Hello there - Nice to see there's a framebuilding forum now! This site keeps growing!
I've been perusing with interest and have some ideas to run by people if anyone has a moment to look at what I'm thinking about. I currently ride a 70's vintage folding Raleigh 20 to and from work daily, about an 8 mile round trip. I love the folder but actually hardly ever need to fold it having space at work and home to store it without collapsing.
I do however love the 20" 406 wheels and nimble steering / handling this affords (as well as the cute looks) and have an idea (well actually some pretty worked out plans) to make a small-wheeled city bike that fits in a space somewhere between the three points of road bike/ bmx bike/ commuter hybrid.
Bikes that fit this description seem quite popular in Japan but none are brands that seem to be marketed in Europe or the US. Seeing a fabulous custom minibike on the Fixed Gear Gallery recently, and m that Dahon have a non-folding bike [called the Hammerhead] out for 2006 has spurred my ideas, though I don't massively care for the design that Dahon have chosen as it looks top-heavy and cranky with it's curved tubes. I wanted my frame to be reasonably low in the stepover (less steel = less weight) and have a more elegant geometry than the bikes I have seen.
I want it to be simple and light. I've recently converted to fixed-gear riding so this thing would not need any brazons or gear hangers - just track ends spaced at 120mm. I'm hoping this that would be something that would keep the cost down a little too because of the lack of fiddly detailling. So it really would just be a light chromoly frame (Alu seems too rigid on a small bike), with 26" sized front disc forks (easier to source) and a set of light bars/stem/saddle and that's about it. I attach my designs made using BikeCad and embellished into a more pretty Adobe Illustrator version — My 'artists' impression (though I doubt I'll run to the £300 back wheel hehe.
Does anyone here see any obvious pitfalls in my first foray into design? I've spent some time on it and to me looks pretty final to me at least, but I've never done this before and have probably missed a million obvious things. It was drawn to scale over a 26" hybrid at the start so things like BB height, toptube length, bar height and seat height should be pretty good for me - a 5'5" 32 year old from London UK.
Also - Are there any issues to getting a 'wishbone' shaped rear seat stay a la Cannondale Badboy bikes? I really like the style of them and would like to hear if people think a custom builder would be sniffy about fabricating something like that?
Any thoughts/tips/links/info/anecdotes on getting it right appreciated really!
Download my BikeCAD file