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Discussion Starter #1
Anybody have any expirence with structural plastics? Would you trust a set of rearsets made out of high density plastic rather than aluminum? would it be cheaper to make them?

lets hear some thoughts.
 

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I have no experience with plastics, so this is probably just blather:

When you stand up on one footpeg to kickstart your bike, there's a lot of downward force applied where the footpeg is mounted to the frame. I think footpeg mounts made from ABS plastic or PVC plastic or even polycarbonate would just sheer off, due to that force. I suppose you could make them huge and strong enough, but they would look too big on a bike.

Pultruded fiberglass might be strong enough. "Pultruded" means that oriented-strand glass fibers and catalyzed resin are pulled into a mold, where they are left to harden. They make window frames and other contoured fiberglass parts that way.
 

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This is just a guess since I have zero experience with plastics or rearsets (yet), but I think if they can make firearms out of plastic, they can probably make rearsets. I doubt they would be cost effective though.

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A composite material, such as boron/carbon fiber in extruded plastic matrix might do it, and you could injection-mold it, but the costs of the equipment necessary, and the tooling required are considerable. It really only makes sense in very large quantities. I suspect that's one of the reasons why metal still reigns here.

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How about plastic molded around a thin but very strong metal piece for the foot peg itself? I think a good set of rear sets machined from aircraft grade aluminum would be nearly as light and probably a lot easier to come by.

Hey someone pas me the wrench........ Ahh screw it where is the torch
 

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i once saw a project that was in internal combustion engine made completely from plastics. it was in an article on the web a while ago. my plastic guy showed it to me. alot of plastic is way more expensive than alum. ti manufacturing is getting cheaper and there is a new process apparently being worked on that is supposed to make ti as cheap to produce as alum. its still going to be a mother fucker to machine though. hold your breath...imagine a ti framed sub 300lb 250 hp street legal sportbike for the going price!

jc
 

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Discussion Starter #7
alright, alright, aluminum it is then.

I just remembered from when I used to do models that the material cost was cheaper than aluminum. I figured that with the way things are going these days there would be some form of plastic or nylon that could be used as a structural bracket (like a rear set bracket) on a bike.

speaking of 250hp sportbikes, anybody see the specs on the new busa?

200hp (claimed). 485lb dry weight (figure 500 lbs wet weight).

With a 200lbs rider that is a power to weight ratio of 3.5 lbs.

This is better than any lemans racing car and puts it in a class with F1 cars and top fuel dragsters (although admittedly the top fuel dragsters still have the edge by a wide margin). This also means that we have street bikes that are very close to what a prostock bike makes now and surpasses what they were making in the 1990s.
 

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Speaking of plastics.... whatever happened to nylon sprockets? They were supposed to be the next big thing - quieter and easier on the chain but they came and went pretty quickly.....

Jim
 

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Discussion Starter #9
quote:
Speaking of plastics.... whatever happened to nylon sprockets? They were supposed to be the next big thing - quieter and easier on the chain but they came and went pretty quickly.....

Jim
Jim, you're alive!!!!!

yeah I think the advent of 135hp sport bikes and stunting pretty much killed that. If you ride your sport bike like it should be ridden then it isn't a problem, but the first burnout and stress cracks galore.
 

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plastics in internal combustion engines have been built in the ninties.And the processes are more expencive. As are track records in reliability and such that you have to throw into the mix for liability and longivity.In manufacturing.

Besides the reason we dont have plastic cars is because the steel industry still rules the roost.

Besides vinyle is final.

Im so far behind ,that I think Im in first.
 

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quote:
plastics in internal combustion engines have been built in the ninties.And the processes are more expencive. As are track records in reliability and such that you have to throw into the mix for liability and longivity.In manufacturing.

Besides the reason we dont have plastic cars is because the steel industry still rules the roost.

Besides vinyle is final.

Im so far behind ,that I think Im in first.
Ford built a version of its 2.3l 4-cyl and raced it for 1 race I think back in the 80s. Info on it is very hard to come by and I lost the webpage it was on, should bookmarked that sucker :(

1978 Yamaha XS400. Stock for now.
 

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Hey, I just wanted to throw my two cents in. I worked for a big time plastics company for a while and got to know plastic pretty well. I know that there are many compounds available that could be used, but the cost of the material alone would be much more expensive than aluminum or even Ti. Then you have look at design costs, mold costs, and the fact that almost any plastics company requires a 10,000 pound minumum run just to justify the costs associated with getting a project like this up and running. Stick with Aluminum. If it's good enough to hold beer it's good enough for me.
 
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