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What does Alto rim brake carbon wheel test tell us?

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What does Alto rim brake carbon wheel test tell us?

Old 12-19-17, 02:20 AM
  #51  
redlude97
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Originally Posted by chaadster View Post
That was not the point of the test. Would have doing so made it a better test? Maybe, but thatís a different test. It was a bad test for a variety of reasons, but not because of uncontrolled variables.
What was the point then? Why not just heat them uniformly until failure and report that value for each wheel? Their test doesnt prove anything of value because it doesnt even attempt to simulate anything real world.
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Old 12-19-17, 03:06 AM
  #52  
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Originally Posted by redlude97 View Post
What was the point then? Why not just heat them uniformly until failure and report that value for each wheel? Their test doesnt prove anything of value because it doesnt even attempt to simulate anything real world.
Thatís a fine critique by me. It was not a good test because it didnít relate to real world, not because of uncontrolled variables.
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Old 12-19-17, 08:06 AM
  #53  
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Originally Posted by Dean V View Post
They didn't say the motor was drawing 1200w.
Just that it was a 1200w motor.
Yes, they did. It was the crux of their experiment. Energy in = energy out. Energy in all equal. Therefore energy to brake track all equal. Sweeting posted about it on various forums.
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Old 12-19-17, 08:08 AM
  #54  
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It would have been a good test if they had accurately measured power in, or controlled it to be actually constant.

Sweeting posted that the reason it was so hard was because if they did "real world" conditions, none of the rims would have failed and that would be boring. Which I agree is true.
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Old 12-19-17, 08:45 AM
  #55  
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Originally Posted by Jiggle View Post
It would have been a good test if they had accurately measured power in, or controlled it to be actually constant.

Sweeting posted that the reason it was so hard was because if they did "real world" conditions, none of the rims would have failed and that would be boring. Which I agree is true.
That raises a couple of question.

1. If none of the rims would fail under real world conditions, why make this video?
2. Did they think this video wasn't boring?
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Old 12-19-17, 09:12 AM
  #56  
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Originally Posted by chaadster View Post
Thatís a fine critique by me. It was not a good test because it didnít relate to real world, not because of uncontrolled variables.
Unequal braking work is an uncontrolled variable by definition. It can't be the output because they didnt measure it
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Old 12-19-17, 09:14 AM
  #57  
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Originally Posted by Jiggle View Post
Yes, they did. It was the crux of their experiment. Energy in = energy out. Energy in all equal. Therefore energy to brake track all equal. Sweeting posted about it on various forums.
Their math doesn't add up based on the speeds between the tests
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Old 12-19-17, 01:06 PM
  #58  
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Originally Posted by Jiggle View Post
Yes, they did. It was the crux of their experiment. Energy in = energy out. Energy in all equal. Therefore energy to brake track all equal. Sweeting posted about it on various forums.
If the motor was drawing a constant 1200w why did the wheel speed vary by a maximum of 1mph (5%)?
Even with different wheels and different coefficients of friction of the braking surface?
Even when the pads lose their effectiveness and rim temps dropped significantly wheel speed hardly changed?
No way was that braking system absorbing a constant 1200w.
They are either flat out lying or somehow got their measuring wrong.
Regardless measuring force/torque at the caliper would of been a much better way of getting a power reading than working off the drive motor.
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Old 12-19-17, 02:17 PM
  #59  
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Riders don't apply n pounds of pressure. The apply enough pressure to slow and stop in a given distance. Bad test.
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Old 12-19-17, 02:36 PM
  #60  
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Originally Posted by Dean V View Post
If the motor was drawing a constant 1200w why did the wheel speed vary by a maximum of 1mph (5%)?
Even with different wheels and different coefficients of friction of the braking surface?
Even when the pads lose their effectiveness and rim temps dropped significantly wheel speed hardly changed?
No way was that braking system absorbing a constant 1200w.
They are either flat out lying or somehow got their measuring wrong.
Regardless measuring force/torque at the caliper would of been a much better way of getting a power reading than working off the drive motor.

I too have a very hard time believing in this particular claim. Im betting they wasnt measuring it at all. It was a 1200w motor, imo. This, imo, is the biggest knock on the test and Alto should really make a rebuttal if they actually ran at 1200w measured.
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Old 12-19-17, 04:56 PM
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Originally Posted by redlude97 View Post
Their math doesn't add up based on the speeds between the tests
Please try to follow the conversation.
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Old 12-19-17, 05:03 PM
  #62  
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Originally Posted by Jiggle View Post
Please try to follow the conversation.
Nothing in this conversation provides an answer one way or another as to whether that is actually true.
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Old 12-21-17, 01:41 PM
  #63  
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Interesting & not overly critical commentary:

Rockets to Sprockets - Rocket Science Applied to Bike Racing by Chris Uberti

Also further down is good explanation of why humid air has less resistance than dry air.
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Old 12-29-17, 08:35 AM
  #64  
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Hey guys, thanks for the great dialogue regarding our test! I'd like to jump in to answer a few questions and offer my two cents on why we did what we did:

As far as the test's realism goes, that is somewhat irrelevant. We wanted to create a study on resin and composite heat transfer properties, nothing more and nothing less. This is why we had to use one type of brake pad for every rim, as opposed to brand specific pads. If we purchased a cheap rim from ebay that comes with cork pads, it may run for 10 minutes on this test. The Enve may run for 8 minutes with Enve pads. What could you then conclude regarding the composite structures? Does the ebay rim have better heat transfer capabilities than Enve? It's impossible to tell, as there would be too many variables.

Also regarding the realism of the test: This is an accelerated destruction test, which is very common in every engineering industry. I'm sure that you read my example that was given by the marine engineer, regarding corrosion resistance of bolts and how they test for it. They simply place the bolts in cups of salt water. Nobody is arguing that the bolts on a boat will be submerged underwater for eternity. But you can use the results to say "the bolt that prevented oxidation longest in the cup of salt water will prevent oxidation longest while on the boat." It's easier to perform that test than to spray the bolts with salt water for 10 minutes every day for a year, and the results will be the same. That's the point of an accelerated destruction test -- the rims that have the greatest resistance to heat fatigue will show the greatest durability to heat fatigue over many years of use. As long as the results are directly proportional and can be extrapolated, that is good reason to perform the test.

Keep in mind that Alto offers unlimited rider weight, a 5 year warranty, and the allowable use of any carbon brake pad. We are the only brand in the world to offer this combination, and it means that we have to test to very extreme scenarios. If a 140kg rider decides to descend Mt. Ventoux and only use his rear brake, we have to ensure that he is safe. That calculation would look something like this: For a 140kg rider descending a 12% grade at 50km/hr: Fb (brake force) = Fg (net gravitational force) = (m)(g)sin(theta) at constant speed. For a 12% gradient (7 degrees) and 140kg rider, this is 167.38 N. At 50km/hr, Power = Fv = (167.38N)(13.89 m/s) = 2324.9 Watts (1162.5 watts per rim). This does not take wind resistance into account, but if you consider any factor of safety then you can see why survival at 1200W is necessary for us at Alto.

Some of you noticed that the Alto wheel begins to speed up throughout both tests (phase 1 and 2). This is due to pad glazing, which occurs after the pad reaches high temperatures for a sustained period of time. It is a property of the pad and will occur on every rim given enough time. You can see it beginning on the Zipp and Enve tests, for example. Also consider that the Phase 2 Alto test had the rim running slower (19.3mph) than any rim in the test, and therefore with more friction force. However, it still ran for 20min at lower temperatures due to the improved conductivity of the resin and its ability to act efficiently as a heat sink. Also keep in mind that the average adult has a grip strength of 100 pounds. So these minor differences in braking power can be measured in the lab, but wouldn't be noticeable to any rider out on the road. Our customers tend to prefer Alto's braking power simply because there is no pulsation from overheating and therefore the deceleration feels much more consistent. But remember that, because we didn't use brand specific pads, braking power is not a proper/accurate takeaway from this test. Some rims would do much better or much worse with their own pads when it comes to stopping power, and a different protocol would be required to test for that.

A few of our competitors gave us credit for creating a resin with such excellent heat transfer properties, but figured that it would make the rim very brittle in impact. We didn't want to simply tell people that this wasn't the case, we wanted to show them. That's more our style, obviously. So we recently conducted an impact test that you can see on our facebook page (I can't post a link here because it won't let me until I have 10 posts, haha).

I don't frequent the forums a ton, but I do want to answer any other questions that you guys may have. Please feel free to reach out to us through the contact page of the Alto website, and we'll get back to you straight away!

Thank you!
Bobby
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Old 12-29-17, 08:52 AM
  #65  
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Thanks @BobbySweeting for adding your viewpoints to the thread!

Here’s your impact test vid:

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