1speeder

So, Tandem users,

The last few weeks I have been dealing with cracks in my Santana Sovereign frameset. I had always thought Santana was one up back in 1996 when I purchased the tandem. I have never had a frame failure on the many single and also tandem rigs I have owned over the years. Now I have to deal with Santana for cracks on the head tube and stokers seat tube on a 1996 frameset. Back then, we were a 300 lb. team, the captain being 180 lbs. The frame is anodized purple, from what I have read, anodizing will harden the surface. Is this hardening enough to cause a stress crack in the head tube and stokers seat tube (just above the seat stay weld to under the stoker seat clamp area). My main worry is that they will want to repair the frame and charge me the paint cost. This is a double edge sword, meaning I purchased this bike because of the anodizing since I sweat so badly, paint peels before my eyes. And yes, the anodizing also shows sweat stains. To me a new frame would be the best solution as I now don't trust the old frame because I feel that it may be brittle do to the anodizing. Anybody have any thoughts?

Thanks, Mike

fietsbob

what is your goal? go fast, organized centuries or go loaded touring in remote regions?


anodizing is a plating of aluminum with more aluminum.

the surface is then honeycombed and will retain die colors in those Pores hard anodizing is an un common process

you see a dark grey-brown color on parts with like Mavic's CD process.


I expect any cracks are metal fatigue , which would happen with a lot of metals when worked often enough
riding is flexing .

just steel has more ductility so the fatigue work cycle count is a lot larger ..

Monoborracho

--------> BOLD PRINT SAYS IT ALL.......To me a new frame would be the best solution as I now don't trust the old frame because I feel that it may be brittle do to the anodizing.

The frame on our Burley cracked a couple a years ago. It was at the front pivot point on the Softbeam attachment. ..........

One of the most experienced tandem riders in this forum said it was the first time he had ever heard of a Burley cracking.

We now have a titanium tandem, just our choice, maybe not everyone's.

She may have to deal with a captain who does stupid stuff, but the mother of my children won't be riding on 1) a patched frame or 2) a tire that has a cut or 3) a tube with a patch.

....just sayin'.......

prathmann

I'd wait for Santana's response before worrying any further. If it's a warranty repair then there shouldn't be any charge for paint or other associated labor and parts. When I've had frames replaced under warranty (albeit not by Santana) it hasn't cost me anything (other than being without the bike for a short period). I would also tend to trust Santana's judgement on the soundness of the frame. They should have lots of experience by now and presumably don't want anyone riding on frames that may be unsafe with their name on the sides.

fietsbob

Original owners receipt handy?

1speeder

Yep, it was the first thing Santana asked for.

Carbon has held up the best for me over the years do to my sweat on single's, titanium also works but due to my body build and pedaling stroke, there is much frame flex.

I had thought the Santana would be the last tandem I owned, but I guess I have to wait to see what they tell me next week.

Thanks,
Mike

qspencer

See the Wikipedia article on fatigue limit. I'm not a materials expert, but based on the explanation in the article, it sounds like steel should never fail as long as the stresses on it do not exceed a certain limit, while aluminum will eventually fail due to fatigue under the same stresses. I once had an aluminum frame fail, a super light Alan frame from the early 1980s which I had bought secondhand and put a lot of miles on myself. I would expect that kind of failure to be less common on more modern aluminum frames, but it's still theoretically possible eventually. So, if you're looking for the frame material least likely to fail over the long term, it's probably steel or titanium.

zonatandem

Failure is possible with any material.
Have broken steel tandem frame twice; once at 50,000 miles and again at 56,000 miles. Also broke an experimental steel tandem fork at 13,000 miles.
Have ridden steel/alloy, ti, alu and carbon fiber tandems.
Our current ride is a 26.5 lb carbon fiber tandem with about 40,000 miles on the odo after 11 years.
See what kind of deal Bill at Santana offers.

Ritterview

Carbon is the best material for half-bikes, as evidenced by its high-end market and racing domination.

So, the starting point for considering tandem frame material is carbon, and ask why should it be different for tandems?

PMK

The anodize process, properly done, is not the root cause of the cracks. Without seeing or inspecting the failures up close, most likely it is a failure from fatigue /cyclic stress, a stress riser from a notch or cross section change, or overloaded area.

I would wait and see the response.

As for the best material, it will depend on who you ask and what priorities they place on their tandem adventures.

PK

KonAaron Snake 

I must say I find your logic a bit illogical here. Does that mean that the best beef is a mcdonalds patty since it sells the best?

Carbon on is the best material for certain applications, and is not ideal for others. I've talked to quite a few pros...and they liked carbon going up the hill, but they prefer steel on the way down. Whether or not carbon is sold the most to racers because of superiority is HIGHLY debatable...it has more to do with profitability, material cost/availability and production costs. Titanium can meet the weight limits, many would argue it's a better all around ride and it is more durable - it was cost and the variable material availability that lead to CF's dominance. Titanium is hard to work with and if you don't know what you're doing, you'll get frame cracks (a distinct disadvantage), but when it's done right...it's awfully hard to argue for other materials for many applications.

Steel is the only material that can be easily cold set and adapted (except the air hardened ones). Apparently it's possible to cold set ti, but It's more difficult. Those are definite advantages. Aluminum is cheap...and cost is an advantage. So the answer really is - the best material depends on what you're using it for. If I had to guess, CF is not the best material for most bicycle applications, for most people.

waynesulak

I disagree that the market determines the best of anything for specific user. It determines the most popular which may or may not be the best for a specific user. Examples abound, cars, houses, phones, music, movies all of which I feel that the most popular type is not best suited for my needs and desires.

On tandem materials I think that:

- A good tandem can be made out of steel, aluminum, carbon, Ti and maybe other materials. It has more to so with design than the material.

- different materials have different advantages that may lead a user to choose that material over others. For example carbon can be strong and light which makes it a popular choice for bikes.

- Out of the materials mentioned above steel has the advantage being the easiest to fabricate by small shops. Carbon is great but if someone wants to buy something that does not have a large volume demand they are out of luck. For example if anyone can find a builder to build me a carbon fork at a reasonable price for my tandem that has 60-65 mm rake, clearance for 42mm tires and canti studs please let me know. I will buy it. I am sure one can be designed and made but the economics of carbon fork construction result in few bike "builders" actually making carbon forks of any kind much less a small volume design. I believe that Calfee, Pateka, Seven, Santana and Comotion do not make their own carbon forks. They make frames and in some cases steel forks. Carbon forks are outsourced and sometimes rebranded. Below are some other bikes that are readily available in steel but not carbon. Ti and aluminum can be used as well (well except for the fork) but fewer small builders operate with them.




- At some level cost is factor for almost every user. I think that aluminum is probably the king here allowing for some really low cost frames. Steel can be cheap but cheap steel is not something that builds a very good bike. While good steel is much cheaper than Ti, magnesium and carbon, it is still more expensive than aluminum.

Team Fab

I'm sorry am i the only one who thinks you got a good life out of that frame. If they will fix it for free. Get it fixed and keep it as a backup bike. Buy a new one. I am sure that even lower end current tandems will perform better than a high end tandem from 1996.

Homeyba

I've broken steel frames, aluminum frames and titanium frames but never a carbon frame. That doesn't mean carbon will not break because it can too. The difference is that carbon failures are almost always a result of damage caused by something other than wear (I've personally have never seen a fatigue failure with carbon). Any high end frame should last, doesn't matter the material. Sometimes things just happen. That's what warranties are for.

KonAaron Snake 

My understanding is that steel and titanium do not fatigue if the stress is below their limits. Aluminum does and CF does. Additionally CF can be affected by things like sunlight, scratches to the clear and UV radiation. I have personally seen far more carbon forks and frames cracked than steel or QUALITY ti.

So if your ti/steel frames cracked it was either due to something catastrophic or manufacture failure. It might be that in the practical course of life cycle fatigue is hypothetical and damage is more likely due to manufacture failure and some material has more risk due to manufacture difficulty (ti and some steels).

1speeder

Also broke an experimental steel tandem fork at 13,000 miles.

Ouch!

1speeder

I would agree on "got a good life out of the frame", if I had 10,000 plus miles out of it. I don't, it has like 3-4k on the bike which was put on the first few years of ownership. And even though it is a 1996, the new Sovereigns have the same geometry, same 1 1/4 steer tube diameter, still has the 160mm rear drop out width. I agree it would be wonderful to have a carbon fork and 10 speeds verses the 8 speeds I have now. The Sach ergo shifters/derailleur on this tandem to me shifts much better than the Sram Force (1st year) on my road bike. So what is lower end these days, something under $4000.?

Thanks for your thought's,
Mike

B. Carfree

When my '88 custom tandem broke after about 35000 miles (stoker seat tube at the bottom bracket; gorilla stoker issue), I did just that. I paid R+E to repair it (very inexpensive) and then had them build me a new one. I guess that means that in practice I agree with you, so theory goes out the window.

Homeyba

"Carbon fiber also has a better fatigue life than steel, titanium, or aluminum" Craig Calfee materials engineer and owner of Calfee design.
Since most CF frames are painted, the UV/sunlight issue is irrelevant and naked ones (like mine) have a UV protection coating. Scratches to the clear coat are not going to cause a catastrophic failure. CF strength comes from the carbon fibers not the epoxy.

prathmann

True, but probably not very meaningful in practice. Building a frame with such thick tubing so as to keep all normal bicycling stresses below the fatigue limit would result in such a heavy bike that it wouldn't sell. So bicycle frames are made where normally expected stresses (such as hard pedaling in a sprint or up a steep slope, hitting potholes at speed, etc.) will exceed the fatigue limit of the metal. Given enough such stresses the frame will fail. So far my personal experience is better with my Al frame than with any of my previous steel ones - but I'm sure it will fail eventually as well (unless I do first).

Homeyba

I don't think I'd be happy with only 10,000 miles on a frame, I ride that many miles in one year. Like Zonatandem, I have bikes with more than 5 times that mileage on them.

KonAaron Snake 

Not sure I'd trust a CF guy on that, I can find you steel builders who say otherwise. The independent stuff I've seen was inconclusive, but cf does fatigue over cycles regardless of stress, like aluminum. Steel and ti don't. I agree that it might be theoretical in application and I'm not a CF assplodes guy...I get your point.

KonAaron Snake 

It's so hard to determine what's true, but I tend to agree with you based on observations. My dislike of aluminum isn't fatigue, it's aesthetics, bias and hatred of a Cannondale 30 years ago.

1speeder

I do agree with you, that's why I am not thrilled having cracks in the frame with 3-4k on the bike. Heck, even the chains haven't been replaced yet (yes it is 8 speed).

The bike has been in storage from year 2000 (yes we do have wonderful kids) and then revived it back into life in 2010, for a few 30ish mile rides. I decided to break my shoulder mountain biking in 2011, so riding seized for the last few years. Now with me and my wife in our later 50's, both having shoulder issues, I just hope to ride together comfortably to keep in shape, and loose the 50ish pounds to be back where we were in the late 90's (huge task). So at this point, after the frame is either repaired or replaced, the real question is, can we still do some metric centuries or even better, a century, which is my goal once again. I would love to have a new tandem, but I need to know first if we can still do at least a metric century without having a ton of pain.

Mike

Leisesturm

I don't know... I mean... storage? I'd crack too if I was rode hard and put away wet for 10 years. I have a friend who owns a bike shop and he flat out won't deal with tandemists. I get a pass because my stoker is blind. Seriously, if I ran Santana I'd void your warranty. At least they are talking to you and offering to fix the frame, maybe even replace it. The issue is moot as to what is the best material for a frame. There are exquisite and awful examples of frames in every material known to man. Including wood, bamboo and plastic. Your frame, repaired by Santana should be perfectly serviceable for the rest of you and your mrs.'s natural lives. BTW riding a tandem really isn't the best way to lose 50ish. It's too efficient. You need to waste energy in a big way. You're my age, I know what I'm talking about. Ideally you would run or row, but that is unlikely. So... cut your sugar intake by 1/2 or more. Do not replace it with Sucralose or Aspartame, Only Stevia or Xylitol. Skip lunch once in awhile. Do not snack. You aren't going to burn enough calories cycling so you have to keep them from going in in the first place. Some people call this dieting but I won't. It's lifeting. FWIW.

H