Factory Five Roadster – Volume 5 3D Printing and Tooling Case Study: Steering Rack Stops

As we move along swiftly with project Project Factory Five Cobra, we’ve found another need for customization – steering rack stops for our manual steering rack.  In particular, the factory-supplied steering rack has too much travel. By that, we mean the wheels turn too much. While a tight turning radius is generally preferred, we want to be careful that our wheels do not contact the inside of the chassis, or worse that we stretch or crimp the brake lines:

Fortunately, there is a straightforward fix: create and install steering stops.  These stops will fit inside the steering rack and limit left and right articulation. For a completely custom approach, we decide to 3D print the stops out of ultra-strong polycarbonate.

3D Printer that prints polycarbonate

Our first step is measuring the steering rack shaft and existing stop diameters:

Once the inner and outer diameters are determined, we turn the rack to the maximum desired travel to avoid crimping the brake lines. 

Now we will measure for the correct spacer width.  Surprisingly, the left and right spacers need to be sized differently.  Because we can make completely custom parts with our 3D printer, this will be easy to perform.

With all measurements noted, we create the base configuration in SolidWorks.  We will create another configuration for the second, smaller steering stop.  This way we can keep both parts in one file.  If we decide to make changes to the underlying design, the changes will carry over to both parts.

We then load the part into Airwolf’s Apex software and choose to create the part in polycarbonate.  Draft settings are fine because we are not overly concerned with surface finish.  We’ll print out two different parts to see which one fits better.  Part of the challenge will be sizing the relief correctly so that part firmly snaps over the steering shaft:

Once the print’s complete, it’s time to remove the part and test-fit

Trying to install the part on the rack, we find the need to improve our design.  In particular, the steering stop cracks when we try to press it onto the shaft. 

The problem is that we do not have enough flex built into the design.  To add flexibility, let’s incorporate a hollow center section.  As referenced above, because of the way we set up the part in SolidWorks, this cavity will be created in both configurations.

Now it’s time to print the part again. Rather than try just one more piece again, we’ll speed up the fitting process by trying a couple of different relief values: 14MM (top) and 16MM (bottom):

STEERING RACK STOPS in APEX slicer

Now we test to see if the ring will work by snapping it onto the steering rack.  It snaps on nicely and is now securely in place.

Finally, let’s test out the articulation…success!

To learn more about the benefits of combining in-house 3D printing and tooling please contact one of our additive manufacturing experts by emailing info@airwolf3d.com

Download our Guide "The Key to 3D Printing Large Polycarbonate Parts"

This guide is intended to shed light on many of the methods we have used since 2014 to master polycarbonate printing on the desktop. In particular, we will pay close attention to temperature requirements, bed adhesion, printer configurations, and best settings practices.Reading time: 15 minutes
The Key to 3D Printing Large Polycarbonate Parts