Sunday, March 17, 2013

Tube Cutting and Jig Fitting

Here are the tubes for Neil's frame going through the process of being cut to fit together in the jig.

First is the seat tube being mitered with the abrasive belt system.  I cut the seat tube using vee blocks in the vice to make sure it's exactly 90 degrees.
Here it the fit to the BB shell.  You can see the scribe line that I "sand" up to.
Next is the BB joint.  You can see that the blocks I use to hold the tubes in the mill are still attached to the down tube. That way I can easily put the tube back in the mill if required.
Here is the head tube joint at the same point in the process.
This frame will have a titanium tube inserted into the top tube to act as a brake cable guide.  Here is the somewhat Rube Goldberg method I use to cut the guide holes for now.
It leads to a nice smooth transition for the entrance and exit.  Once bonded in place the tube will but ground flush with the carbon.
Finally, just for Neil, who likes this sort of thing, the weight of the titanium guide tube (prior to being trimmed on each end).  Not including the cap of course.
Next step is bonding in the tubes and bottle bosses.

Sunday, March 10, 2013

Tube Marking

The next step is carefully marking the tubes for cutting and mitering.  I use a silver marker on the carbon then lightly scribe it away to mark cut locations.
I have a .01" graduated ruler I use for marks longer that the 12" calipers can reach.
I mark a cut length, miter location line, miter diameter and angle to make it very clear.
When all the tubes are complete I check them against the drawing once more.  I don't want to make any mistakes and have to get another tube.
Next step is to cut the tubing and fit it in the jig that already been set to the correct dimensions from the CAD drawing.

Sunday, March 03, 2013

Neil's Frame Begins

Neil's new frame was set in motion today.  It will be a lighter version of his first prototype frame with ENVE tubing and twin seat stay tubes.  It should be somewhere around 900g when complete (but we'll see).

First the jig was set up according to the CAD drawing.
Then the head tube was cut to length (then turned on the lathe to exact length and to true the ends).  I cut tubes with a fine tooth band saw running on medium speed with a very slow down feed rate.  I found this does not snag or pull any fibers.

 Here is the progression of creating an external butted section to accommodate Neil's seat post clamp at 33.9mm.  It shows the wrapped pre-preg, the shrink tape, the cured tube and the turned, sanded finished end.

 Here we have the parts in process back on the shelf.  Dropouts are ready to bond when the time comes.