Monday, January 21, 2008

4 IsoTruss Open Lattice Structure for Bicycle Frames




I believe I have jumped late on this topic but its not that I haven't been following the news. For those clueless about what I'm talking about, I was referring to the Arantix Delta 7 mountain bike shown at Interbike last year, that sent out some sticker shocks.

Many bloggers have already commented on the XC bicycle, what it is, how its made and models available. I'll make your search less troublesome. Read this and this for quality material. James at Bicycle Design again has a good report on the development stages of the bicycle.



The Isotruss Open Lattice Structure (courtesy Triple Crankset)






Spiderwebs?

The "Arantix" Company name (supposedly) partly derives from the scientific name for Orb weaver spiders, called Araneidae. Or it might be the Argiope aurantia, commonly known as the Black and Yellow Garden Spider or Writing Spider.

But whichever spider it is, I wonder if this was just a ploy by the company to identify with consumers or just something creative to name their bike. If its the latter, it might not be very accurate and I'm sure they might already know this (or they're ignorant of nature)

I feel this way because the fundamental isotruss structure for the frame (although it looks similar to a web from a distance) really has quite a different geometry to the natural engineer's web (the spider, ofcourse he's a cunning engineer!).

An Isotruss structure is a 3-dimensional tubular circumferentially and longitudinally periodic grid structure. There are longitudinal members running along the length of the structure, and helical members spiraling around the longitudinal members. The former carry the axial and bending loads while the latter members has several interesting benefits including resisting torsional loads and improving the compressive strength of the overall structure by reducing the buckling length of the longitudinal members. [See "Local and Global Buckling of Lightweight Isotruss Structures", Jensen et.al, Department of Civil and Environmental, Engineering Brigham Young University, UT]

Isotruss Structures Inc based in Utah holds exclusive license to this technology. Tyler Evans, a student researcher applied the technology to a bicycle project at school and some Composites builders were deeply interested in taking that to the market.




A spider web is so much different if you look from a structural standpoint. To me, it looks very two dimensional. Moreover, the web starts out with a bridge thread, and then anchor threads formed from a typical Y structure made of a loose thread and the initial bridge. Then it forms nonsticky radius threads for it to walk on, and then starting at the center, it forms auxiliary reference spiral threads outwards. Finally, sticky spiral threads are spun inwards towards the center using the reference spiral spun earlier.


The point I'm trying to make here is, Isotruss and spider webs are fundamentally different. There's no point in calling the Arantix bike a "spider bike" from a technical standpoint.

I may be wrong but if any of you are experts, please correct my observation.


How Good?

I like the structural technology and innovation. It has a very good market in the infrastructure business, like buildings and electric poles where strength to weight ratio and construction setups matter. The general fact is that this technology involves lesser material, offering material savings and good strength characteristics [Composites World].

But lets avoid all the hype and talk and get to the point. We're talking about a bicycle. Ride stability and quality are very subjective so dumping all that out of the equation, how much stiffer and lighter can a frame made with isotruss be, compared to a top of the line monocoque or two piece composite bicycle frame?? Just for kicks, please compare a Cervelo SLC-sl or a Colnago Extreme Power to to an Isotruss bicycle frame. I'd like to see that margin. Some specific finite element analysis and real world test results would be great to see.
Other things to note are fairly easy to see. Many folks see the obvious incompatibility of an opentruss design in offroad racing, particularly of the chance for the tubes to collect dirt and grime, tree branches and what not. A famous cycling blogger calls the design "Cheese Grater" while a comment on the same from someone named Graeme reports the following :

The down tube is perfect for collecting small rocks. As such, it will make a great sampling device for the geologist on the move. “Can’t be bothered stopping to collect samples? No problem: let the Delta 7 sample collection/transport system handle it for you.” The rattle of trapped gravel will also keep stray deer aware of your passage through the woods.

Apart from those issues, in the world of tear drop shaped cross sections and other low profile designs, how will the bike live up to aerodynamics? All those little trusses, I imagine, will churn up the air. What about a water bottle cage mount? Etc etc etc....

Costs, and A Road Bike in 2009?

Word is out that a lightweight road bike involving the same technology will pop up around 2009. When the XC mountain bike was shown at Interbike last year, and shortly released thereafter, the price on it was a staggering 7000 dollars for the frame, and upto 11,000 dollars for the entire setup.

It sends funny pains in my trousers, especially around the wallet area.

The fact is that a viable manufacturing technique was not devised. The frames were handwoven and a total of 300 man hours was taken per frame. By todays industry standards, thats a lot. So the price reflects the cost of licensing the technology, cost of production, and other margins for profit. Even today, the company only has the resources to make 200 units per year as reflected on its website. Its costly for them and for consumers!

A way to bring down the price is to go for technological solutions to manufacture the frame. Automation quickly comes to mind. While the capital costs can be huge, the resulting reduction in manpower, wastage, mass production and fast time to market will all provide a handsome return on investment in the long run. I heard that recently, Professor Jensen, who was originally responsible for the Isotruss design and research, brought out a plan for automated production of the grid structures. What is encouraging is that his idea was chosen as one of the 25 semi finalists in Modern Marvels 2007 Invent Now Challenge (a part of History channel programming)

How this automated process is done, and how that will be put to use to mass produce the Arantix bicycle frames have yet to be seen.

The other critical factor is demand for these bikes. My guess is that maybe not a lot of people will be interested in something like this. Costs aside, they won't really understand how the design aids the bike, not a lot will want to see an open structure for a frame and personally, it looks something out of a set for the showcase display. We are told the company put some sort of transparent sheath on the structure at Interbike last year, but is that what we really want? Performance is no more just everything today. Looks and design matter a lot. Its like buying a car, or a computer. Some years back, we saw something similar from Calfee, called Spider Bike but it is no isotruss. The bike may have been structurally a sound idea, but by golly, the thing looks like a horror! Its easy to bring something new out in the market, but its the success of marketing the idea and producing a positive change in the industry that will spell fortitude for anyone in the area of cycling.

And ofcourse, unless pros start riding isotrusses in the Tour de france or the Paris Roubaix or even at the domestic circuit, I doubt the bike will get a lot of money making attention. How else in todays competitive industry can you stand at par with competitors?

Its simple in concept. Bring the costs down, design a sweet looking frame, test its deflection, fatigue properties, take it to a wind tunnel and ramp up the air to 30 mph and see what comes out, kick in some quality for the production and distribution processes, and get lots of air time at the races. ;)

How the Arantix manages the above will depend a lot on the smartness and strategies of the company. Meanwhile I just want to be somewhat optimistic about the design, if not snobbish. The fact is that some folks have plenty of money and will buy anything that meets their eye.

UPDATE (July 2008) - I'd like to correct one factual error in this post, as pointed out by a reader. The license for IsoTruss products is now held by Advanced Composite Solutions (ACS) since one year ago, a Payson, Utah company unrelated to IsoTruss Structures Inc. (ISI). See http://acs-companies.com/index.htm.

IsoTruss Structures Inc. no longer has license to build any IsoTruss product or use the trademark/tradename. The same people have changed their name or created a new business entity known as Composite Tower Solutions, producing meteorological towers only that look much like an IsoTruss. (It is unknown at this time whether there is patent infringement)

4 comments:

  1. And the good news is those folks with the money to buy will be getting more for their money than just an innovative design... they'll also have a handy cheese grater while out on the trail. Just watch your thighs while riding!

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  2. Johnny Sprocket2:01 AM

    And.. you won't have to shave your legs again. This thing will just catch and rip the hairs right outta your legs as you pedal !

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  3. Anonymous6:00 PM

    I beg to differ with the notion that a spider web and the isotruss structure are fundamentally different. From a purely geometric stand point, (disk vs. cyinder) this may be true, but both of the structures gain their strength from a nodular design based on a helix pattern. From a structural stand point, the different elements serve the same purpose. The capture spiral (while fundamentally used to "capture" insects that would otherwise pass through the radii) provides resistance to torsion (in the same plane as the web, mind you) and the radii provide resistance to bending. Although inherently different in geometry, a transformation from the plane of the spiders web to the cylinder of the isotruss reveals that there are many structural similarities.

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  4. I was hoping for a more in-depth discussion of the engineering of the isotruss rather than simply a discussion of why the word 'spider' is an inappropriate moniker.

    I am curious if it genuinely is stronger. Surely if it is, a light sheath material could be applied quite easily, either transparent, opaque or translucent to some degree. If it is stronger, then surely it can be built lighter... Then the aerodynamics could be addressed.

    Regarding the aerodynamics, I am feeling that the tests might also have been looking at the tubing as an aerofoil shape with the wind perpendicular to the tubing rather than in-line with the tubing as occurs on a bicycle. In that case, the aerodynamic considerations are MUCH different. Aerodynamics of a bicycle are primarily directional, so angle of attack is critical for gathering correct data.

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