For the last several months I have been designing and welding my own bike frame (personal projects are slow going...) I thought it would be cool to personalize a few parts by designing and machining them. First up, bike seat clamp!
Autodesk Inventor or Fusion
Step 1: Measure and Sketch
Measure the diameter of your bikes seat tube. I used my calipers to get approx. 29.5mm.
I sketched a simple design I liked and modeled it around the tube diameter. I added ~.5mm to my diameter to allow for some wiggle room as well as a powder coat. To make sure I had enough room for the 5m bolt, I measured out the socket head diameter to fit. I may have gone back and fiddled with the numbers to make it all work. Extrude!
Step 2: Finishing Functionality
Make a 2mm rectangle extrude cut to allow the clamp to pinch effectively. You can play around with this number and make it look slicker. The wall thickness around the tube diameter play an important role in the clamping ability. If they are too thick and it may not clamp as well because of the counteracting forces pushing and pulling. Alternatively, If the walls are too thin and you could permanently deform the metal when it is tightened. My walls are just over 1/8" thick.
Rotate the piece 90 degrees. Select new offset plane and offset from the extrude cut (I chose 16mm). Sketch a point on that plane in the center of the part. That will be the bolt center hole. Select new hole. I used a 5m socket head bolt.
I shared the sketch and selected hole again but this time i chose the threaded hole spec to model in through threads.
Step 3: Make It Pretty
To the finish the part off, I placed fillets on the hard edges.
I used a 2mm chamfer on the inside of each side of the bike seat hole. This will just make it easier to slide on and off the tube.
For the outside, I used a .5mm chamfer to clean up the edges and make it finger safe.
On to CAM!