Originally Posted by crofrog
... I'm not sure about composite frames for an off-road bike. While strong there failure mode is shitty compared to metal.
There is a lot more to it than the "failure mode is shitty". In fact, composites can have better
failure characteristics than many metals because cracks don't tend to propagate in a composite
part like they do in many metals. Many helicopter rotor blades are made of composites. Do you
think they are using those materials because they cannot afford to use metals ? How about the
structure of the largest Airbus ? Did they use composites because they weren't worried about failure ?
Or perhaps you'd like to consider the empennage of the F-18 fighter. Again, composites were used and
they could use any materials they wished. Bulletproof vests are made of composites ... etc.
Composites can be designed to deal with a LOT of abuse. It's common to see a composite mountain
bike frame these days. The "tub" in virtually all Formula 1 cars is composite and is much stronger for
its weight than it could otherwise be if it were made of metals. Drivers routinely survive crashes which
would have been fatal in the days of Mallite ( alloy sandwiched with end-grain balsa ) chassis or "birdcage"
chassis ( a KTM 950 frame is a birdcage structure ). Composites are absolutely the way forward, though as
long as motorcycles continue to sell with the old tech there is no reason for the manufacturers to change what
In any case, for bikes to be much lighter than they now are, it's going to take more changes than simply
using pressure casting instead of sand casting. A reduction in engine displacement is not going to magically
drop 50 pounds or more from the weight of a bike. Fundamental changes in how the bike is designed and built
are the things which will make this possible.
Those who don't want to wait and wish and who want a twin can emulate the work done by
Powercell with his 950 Super Enduro.
But I would like to see KTM sell a 690 Enduro with a wide-ratio gearbox and a real-world 250 mile range.
That is the bike which would come closest to being ideal for all-round adventure riding. A twin will get worse
fuel economy than an optimized single because of added reciprocating mass and friction, and will not be
as light as a single, other things ( such as materials and casting methods ) being equal. The 690 is a very
smooth engine considering it is a single, and it has more than enough power. The 690 has other issues which need
to be addressed ( all of which have been discussed on this forum ) but the smoothness and power should not be
deal-breakers for a rider who understands that a single brings benefits which are not possible with a twin.
So, "can" KTM build a significantly lighter 700-800cc twin ? Of course. Will KTM do this ?
I doubt it. They might build a twin which has 750cc displacement, but
they are not going to spend the money required to build a significantly lighter bike
because the bike would not sell in large enough numbers to justify the capital expense
required to tool up to build a significantly lighter bike. Maybe when 1,000 of us line up
and give KTM a full $16,000 deposit KTM might change its mind on whether to embark
on building this lighter bike, but that's not going to happen, so for KTM to actually
build a revolutionary light weight twin someone at KTM is going to have to stick his neck
out pretty far, with the awareness that failure could cost him his career. That's not
what a smart and rational person who is high enough in the KTM hierarchy to have the power
to make such decisions is likely to do, especially not when they are selling all the bikes
they make already.