I’ve cracked three frames in the past year, a steel one at the seat stay/chain stay and two aluminium ones at the seat tube.
I’ve recently bought a second hand scandium frame (a Kona Big Unit 29er, since you ask)
I was told today that scandium frames are biased far more towards light weight than durability.
This isn’t looking good, is it ?
Should I sell it again while it’s still in one piece and get something else ?
If so, what ?

A tractor?

My .243 SL frame. You aint gonna break that!

Isn’t a scandium frame basically aluminium with a small amount of scandium as an alloying component? Is there much difference in ride between it and a reg Al frame?

I’m sure the material properties of alloys can be very sensitive to small changes in composition – just wondering what the real world difference is in the ride.

you really do trailguest to the power of sic

Isn’t a scandium frame basically aluminium with a small amount of scandium as an alloying component? Is there much difference in ride between it and a reg Al frame?

Yup, it’s just an element used for alloying with Aluminium. Tiny quantities are used to increase the strength, so less material can be used, to create a lighter frame. It is expensive though…

I was under the impression it could used to be lighter than most aluminium alloys and cheaper than carbon (though perhaps not as light)
Whether it is cheaper not having the layup/mold per frame design/size costs of using carbon fibre etc I don’t know, but kona for one use it in some of their full suspension models
Perhaps unusually for the size Kona is as a bike company they do seem to offer a ot of frame sizes
The cadabra/abra cadabra full suss (the 4/6″ish magic link one – only 2 models) is available in: 14″, 16″, 17″, 18″, 19″, 20″ and 22″. Who else offers 7 frame sizes? On a high ish end framed full build full suss bike? Its not like kona are known for selling loads of frames only, at least not in the UK?
The frame size specific layup/molding costs for carbon would be huge for kona I’d guess?

EDIT: They also offer the scandium 2+2 (50/100mm magic link, just 2 models again) in 6 sizes, and the scandium 100mm Hei Hei (1 model) in another 6 sizes

lightweight aluminium isn’t it……..not sure theres a point to it.

Sounds like you need to weld together some scaffolding though.

scandium makes the crystal formation in the welds small so the bond is stronger meaning you can use less material for the same strength. So basically you end up with thinner tubes making a lighter more supple frame (behaves much like titanium) depending on the tube profile and wall thickness.

A propper light weight scandium frame for xc is brilliant. Not something you’d ever want to crash in the peak district though as the super thin tube walls would be horribly mangled.

Metallic scandium is much more rare and expensive than Ti though hence why only small volumes are used in alloys.

The russians love the stuff as it’s used in migs and nose cones of nuclear missiles

tazzy- you are such a geek!

cheers pop those “easy hills” tomorrow just got bigger 😉

My magic new bike will help me out i’m sure (fingers crossed)

Scandium can degrade. Well my kcnc stem did, crumbled into dust. 😯

Doubt that was the scandium, the amount in the alloy is tiny – you don’t need much. Look at the composition of normal steel and stainless to see the profound effect of alloying metals.

Tazzy, I read that wikipedia article too. 😉
It’s kind of niche owning a frame made out of scandium when there’s only 10kg of it being produced worldwide per year, although “made out of” may not be strictly accurate when it’s alloyed with aluminium at 0.1% to 0.5%.

So, to summarise with my layman’s knowledge.
An aluminium/scandium alloy frame will be less weakened by welding than any other aluminium alloy frame.
As the welds are the weakest point of any frame, this allows the manufacturers to use thinner walled tubes.
So, a scandium frame is more prone to dents, but less prone to weld failures.
Does that sound about right ?

Aren’t aluminium frame tubes butted though ?
So scandium would just reduce the amount of butting required at the weld areas, leaving the rest of the tube the same thickness.

Or is it just that, all other things being equal, a scandium frame will have stronger welds ?

So, a scandium frame is more prone to dents, but less prone to weld failures.

If they use less material, they’re probably aiming for “equally prone to weld failures”?

If they used the same amount, you could say they were stronger. But they don’t. They use less?

My CX is Scandium it’s kinda scary seeing how the tubing moves when you press it with your finger

I remember, from when I were lad, the 1998 Kona catalogue entry for their scandium-alloy framed bike (Kula Deluxe…?) mentioning the Soviet missile connection – in there they said it was so the missiles could be fired from submarines from below and through the Arctic ice.

So I guess if it’s on the nose of the missile, that’s the point of scandium [poker face]

What about those Salsa FS frames? I noticed the cheapish El Kaboings on CRC yesterday. They look interesting but mostly a little terrifying. Flexing Scandium seatstays instead of an extra pivot around the dropout. Still, Salsa offered 5yr guarentees on them before discontinuing them (which is what makes me suspicious). Can’t find any reports of them breaking though.

dont worry kona scandium is very good, been abusing mine for years now so durability seems good but they are certainly lighter than any aluminium bike i’ve had.
my alu xtc has a massive ding in the chain stay but still rides fine but if i did than on the scandium kona i think i’d bin it to be safe as the walls are much thinner.
its probably not the best choice if rocky terrain is your thing or if your a heavy weight

…I’m loving my KCNC Wing Stem – Scandium is my new favourite material

MTG- I might of had something to do with that entry in sillipedia 😉

There are a whole variety of different types of aluminium alloys: usually developed to provide greater ultimate tensile strength (UTS), corrosion resistance etc .
There are a whole variety of reasons why things break, but it is not always a lack of UTS; yield strength is important as well as fracture toughness and resistance to stress corrosion cracking must also be considered.

Put Ashby Fracture toughness chart into google, yahoo etc
http://books.google.co.uk/books?id=Og2C4bCDSX8C&pg=PA172&lpg=PA172&dq=ashby+fracture+toughness+chart&source=bl&ots=Z6QZkPXqU3&sig=Oiw7WrIYzdN0cGIW3a_u-ypcx4E&hl=en#v=onepage&q&f=false

Page 173 onwards .
“All the [aluminium] alloys have a higher strength and lower toughness than pure aluminium.”

Page 181
“Toughness is the resistance of a material to the propagation of a crack. Tough materials are forgiving: they tolerate the presence of cracks, they absorb impact without shattering and, if overloaded, they yield rather than fracture. The dominance of steel as a structural material derives from its unbeatable combination of low cost, high stiffness and strength, and high toughness.”

My SCandium Dos Niner doesn’t seem to have had any problems yet and I’m not exactly skinny at 15.5 stone. The most creaking I get from it is the bloody seatpost/saddle

They have not necessarily used scandium ally alloy to make a lighter frame – if the tube profiles remained similar to whatever 7005 (or whatever) frame they were basing it on, it could be stronger.

I like ‘scandium frames’ – very light, but also very cheap, becuase everyone who wants an XC race frame now wants carbon.

“What is the point of scandium ?”

To sell more bikes. It’s just one way of bike manufacturers saying their bike is better than others so buy ours.

Specialized bleet on about their top end bikes being scandium but they are certainly no lighter than other top end ally bikes and do not ride magically differently which the marketing will have you beleive.

I don’t think there is a point to scandium. I think it just exists.

MidlandsTrailquestsGraham,

You tend to break a lot of stuff, no? 😆

Yes, without making any claims I can’t back up, I think it would be fair to say that it’s rare to find anyone heavier than me riding further and faster.
If any manufacturers are looking for a test rider, I’m available. If I can’t break it or wear it out, your product’s a good ‘un.

Thanks for all the other replies, I feel a bit reassured now.