Frame Fixture
I am building a frame fixture using 8020 and some simple machined parts. This is based on my learnings from the simpler one that I built, plus inspiration from photos of the Arctos Jig.
My fixture has these design goals:
* Flexible so that it can be used for oddball bikes (cargo bikes, tandems, etc)
* Breaks down into small linear sections for storage
* Cheaper than a used Nortac or similar jig. It looks like my total cost will be about $300 and ~20 hours of machine time.
* Not annoying to use, but also not designed to be very quick to dial in like most professional jigs. I have no plans to become a professional framebuilder and don't mind spending 30-45 minutes setting up a jig.
* My first jig was too adjustable, which made it easy to get things off of the centerline. On this one I fixed the centerline at 2.5" and am machining parts accurately so that I don't need to make them adjustable.
I'm highly influenced by the Arctos jig since that had a lot of design similarities (with much nicer execution) to my first jig. The rear triangle dummy axle is going to be a complete ripoff of the Arctos since I never came up with a design that I liked before. The Arctos is much slicker when it comes to setting angles.
Read MoreMy fixture has these design goals:
* Flexible so that it can be used for oddball bikes (cargo bikes, tandems, etc)
* Breaks down into small linear sections for storage
* Cheaper than a used Nortac or similar jig. It looks like my total cost will be about $300 and ~20 hours of machine time.
* Not annoying to use, but also not designed to be very quick to dial in like most professional jigs. I have no plans to become a professional framebuilder and don't mind spending 30-45 minutes setting up a jig.
* My first jig was too adjustable, which made it easy to get things off of the centerline. On this one I fixed the centerline at 2.5" and am machining parts accurately so that I don't need to make them adjustable.
I'm highly influenced by the Arctos jig since that had a lot of design similarities (with much nicer execution) to my first jig. The rear triangle dummy axle is going to be a complete ripoff of the Arctos since I never came up with a design that I liked before. The Arctos is much slicker when it comes to setting angles.
The assembled bottom bracket post.
It is important to make sure that the post is exactly perpendicular to the supporting block. This is done by locking the bottom shaft collar and the top of the adjustable shaft collar. Expand the adjustable shaft collar to lock the bottom against the supporting block. Tighten the bottom of the adjustable shaft collar. Since the supporting block is machined flat the tube will be perfectly perpendicular.
Once this is done the top of the adjustable shaft collar can be opened and used for height adjustment.
The cones are from my previous fixture and have a shallower angle than I'd use now. They work fine though.
