If you want Di2 on your bike, but you don’t have an extra few thousand dollars burning a hole in your pocket, Computer Engineer Nabil Tewolde has a perfect solution for you. His DIY electronic shifting system is, for the most part, made from parts found at his local hardware store, electronics shop, and hobby shop. Sure it could use a bit of refinement from an aesthetic standpoint, but Nabil points out that this electronic derailleur was part of a larger project to build the ultimate bicycle computer, which you canread about on his blog.
The old song goes "the best things in life are free".. and the same goes for bikes.
I have had two bikes which I found in the dumpster (rubbish bin here in Australia). With some time and elbow grease, and sometimes a little bit of money you can restore a bike which was destined for the dump into something that is fast and fun to ride around.
This instructible shows you how to restore a dumpster bike – in this case a 10-speed road/touring bike. These bikes are commonly thrown out, can be converted into a single speed or easily renovated into a working bike.
I have concentrated mainly on providing the resources and hints, rather than the in-depth detail for each section of the bike. The reason for this is that no two bikes are the same and if I go into too much detail for one part (eg. the headset).