Monday, March 31, 2008

More unrelated pictures - stuff I'm working on today

First one's for Fritz - first pic of his new 4" travel 29er. As you can probably tell from the photo, Fritz is a pretty tall dude. A 6.75" head tube on a 100mm travel 29er? Absurd! It should be a fun bike for railing the trails up in Leadville, and there's room for like 4 of 5 head tube decals!

Second shot is for Nick (team guy) - I'm building him a super-weightweenie Actiontec frame/fork. Since the AT fork takes a 1 1/4" head tube, and the only stock I could find was 1.6mm wall tandem tubing (massive overkill for a dude who's 135 pounds), I machined the head tube down a little bit on the lathe (to about 1.0mm wall in the relieved section). I was surprised how much weight this saved - almost 40 grams. Probably something I'll do with all of my AT frames in the future - though given that I build about 2 a year, that's not saying much.

I probably *could* have taken off more material, but below 1mm thickness, I start to have real reservations about head tube strength (admittedly, it's 1 1/4", not 1 1/8", so it's about 10% more material than a standard head tube). Given that machining the tube down on the lathe like this also weakens it a bit more than you'd expect based on the thickness, and that the material itself is just basic cromoly (I usually use OX platinum tubing, which is considerably stronger, for all my head tubes), I felt this was a good conservative amount of material to remove without having to worry about anything.


Anonymous said...

Nice job Walt. What weight did the frame come in at?

Walt said...

1660 grams, Mr. Nick. Will be interesting to see what the PC adds. My guess is ~60-80 grams.