Here’s where things get interesting. Today I spent some time getting a design started for the frame modification. This effort starts with a single question — where does the front mount for the 4-link suspension go, relative to the frame? The second question is then, how do I reshape the frame to accommodate the mount, and allow for suspension travel? The way I’ve chosen to work this out is in a full-scale drawing on a rigid surface, on which I can trace the parts.

Erik came up with the perfect surface on which to do this, and I’m really impressed with it. I was planning to use cardboard but this masonite board with its dry-erase surface is much more rigid and has the benefit of being markable with a dry-erase marker for temporary sketches and semi-permanently with a Sharpie for anything that’s fairly certain. And even the Sharpie marks are not indelible; they can be easily removed with a cleaning solvent.

The drawing started out a bit haphazardly, as I didn’t think I had anything to go on, to tell me what the orientation of the axle mounts should be. They’re a rounded, curvy shape, with no features to indicate what really should be vertical. I made my best guess and clipped the mount to the board to trace around it. I felt a bit uneasy about being so cavalier and as it turned out, my hunch was correct. There are actually “correct” dimensions (you’re not supposed to just eyeball it), provided in an engineering drawing which I found this afternoon. As elaborate as the geometry can get when adjusting a 4-link setup, it makes a lot more sense that building one is also done against rigorous specification.

I drew a ground line 14″ from the axle center based on a 28″ wheel. I then measured down from a specific point on the frame near the front of the truck to get a point known to be on the ground on a stock S-10. I stretched a string between these two points and used that to transfer a line onto the drawing representing the ground. With reference lines for the front and axle suspension mounts, I could then redraw the axle mount and position the front mount and be confident that I’m doing it correctly.

Exactly where the front mount will go relative to the frame — our first pivotal question to answer — will remain unsolved for the time being, until I decide on how high I want the truck to ride. And that is a question which combines elements of style with racing physics, battery box height and suspension travel allowance. I’d hoped on being able to lower the truck a couple inches, and so my next steps are to investigate how doable that is. Since the suspension will be directly beneath the frame, I don’t have as much room as most folks, and the shape of the axle suspension mounts doesn’t help, but we’ll see.

Pictures of today’s drawing activities are in a new gallery section called Planning the Suspension.