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Any in House Seven [Ti Cycles] experience/expert?
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Brian Nystrom
Joined: 26 Jan 2004
Posts: 4303
Location: Nashua, NH

5/15/13 5:35 AM

I wasn't refering to the type or "hybrid"...

...that April and others have mentioned. What I was pondering was aluminum frames with strategically placed carbon overlays to fine-tune the stiffness and ride characteristics. The complexity and cost would be considerably less than all-carbon construction and should there be any bonding failures, they would not be catastrophic (unlike with tube-lug bonds).

There seems to be a growing consensus that high-end aluminum frames are better than low-end carbon at a similar price point. Carbon enhanced aluminum would create something in between, essentially raising the performance of aluminum another notch without the high cost of high-end carbon.

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April
Joined: 13 Dec 2003
Posts: 6495
Location: Westchester/NYC

5/15/13 7:43 AM


quote:
The complexity and cost would be considerably less than all-carbon construction

That's the part I'm not entirely sure of.

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BobB
Joined: 13 Jan 2004
Posts: 170
Location: Columbus, OH

5/17/13 10:51 PM

I really liked the ride of those Trek carbon tube-aluminum lug frames. Like April, I had a Trek 2320 frame. That frame replaced the frame of a 2100 bike that broke. Before that I had a 2300 bike whose broken frame they let me replace with an upgraded 5500 all-carbon frame for $500. All three frames "disbonded" (such a great Trek euphamism) about 100 miles after I rode in 20s and below temperatures. The 2300 I rode in the record low Columbus temperature of -14 degrees. At the time I didn't think much about the "chink" sound it made when I rode it off a curb. A couple of weeks later I got a call from the LBS telling me that during a routine service check they noticed that the seat tube had disbonded at the aluminum BB lug. (I realized then why the front der would move in and out on its own while riding!) The 2100 broke at the aluminum seat cluster lug. I was finally cured of my affection for these frames when the top tube of the 2320 broke at the headset while riding about 7 miles an hour on the trail. The whole front end of the bike completly separated from the back end of the bike because -- unknown to me -- the down tube had previously disbonded at the headset. Just 5 minutes before I had been riding 30+ mph down a steep road. It's still scary to remember!

So I am done with bikes made of dissimilar materials. My theory is that the materials had different coefficients of expansion. The Trek frames all had aluminum lugs inside of the carbon tubes, and I think in very cold weather the aluminum shrank more than the carbon tubes. With the resulting stress on the bonding agent, it didn't take much more stress to break the bond.

I have noticed that in every mixed material frame I have seen since, the carbon tube is inside of the metal lug or tube. Yes, those Sevens are beautiful, but I am content now to just look....

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ErikS
Joined: 19 May 2005
Posts: 8310
Location: Slowing boiling over in the steamy south, Global Warming is real

5/18/13 4:50 AM

Those frames were noodle and as you found prone to falling apart. You are correct about the reason for the failures along with the fact that the things were just glued together.

I had a carbon Bikes direct frame come apart at the bottom bracket because glue failure. It had carbon lugs so the expansion rate was not the mode of failure. It was promptly replaced by them.

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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA

5/18/13 6:37 AM

All Aluminum


quote:
The Trek frames all had aluminum lugs inside of the carbon tubes, and I think in very cold weather the aluminum shrank more than the carbon tubes. With the resulting stress on the bonding agent, it didn't take much more stress to break the bond.

Trek's first foray into bonded frames were the 1000, 1200, 1400 series of bonded aluminum tubes with aluminum internal lugs in the late '80's into the 90's. While you heard of occasional bond failures with these, they were generally pretty durable. Trek discontinued them in favorable of all-welded Aluminum frames for cost considerations, not durability. I had a '92 1420 that I rode for almost 20,000 miles, including some pretty cold days (14F was the lowest, not -14 thank you). My son still rides it as his several day a week commuter. So far no problems at all.

I was also leery of bonded dissimilar materials and, while I considered buying a 2300 in 1996, I decided to go with a Litespeed Catalyst. And 70,000 miles later I have never regretted that decision one bit.

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Sparky
Joined: 08 Dec 2003
Posts: 17125
Location: Portland, OR

5/18/13 10:33 AM

I will say it again, my brain just tweets 'danger Will Robinson' to me with bonds. At least welding makes the parts one.

Each material [required/design] has good and bad using it brings to the equation.

My question is why do XCR frames cost near as much as Ti? Will this shange when the honeymoon period subsides?

Steel takes a long time to rust, and with the alloying over the last 20 years the weight is more than reasonable perhaps[Unless you want to break the 3lb barrier for a 56+ frame]

So does this pretty much make the Stainless and Ti bike's strong anti oxidizing properties moot?

Funny how the 1st ten years I got to riding again, never keeping a bike long enough to worry about it rusting has changed. ;)

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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA

5/18/13 2:46 PM

Well....


quote:
Steel takes a long time to rust, and with the alloying over the last 20 years the weight is more than reasonable perhaps[Unless you want to break the 3lb barrier for a 56+ frame]

So does this pretty much make the Stainless and Ti bike's strong anti oxidizing properties moot?

"Undercoated" with Weigel Frame Saver or similar, and the paint kept touched up, yes, steel frames can last nearly forever. However, even at it's best, steel is not as strong per unit weight as Ti so there is an inherent advantage if weight is a serious consideration and Ti's corrosion resistance is a bonus.

Stainless steel tubing has a tougher time justifying it's existence. It's as heavy as Cr-Mo steel, as hard on tooling as Ti, expensive, and, as you note, has only corrosion resistance in its favor.

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Sparky
Joined: 08 Dec 2003
Posts: 17125
Location: Portland, OR

5/18/13 4:34 PM

The problem I have with Ti is you have to spend a lot more in labor over the extra material cost to overcome some of the materials property. It has too much elasticity? basically I think is what it is?

Not that I have ridden that many, but the Ti Frames I have ridden that where not noodles where either straight ga round tubes or massively worked and massively expensive.

The Blade I have is so stiff it is not funny. The Saber I had prior was much more compliant. If I did not buy the Blade frame for the same $ I sold the saber for... In other words if I had paid the extra 1000.00 in price difference IIRC between the two, I'd say moving away from the Saber to the Blade was not a good move.

Every Classic I had or rode had a lot of BB sway. Although I am so slow compared to when I did ride these as to admit they would probably be fine today.

The early Catalyst whee a joke to me, early Classic better by a little. And by 2000 the Classic even better. Again, all I was doing was stomping pedals back then.

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Rickk
Joined: 01 Jun 2004
Posts: 526
Location: Montreal

5/21/13 6:07 PM

Thread drift

re. bonding coming apart, especially at junction of different materials...

What about those 1st - 2nd generation carbon forks (before full carbon forks) that were glued to an aluminum steerer at the crown?

Same risks re. coming apart at the glued joint - spontaneously?

any thoughts?

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 4303
Location: Nashua, NH

5/22/13 5:09 AM

They've been around for decades...

...so apparently it's not an issue. I've got carbon forks from the mid '90's with bonded steel and Al steerers that are still going strong.

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April
Joined: 13 Dec 2003
Posts: 6495
Location: Westchester/NYC

5/22/13 7:49 AM

Could be different mode of stress?

Fork crown to leg connection sustain mostly longitudinal stress while the frame joints withstand more lateral stress...

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