Factory Five Roadster – Part 1, 3D Printing A Muffler Mockup

3D PRINTED MUFFLER PROTOTYPE COBRA

Airwolf was started for the purpose of making prototype parts for automobiles.  However, before we could start building car parts, we started building 3D printers.  Before we knew it, our days, nights, and weekends were entirely consumed with building, selling and servicing 3D printers.  Fast forward seven (7) years and many thousands of 3D printers later, and we are circling back to focus again on our automotive ambitions.

As many of our readers know, we have a slightly derelict 1988 Mustang LX 5.0 that is in need of a full restoration.  While the Mustang is a wonderful, powerful, and incredible sounding vehicle, a run-in with an RV several months back sealed its fate.

1988 Mustang LX 5.0 that is in need of a full restoration

Rather than restoring the Mustang, we’ve decided to repurpose the critical components of the car into a legendary 427 Cobra replica.

The kit we’ve chosen is a Factory Five Roadster.  The concept of the Factory Five Roadster is to build a steel-tube frame akin to the original-only better-that uses the suspension and drivetrain of the popular Fox-body 5.0 Mustang (’79-’93), and tops it off with a true-to-scale body

factory five COBRA IN BLACK mk4-base-kit_LR

By all accounts, the Factory Five Roadster is one of the best selling and best-engineered replicas on the market.  We’re starting with a base kit that will utilize as many possible parts of our donor Mustang as possible. For instance, we’ll be repurposing the V-8 engine, transmission, read end, and much of the wiring.

The intent of the project is to create a true-to-form replica of a 1965-1967 427 Street Cobra.  The Street Cobra is similar to the more popularly recreated Semi-Competition (“S/C”), but without a roll bar or hood scoop.  In addition, the Street Cobra has an under-car exhaust rather than a side exhaust, most likely so that customers would not inadvertently burn their legs getting into and out of the car.

Street Cobra RF

The car will be built right here in Airwolf’s shop in Fountain Valley, CA and feature many projects involving 3D printing.  The goal is to build a lightweight and accurate recreation of the original street Cobra on a reasonable budget. We’ll show how you can use your 3D printer to prototype many of the parts for the project and to even create final, end-use automotive parts.

While Airwolf’s Roadster is currently in transit, we’ve already started planning the build. For the first installment, we will focus on the exhaust system.  One of the most challenging aspects will be building an under-car exhaust with sufficient ground clearance. We want to be able to confidently clear speed bumps and generally not have any extraneous items hanging from beneath the car.

Our planned under car exhaust will travel through frame rails in the chassis (more on that later), underneath the floor, above the rear axle, and finally out to the rear of the car.

rear of the car

3D Printing A Muffler Prototype

The mufflers will also need to tuck neatly under the floor of the car, approximately where the seats reside.  With some research, we discovered Spintech, who claims to build the lowest profile street muffler in existence (https://spintechmufflers.com/7000-cruiser-round-collars-low-profile-muffler/):

7000-cruiser-round-collars-low-profile-muffler

Before purchasing the muffler, we wanted to mock it up using an EVO22 printer.  We first designed a quick prototype of the muffler in SolidWorks using the given dimensions:

prototype of the muffler in SolidWorks

We then dropped the STL into APEX and set up the print using a 1.0mm nozzle and ABS.  We selected the 1.0mm nozzle, because the effective print speed is more than three times faster than with a standard .5mm nozzle (see article on printing large ABS parts).  We selected ABS because it is a strong, stable material that will not deflect when exposed to heat and/or sunlight. In addition, we can easily sand and paint ABS to replicate the actual item.

Finally, we selected the EVO22 as our printer of choice because it has a very large (12” x 12” x 22”) build volume suitable for this large muffler.  

Large muffler Solidworks

Our first however was a slight disappointment.  We forgot to turn the chamber heaters on and ended up with several cracks in the part:

chamber heaters were off

 

Going back to APEX, we turned the chamber heater on (APEX automatically sets to 60C for large ABS parts) and were rewarded with a strong and accurate representation of the Spintech muffler.  The EVO22’s chamber heaters not only helped create stronger layer-layer bonding, they also improved the surface finish of the part:

3D Printed SPINTECH MUFFLER IN EVO22

With APEX’s new same material solid support feature, removing support is easy and the surface finish is remarkable:

3D Printing A Muffler Prototype

Stay tuned for more automotive excitement!  Follow this project on social media #WOLF427