3D Printing Application: Functional Prototyping

Replacement parts for vintage race cars are often difficult to obtain because they are no longer produced. The demand may be too small for the manufacturer to justify or in some cases, the manufacturer may no longer exist. Using functional prototyping with 3D printed parts allows cost effective small-batch production of parts as needed, minimizing inventory.

Application Outline

Vintage Formula Style race cars (1960s to 1990s) use British-built manual gearboxes that leak gear oil from the shifter linkage opening. Taylor Race Engineering designed a retrofit seal kit to solve this problem. The original kit used an aluminum seal holder, but it was difficult to machine and the annual production volume is low. 3D printed parts made from Diran™ 410MF07 and PC-ABS were chosen to replace aluminum in this application. These materials have the desired strength, relatively high HDT (90 and 110 °C respectively), and are available on the Stratasys F370™ printer. Seal holders were printed in lots of 10 using both materials on a Stratasys F370. They were then tested to make sure sealing, strength, and temperature requirements were met.

Customer Story

Taylor Race Engineering is a small engineering specialist company focused on current and vintage race car transmission parts. They stock replacement/repair parts for about 10 different transmission types common in race cars built from the 1960s to the present. Since many of the transmission manufacturers are no longer in business and spare parts do not exist, Taylor will often machine their own replacement parts – mostly gears or shafts unique to these transmissions.

In some cases, chronic issues with the original design can be fixed with retrofit kits or parts. The shifter shaft seal kit is one of these retrofit kits that improves on the original design of the Hewland “MK” transmission. The shifter shaft seal area is a frequent leak point on the original design, as the shifter rod wears into the aluminum case cover. The shaft seal kit retains two external seals to the outside of the transmission case and it is attached by three #6-32 screws. Rather than manually machine these seal holders from aluminum, Taylor decided to 3D print the parts in PC-ABS and Diran using an F370 printer.

Functional Prototyping Application is a Best Fit When:

• Part operating temperatures are 150 °F or lower
• Sliding interface that benefits from the lubricity of Diran
• Possible oil exposure – Diran is resistant to oil/hydrocarbon fluids

Benefits Over Traditional Methods:

• Parts can be produced as needed, not kept in inventory
• Time/cost savings for small production lots (10-20 pieces printed in one batch)
• Easy to prototype two different materials before selecting the one that best meets the demands of the application