Extron

You may try PA66 Glass filled, it has higher strength.

Could you please elaborate a little more? I googled PA 66, and the spec sheets i found showed that the tensile strength and flexural modulus was less that the Extron. I also found a company making PA 66 but under the trademark Ultramid. Problem is, there are about 30 different types. If i just specify that i want them made from PA 66 then its going to end being a lucky dip, and god knows what i will end up with. Thanks alot.

In my experience the sprockets on a derailleur type of bicycle would not tolerate the peak stresses and off axis loading if they were made of a fiber reinforced engineering plastic. As a test, see if any of the leading road bike parts makers use anything like this.

A cart is far less stressful, in my opinion.

searches

http://www.google.ca/search?hl=en&safe=off&biw=1275&bih=669&q=%22bicycle%22+%2B%22plastic+sprocket%22&btnG=Search&aq=f&aqi=&aql=&oq=

http://www.alibaba.com/showroom/bicycle-sprocket-wheel.html

Thanks for the links aurizon. I have searched alibaba high and low and have had no luck there, but i have found a a good quality moulding OS facility that will ba able to do them for me, i just need to decide on a material composition to use/try.

The sprocket would not be for a derailleur type of bicycle. They are for a BMX which is a single speed. I am not looking at getting the hub gear done in a composite material as there would be to much stress i would think.

The front sprocket on a BMX ranges in size between 23 and 49 teeth, but i would only want to be making 26T and 29T versions.

I know the smallest race cart sprocket is about 72 teeth or something and they obviously have alot smaller pitch than a BMX sprocket, so the load is spread over a greater area, but some of those carts run 125cc engines and they can handle the side torsional load ok without buckling and disintergrating. They actually run better than an aluminium sprockets (quiter, smoother, less wear) if im to believe people that i have spoken to that are into carts. The BMX sprocket cross section would be at least 2X that of a race cart sprocket, and as long as i can come up with a decent design, i still think its worth attempting to put the time in to see if it is a feasible option.

As for other manufacturers not making them? I have no idea why not. Maybe they have tried and failed, or maybe im the first to come up with the idea (highly unlikely i know). But as long as i havent seen one, heard of one, and havent had someone tell me specifically it doesnt work through some proof, im dead keen to give this a go.

This was done in the early eighty's with limited success, sprocket deflection at the gate start allowed the chain to jump off with unpleasant results to the rider. I have raced BMX and the loading of the drive system is extremely high at the gate start, chrome-moly freewheels would sometimes split during the start of the race but never during the race. Good luck!

Good point. And GA. It's the peak load that you need to worry about, not the wear. I'd be willing to bet that they would work fine in every way, if you didn't have those spikes in load at the start.