I need an 18" seat tube. You have to cut off more than your going to use, I say by a couple inches. Then you miter the bottom of the tube to contour where it's going to meet the bottom bracket.
-
I can make the miter with a hacksaw file, but I have a Joint Jigger. A bottom bracket has a diameter of 1-1/2". Set the angle of the joint Jigger to 90 degrees, then put on a 1-1/2" hole saw, and then get to cutt'n.
-
With a little filing you can get what you want. A nice clean miter.
-
I've decided to have a 74 degree seat tube angle. I've always liked the forward position. Most people like them 72.5 - 73.0 . . . or it seems the manufactures do.
-
Setting this angle doesn't set anything in stone. 99% of seats have rails that allow you to move the seat back and forth a few inches either way. What matters most is the the combination of the frame, seatpost, and seat allow you to get your seat in the relationship to the bottom bracket that you like. For example some people like the front of the seat to be 7cm behind the centerline of the bottom bracket. . . . and the seat post brings up an interesting component to this equation . They make straight seat posts where the seat clamp sitts straigh on top the seat post tube, most popular being the Thomson. Most manufactures make their seat posts with the clamping mechanision behind the seat post tube, I guess most people refer to these posts as being laid back seat posts.
-
Now clamped up in the jig.
-
I can make the miter with a hacksaw file, but I have a Joint Jigger. A bottom bracket has a diameter of 1-1/2". Set the angle of the joint Jigger to 90 degrees, then put on a 1-1/2" hole saw, and then get to cutt'n.
-
With a little filing you can get what you want. A nice clean miter.
-
I've decided to have a 74 degree seat tube angle. I've always liked the forward position. Most people like them 72.5 - 73.0 . . . or it seems the manufactures do.
-
Setting this angle doesn't set anything in stone. 99% of seats have rails that allow you to move the seat back and forth a few inches either way. What matters most is the the combination of the frame, seatpost, and seat allow you to get your seat in the relationship to the bottom bracket that you like. For example some people like the front of the seat to be 7cm behind the centerline of the bottom bracket. . . . and the seat post brings up an interesting component to this equation . They make straight seat posts where the seat clamp sitts straigh on top the seat post tube, most popular being the Thomson. Most manufactures make their seat posts with the clamping mechanision behind the seat post tube, I guess most people refer to these posts as being laid back seat posts.
-
Now clamped up in the jig.
No comments:
Post a Comment