Straight vs. Cut/Welded Linkage Arm Design Using Ball Joints for Bearings

[January 29, 2010] From Graham Butler:

After our last meeting I thought long and hard about the design of the linkage arms.  You guys were right about the cut and welded design being a difficult thing to manufacture. So I started working on some simpler linkage arms, where we would have some stock billet aluminum parts that were welded to straight tubes.  I have attached some screen shots of how this would look.

I don't really like this  (please let me know your impressions and opinions).  I think that the upper linkage arm is one of the most visually dominant parts of this bike, and I think that if it looks great, then the entire bike will have a better aspect.  So I went back to tubes, but this time bent instead of cut and welded.  ( I should be able to make a bending die that will be able to take care of this).  This time however, I put in the tie rod ends as the pivot points.  This would legitimately save us from machining precision bearing seats.  As long as the linkages are stiff, it should work fine.  I have attached some screen shots of this.

Having been around the mulberry bush a few times now, I think that really we are now at a choice junction.  We need to decide on the direction of design for out pivots bearings or tie rods.

Bent welded linkage arms.

Example of straight linkage arms.
Machined plug inserted and welded into square aluminum tubing.
Straight tube linkage arm.

Cut/welded linkage arm. (From hard will it be to make this?)
Ball joints used for bearings.
Another view.
Top view of cut/welded design.