What's a knuckle? The knuckle mainly holds the wheel in place but also allows the tire to rotate on three axes. Not only can the tire spin and turn, but the knuckle also allows the entire assembly to rotate when lifting the front end. Our knuckle is made up of a bearing plate, two knuckle brackets, and two pivot brackets.
We've had a version of a knuckle on the previous two designs. The new design has an extra degree of freedom. I also added a lip to the bearing plate to prevent the bearings from squeezing out--the issue that ended our last race. I rounded the back of the knuckle brackets so we could get ±45° of turn. I also thickened the bottom of the bracket to better accommodate a bearing.
The new bearing plates were done previously, so I began this push with the upgraded knuckle brackets. I manually machined aluminum stock to the dimensions I needed to carve the parts out on the Tormach.
Because these brackets are one of the smallest of the CNC'd parts, I was able to make four of them on the same day. Until now, most parts have taken a day each. After the main parts were done, I used the manual mill to add mounting holes needed to connect the knuckle brackets to the steering components.
The pivot bracket was another story. This bracket has to attach to and rotate around the suspension legs while also attaching to the other pivot bracket above it, and also support the knuckle brackets. In order to accomplish all this, I had to run setups on four sides of each aluminum block. Usually, only two sides are machined to make a part. The top side "Han in carbonite" setup carved out most of the parts' features. I had to use extra long end mills to reach all the surfaces.
I then moved on to the features on the sides: a through-hole larger than the 3/4-inch threaded rod going through it, and a "cup" for a bearing. The two sides, though, had to be aligned with each other. I used the newly machined top and back faces to set my origin for both sides. Because both surfaces were machined, I was fairly confident that the starting point for each side was the same.
Both setups ran the same operations. First, the bearing cup was carved out. Then, the clearance hole was bored. I didn't have an end mill long enough to get all the way through the part, so I only went down halfway on the clearance hole.
There were slight variations between the two sides, but it was small enough that a 3/4 inch threaded rod still fit all the way through the part. And that's all that we need. 😎
The last setup was for the bottom side of the part. Weight is always a concern, so I removed most of the extra material and left a cross pattern centered around the knuckle bracket mounting hole. The "T" cross-section will help minimize flexing of the bracket's "floor".
With the four knuckle brackets and the four pivot brackets completed, we are now 83% done with the build! Not far now.
The last six parts are on deck. These parts include the arms that actuate the scissor lift function and the brackets that the arms rotate around. There are aluminum and steel parts, and I'll need the Tormach for all of it.
For the Glory!
