the extra long inserts used on the carbon frames and which is probably about right for the titanium couplers used in the past. Again, I'm pretty sure all S&S couplers use the same stainless steel coupling nuts so the lion's share of any weight difference would be in the coupler inserts.