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Old 11-02-2012, 01:03 PM   #143
geometrician
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Joined: May 2008
Location: West-By-God Virginia
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Carbon Fiber Foolery & more

Quote:
Originally Posted by It'sNotTheBike View Post
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 they offer
Cost. There's the reason. A single tail rotor blade in composite for a 5-decade old UH-1 is $12,000 currently... and there are two of them, not counting the main rotor. A good friend is an airframe maintenance supervisor for the US Army and quotes over $370,000 for a single main rotor blade- which have to be purchased in pairs as they are balanced against each other... and it gets more complex with 5-blade 'copters. Even the slightest contact damages them. As to whether they can afford it in the world of military spending- remember we had $600 toilet seats and now a $17,000 drip pan for catching hydraulic fluids in a Black Hawk helicopter


Composites have been around a long time starting before WWII with aircraft. Kawasaki in the 1970's used composite/monocoque frames (aluminum & otherwise) ending with their KR500 F1 roadracers. (Honda did too with their NR500) Some improvements we enjoy today followed the lead of many small European teams that used the talents of young engineering students who saw another way of doing things- since it hadn't been "done" yet they forged ahead to create many capable bikes/systems. Bimota, KTM, Ducati, Husqvarna, Aprilia et al have used just a handful of designers to create most of the designs we use today (including our beloved LC8). These one-off bikes were closely watched & even purchased by the motorcycle manufacturers to act as rolling laboratories, or to "own" the intellectual rights. Usually they were F2 bikes as the F1 bikes were expensive and already riding beyond the limits of tires, brakes & suspension technology and remained the factories' domain.

Composites are not the end-all, to be sure. At this time components must be carefully hand-laid-up, vacuum-compressed & autoclaved to create the finished product. Even in near-perfect production environments they have widely scattered results/rejections after testing. Most of the cost of modern aircraft are associated solely with creation of production techniques & the actual assembly line.

When damaged the layers pull apart & are fiber unions torn so they don't appear to propagate cracks but in fact that's how they are damaged- you just can't see it like other materials. When fiber-based composites are damaged (or fail for whatever reason) they are (usually, nearly) impossible to repair as they rely on the continuous structure to provide the required strength. It's brittle by nature, so one has to introduce more resin or layers to create survivability which increases weight & costs. How many CF skid plates/expansion chamber guards have I seen cracked after contact? All of 'em, many in their first "use"- and FWIW the expansion chambers gets dented anyway. Also the fibers are quite dangerous once exposed and can easily cut riding gear & skin, or fuel/vacuum lines, wiring looms, etc.

F1 drivers buckets are built to absorb/disperse energy & protect in a naturally self-reinforcing shape. Again, huge cost, one-off production. And after damage they are replaced...

As for Airbus, do you know how many governments & corporations (even economies) have stuck their necks out on this gamble to trade more sold seats per flight vs. aircraft weight? And how many years did it take with the best aerospace engineers with millennia of combined experience to get it done? KTM ain't gonna do it...

With bullet-proof vests, they are designed to disperse energy spikes at a certain rate coming from one direction to prevent penetration to the wearer. They are retired/returned to the manufacturer for examination after "use".

LC8's have "trellis frames", never heard "bird cage" used, neither had Google when I looked

Motorcycle frames must maintain wheel alignment, hold engine/etc, direct suspension energies & be able to handle reasonable crash damage over it's entire life (10-15yrs?). I've thrown 5 metal-framed bikes down the road/track at over 100mph and 3 of them were still rideable, The inertial energies involved compare to a loaded Adventure Bike at 70mph, a reasonable top speed for any motorcycle. Our engine-based sidestand mounts are an example of something that would work in a static environment but fail in a dynamic one. So, for now, metal is here to stay as the material of choice for a frame.

In the real-world of Adventure Bikes composite frames don't meet the criteria of a go-anywhere vehicle. How's a rider or mechanic in the middle of Africa gonna be able effect repairs? Or even Seattle or Los Angeles where composite assembly lines & experience abounds in the local populations? You can't weld/braze it, or even drill holes & bolt stuff up- you're concentrating energy in ways composites don't work- in a system that relies on every fiber's participation to maintain it's function. There are plenty of Inmates in OC alone that have spent many hours/days building new airboxes, inner fenders, fuel cells. fairings or even a luggage rack in carbon fiber/resin composites- it HAS potentials galore and some day it will be used on cars (already a few out there prototyping) sold to the public- but this will have more to do with the relative energies involved in smelting metals & creating/working alloys versus the MPG (or miles/amphour for electrics!) gained over the life of the vehicle.

Quote:
Originally Posted by It'sNotTheBike View Post
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 neckout 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
Agreed, other than they're hoping for unit sales of 50,000+ for a model over it's lifetime- plus $16,000 is WAY too much money!

KTM sunk millions of Euros into their 350SXF project- they thought they were getting a head-start on the "premier moto/supercross switches from 450cc to 350cc" move that didn't occur (conspiracy theories suggest the Big Four lobbied FIM/AMA/etc as per usual to keep with 450cc thus hurting KTM). They ended up with a bike that had to run against 450s as it couldn't race in 250 class. We couldn't give those things away at our dealership- everyone wanted the 450. That one move seriously fucked the company up; moreover the engine they ended up with has a limited lifespan from being designed with weight in mind (cases crack internally among others)- so you can bet they are going to be really careful in the future- hence the "bigger is better" 1190 re-purposed RC8-engined Adventure we have coming now

In the end I think it's funny people obsess so much on weight- lose weight/exercise, take a poop before you ride, carry less stuff with you, put less fuel in when riding offroad- Fabrizio Meoni was a little guy riding a taller bike than any "high" early "S" models- and he kicked ass at the Dakar. Hey, it ain't the bike, right?

Quote:
Originally Posted by jerdog53 View Post
What I guess bothers me the most it that KTM will invest in building a 375 twin for the Duke for sale in lesser world countries, dumb it down and sell volumes rather than build a midsized twin to put into a slightly modified 690 frame
A rumor and the idea of twice the parts, machining/cost/weight- it ain't gonna happen. As for "lesser-world" countries, they have more unit sales there than in all of North America, Europe & Australia combined. A 125/200 Duke single is like a Porsche in India where the Honda-based 100/125's started life on a 1960's drawing board.

Quote:
Originally Posted by crofrog View Post
stick a really really heavy flywheel on it.
that doesn't do it! You need an additional counterbalancer as per the KLR600/650 to seriously quell vibrations. All 690s buzz & shake like hell and feel busy at highway speeds which prevent some people for riding them a long time- yeah I know us guys are all hardcore but when you deal with John Q Customer that's what I hear, and that keeps them close to home not roaming the world. People have ridden Honda CB125's & even 50cc scooters across the US- but that doesn't mean I want to (or other Adventure Bike riders who average 38 yrs old so a survey says)... in the words of Chis Rock, "you can drive a car with your feet- but that doesn't make it a good idea"
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'06 KTM 950 Adv 'S'
'03 KTM 250 EXC
'87 KLR650 - <200K miles "Like the Energizer Bunny, just keeps going & going..."
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