The Vacmaster AM1202R Cardio54 became my fan of choice for indoor cycling. However, there is always potential for improvement, as the stock shroud is quite directional in regards to elevation.
Luckily someone designed an aerodynamically optimized wide angle shroud for this unit, that even features venturi ducts to smoothen the airflow. The model files can be purchased on Cults3d: https://cults3d.com/en/3d-model/various/vacmaster-cardio-am1202-air-mover-wide-angle-shroud-diffuser
I printed the design on a slightly upgraded Ender 3 Pro. You have to cut away about 2 mm on each side to make the model fit laying down on the print bed. Alternatively you could also print it standing up, but I fear that print quality will suffer.
It's also very important that you support-block the lower parts of the model (when printing it like I did, the outlet facing downwards). The only support you need are where the shroud connects to the fan case. You can't use organic supports, as they will be off the build plate. Use supports that generate within the model. You also need to disable any kind of brim and skirt, as they will be off the build plate too.
My slicer settings are 0,2mm layer height and 10% infill. PLA came out at 1d 16h print time. In the end I had to use PETG for the print, which I also set to a slightly lower speed for a total print time of 1d 20h.
The print used 281g/95m of filament.
There are a number of Phillips-screws on the fan that need to be removed to change out the shroud. A single security screw (Torx-TR) is located below the control panel, however, there is no need to loosen this screw. The case flexes more than enough to allow for an easy installation of the shroud.
I did conduct a simple performance test comparing the wind speeds at 1m (3') of distance.
Here are the results:
| Setting | Stock Shroud | Venturi Shroud |
| 1 | 22.6 kph | 10.0 kph |
| 2 | 26.6 kph | 11.8 kph |
| 3 | 32.4 kph | 13.6 kph |
I did not work out a test procedure for measuring the actual vertical flow angle before and after. However, I can tell that it massively improved. The stock shrouds vertical opening angle was very narrow with sharp edges. Now the opening angle is multiple times higher and airflow smoothes out towards the edges. It's exactly as imagined.
By placing a piece of paper on the venturi ducts we can also see them working correctly.
Thank you very much for the review. I have now made a 220mm version available as an included extra version on cults3d. I have printed it on a Bamboo P1S, much quicker I think, but don't remember exactly. Mine is PLA and holding up fine. But I do think PETG holds up better to wear and tear. But it might be harder to print, especially on an open printer like an Ender 3. Thanks for the review, and of course for buying me a pint of pale ale through your purchase!