designengine

I am part of a team developing this cross country racer for a Denver mnt team. Cabron tubes are glued in if you can believe it just like Boeing's 787 The design is a hi pivot design created from the chromoly frame they raced the last 3 years. If you search 'design engine instagram' you can see the design


Im not able to post a picture till I get 10 posts LOL


bart brejcha
design-engine

unterhausen

yes, you can't post pics because we get a lot of spammers. What did you want to post?
What are the joints made out of?

squirtdad

doesn't look like there is a lot of surface are for gluing********** "Just like 787" is apples/oranges as any application in a 787 is going to be bit different from the application in a bike

unterhausen

it used to be a lot more common to have metal joints and carbon tubes. People are still making them that way. I have never heard of one coming apart

Andrew R Stewart 

Well there was that production run of Specialized Allezs in the early 1990s (IIRC) that had some chainstay/BB issues. I never saw one that had complete bonding failure but have heard of a few that did. From what I was told the shell/stay fit up didn't isolate the carbon from the AL and the shell's surface would galvanically react with the carbon stay. But one would hope that issue is well understood and accounted for these days. Andy

TiHabanero

Don't forget the Trek OCLV BB failures of the 90's and the galvanic corrosion issue Trek had with the Composite series machines (I had one that suffered badly from it). Graftek frames popped apart, so I am told, and Alan had an issue as well. As Andy pointed out, these issues have been addressed.

bulgie 

This is one of my favorite pictures of all time. Metal joint and carbon tube, come apart.

The model name was "Team Machine", but then it broke in a way that the last bit of the M in Team became an R -- "Tear Machine".
It works on at least two levels -- it "tore" right there, and then tears were shed. So perfect.

The toptube tore only after the carbon downtube popped out of the aluminum lug.

Mark B in Seattle

bulgie 

One problem with aluminum lug carbon tube Allez frames was cracking of the glue joint holding the chainstay bridge to the chainstays. It looked bad, having a crack in your frame, but it didn't affect the ride much if at all.
They got tired of the warranty claims and the damage to their brand from their prestige flagship breaking. Their brilliant solution: Just leave out the chainstay bridge -- problem solved!

Mark B in Seattle

bulgie 

Are you really using "dumbass" tubes, ("cabron" in Spanish)? Was that a typo, or a Freudian slip?


If it's for real, good luck marketing it in Spanish-speaking countries.

Mark B in Seattle

bulgie 

More CF tubes coming out of metal lugs:


I had a circa '76 Exxon Graftek for a few years, but never rode it, too scary. I sold it to a guy in The Netherlands. Hopefully his next of kin will not come after me...

I do trust that glue has gotten better since then, but I still am not interested in riding one.

unterhausen

failure on the very first carbon bike, who could have expected? Wasn't that really a carbon wrapped aluminum bike with stainless lugs though?

Similarly, I will never buy a Ti bike because I had two Teledyne Titans break at the bb shell

Andrew R Stewart 

Eric- I take this (bolded) as tongue in cheek. Just as we don't use mobile phones because the early ones had such bad connections and were huge blocks. Andy (who still doesn't have a data plan for his flip phone)

Andrew R Stewart 

Mark- The Specialized Allezs that I saw that might have later been a problem had "white powder like stuff" building up at the BB socket's edge/shore lines. I've seen the same at the head tube lug edges too but never heard of that area coming apart. One industry guy suggested that the powder was Alu Oxide. he also said that if the socket had been anodized the reaction would have been either slowed down dramatically or completely avoided. I've read of using a ply or two of fiberglass cloth as an insulator too. The Allezs were Giant manufactured IIRC and the ones that I saw already had no chain stay bridge.

My understanding of this type of problem is because of sub standard bonding agents, improper tube/socket insulation from each other, too little surface area of the bonded joint WRT the stresses a frame sees, joint fit up clearances being either too tight or too loose for the bonding agent to handle or joint contamination during assembly. Pick one, hell pick a few with those early frames. Andy

unterhausen

They may not have understood that carbon and metals have a galvanic corrosion problem. Trek had this problem on enough bonded aluminum dropouts that I have seen one that de-bonded.

Probably not wise to ride a 45 year old (pretty much experimental) carbon bike.

I do harbor a bias against Ti even though I know the issue with the teledynes was they used commercially pure Ti. Which is malpractice.

bulgie 

You didn't say who you were referring to, but in case it's me ("I do trust that glue has gotten better since then, but I still am not interested in riding one"):
My disinterest in riding carbon frames has nothing to do with Grafteks. Sorry if me juxtaposing those two thoughts gave the wrong impression. I really do trust that the glue and galvanic problems have been worked out, but I am still not interested, for other reasons. Just don't like carbon fiber (nor cabrón fiber either!). I don't hate it, I just avoid it without being religious about it. Personal preference. I know most people don't share my preference, and that's perfectly OK.

Graftek wasn't quite the first carbon frame, it was maybe the fourth after Mossberg, Graphite USA, and one other I'm forgetting at the moment. But yeah, it was definitely not mature tech at the time. Good enough to win US road natz and a bunch of other races, but there were rumors of Howard, the Stetina bros. et al. breaking a few of them. Sadly in the years since then a number have broken fully within the stainless lug or dropout, a completely self-inflicted fail that had nothing to do with carbon or glue.

unterhausen

The Exxon seat lug/seat stay joint in the seat lug was particularly bad, I'm a little surprised that they lived long enough for any other failures.

TiHabanero

Amazingly the Specialized Epic SWorks mountain frame I hammered for 5 years never had any issues. It was a 1990ish model and very stout. Composite glued to cromo lugs. The 2100 Trek Composite I had rotted out within 5 years. It just couldn't handle the salt from sweat. I called it the Ralph Nadar bike as it became unsafe to ride at any speed. lol

bulgie 

Yeah that was the worst. I heard rumors that the glue joints did pop sometimes, with some people saying it happened more at low (cold) temperatures. Maybe that makes sense due to the core of the tube being aluminum, shrinking away from the steel lug. Or maybe cold just makes the glue brittle.

That sort of fail can be repaired, with modern glue probably better than new. Except when one joint pops, it often causes damage elsewhere, as we saw with the "Tear Machine".

Oh here's a good example, found on the ClassicRendezvous mailing list. A thread called "Graftek frames breaking..."
Dale Brown (the list owner) wrote:Wesley Hatakeyama wrote:Robert Hershoff wrote:So, I mentioned "rumors", but those are all pretty solid first-hand accounts. Two glue joints (one at cold temperature), one seatstay "lug".

Some people say there were good and bad batches, with some saying the last ones produced were very reliable. Makes sense that they'd learn from their failures and get better. Earlier ones had Campy 1010/A rear dropouts and a normal steel fork. Later ones had unique cast-stainless dropouts, and the fork was steel but covered in carbon. Not that the carbon on the blades did anything for you, but it's a good sign in that it means later production, when the glue joints on the frame may have been better.

Mark B

unterhausen

I really didn't know they sold very many. I don't remember anyone having one, but if Dale Brown sold them, there were people near me that bought one. I saw them at some of the races he put on when the national team riders had them

designengine

This bike will be a prototype racer. We are doing it to learn and break. We did break the alpha version in a race and learned from that bike. They build 3 of those as chromoly examples.. This one if we can we will start a proto build before June. I wonder with our social distancing if we will even race this year.... Notice the honeycomb inside the shell. Im eager to organize that honeycomb with generative design but have not yet. Gle will go on the end of the carbon tubes and if CNC'd then the weld will go down the middle halfs.







Bart Brejcha
Design-engine.com

unterhausen

what are the joints made out of? I assume additive manufacturing?

I'm a bit curious about the 787 claim.

repechage

Sailboats are often bonding carbon to aluminum, one of the items that a well engineered joint seem to address is engagement on both sides of the carbon wall.
Galvanic corrosion with carbon hulls is now a well documented concern, glass fibre insulators go a long way.

designengine

the 787 is glued. We are using small glass beads to glue the carbon into the aluminum. It's both a chemical and mechanical bond. If we break it will be someplace else is my hunch. Trying stuff.

Bart Brejcha
Design-engine.com