Gazelle Trim Trophy, EG Bates Track Bike, HR Bates Cantiflex bike, Nigel Dean fixed gear conversion, Raleigh Royal, Falcon Westminster.
How are seatposts measured?
I need to put about 40 mm more in length on my seatpost for the R20, and the longest seatpost I can find online is 400mm. If that's a measurement of how much exposed seatpost you can have, then it'll be plenty, but I'm not sure what the length measures on seatposts actually refer to. Does anyone here?
Wanted - SRAM/Sachs Elan 12 shifter and clickstick
You don't need to cut up an old frame. For a seatpost that long I'd buy some 1 1/8" OD steel tubing with a 1" ID. Aircraft Spruce (http://www.aircraftspruce.com) is a good source of this.
You can then pin a 1" seatpost in the top of that. This makes a very long 28.6mm (1 1/8") seatpost. You can use stainless steel or have the tubing nickle plated.
This is how the seatposts were originally made for the steel NY Swift Folders.
This will give you a much stronger seatpost than cutting out an old frame tube. The frame tube will likely be .6mm for most of it's length, butted to .9mm at the base (where you don't need the extra strength). The tube that I suggest will be 1.6mm wall thickness.