I Told You This Was Going To Work...No Problem

With an assist from Andee, we assembled the new suspension system for the Aluminum Falcon! 

Nice, right? I spent most of a week preparing for the effort by test fitting one side to determine the number of bolts, nuts, and bearings needed to complete the assembly. 

After I cut lengths of 1/2-inch and 3/4-in threaded rod for attaching parts together and drilled holes into the chassis to connect the fulcrum brackets, I discovered two design fails that needed to be corrected before I could assemble the suspension, both related to the hangers. 

Each hanger is made from a couple of tubes connected by two bars, forming an "H". The problem with the inside hanger was that a crossbar on the chassis prevented installation. The problem was there the whole time and I just didn't notice it.🤦🏽‍♂️ Or I noticed it and forgot. Whatever. Look out the window.

Luckily, it was easy enough to fix. I cut a slot out from the lower tubes that was both wide enough to get around the chassis crossbar and installed additional bearings into the newly revealed holes.

The outside hangers had a different interference issue. We needed the attachment plate on the lower leg of fulcrum bracket to fit through the hanger, but the attachment plate was too big.🤦🏽‍♂️ 

To fix this issue, I used a bandsaw to trim down the length and width of the attachment plates to fit within the "H" of the hangers. I then used an angle grinder to round the corners to clear the welds on the hangers.

Once the hangers and fulcrum brackets were modified, I also had to make slight modifications to some of the bronze bearings we use to support the joints. I could not find bearings in the length I needed. I needed 1-1/2 inch sleeve bearings, but I could only find 2 inch. I needed 7/8 inch long flanged bearings but I could only find 1 inch. I had to buy the longer bearings and adjust them in the machine shop. 

I turned the sleeve bearings down to size using the lathe. That was easy enough to do. The flanged bearings were not as easy. They were impossible to hold in the lathe because the flange stuck out like the rim of a top hat.  Instead, I had to use the mill, but holding the flange in the vice was still tricky to do.

Because bronze is soft, it deforms if you squeeze too hard but the vice needs to be tight enough to hold the part while it was machined. I turned two round bearings into eggs finding that out. To avoid ruining more bearings, I made soft jaws out of plastic. The plastic is softer than bronze, so it got squeezed instead of the bearings.

This allowed me to hold the bearings more tightly without damaging them.

Once the stop nuts, washers, custom bolts, and bearings were ready, I made assembly kits for each side. 

After days of preparation, Andee and I got to work assembling the new suspension.

The last piece of the suspension system--that holds the whole thing together and makes it all work--was a heavy-duty tension rod that connects the two lever arms. After a healthy dose of WD40 on the threads, I attached the rod. 

Spinning the turnbuckle in one direction pushes the levers out, lowering the chassis into race mode. Spinning in the other direction pulls the levers in, raising the chassis six inches to get us through the mud and water.😎

Next up: I have to install the differential to complete the assembly of the front axle. That requires rethinking the support brackets...again. But I have a plan for that. I also have to make and install all the steering components. The work continues. For the Glory!

Rudy July 31, 2025

Read more

You Don't Have To Do This To Impress Me

I often show the Tormach making the parts, but there's more to the process. I design the part in 3D, then I write a program to carve the part out of stock material. I then have to mill stock material down so that it's the same dimensions or slightly smaller then the carving program expects. I have to precisely set the X, Y and Z axes and measure the heights on all the cutting tools used. After all that, I can finally run the program that makes the part. These are all the steps I take when I say the part was "straightforward" to make.

The two lever-assist arms were straightforward to make. After setup, I was able to make both of them in one afternoon. That's the best feature of the CNC mill. I can make the same part over and over, but I usually only have to do the setup once.

The Final Four

Previously, I described the suspension as a seesaw. The wheel is attached to one end of the seesaw and the other end is pinned to the central frame. A lever arm rotating around a fulcrum moves the seesaw, pushing the wheels into the ground and lifting the front end. The last four parts to be made were the two lever arms and the two fulcrum brackets. 

The original design of the lever arm was pretty basic (shown above). Before I actually made these parts, I redesigned the interior of the arms to look a little more Star Warsy. I always say that, to me, the engineering is the art and this was a great example. Each arm took most of a day to run, and they came out really cool!

The fulcrum bracket is the physical connection between the chassis and the point in space where the fulcrum is located. The lever arms attach to and rotate around the fulcrum bracket. I designed a simple bracket oriented at an exotic angle. Two long tubes connected to the chassis and also to each other. Because the tube intersections created complex profiles and because the placement and shape of those profiles had to be fairly precise, I used the Tormach to make them before I began carving out the lever arms .

I also made the cross-pieces for the fulcrum brackets–the attachment plates and pivot tubes–on the lathe at the same time. Once the pieces were made, I set about welding them into brackets while the Tormach worked on the lever arms. 

First, I clamped up and welded the attachment plates and pivot tubes onto the ends of the long tubes. Those connections were perpendicular, so I only needed one clamp to hold them together.

Once the pieces were welded onto the long tubes, I then had to arrange and hold the long tubes at the correct angle. Getting them positioned correctly took some effort.  I did have a short truss that was the same shape as the Falcon's truss. I was able to use that as a jig to prepare the final joints.

After clamping the long tubes to the truss using hose clamps, I used angle gauges to set the 34 degree angle between them. I moved the two legs around until they were snug up against the gauges.

I spent a lot of time getting this angle right. If the fulcrum ended up in the wrong spot, it would make assembling everything much more difficult. I checked the position of the brackets relative to the chassis by putting a level on the chassis, then putting the level across the fulcrum tubes, and comparing the reading. Everything lined up.

I tack welded the last joint on each bracket to make sure they did not shift while I worked on them. Then, I began to weld. The TIG torch had sprung a leak and could not be used, so I had to use the MIG welder instead. MIG is an ax to the TIG's scalpel. TIG melts and you add metal in small drops. MIG adds metal as it melts. I had to be extra careful. I could easily add too much metal or worse, burn holes into the tubes.

The perfect TIG technique refers to "stacking dimes," or laying out the beads so they overlap each other. If you do it right, your welds look like a necklace. I have flashes of competency, but my TIG welds are usually very ugly. Since I had to use MIG, I decided to try to fake the dimes. As the machine fed out wire, I made small, circular, overlapping motions.

I slowly made my way around all the joints, taking breaks to let the metal cool down, until the brackets were completed.

With that, ALL 36 parts for the new suspension were fabricated.

Next up, put all the pieces together to see where reality differed from virtual. For the Glory! 

Rudy July 17, 2025

Read more

Oh Yeah? Watch This.

 

After fabricating most of the interior parts of the new suspension, I tackled the parts that make up the knuckles. 

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! 

Rudy July 08, 2025

Read more