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Old 09-01-2012, 08:24 AM   #776
theantipaul
Reforming Neandertal
 
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Joined: Nov 2008
Location: Niwot
Oddometer: 1,119
Quote:
Originally Posted by jesusgatos View Post
But if you're trying to protect riders (tileman), first thing I'd want to do is reorient the supporting members so they'd would be more likely to give on impact (from the top down). Think that kind of redesign would be a much bigger improvement than simply switching materials.
Design is almost always a compromise of priorites, I haven't come up with an elegant solution for keeping everything simple, small, light, strong and tight to the bars, survivable, easily replacable and completely safe for rider and gear. But the beauty of this thread for me is sharing the info and building on it.

Quote:
Originally Posted by 640 Armageddon View Post
Mechanically speaking, nobody said that HDPE has higher Young's Modulus than Aluminium, load to weight ratio etc... But you have you always have to ask yourself what you need in any given design. The sentence ''nobody has done it before'' or ''they are not using this material for this type of design'' proves nothing to me and I am an Engineer... Let alone if you are not one and you are just a member who reads these two sentences
Quote:
Originally Posted by Gany View Post
Nice work Paul. What thickness HDPE did you end up running with? Thick enough, too thick, rigid enough?
This was my thought exactlly, this application does not demand a higher Young's, my aluminum side plates are 3/16" thick, I did make them out of 1/8" to try, they were too flimsy in my opinion, my concern was impacts as well as vibration and fatique. The HDPE side plates are 1/4" and the lowers are 3/16". The design inherently supports verticle loads, the concerns of vibration and fatique go away with HDPE, to the extent that the feet that attach the side plates to the lower triple might be totally unnecessary. On the aluminum versions the feet are only to mitigate vibration, the loads are taken by the plate sandwiched between the lower handlebar clamps and the upper triple.

I had a design that lent itself to testing this concept easily in such a way that it appealed to me. It actually works for me and I'll be leaving it on the bike till something I see as better comes along. It's not perfect, tweaking here and there is what testing is all about, but I think it has enough promise at this time to continue down this road. This was prompted by the thoughts from this thread! I would have not come up with it, let's keep it going.
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