As I mentioned in an earlier post, I didn't like the way my lower shock mount turned out. I decided to cut it off and make a new one. I searched around in the McMaster-Carr
catalog for a 12mm ID spherical bearing
that would match the M12 shock mount bolt and found one with dimensions 12x30x16 that I thought would work. I also found some 17x30x7 oil seals that had the same OD as the bearing that I thought I could use to keep dirt out of the bearing.
Here's how the old mount I cut off compares to my new design. Once I got the arm installed I found I needed to grind down the smaller front gusset to clear the shock's mounting clevis.
I made the bearing holder from a piece of large mild steel round stock I had. I bored the hole out with this setup to give a press fit to the bearing.
Here's the bearing mount tacked to the swingarm. I made it wide enough to accept the bearing and the two seals on each side of the bearing.
I was thinking to add a box section to the bottom of the swingarm to strengthen it. I cut the sections at the bottom of this photo from a length of mild steel rectangular tube.
I needed to grind a curve in the ends where the box intersects the swingarm tube. It is a little difficult to explain, but to lay out the curve I found a short plastic ring the same diameter as the swingarm tube, and with the plastic ring set into the box section I sighted down the ring and marked the intersection with a Sharpie pen, then ground out the curve with a bench grinder. Here are the parts tacked to the swingarm.
The swingarm all welded together. The box section looks big and heavy, but the tube had a thin wall so it doesn't actually add much weight.
Here's a view of the bottom showing the box section. The rear part is just a little too close to the outer final drive mounting nut to get a socket on the nut. I did a little grinding to make room.
After welding the bearing holder and gussets to the swingarm I found that the bearing holder was distorted enough that the bearing could no longer be pressed in. It took a while to get setup, but I mounted the swingarm on a vertical mill and re-bored the bearing hole.
In retrospect, I think a much better way to do the bearing holder would have been to turn the OD of the holder, but not bore the hole, then weld that un-bored holder to the arm and use my arm fixture to get the arm mounted on the mill to drill and bore the hole.
Here's a side view of the arm with the bearing installed which also shows the shortened front bearing mount gusset.
And a view of the bearing mount. The oil seals press in just outside the bearing.
And a view with the arm installed on the bike.
I still want to make a vent for the arm. I just need to drill and tap a hole in the front of the arm somewhere, but I'll wait until I have the fender, exhaust, and whatever else it needs to clear installed before doing that.