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

Ciamillo Gravitas carbon fiber alloy crankset details

We’ve posted a ton on these recently, and I started this as a mere update to the post earlier this week. But, the more I spoke with Ted, the more info came out and, well, here we are with lots of great details on the construction of his Gravitas cranks.

First off, they’re shipping. The first few units have mailed to some of his long-standing customers, and more will trickle out each week until they’re up to full speed. Orders placed now will likely ship in five or six weeks. Second, given the overriding theme among the comments, I asked directly about the stiffness of the design and why use carbon tubes. Here’s Ted’s response:

“We’re shooting for a sub-400g crankset that’s as stiff as or stiffer than Dura-Ace. The tubes are made by a company that specializes in hi-mod carbon tubes. We started this process by reverse engineering other cranks on the market, and this three-tube design can be made stiffer. The engineer designed these tubes to be 1.5x as stiff as the Rotor cranks, and the end result is slightly less than 1.5x because of the alloy parts interface. 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. I wanted to have the lightest component in that arena without compromise.”

Read on to see how it all comes together, and get a promo code to enter to win a set of these and his brakes!

Ciamillo Gravitas carbon fiber alloy crankset details

The Gravitas crankset's pins can be anodized or powdercoated in a variety of custom colors.

A two part process connects the carbon tubes and alloy ends. First, they’re bonded together. The bonding agent fills in any gaps, providing a solid connection. Then holes are bored through both the alloy parts and carbon tubes, and pins (blue in the top pic) are threaded together inside the holes. It’s called PTS for Pinned Tube System. These both lock the carbon tubes in place and prevent them from rotating.

The other side of the story is customization. This design lets them very easily make custom lengths and Q-factors without needing a ton of size-specific tooling. To get the exact length a rider needs/wants, they simply cut the tubes accordingly. Depending on the frame’s BB width, they have a range of spindle widths they can use, too, with spacers taking up any slack. A narrower 68mm BB shell would give you a wider range of customization than an 86mm one, of course.

They can also change the spider’s mounting width to tweak the spacing between chainrings to accommodate different rings in both 10- and 11-speed. The spider is interchangeable, letting you run standard or compact with the same arms.

Several spindle options will be offered to accommodate all modern bottom bracket sizes, BB30 first. A 24mm BSA spindle should be available in a couple weeks, which is likely to be a bit heavier because the spindle’s wall thickness will have to increase.

WANNA WIN ONE?

They’ll be giving away a crankset/Gravitas SL brakeset combo on January 22nd, details at CAW-Designs.com. Enter “Ciao123″ in the message field and you’ll have a shot at one of 200 t-shirts, too.

Comments

Topmounter - 12/21/12 - 5:17pm

So are they saying that they will replace the tubes with stiffer tubes if there just happened to be an issue with stiffness?

Mark W. - 12/21/12 - 6:52pm

“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?

Gillis - 12/21/12 - 7:09pm

Mark W, you’re equating “stiffer” as being better, which is not always the case. If it’s as he says, stiffer than Dura-Ace, which is plenty stiff imo, there is no reason to make it stiffer (unless your real name is Chris Hoy).

tom - 12/21/12 - 8:10pm

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.

Moab Bob - 12/21/12 - 8:51pm

No guys, he didn’t say he WILL make them stiffer, he said all he had to do to make them stiffer was increase the wall thickness, which he did already. Not sure how that sounded like it was still being figured out, it’s done and it’s shipping. Ted’s goal was met, to make the stiffest sub-400 gram crank. At this point, he is tweaking color combinations and custom lengths, which will be able to accommodate people who have one leg slightly longer or shorter than the other; something nobody else can do. I ordered mine in the black/blue combo seen in the pictures; should be here by Feb 1, 2013, with the matching Gravitas brakes. I still have to decide if I want to spend the extra $ to get the brakes blue-tinted to go with the cranks, another thing only Ciamillo does. I’ll post a picture of them when they arrive; prepare to change your underwear.

Mythbuster - 12/21/12 - 9:20pm

@Gillis When is stiffer not better?

Psi Squared - 12/21/12 - 9:40pm

Hey, Mythbuster, show me a study that details the energy losses in a crankset and that concludes that stiffer no matter what is better, then you’ll be right. Your question would be better posed if it asked, “Will I actually benefit from and perceive the difference in a stiffer crank?”

Topmounter - 12/21/12 - 11:43pm

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

When is stiffer worse for a crank arm?

G... - 12/22/12 - 12:30am

I’ve entered to win. When I do, I’ll tell you ALL how they perform, as I’ll actually have a set in my hands, rather than having a banal slapfest over pictures.

Fredrick - 12/22/12 - 2:14am

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

Cedric - 12/22/12 - 4:27am

That’s just bad engineering,
1) round tubes make me think that the only deflection they’ve tried to improve is planar to the chaindrive plane. It’s not, cranks twist probably as much as they bend.
2) why are they using 3 tube? the one in the middle does nothing if not add weight.

solution: use 1 oval tube, cheaper, lighter, more aero, stiffer, looks sleeker.

Bog - 12/22/12 - 3:05pm

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.

Loyd flanders - 12/22/12 - 4:33pm

Doesn’t matter how stiff they are, they aren’t the nicest cranks on the market. I think magic motorcycle nailed it for custom cranks, I actually liked the look of the old camillio cranks as well. Are these As light as
Morati ti cranks??

CE - 12/22/12 - 4:40pm

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.

Mindless - 12/22/12 - 4:45pm

No way it is torsionally as stiff.

Mythbuster - 12/22/12 - 9:36pm

@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.

Sam - 12/22/12 - 9:51pm

It doesn’t matter if they’re stiffer because you can’t mount Dura Ace 9000 chainrings on ‘em. These cranks look just plain dangerous. I’d rather not leave my safety to the strength of an adhesive–in shear no less. I’ll give ‘em a couple years on the market at best.

Psi Squared - 12/23/12 - 2:55am

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.

JB - 12/23/12 - 5:02am

Ugh – that middle carbon bar is just pointless extra weight. It’s right on the neutral axis of bending and dead center on the axis of torsion. All it really helps is lateral stiffness, which should be the least of your concerns on a crank.

Why did they leave that in – or rather, put it back in after the fact? If you wanted light weight, no compromises, then look towards that middle tube. Hell, even a cursory FEA analysis would show the incredibly low stresses in that member, a pretty good hint it ain’t doing jack except adding weight.

Oh well, guess it doesn’t really matter, the stress risers from the square-edge carbon-alloy interface (and right on a discontinuity in the stiffness will take these things out of circulation pretty quickly anyway. Cyclic high cycle loading and stress risers don’t mix, folks.

Mythbuster - 12/23/12 - 6:50am

@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.

Dans - 12/23/12 - 10:59am

@Psi you are an idiot.

Loki - 12/24/12 - 10:53am

…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 Squared - 12/24/12 - 11:09am

I’m not sure, Loki, about you ideas about something starting to flex only at a certain point. Take a look at a stress-strain curve. Things that don’t flex (deform) are brittle and break. Generally that’s not a good thing for….uhm….anything except chalk.

The idea that stiff is always better is still wrong in that it just doesn’t matter how stiff something is after a certain point. Certainly on a bike, if you can’t resolve a difference in crank stiffness on a power meter or on a finish line timer, it doesn’t matter. As stated earlier and also by many more people, there is no study that correlates stiffness of cranks with performance benefits or with a given magnitude of performance benefits. I’d be willing to put money on the statement that someone racing on a Shimano 7700 crankset would be at no resolvable performance disadvantage to someone else riding the stiffest crank possible.

Loki - 12/24/12 - 12:27pm

@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.

Psi Squared - 12/24/12 - 1:20pm

You’ll have to point out where I stated that stiffer cranks did not transfer energy more efficiently, because I did’t state that. I did state that stiffer is not necessarily better and that stiffer does not necessarily correlate with better cycling performance.

I’m willing to bet you whatever sum of money you’d like that all cranks flex to some degree under all riders. It’s a fair bet, and given your position, we can stipulate that any flex at all, no matter how small, means you lose the bet. There’s an optical instrument I used that has a resolution of 25 picometers. That should be sufficient for determining how much cranks flex. How much money do you want to wager?

Loki - 12/24/12 - 3:26pm

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 Squared - 12/24/12 - 7:14pm

Loki, apologies for misinterpreting your first post. It’s not a discussion to be won but one that isn’t seen enough in these stiffness driven marketing days. Comments here and elsewhere quite often sneer at or ridicule the marketing speak a lot of companies dole out, but the commenters then in another instant will respond with comments of the same kind, in this case about stiffness, as if there is some stated value for what is acceptable stiffness. The commenters just repeat the stiffness song sung by the marketeers, just in different words.

While the Ciamillo design might be suboptimal in terms of maximizing stiffness, it doesn’t really matter so long as they perform as the owner needs. All the armchair engineering that happens doesn’t address that point at all.

mythbuster - 12/24/12 - 10:21pm

@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.

patrik - 12/24/12 - 11:21pm

I’m not an engineer, but I am a fashion designer. And I can say with certainty that, aside from a banana seat, those are the ugliest things to adorn a bicycle in quite a long time.

Of course, they’re probably going to sell a boatload of them. Like Jones Bicycles, which are also one of the ugliest bicycle products ever to be produced, these things are acquired merely for the trailhead conversation starters that they are. You might as well weld a windmill onto a Studebaker if you want to start mindless chitchat instead of actually riding when you roll up to the trailhead.

I did some armchair analysis and figured out that people with boutique bikes ride about 1 minute for every 63 minutes they spend telling anyone within earshot of their latest purchase at the trailhead. You see them slowly unloading their bikes from their cars, waiting until someone else is nearby. Then, as soon as someone comes up, “Hey, is that a Jones (or other boutique, one-off meant only to start conversations)?” then within 0.4 seconds they’re, “Yes it is, my name is Briarpatch, I drink lots of IPAs, my bike is awesome, isn’t it? It’s the best bike (until I buy a triangle-wheele bike at next year’s Patchouli Handbuilt Bearing Festival in Guerneville).”

Bog - 12/25/12 - 12:37am

@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.

JB - 12/25/12 - 1:19am

The argument here is a bit ridiculous – and people are talking past each other. The term that’s missing, right now, is hysteresis – or, more specifically, the energy loss due to hysteresis. One side is arguing that a stiffer crank means lower hysteresis, and therefore is more efficient. The other is arguing that it may not be the case. Here’s the answer – it’s much more material and design dependent than just a straight up “stiffer is better” answer.

There’s also a hell of a lot of misconceptions here about stress-strain curves and force-displacement curves. In a finished product, stress-strain curves aren’t what you’re looking for (they are, however, if you’re evaluating components of that product) – force-displacement curves are. But that’s also assuming stiffness (F/disp) is what you’re trying to optimize around. For some applications, it is. For some, it isn’t. For most applications, there’s a number over which increasing stiffness yields minimal performance gains, and optimization efforts are better spent elsewhere. Unless you’re building high precision measurement devices or extremely accurate mechatronics, this number is often surprisingly low.

The marketing, here – “stiffer than Dura-Ace” – is also pretty misleading. In what direction is it stiffer – laterally, vertically, torsion about the length of the crank arm? Under what loading conditions – axial, normal to the length of the arm but applied in plane, or (as it should be) at a specified distance away from the pedal thread to replicate rider weight? And what part of the system is stiffer – just the crank clamped down to a fixture, or the whole system including spider and chainrings?

I will say, as I’ve said before – the mechanical design of this crank is suspect at best, especially for something that is supposed to be optimized for light weight. For those of you who want to be armchair engineers, here’s a hint: any time you see sharp inside corners in areas of high stress (say, right near the BB interface), it’s not a great design. Doubly so when you have a large change in cross section, material, or geometry. A cursory glance at the design shows you have all three here – not a good start.

Mindless - 12/25/12 - 4:18am

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.

MattK - 12/26/12 - 9:03pm

Personally I liked the original design they showed on weightweenies. The original was sleeker and more aero (however the drag of a crank is not going to amount to much). Nonetheless, I would be glad to try these out if I won…just need the brakes to get the anodized red accent treatment to match everything else on my bike.

D.Krisz - 11/18/13 - 3:21pm

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!

Hadden 67 - 03/06/14 - 11:04am

Not very aerodynamic.

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