Weight Weenies
* FAQ    * Search    * Trending Topics
* Login   * Register
HOME Listings Blog NEW Galleries NEW FAQ Contact About Impressum
It is currently Tue Dec 12, 2017 5:44 am

All times are UTC+01:00

Post new topic  Reply to topic  [ 35 posts ]  Go to page Previous 1 2 3
Author Message
PostPosted: Thu Apr 17, 2014 1:16 am 

Joined: Tue Feb 07, 2012 7:17 pm
Posts: 556
desperado, you are coming off the regular ti ones. I am interested in getting a pair of these but all this alu failure talk has me thinking of sticking with ti.

Casati Vola SLi and Dolan Preffisio
viewtopic.php?f=10&t=108931" onclick="window.open(this.href);return false;"
btompkins0112 wrote:
It has the H2 geo......one step racier than a hybrid bike

Posted: Thu Apr 17, 2014 1:16 am 

PostPosted: Thu Apr 17, 2014 10:06 am 

Joined: Wed Mar 28, 2007 12:49 pm
Posts: 1604
Location: Near Horgen, Switzerland
It doesn't take much common sense to work out that an aluminium pedal splindle is not a free lunch:
1) Nobody else in the industry currently offers an aluminium spindle
2) It was tried before and the pedals frequently broke
3) The material used here is a standard engineering aluminium alloy. It does not offer magical new properties which increase young's modulus, yield strength and fatigue limits
4) A quick look around the bicycle shows how big aluminium components need to be in order to resist pedalling loads. While the load cases are somewhat different, cranks and bb30 bottom bracket spindles are reliable and are much larger than pedal spindles.

That said, with a proper Engineering approach, it could be that an aluminium spindle might work in this application. Some thoughts:
1) The pedal uses a plain bearing, so the spindle can be somewhat larger diameter than a pedal using a ball or roller bearing. Since stress in the surface of the spindle decreases with the cube of shaft diameter, a small increase in diameter may enable a decent life
2) Use of a plain bearing means that the shaft is subject to wear. Imagine the case where a piece of quartz somehow enters the bearing area. This will notch the shaft and add a stress concentrations which may negate the benefits of (1).
3) The geometry of the shaft could be improved over the steel or titanium part. A quick look at their website shows the steel shaft is a constant diameter cylinder with a few flanges to locate the crank and pedal body. However, an aluminium shaft could be conical with a larger diameter at the crank. This would move the point of maximum bending stress in the shaft from the crank to the edge of the pedal body.
4) Static stress calculations (such as those mentioned by the manufacturer) are not a complete approach to analyse shaft stresses. For example ASTM standards suggest safety factors of 2-3 where rotating shafts experience heavy shock loading.

So in summary it might work, but only if the shaft diameter and geometry are changed to enable use of the different material. A straight material swap will not offer the same reliability.

PostPosted: Thu Apr 17, 2014 4:52 pm 

Joined: Wed Apr 08, 2009 7:49 pm
Posts: 55
As I said, I am definitely not a metallurgist as I said. All I know is that the pedal feels every bit as stiff as the ti. I won't say stiffer because I never felt the ti flex at all either. (I am currently about 190 pounds). I will take your comments and send them to Aerolite and see if I can get them to register for Weight Weenies and weigh in. I am told that the switch to the aerospace aluminum alloy with the special coating was recommended by an aerospace metallurgist, perhaps he can shed some light on his thinking. I believe the hard black coating on the simply protects the alloy spindle from gouging and provides a super slick relatively friction-free surface for the turcite sleeve to rotate over. The timetrial model should be out now and be slightly shorter (and lighter) and even less prone to stress. Their test showed that the ti pedal bent at 3,000 pounds and the aerospace alloy at 6,000....but they did not break. I still suspect that to be the case if fatigue is really a factor.

PostPosted: Thu Apr 17, 2014 5:11 pm 
in the industry
User avatar

Joined: Sun Dec 16, 2007 9:33 pm
Posts: 713
Location: Luxembourg / Sweden
7068-T6511 would be the only commercially available alloy that is stronger than 7075. I guess you could call it a rocketsurgery alloy.
https://online.kaiseraluminum.com/depot ... ochure.pdf


PostPosted: Thu Apr 17, 2014 5:41 pm 
User avatar

Joined: Fri Apr 04, 2008 2:49 am
Posts: 1489
Location: Europe
There are other aluminum alloys stronger than 7075-T6. As it happens, 7068 is extremely expensive and not that much stronger. 6Al/4V titanium is a cheaper and stronger option. Not my choice if I were making a reliable pedal axle.

“I always find it amazing that a material can actually sell a product when it’s really the engineering that creates and dictates how well that material will behave or perform.” — Chuck Teixeira

Wert Cycling on Facebook

Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 35 posts ]  Go to page Previous 1 2 3

   Similar Topics   Author   Replies   Views   Last post 
There are no new unread posts for this topic. Leather top vs. Carbon Fiber saddles (SMP Forma vs. Carbon Lite)

in Road




Thu Aug 31, 2017 11:52 am

kgt View the latest post

All times are UTC+01:00

Who is online

Users browsing this forum: clipsed, fezi, Google Adsense [Bot], toronto-rider and 28 guests

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited