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Old 06-22-2010, 04:48 PM   #169
poonbean
gottago
 
Joined: Jul 2007
Location: Orinda, CA
Oddometer: 44
Quote:
Josh69 - OK, I'll preface this by saying I'm planning on buying Motoport gear.
...

So - Motoport gear appears to work but you cannot take any note of the technical claims on their website.
That is quite helpful - you bring some clarity to Wayne's world. I'm just on my second set of CP clothing and really like it, but never quite bought into all of Wayne's descriptions. As a different kind of engineer and geologist, his descriptions did not make complete sense to me either.

Anyways - I do have a question from your discussion:

You initially say that "Steel is very stiff. If you want to transfer energy, using a lump of rigid steel to do it is a good way."

I think your comments on Wayne mix up the perspective. In this case, the test is using the moving steel to transfer kinetic energy to the armor to see how much energy is absorbed. However, when I'm moving and my kinetic energy hits sufficiently thick steel (a bridge girder comes to mind), instruments on the steel are unlikely to measure much, if any, transfer of my kinetic energy. What little kinetic energy that is absorbed occurs by subtle flexing, friction, heat, deformation, or if it is perfectly rigid, it is transfered to and absorbed by the ground at its attachments. The rest of the energy is, unfortunately, absorbed by the "weaker" item that hit it - the bike, me, and the quad4 armor. Obviously, the less energy the body is asked to absorb the better. If I were to hit a girder, clearly not enough of that energy from that impact would be abosrbed or transfered out of the impact by the girder and I and my quad4 armor would have to absorb the rest. Just like a hammer hitting the girder - the hammer bounces back and absorbs (along with the arm that swung it) much of the kinetic energy in that impact, and just a little kinetic energy is absorbed by the girder in heat or transfered to the ground.

Your steel statement seems to contradict your comment further down that says "The forces in a bad bike crash are so large that the armor needs to be reasonably stiff - or not feel soft to the touch - to absorb the impact."

So, which is it - does steel transfer or absorb?

It does seem to me that armor needs to find that balance between soft/flexible to absorb as much energy as possible while remaining somewhat stiff for durability and strong enough to spread (transfer) what it can't absorb over aa wide an area on the body as possible. All, of course, without sacrifcing comfort and good looks.

poonbean screwed with this post 06-22-2010 at 06:11 PM
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