Working on cars like Project Cobra can be very rewarding. However, at times there will be a few hiccups along the way. Here we encountered such an issue replacing our rear axles. As astute readers may know, in order to outfit project Cobra with vintage-style Halibrand wheels, we must convert the standard 4 lug mustang axles to 5 lug versions.
While replacing the axles, we noticed our axles seals needed replacement. After removing the seals, we discovered that replacing the seals with new versions would require a bit of thoughtful planning…and maybe a 3D printer.
One minor, and in some cases major, inconvenience of working on cars relates to special tools. Specifically, special tools are frequently necessary to perform maintenance and repairs correctly. Special tools can include all types of equipment needed for working on specific parts of the vehicle such as belt tensioners, pulley removers, and seal installers.
The rear axle seals on our Ford Mustang 8.8” rear end keep differential oil from leaking onto the brakes and potentially affecting stopping distances. The seals are designed to have an interference fit with the differential housing. This means the outer diameter of the seal is slightly larger than the inner diameter of the housing. The overlapping diameters ensure the seal will stay snug in the housing. While the fit is optimal, installation can be challenging as we will need to force the seal into the housing.
The first approach is usually to take a hammer to try and seat the seal within the housing. While experienced mechanics may be able to pull this off without damaging the seal, this is the exception, not the rule. Using this approach will most likely damage the seal, causing frustration, expense, and the delay of waiting for a new part to arrive. The worst-case scenario would be to install the seal, not realizing it was damaged, only to have to remove the axle again after the car was back together.
The correct approach is to use a special axle seal installation tool. In this case, such tools are offered from a number of different vendors in many different forms, costing up to $175.
While these tools will correctly install the seals, unless you are replacing rear axle seals often, the tool will probably only be used once or twice. When factoring in cost and the inconvenience of waiting for the tool, we are convinced better alternatives must exist.
What we need is an affordable tool that is rigid and strong enough to withstand repeated blows from a hammer to seat the seal. We’d also like to save some money and have the tool ready to use in less time than it takes Amazon to deliver it.
First, let’s set some basic parameters. For material, the best choice will tend to be the strongest. Polycarbonate is the foundation for bullet-proof glass and is one of the strongest thermoplastics available for 3D printing. Because we need strength and durability for this tool, polycarbonate is just right.
Second, let’s talk about our tool’s size. While we could make the tool small, we would need to incorporate other parts like bolts and separate fittings. Additionally, the tool may be inconvenient or difficult to use. We want this tool to be functional, ergonomically correct and not require other components. For that reason, we will design a one-piece tool that can be easily grasped with one hand, using the other hand for a hammer.
In SolidWorks the design process is straightforward. We will create a sketch of one half of the part, inserting the appropriate dimensions for the axle housing and bearing and creating a section approximating dimensions of a human hand. We’ll also add a slight draft angle to the tip of the tool to make sure it easily installs into our axle housing without damaging the bearings:
Once the sketch is completed, we will revolve around the sketch to form a solid part. After revolving, we will add some fillets to remove sharp edges and clean the aesthetics up a bit:
As shown above, the axle seal installer tool is relatively large at about 8” in height. This will provide us room to safely grasp the tool with one hand and a hammer with the other while installing the axle seals. We also sized the grip of the tool consistent with the diameter of a motorcycle grip (1 ⅛”) to make it comfortable to use.
With the part designed, we must now select the proper machine. Because we are working in an office and conscience of space, noise, smell, and energy consumption, we will be using an enclosed desktop 3D printer with active air filtration.
We will select the Airwolf EVO series of 3D printers because these enclosed and actively filtered desktop machines are specifically configured to print in strong, high-temperature materials such as polycarbonate and nylon (in addition to nearly all other 3D-printable thermoplastics). The EVO printers also use linear guides, internal chamber heaters, and proprietary software and componentry specifically tailored to making large, strong parts such as the tool we are focusing on here.
While the tool can be made on either an EVO or EVO 22, we will choose the EVO 22 because it comes standard with .8mm nozzles which will enable us to print the part faster and stronger than with a more conventional .5mm nozzle. We will use Airwolf’s Apex software to set up the part:
Apex makes part creation easy as we only need to specify a few parameters and the software will take care of the rest, creating ready-to-execute gCode specifically configured for Airwolf 3D printers. In this instance, there are several considerations. First, we will select polycarbonate as our material for its strength and durability. When making tools, we want to make them as strong as reasonably possible.
Now let’s consider other factors such as time and strength. To minimize time, let’s set Quality to Draft so that the EVO will build the part with higher layer heights. Similarly, we will select a .8mm nozzle to output a larger volume of material than a .5mm nozzle. The larger material output will enable us to save print time and create a stronger part. Specifically, by creating a part with thicker walls and higher layers, we will rely less on layer-layer and wall-wall bonding, tending to create a stronger part.
Finally, we’ll set our strength setting to High and turn the Chamber to Heat On. On High, our strength setting will increase infill density and in some cases increase the number of perimeter walls. Turning on the chamber will heat the enclosure to 70C to create a more uniform part and promote stronger layer-layer and wall-wall bonding.
Apex will take of the rest. Specifically, with the EVO and Apex 1.6.0, the correct head (300C), chamber (70C) and bed (158C) temperatures will be set according to the parameters of our tool. Apex will look at material type, part size, and the remainder of the settings from the Quickprint menu to automatically generate correct layer heights, infill densities, wall diameters, and print speeds to ensure the part is printed optimally.
All that is needed to start our print is to insert a thumb drive with our file in the USB port, apply Wolfbite Mega to the bed, and insert polycarbonate filament into the EVO’s feeder.
The next morning we have our part:
As shown here, the finished part is ready to use right off the print bed! We designed the tool with optimal angles for printing so we would not need support. This helps minimize print time and eliminate post-processing.
In total it took about 20 minutes to measure and design the part in SolidWorks, 6 hours overnight for the EVO to print in polycarbonate, and less than $20 in total materials. In use, the tool works as intended, withstanding repeated strikes from the hammer and successfully inserting the rear axle seals into Project Cobra’s 8.8” Mustang rear axle.
This is the final goal! Check back for updates and follow along with us on this project.