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Home > Forum > Triathlon Forum > Carbon Cranks: Getting unexpected stiffness results to our testing.

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Carbon Cranks: Getting unexpected stiffness results to our testing.
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Tom Demerly
Mar 15, 03 8:08
Post #1 of 14 (3778 views)
We've enlisted the help of automotive prototype designer, test apparatus designer and builder and test engineer John Laidlaw of Ford Motor Company. John designs test apparatus for, among other things, automotive drivetrain components. Then he leads the team in the fabrication of the apparatus and the testing. John built (on his own time) a test apparatus to measure the stiffness of cranks. We are in the process of weighing and testing the stiffness of Shimano Dura-Ace, FSA Carbon Pro Team, Shimano Ultegra, Truvativ, FSA Gossamer and other cranks. The results will be posted on our website (www.bikesportmichigan.com) next week, but I can tell you, as the testing progresses now- the things the manufacturers are representing to us in their sales literature is very different from the test results we are getting- even with basic information such as weight. I should point out that John is also an expereinced time trial cyclist. This is turning out to be a very interesting test.
Tom Demerly
The Tri Shop.com
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [Tom Demerly] [ In reply to ]
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tri_db
Mar 15, 03 8:22
Post #2 of 14 (3766 views)
This will be excellent information to have! I look forward to the results. Thanks for putting this together!

Regards,

Daniel.
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [tri_db] [ In reply to ]
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Tom Demerly
Mar 15, 03 8:28
Post #3 of 14 (3762 views)
We're excited about this test. Clearly, the test protocols are good but not 100% entirely perfect. We will discuss their strengths and weaknesses in the test article. I think this will be a better insight than just taking the sales literature at face value. Already the claims of weight are coming out differently than we anticipated. We are excited to be able to tell our customers something more substantial than just the sales hype. We bought each of the test sample cranks so we know they are what is actually shipping to consumers.
Tom Demerly
The Tri Shop.com
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [Tom Demerly] [ In reply to ]
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taku
Mar 15, 03 10:53
Post #4 of 14 (3717 views)
I am excited to read this article... it also has me thinking about the importance of independant testing of equipment. kind of a consumer reports for biking... again the problem we always run in to would be who would pay for it? especially becuase who would the information benefit? the consumer? the manufacturer?

with the consumer it also brings up the question about what to measure... Is performance the only thing that matters? how would you measure comfort?



very interesting stuff... I think that there is a need for more information, it will be interesting to see if a consumer movement like this could start and if the companies would respond.
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [Tom Demerly] [ In reply to ]
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ajfranke
Mar 15, 03 11:00
Post #5 of 14 (3710 views)
Tom, just how important is crank stiffness to your run of the mill 200 to 300 watt kind of triathlete or time trialist? My perception of DA cranks is that they are infinitely stiff for the sorts of forces I put on it. I can see how TDF riders and sprinters would consider this to be a big deal, but I never understood why this would be an important parameter to most of us.

Also, no one has ever convinced me that even the hottest carbon crank is significantly lighter than DA cranks. I look forward to your article.
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [ajfranke] [ In reply to ]
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Tom Demerly
Mar 15, 03 11:10
Post #6 of 14 (3703 views)
Good question... I have no idea. The thing that has bothered me is I can't find any crank manufacturer to tell me "We have the second lightest, second stiffest crank available". They all claim to be the "best". We are making an attempt to offer a different perspective on that. We'll see how it works.
Tom Demerly
The Tri Shop.com
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Manufacturer weight and stiffness claims. [Tom Demerly] [ In reply to ]
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Frank Day
Mar 15, 03 12:21
Post #7 of 14 (3657 views)
PowerCranks claims to be the heaviest cranks out there and make no claims for stiffness, although it would be hard to imagine another crank that is stiffer. :-)

I am working on a carbon racing crank and don't expect it to be the lightest (until I can make the clutch out of paper mache) or to make any stiffness claims on it either.

The problem with dealing with (and measuring) crank stiffness alone, IMHO, is a stiff crank on a flexible frame may be less efficient than a "flexible" crank on a stiff frame. One has to look at the total package.
--------------
Frank,
An original Ironman and the Inventor of PowerCranks
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Re: Manufacturer weight and stiffness claims. [Frank Day] [ In reply to ]
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Tom Demerly
Mar 15, 03 12:29
Post #8 of 14 (3651 views)
When John was designing the test fixture he took that into account, and actually built a test fixture that approximates some degree of frame flex (from an aluminum frame) and a realistic amount of force applied by a pedal spindle in the test apparatus. It seems like a fairly "real world" test from this perspective. I welcome your comments on the testing when it hits our website next week.
Tom Demerly
The Tri Shop.com
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [Tom Demerly] [ In reply to ]
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2WheelsGood
Mar 15, 03 12:38
Post #9 of 14 (3646 views)
Is this testing cranks only, or their respective BB's also? I would love to see how the new XTR cranks/bottom bracket compare to anything else on the market. Obviously those are mountain bike cranks, but hey, if you've got the equipment to test, why stop at road cranks. :)
Last edited by: 2WheelsGood: Mar 15, 03 12:39
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [2WheelsGood] [ In reply to ]
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Tom Demerly
Mar 15, 03 13:20
Post #10 of 14 (3632 views)
XTR? What is that? Mountain bikes? Do they still make those? I think I saw one a few months ago in a shop that was going out of business..... Seriously. Nope, we don't the mountain bike thing too much anymore. There is just no business there. We sell about 1 mountain bike every 2-3 weeks. One of the hard things about this test is when to cut it short....
Tom Demerly
The Tri Shop.com
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [Tom Demerly] [ In reply to ]
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canwi
Mar 15, 03 16:04
Post #11 of 14 (3574 views)
You obviously don't live in british columbia where mt. biking dominates over road and they'd probably say the same thing about dura ace:) Seriously though I'd love to see those results when they are available
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [Tom Demerly] [ In reply to ]
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JustCurious
Mar 15, 03 18:15
Post #12 of 14 (3529 views)
In Reply To:
XTR? What is that? Mountain bikes? Do they still make those? I think I saw one a few months ago in a shop that was going out of business..... Seriously. Nope, we don't the mountain bike thing too much anymore. There is just no business there. We sell about 1 mountain bike every 2-3 weeks. One of the hard things about this test is when to cut it short....
From what I'm hearing, the next generation D/A is going to be pretty much like the new XTR. Adding XTR cranks/bb to the mix might be valuable.
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [ajfranke] [ In reply to ]
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cerveloguy
Mar 15, 03 19:53
Post #13 of 14 (3497 views)
"Tom, just how important is crank stiffness to your run of the mill 200 to 300 watt kind of triathlete or time trialist? "

Thankyou for asking the question before I did.
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Re: Carbon Cranks: Getting unexpected stiffness results to our testing. [canwi] [ In reply to ]
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Shawn.Skene
Mar 16, 03 19:33
Post #14 of 14 (3346 views)
I am a little surprised that MT biking was so quickly slammed... or looked down upon Canwi. (Hi Sean) Might be a good theme for a new thread... Supplementing tri bike training with some MT biking. I know it is great break from the road... plus it is a ton of fun. In addition it helps to develop your bike handling skills that no matter how much time you put on the road you never obtain. It has made me a much better cyclist overall. I know you do a fair amount MT biking in season and off season Canwi; hasn't hurt your tri biking performance.

Shawn1
Shawn Skene
Last edited by: Shawn_1: Mar 16, 03 19:35
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