JesperXT-
Thanks! Probably gonna print and figure out the jig part while Im in Hungary so that when I go back to London I can get it done straight away.
BMC project: It really annoyed me that there was a gap between the seat tube and the seat post, then I figured probably there was a rubber cover there originally. Given that its long gone, I made up one in Fusion 360 and will try to print it from the same flexible material that I made the cable guides on the Space chicken. It has a 3mm tall and 0.4mm thin edge that should wedge between the seatpost and the frame, and also has a really snug fit on the seatpost so that theres no gap for any water to get in.
First ive taken a pic of the seat tube, and took measurements of the inside of the seat tube, and the seatpost
Then I used this as a canvas with reference points based on the measurements to draw up a quick design
Voila!
Made another version that has an outer lip too so that it fully covers the top of the frame. Once I can borrow a printer I'll try which one works best.
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kiskubai
Repurposed this thread to keep track of all my bike related tinkering and projects :)
Next up, fixing my broken Dolan Track Champion! Or more like crack champion...
This is the current state of affairs:
Whatever the solution is, it has to cost me less than £100, as for that price I could easily buy another frame. But the idea is that I'd rather not trash an otherwise perfectly fine frame. Im not counting the hours ive already invested into this, just material / tool costs.
Possible solutions that I've explored:
Machine an insert with 27.2mm outer diameter, 25mm inner diameter, and a collar to take on a standard seatpost clamp. Then glue this insert into the frame. Probably the least complicated solution, but need my mate to do the machining part (hey @hma !), ship it to me...etc. Also not the cleanest look. I'd need further tools to level the top of the seattube.
Make a quill seatpost. Upon closer inspection only the first ~10cm of the frame is bored to 27.2mm, after that it extends into the aero shape, so adjustability would be minimal.
Glue a 27.2 carbon or AL tube into the frame, and use a seatmast topper. Limited adjustability, and apparently seatmast toppers are neither cheap, nor easy to find.
And probably the most complicated version: Create a jig for a dremel that rotates around the seat tube and machines it down to a uniform 31.8mm that will accept a standard seatpost clamp. Ive seen this done on the same frame by Dolan as a warranty job (and on later models of the Track Champion they adopted a seatpost clamp that follows the shape of the seattube).
Here's where I am with the jig design:
First there's a quill mechanism that fixes itself into the seattube, and has a collar on top to provide a level surface to rotate on. The jig itself is 3D printed and assembled with some standard M5 nuts and bolts. It has a stopper to avoid accidentally machining it smaller than the desired diameter, and it will have a spring (tensioned by a screw from behind) pushing on the sliding dremel mount to force it in the direction it needs to machine off.
Ignore the rectangular protruding thingies, thats a leftover from a previous version that was only 2mm thick (to bring the dremels head as close as possible to the working surface), so it was a place for some steel rods to hold it all together. The dremel head is plenty close, so made the body 10mm thick at the end.
I'll probably finalize this design and do some prints over the next few days, lets see how it goes! If anyone has any suggestions design-wise, Im all ears! Im not an engineer, just played a lot with Legos as a kid :P
PS: .....Anyone has a Dremel I could borrow for a weekend in January? :D