Dual Density Insert Design
Not as Straight Forward as it Seems!
After creating the Rimpact ORIGINAL we went back to the drawing board to design a no compromises Insert. This became the Rimpact PRO and later used on the CX and EDH inserts as well.
We theorized that upping the density of the material used would yield increased protection in the form of greater energy dissipation. We expected to see these results in a linear fashion but when using our test jig to destroy many wheels the data showed something unexpected.
What we found was an increase in density in the materials we tested did not correlate to increased protection past a certain point as seen by rim damage, tyre failure and decreased comfort out on the trail. The data showed us a point in which materials effectively became too dense and began to transfer force applied to it through to the surface below - your tyre bead, rim, suspension and hands.
Combination of Strengths
After learning this we realised that we needed a fresh approach. The particular foam we used for Rimpact ORIGINAL already performed very well for it's weight but an increase in density negatively affected it's trail feel.
We looked at other materials that would provide a better sharp edge impact absorption but all were much heavier than the Rimpact foam already used. These also significantly effected ease of fitting due to their stiffness. We were trying to find a single material with all of the following properties:
-
More impact absorption
-
Equal or better vibration damping
-
Low weight so ride quality isn't negatively affected
-
Malleable enough to allow for easy installation
-
Affordable
-
Durable
After trying many different materials we eventually realized that one single density of foam wasn't ever going to meet all of our requirements but combining two could hit these goals. This is what sparked the idea for the Dual Density design of Rimpact PRO.
Solution
We looked at other industries to see how similar problems were solved and came across an Energy Sensitive material that remains supple whilst under minor forces like general riding and installation but increases it's impact performance under heavier loads.
Once energy is applied, (think sharp rock impact), the material stiffens and dissipated force across both its surface and the surface of the Rimpact ORIGINAL foam below.
Placing the Pro Layer on the top meant that the Original foam below continued to act as a vibration damper, the insert remained easy to install and the slow speed impacts did not force the wheel to deflect off of the desired line. When the impact force was increased the Pro later would stiffen and protect the foam and rim below. The Original foam would act as the initial supple spring before bottoming out and the Pro layer acting as the bump stop akin to a variable rate spring.
As low weight was a top priority, using the two materials in conjunction allowed for a significantly lighter design of just ~150 grams for a 27.5" wheel whilst out performing Inserts that were 100+ grams heavier.
We were also able to retained the superior vibration damping that Rimpact ORIGINAL provides as denser, single materials failed to absorb the high frequency trail vibrations that ORIGINAL currently eliminates.
From there we developed the design into the CX and the EDH inserts to best suit their respective disciplines.