Road Bike, Cycling Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
777 Posts
To my knowledge, Griffen is the only builder working with MMCs right now. They are not significantly different in density from the base metal, the difference is in strength. Stronger material can mean less of it used to make an equivalently strong structure, but current aluminium frames are pushing the "beer can" limit anyway, and stronger metals won't help there.

Also, the fact that the bicycle market has pretty much abandoned bonding limits the choice of metallic composites, as many can't be welded. This is what did in the Specialized MMC frames. They used an Al / AlO2 composite, and, when the tubes were welded, the AlO2 crystals migrated away from the joints, leaving just the Al base metal. The tubes were too thin, if they were made from just aluminum, so the MMC frames got a well-deserved reputation for cracking at the welds. Not a fault of the material, really, just the way it was used, but MMCs got a bad rap, and that was the end of it.

MMCs have they potential to be a fantastic material for bicycle frames, it's just that nobody's figured out the right way to do it yet.

--Shannon
 

·
Registered
Joined
·
400 Posts
Adhesive bonding to some type of lug might be the only way but then, MMC's would have tough time competing against carbon fiber. If there was a way to keep strengthening crystal structure away from the weld area then it might be possible but to do this, would require some major investment by the tubing people.
 

·
Registered
Joined
·
777 Posts
BATMAN said:
Shannon, interesting not on the welds at the joints.

Is this why Griffen has such thick and ugly welds?
The issue with the M2 MMC frames was not something that can be generalized to all metallic composites. The specific Aluminum / Aluminum Dioxide composite that Specialized's builder was using didn't react well to welding. Some metallic composites can be welded, some can't, and others can be, but only under certain conditions. Memory says that the alloy Specialized used was in that last category, and the conditions weren't met, but I might be wrong. The part about the oxide (ceramic) particles migrating away from the welds I remember clearly.

As to competition with carbon composites, properly selected MMCs used in bike frames designed around their properties have the potential to be a better choice than CF, if only because of their much greater damage resistance. But again, that's not true of all metallic composites, the range of properties is very wide.

"Magic" materials come and go. A few years back, some framebuilders experimented with an exotic, ultra-high-strength aerospace steel called Aermet. Tubes were drawn out to 0.5/0.3/0.5 mm wall thickness. Very light, very strong frames were built. The downside? The stuff is so hard that miters had to be ground with a diamond wheel. It's just too difficult to work with for a low-profit business like bicycle frames. Some of the exotic areospace stainless steels have strengths in the 400 - 500 ksi range, many times stronger than any material currently used to build bicycle frames. No one's doing it. Why? Materials cost, for one, but difficulty of manufacture is the other biggie.

MMCs may be the "next big thing" once the carbon craze dies out (it will... we've been here before), but there are some significant engineering challenges to overcome first.

--Shannon
 

·
Registered
Joined
·
79 Posts
Univega used to have MM frames using Boralyn, supposedly Soviet military stuff used on sub-based ICBMs to pierce Arctic ice. A major bike mag at the time (10 yrs ago) reviewed it and said it had the typical harsh ride of AL, but with even more responsiveness to pedal strokes. I don't remember the reviewers saying anything great about performance and ride nor did they go out of their way to sway the nike buying public to buy Boralyn bikes. Univega made their top road and MTB frames and bikes from this for several years but I've never seen one despite the big ads they bought in bike mags. They were kinda ugly, with a matte gray finish & bulging welds. These bikes came out about the same time Specialized started using MM .
 

·
Registered
Joined
·
168 Posts
Master Killer said:
Univega used to have MM frames using Boralyn, supposedly Soviet military stuff used on sub-based ICBMs to pierce Arctic ice. A major bike mag at the time (10 yrs ago) reviewed it and said it had the typical harsh ride of AL, but with even more responsiveness to pedal strokes. I don't remember the reviewers saying anything great about performance and ride nor did they go out of their way to sway the nike buying public to buy Boralyn bikes. Univega made their top road and MTB frames and bikes from this for several years but I've never seen one despite the big ads they bought in bike mags. They were kinda ugly, with a matte gray finish & bulging welds. These bikes came out about the same time Specialized started using MM .
You beat me to it. I was thinking about the old Univega Boralyn frames too. You're right, from what I remember, they were considered pretty harsh riding frames. Same goes for a hardtail Dean was making out of some MMC that went by a different name. I don't recall the name or whether it was proprietary or the same stuff called by a different name, but Dean long ago stopped using it in favor of ti. Clark Kent was rumored to have a sub 2lb MMC road bike in the works in the mid-90s before they disappeared off the face of the Earth.

I'm not a metallurgist, but from what I understand MMCs merely are an alloy to aluminum that increases its strength, thereby allowing a manufacturer to use less of it. It's basic limitation is that it doesn't really change the riding qualities of aluminum all that much, which is a less desirable frame building material than carbon because it's inherently harsh ride..

I don't think MMCs are poised to make a comeback and become the "next big thing" for this reason. Isn't scandium alloy considered a MMC? It's alloyed to aluminum, allows for a lighter frame than regular aluminum alloy, maybe a better ride, but it hasn't really caught on. You now find scandium on middle to upper range bikes....pricier than aluminum frames, but not top of the line carbon.
 

·
Registered
Joined
·
3,115 Posts
I have Boralyn and Boralite hardtails, and while they're not pretty, they ride well. I wouldn't say they're any more harsh than "conventional" Al bikes I've ridden, but, to be fair, somebody my size can smooth out the ride of almost anything. I haven't noticed any signs of impending doom, such as cracks, weakening of the joints, etc. I do get some strange looks on the trails, though, when people realize what they're seeing....
 

·
Registered
Joined
·
777 Posts
Scandium isn't an MMC, it's an alloy of aluminum. There isn't much scandium in the alloy, but it increases the strength of the tubing enough to allow for thinner walls. As to ride qualities, that's much more about tube geometry, especially diameter, that it is about material. Most current aluminum bikes are simply too stiff to ride well, IMHO. At those dimensions, any metal would produce a bone-jarring ride. If you doubt me, ride a Vitus.

Not all MMCs are aluminum based. I think that all of the ones used to make bicycles have been, but the spectrum of metallic composites is much wider than that. The only thing that defines an MMC is the combination of a base metal and a non-metallic particulate, usually some form of ceramic. Various base metals and ceramics have been used, depending on the application. These are engineered materials, typically designed for specific uses. So far as I know, no MMCs have been specifically designed for making bicycle frames. Most of these materials have been designed for the aerospace industry, as that's where the engineering expertise and all of the money are.

Regarding the "next big thing," metals have some significant advantages over non-metals for making things like bicycle frames. Ease of manufacture being first among them. It's much easier to set up a production line if you're welding, rather than molding. QA's quite a bit easier, too. In theory, at least, metallic composites can exceed the strength / weight ratio of carbon composites, while still allowing welding of the tubes. The right material for this is out there, but I don't know if anyone's really looking for it right now. The hype surrounding the early MMC frames, and the generally poor results of those attempts put a serious dent in the acceptance of the material itself. The cost of these materials doesn't help either. Shaving off 5 - 10% from the weight of frames that are already around 2 pounds won't justify doubling the cost to build each frame. The added reliability that could be acheived hasn't been a priority for most of the industry anyway, and I don't expect that to change any time soon.

--Shannon
 
1 - 10 of 10 Posts
Top