140 mm Fan Intake, Blade Tip Spacer & Exhaust Cone

The Backstory

I needed to improve the volume of air moved by my two 140 mm X 140 mm muffin fans to exchange the air in the cargo area of my vehicle, where my dog rides. Knowing nothing about fluid dynamics, I turned to AI and learned a great deal about how ratios and shapes affect airflow.

I designed parabolic struts to support the center cone of the intake, a specific bell-mouth curve radius, and an optimized intake cone shape and height. I also added an exhaust cone and a blade-tip gap spacer to reduce the gap to just 1 mm, forcing the air out much more efficiently. I settled on these final measurements because they gave the best results without becoming too massive or hitting diminishing returns.

The Results

My anemometer shows a 2.5x improvement at 30 cm/12" away—the difference is incredibly noticeable, yet it is still fairly quiet!

⚠️One caveat: The tolerances on inexpensive muffin fans can be inconsistent, so the spacer thickness might present a tight fit. If it doesn't fit your specific fan and you are unable to scale it, just using the intake and the exhaust will still give you a significant improvement. AI also suggested adding airflow-straightening fins to the exhaust cone, but frankly, it’s over-engineered enough already! I'm sure others have uploaded designs with those if you're interested.

What to Print & Assembly

There are three separate parts to download and print if you want the entire package:

1. Combined intake bell curve
2. Fan blade-tip gap spacer (optional as very tight tolerances)
3. Exhaust cone

The fan blade-tip spacer is securely held in place simply by being sandwiched between the intake and exhaust parts.

Print Settings & Material

I printed these parts in ASA because they live in my car, meaning they need high heat and UV tolerance. The print dimensions are slightly exaggerated to compensate for ASA shrinkage (1.011%), so keep that in mind if you go with a different filament. Given the varying tolerances of different muffin fans on the market, you may need to play with the scaling slightly to fit your specific setup. Additionally, I added a 45-degree ramp to the bell-mouth curve, so no supports are needed for any of the parts.

Any constructive feedback is always welcome as I'm still learning! Please give me a thumbs up if you like it—it really helps, and it's a fair trade for a free print! 😉