Ciamillo Gravitas Cranks Update – Construction, Engineering Details & Giveaway!

“But, all we have to do is slightly increase the wall thickness and/or diameter of the tubes and we can make this the stiffest crank on the market without adding any weight”

Wait a minute. So they could have made it better crank at the same weight but they didn’t?

Thanks to all of the comments, I think I’m going to buy a pair just to annoy the crap out of every one I see on the road.

@Gillis When is stiffer not better?

The question should be, all other things being equal (e.g. weight)….

When is stiffer worse for a crank arm?

These will be bad@ss on my ultra light carbon racing recumbent!!!!!!

I would really love to know how and in what direction they’re measure stiffness. Just saying that it is as stiff or stiffer doesn’t mean much unless you back it up at an independent lab. Stiffer torsionally, laterally, vertically, stiffer spider, stiffer chainrings, …. what?! Pretty much the same as just saying that it is better in my books.

The idea of interlocking rods and bolts is novel. For all I know it makes a stiffer crank arm. Considering system stiffness equals the stiffness of the least stiff part, however, I am highly suspect of the 2mm thick aluminum spider. That said, I suspect these cranks will make somebody’s dentist very happy. The mechanic charged with getting rid of the creak in said dentist’s bike, not so much.

@Psi It is a basic theorem in physics. Do you also want a study on oxygen allowing combustion to occur?

To explain in terms that relate to hopefully familiar concepts, twisting is a basic principle of how a torsion bar suspension operates in cars. In the case of cars hysteresis (damping) is achieved through use of …dampers/shock absorbers, in case of bikes hysteresis is achieved through the flesh of your body. There is no nonsensical “energy return” as advocated by some confused bike companies.

Then if this is not sufficient, think of force/energy needed to twist something. Nothing solid twists on its own, it requires input of energy thus you ARE spending your energy on twisting something, in this case a crank set. The fact that it untwists on its own once you cease applying force does not help you recover the energy that you spent in twisting it.

Twisting is not a finite equation unless catastrophic failure/plastic deformation occurs, thus the more you push the more you twist and the more energy you waste on twisting the crank instead of moving forward.

If even this does not help, think of twisting/flexing of anything as a time loss while overcoming inertia. As you are attempting to accelerate you are overcoming inertia, if the stiffness of the system you are trying to accelerate is below the force required to overcome inertia, you will be wasting your time as your system (crankset, wheels, frame) will be twisting around the torque axis, instead of moving forward.

Let me know if you’d like more examples and I’ll try to think of some.

Actually, mythbuster, you haven’t proven anything. Therein lies the rub: there is no study the quantifies what sort of losses can be expected. More to the point, there is absolutely nothing that shows that increases in stiffness beyond a given point are measurable in a lab or provide a measurable performance difference. I would challenge anyone to show where the stiffness in a crank cost someone a race.

“Stiffness” is thrown around by the industry as if stiffness means everything, and it is also swallowed greedily by customers seduced by the magic of stiffness. I prefer data that shows increased crank stiffness correlates with a measurable increase in performance. I prefer data that shows that increased frame stiffness correlates with an increase in performance. Yeah, I have got that whole healthy skepticism thing that us scientists have going on.

Oh, as a physics guy I can tell you there is no theorem in physics which states that increased stiffness, no matter what, is always better. I can give examples if you need some. Let me know.

@Psi it is good to be skeptical, but observe that I did not give you hypotheses, but examples. There is nothing to be skeptical about in the examples that I gave you.

As to whether system stiffness increases the performance of a pedal driven vehicle, of course it does. How much, no idea. Not having data does not mean that something does not exist. It just means that it has not been quantified.

Regarding examples where stiffness is not always better when it comes to power transmission, or control of force vectors, I’d love to see them, given the boundaries explained below:

The only boundaries placed on absolute stiffness are cost constraints, weight constraints, material performance limitations, dimensional constraints, from the engineering world – packaging constraints, and from consumer land “will they buy it?” constraint. You will find that the industry thus mainly talks about stiffness. It is simpler, cheaper and more profitable that way.

…where angels fear to tread. These arguments are all linear and singular. ‘Better’ is not a formula. That a stiffer crank transfers energy more effectively is not in doubt. That a stiffer crank is ‘better’ is.

Firstly, it just needs to be stiffer than our power output potential for deflection of the item. If the strongest rider at peak puts out 100nm of force and the cranks will only deflect at 120nm then there is no benefit to making them withstand 150nm (fictitious example alert). Stiffer in this instance would be tough to describe as ‘better’.

Secondly, stiffer can come at the cost of more material, which means more weight. Sometimes the loss of energy in minor deflection is worth the energy saving in propelling a lighter vehicle.

Thirdly, stiffer can come at the cost of engineering which can drive costs up. To some people a cost prohibitive item is not ‘better’.

Lastly stiffer can transmit road shocks to the determent of the engine (you) causing less efficiency. One just has to look at the trend away from building the stiffest frame that was prevalent 7-8 years ago. Tom Boonen at the Paris-Roubaiux would disagree with a blanket stiffer is better argument.

Too often it seems that we can’t tell the difference between ‘ that bike is ugly’ and ‘I think that bike is ugly’.

@Psi – they’re not my ideas, they’re available in most engineering text books. Stress-strain curves for various substances don’t start at zero. Further, very few substances exhibit linear increases, most ramp up pretty steeply until you approach yield point making the stress from a riders legs all but negligible until a certain point.

The fact that stiffer cranks transfer energy more effectively is irrefutable. That it matters, that it’s ‘better’ is not.

Apologies if this is direct but it is becoming inane. My first post actually supported your side of the fence – stiffness is not the holy grail, it’s just a factor. Now, however, in defense of an imagined attack were getting into exactly what I didn’t want a part of . Your wager is exactly symptomatic of what you are accusing others; fuzzy and non-empirical.

Cranks are a system, arms, spider, chain rings, BB, shell etc. Are we isolating just the arms?. Further how much force is applied by the ‘under all riders’? 0.005nm? Are you saying any crank no matter what thickness or substance flex / even one made from 1112 CR steel or Ni-Cr-Mo ? Etc. ad nauseam

Anyway, I don’t want to argue; you win.

@Psi. No, the “armchair engineers” who are anything but, are roused by Ciamillo’s claim that the cranks are as stiff as Dura-Ace. Had they kept quiet about stiffness claims it is very likely that the comments would not focus on discussing stiffness.

The rest of the discourse which you clearly have trouble following is to do with whether stiffness matters, and why it matters. The design choices are also discussed with a lot of valid engineering questions being raised regarding Ciamillo’s stated low weight objectives as well.

You are just about the only one who is forcing to put a number on HOW MUCH stiffness matters. These are two separate questions. To simplify:

Does stiffness matter?
How much does stiffness matter?

…see, different questions.

@Loki, you are confusing a stress-strain curve with a force-displacement curve. A force-displacement curve does star from zero and moves immediately away from zero with the smallest amount of force no matter how stiff the structure is. This has nothing to do with yielding of the material if you stay in the elastic region of the stress strain curve (yes, all materials behave differently and have different curves).

This force-displacement curve is the curve of stiffness and not the stress-strain curve as you have noted until you yield the material. We’re not talking about yielding here, we’re talking about stiffness.

When talking about stiffness there are also different kinds as I have noted earlier. Personally I don’t believe that the stiffest structure is the most efficient but your comparison using Tom Boonen is based upon fatigue during a race and likely not drivetrain efficiency.

No frigging way wold I trust my life and limbs to such a showoff contraption. Every single frigging time people want to cut cost and corners and lug simple composite tubes, it fails.

Do you know what happens when crank fails under you? If you ride anything harder than a bikepath, you do not really want to find out. This is garbage design.

I would not recommended anyone to purchase anything from Ted Ciamillo! (Caw-designs)
I purchased a crankset on 19th January which I received 7 weeks later. It has got several problems with it’s painting and it has several scratches as well. It wasn’t even the color I asked for.
The product went broken on it’s very firs use!
Since that I have received several promises from Ted, but even until today (11.18.2013) neither have I received a new product nor got the pice I paid for the product back. (Despite the fact he promised it several times) On the other hand I send the crooked product back to him.
The warranty is a simple lie! Don’t be fooled by him!