Pinkbike, the world's leading off-road bike community and reference, has enlisted the services of Creaform to provide suspension analysis for users and enthusiasts around the world. Their latest series of "Behind the Numbers" blog posts, contributed by engineer and cyclist Dan Roberts, is dedicated to in-depth analyses of various suspensions.
Among the abundance of technical information and product data, blog contributors were looking for new technologies to analyze short-link ATVs (such as the Santa Cruz Megatower)This was when Dan Roberts, based in Switzerland, contacted our company, which develops, produces and markets metrology instruments, such as 3D scanners and reverse-engineering software. That's when Dan Roberts, based in Switzerland, contacted our company, which develops, produces and markets metrology instruments such as 3D scanners and reverse engineering software.
Although geographical distance might have been reason enough to end the adventure between Creaform and Pinkbike, for Dan and his geeky nature, the decision was already made. The project could therefore continue, for the benefit of mountain bike enthusiasts with a taste for technique and precise data.
Below, we present the metrology project that resulted in accurate measurements and reliable data for all cycling enthusiasts.
Since the linkage defines the position of the center at all times, even the smallest changes in the pivot points of bikes with short-link geometry can have a big influence on the bike's behavior. The team sums it up this way: "Before we got our hands on Megatower, we had analyzed bikes with relatively large linkages. And our measurement accuracy was more than sufficient for these configurations.
Creaform was keen to support Dan Roberts in his goal of providing rich, accurate suspension data and figures for all enthusiasts who take cycling seriously. In the metrology industry, we offer particularly fast scanning instruments. Not only do our tools enable rapid preparation and scanning without any surface preparation, but the time needed to place the targets before the scanner can finally be operated is also very short.
As a result, the team sought out a Santa Cruz Megatower for analysis. As chance would have it, the bike store Mathieu Performance in Quebec City (a few kilometers from Creaform headquarters) had this model in stock.
The Creaform team was ready to get down to business: they went to the store in question, measured the pivot points, axes and tubes of the fork and seat, and extracted their geometries. The scanner's portability proved invaluable. Creaform was a particularly suitable partner for this mission.
The use of 3D scanning technologies for this project also enabled volumetric positioning to be accurately captured, and the solution provided an accuracy of 0.1 mm on distances from one end of the bike to the other. Little did we know at the time that this accuracy was more than sufficient for analysis purposes, and even better than the tolerances used for manufacturing in the cycling industry.
1. Rapid preparation and creation of a reference framework
Setting up the equipment for this project, as for any other, didn't require any rigid, fixed and/or cumbersome equipment: the bike was placed in front of a cardboard box on which the team applied the positioning targets.
Positioning targets are reflective stickers used to create a frame of reference to enable the 3D scanner to automatically position itself in space. They can be placed on the scanned object or within its immediate environment. In order to guarantee optimal tracking, we had to use a few additional targets.
In order to generate a mesh, the scanner had to detect at least three targets at each instant in its field of view, but given that the geometry and volume of material of a bike are generally irregular, we had to place a cardboard box in the background of the bike to place more targets.
The HandySCAN 3D has a field of view of around 30 by 35 cm, which means that the targets had to be between 5 and 15 cm apart, placed randomly. In this case, they were placed relatively close together, both on the cardboard box and the bike itself, since some components of the scanned object had complex geometries, distinct features and numerous textures.
Basically, whatever the overall complexity of the task, Creaform's portable 3D scanners make measuring fast and easy, on objects large and small, in the workshop and even in the back room of a bike store!
2. Redefining accuracy in ATV suspension digitizing
Creaform's HandySCAN 3D, used to analyze the suspension of a short-link mountain bike, achieved a local accuracy of 0.025 mm. This means that scanning the bike with the HandySCAN 3D revealed even the smallest variations between the design tolerances and the manufacturer's specifications, compared with the bike itself. In other applications, such as quality control during bicycle manufacturing, such a level of accuracy is not only enviable, but also desirable!
3. Meshing: Calculation, creation, processing
The output format for digitized surfaces is known as a mesh or mesh file. It takes its name from what virtually resembles the 3D rendering of an object: a kind of woven net or wire mesh composed of millions of small triangular surfaces. For this project, we used a triangle size of 0.35 mm to capture the details of the features we needed to extract, but decimated the mesh (i.e. we created larger triangles on the flat areas and kept the smaller triangles on the detailed areas). HandySCAN 3D can provide a blank mesh surface with triangles as small as 0.1 mm, which were used to create the bike's surfaces, however complex. Zooming in on the components can be quite revealing: the number of triangles that form the mesh varies according to the level of detail required and the area scanned. You can refer to the visual below to observe the level of detail captured by the scanner.
Live meshing is a particularly practical feature of Creaform solutions. As the user scans the actual object, the exact data captured can be viewed in the VXelements software interface. This produces an STL file for easy use in CAD software. In this way, the user can instantly visualize on a surface or feature that does not appear during the scanning process.
Logically enough, the scan file can be quite large, so it's a good idea to obtain a decimated version to speed up the overall process.
In this case, the main elements to be captured were pivot points, axles, fork tubes and seatpost. Ultimately, the data captured from the extracted points would be used to display the bike's geometry and kinematics.
It may seem like a lot of work to get a 2D sketch of the bike, but it's a very quick process and the accuracy achieved is so high that we could examine the tolerances of individual bike parts.
4. Output format and export to CAD software
To finalize the digitizing process, geometric entities, such as the pivot point, can be imported directly into the user's preferred CAD software, thanks to Creaform's proprietary VXmodel software module. It integrates seamlessly with VXelements, enabling 3D scan data to be finalized. While the CAD software comes with all the design and modeling capabilities you need, VXmodel provides the tools you need to quickly and seamlessly integrate a scan-based design process.
Features and benefits: precise, fast, versatile, portable, no surface preparation required
The "Behind the numbers" series of posts wouldn't be as reliable if the figures presented weren't as accurate. Creaform provided Dan Robert with the means (on the other side of the world!) to accurately measure data that the team was struggling to describe: short-link suspensions.
Now in possession of these figures, Dan Robert has carried out in-depth kinematic analyses of short-link bikes, to determine the real values concerning leverage ratio, anti-sag, anti-derailment, axle travel, etc.
Scanning took around 15 minutes, and the whole process, from preparation to the final 3D model, took less than an hour.
With the benefit of hindsight, we can assure readers that they can rely on the Behind The Numbers series of posts, as the contributors have gone to great lengths to ensure the accuracy of all measurements for all bikes and configurations.
In the end, this joint venture provided accurate data on short-link suspensions, to pave the way for methods of positioning pivot points more finely than had been anticipated during the design stage. In reality, they have barely scratched the surface of what can be achieved with 3D scanning in the ATV industry.
Manufacturers in all sectors, who haven't already tried it or implemented it, can benefit from 3D scanning technologies to validate concepts, inspect and compare components, and create intelligent product designs.
Pinkbike and Creaform would like to thank Santa Cruz for their openness to discussion and their efforts in the quest for accuracy and consistency. We'd also like to thank Mathieu Performance bike store in Quebec City, who opened their doors to us to play with their Santa Cruz Megatower, as part of this project. Finally, a big thank you to Dan Robert, the instigator of the Behind the Numbers article, which helps illustrate Creaform's 3D scanning technologies. A former senior bicycle engineer with Scott Sports, Dan Robert created the Garage Bike project, engineering services for the bicycle industry, based in Champéry, Switzerland.
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