Really like the grill that you made! Your flea market bike is kind of cool. I like how someone used a wooden tank for a quick gender bender on that bike.
I haven't measured the diameter. Just eye balling it, it looks like a standard 1"/25.4mm post. Probably not much difference visually between 25.4 and 27.2mmNear as I can figure, it looks like an older Madone seatpost, a carbon road bike from the mid to late '00s. There are about three choices of clamp/guts, but I think this might be yours. Is it a 27.2 mm diameter seatpost?
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This is from the trekbikes.com website. The only size they still have left is the smallest 7x7mm . There are knock-offs on ebay, but you would be gambling there.
The thing about carbon posts and clamps is that you have to stick very stringently to the torque parameters or you will break the post. Very strong and compliant vertically, but can't take too much clamping pressure.
This reminds me of the old pinewood derby cars! Very cool.
ThatNot Pinewood derby cars, but I've been building wooden toy cars for my grandkids. I build a race car every year for their birthday with their age for the car's number. Here's the grandson's car for this year. He's into "Cars" movies and videos. This one is an experimental car using skateboard wheels.