What I’d hoped to be a small task for the first part of the day ended up being an all-day affair, but I’m glad it’s done and I think it turned out well. You may recall having seen in previously-posted pictures of my plan drawing, a top hole in the suspension front mount that seemed to be separated from the others. It appeared to be separated because it actually wasn’t provided on the parts I had. In fact, I would need to add the piece of metal in which this extra hole would be drilled. The purpose of this hole and the reason it wasn’t provided end up being a nontrivial story.

In a “hot rod” 4-link suspension, the upper and lower link bars are positioned to form two legs of a long triangle, and the point where they (virtually) intersect is important in the physics of tuning how a vehicle’s weight is transferred while launching under high torque. While this is important for the drag strip, it has a serious drawback for more normal driving on bumpy roads. Because the link bars are not parallel, the rear axle will not be able to articulate when one wheel hits a bump.

Street 4-link designs are parallel for this reason. I’ve decided to add a set of holes above the top holes in my front mounts, to allow better handling on the street. It still won’t be perfect as the top link bars in my setup are slightly shorter than the bottom ones, but it should be a significant improvement. To make this happen required some new pieces cut out of 3/16-inch steel, and some of the first substantial welding I’ve done in this project.

I didn’t have any steel plate of the proper thickness lying around, but I did have some rectangular tubing that supposedly had a 3/16-inch wall thickness. I hacked a couple pieces off of it and cut it apart, and it turned out to be exactly the size and thickness needed. I made a paper template, traced it, and cut the shapes out on the bandsaw, which ended up taking several hours. After welding and drilling, the front mounts now match the drawing, which means they’re ready to build into the frame.

I’ve posted pictures of this exercise in a new sub-album in the gallery.