Greetings all. The time has come to post some info on my efforts, although a lot of this build diary may be days or weeks after the fact.
Firstly a big thank you to contributors on this forum. I have to admit I haven't read all 83 pages of THE BIG THREAD that started all of this (about half of it anyway). I have been greatly inspired by numerous contributors such as Miles, recumpence, Erth64net, liveforphysics, scottclarke, Jason, john tetz. I think my build will end up most closely resembling Erth64net's build.
In this build I will be quoting costs in Aussie dollars (that's about US$0.65c at the moment), and metric measurements.
The first photo shows my previous e-bike, which I forgot to lock up in the yard at home one day and it unfortunately disappeared. The main downsides were not enough power and way too heavy - 20kg for bike plus another 12kg for hub motor and SLAs.
A year later, it was time to get a new bike, purchased 20-Jan-09. I did have motorising in mind when I bought it, although the plan wasn't clear. I wanted a mountain bike for its strength more than off-road capability, plus disc brakes for good stopping power. I have a commute to work of 6 km, mostly downhill, which would mean a hard ride home. I haven't ridden a bike to work for a couple of years now, hopefully that will change soon.
Where I live, it's not uncommon to have temperatures of 40 deg C in summer, and the coldest winter mornings are about 7 deg C (no snow!), so motor and ESC cooling will be an issue.
By "Medium" power I mean something a little more than Australia's 200W legal limit (...is that motor running???), but less than the 3+ kW builds (expensive and SCARY
My first plan was for a step up from my previous bike's 24V hub motor to a xlyte-408 or similar hub motor. I was looking at running it on 48V LiFePOs, which would probably have cost me around AU$1200 including batteries. I also looked at sy-clone kits, but decided I didn't want to mess with the cranks. After discovering the ES group, I have now decided to build something for similar price (less would be good) and power (approx 900W) but lighter and smaller.
Second photo shows new bike with a mock-up to see where things can fit.