MUST WATCH: E-Thirteen Finally Answers the Age-Old Question

[Iwan Kemp]

http://www.pinkbike.com/news/e-thirteen-finally-answers-the-age-old-question.html

 

E-thirteen, came to Eurobike 2014 with a simple science project, inspired by a hands-on display at the San Francisco Museum of Science and Industry. The experiment consists of two identical wheels of equal weight and diameter that roll down a steel track. The plastic wheels are weighted with brass cylinders. One with the cylinders positioned at the outer extreme of the wheel and a second, with the brass inserts positioned near the hubhttp://ep1.pinkbike.org/p4pb11349025/p4pb11349025.jpg

[droo]

So simple you kinda wonder why nobody thought of it sooner...

[Catatonic_Joe]

So 26ers are faster than 29ers? And I should attach weights to my hubs to accelerate faster

[Wolfie1]

Iwan i can see you posting this is not going to go down well

[Rocket-Boy]

Its not as simple as the experiment makes it out to be though.

All that proves is acceleration at the centre is faster if the weight is closer to the centre.

It doesnt take into account things like momentum which would affect how much force is required to keep the object rolling once it gets up to speed.

There is more to the whole argument than that and they would need to look at factors like friction and what the actual effect is when outside circumference is load bearing.

[Iwan Kemp]

Iwan i can see you posting this is not going to go down well

It's a chance I'm willing to take!

[Pabloesque]

So 26ers are faster than 29ers? And I should attach weights to my hubs to accelerate faster

no, its not a statement about which wheel size is faster. It is saying that a 26er can ACCELERATE faster, because a 29er has more weight distributed further from the hub than a 26er. Its pretty obvious - you can accelerate much faster on a BMX. Its horses for courses - not sure you would ride a BMX in XCM, but at the same time, you won't ride a 29er in a BMX race

[droo]

Not everything is about the size of your... wheel.

 

The point they're making is that weight saved from the circumference of the wheel makes more of a difference than weight saved at the centre.

 

There are ramifications for different sized wheels, for sure, but mainly (IMO) it's about weight distribution.

[Catatonic_Joe]

no, its not a statement about which wheel size is faster. It is saying that a 26er can ACCELERATE faster, because a 29er has more weight distributed further from the hub than a 26er. Its pretty obvious - you can accelerate much faster on a BMX. Its horses for courses - not sure you would ride a BMX in XCM, but at the same time, you won't ride a 29er in a BMX race

 

Yeah, I was just kidding. Trying to create some controversy... maybe that was a bit too honest.

 

BTW, Iwan Kemp, I see yo're also very active on mtbr, nice to see familiar 'faces' on other forums.

[Captain Fastbastard Mayhem]

Not everything is about the size of your... wheel.

 

The point they're making is that weight saved from the circumference of the wheel makes more of a difference than weight saved at the centre.

 

There are ramifications for different sized wheels, for sure, but mainly (IMO) it's about weight distribution.

 

Precisely why my Spank Subrosa & Magic Mary combo will always accelerate slower than a 9er with Crest and killer bees. Especially if I'm in the saddle...

[Pabloesque]

Its not as simple as the experiment makes it out to be though.

All that proves is acceleration at the centre is faster if the weight is closer to the centre. Not true - it proves that OVERALL acceleration is faster where weight is at the centre. The conclusion is that because 29er wheels have more weight further from the hub than 26er wheels, they cannot accelerate as fast as 26ers

It doesnt take into account things like momentum which would affect how much force is required to keep the object rolling once it gets up to speed Momentum is not relevant in an acceleration test - in the experiment, both wheels had a standing start

There is more to the whole argument than that and they would need to look at factors like friction and what the actual effect is when outside circumference is load bearing.​ friction is affected by wheel width and grip - the experiment is saying that if you make these conditions identical - i.e. take a 26er and 29er with the same width and grip, under the same load, the friction is the same, then the 26er would accelerate faster

Edited August 28, 2014 by Pabloesque

[No Hare]

(Troll post)

 

Blasphemy!!!!

[Paul Ruinaard]

http://www.pinkbike....d-question.html

 

E-thirteen, came to Eurobike 2014 with a simple science project, inspired by a hands-on display at the San Francisco Museum of Science and Industry. The experiment consists of two identical wheels of equal weight and diameter that roll down a steel track. The plastic wheels are weighted with brass cylinders. One with the cylinders positioned at the outer extreme of the wheel and a second, with the brass inserts positioned near the hubhttp://ep1.pinkbike.org/p4pb11349025/p4pb11349025.jpg

did you read the comments below where an engineer explains it in formulas. That is what matters. This demo is also out to prove that physics works. It doenst hold much relevance for wheel sizes over varying terrains...

[porqui]

I would like the input of an engineer here.

In this experiment the wheels spin around an almost centre point so really spinning

The thing about a wheel that is in contact with the ground is that the tyre is stationary when on the ground but moving at 2X the cycle speed when at the top of the wheel - rolling. It has 0 momentum at the bottom and then momentum increases to a max in 1/2 a circumference. In experiment momentum is almost constant.

How would the forces differ.

 

 

[Rocket-Boy]

I think you may have missed the point I was making. Its not really about a 26 vs 29 thing, its a test to prove that less weight at the outer edge accelerates faster.

Its not a conclusive test about any of the other variables, it only tests a statement that has been made many times in the past.

[Rocket-Boy]

I would like the input of an engineer here.

In this experiment the wheels spin around an almost centre point so really spinning

The thing about a wheel that is in contact with the ground is that the tyre is stationary when on the ground but moving at 2X the cycle speed when at the top of the wheel - rolling. It has 0 momentum at the bottom and then momentum increases to a max in 1/2 a circumference. In experiment momentum is almost constant.

How would the forces differ.

 

 

 

Take two wheels with different weights and roll them down a hill at the same time, see which gets to the bottom faster