Mechanical SpiroMètre

Design Inspiration

I designed and made an electronic spirometer with my grandfather while I was in high school. For fun and to challenge my self, I tried to remake it, but using only gears and rod-cranks.
PS. Sorry for broken English.

Printing indications

Nozzle 0.4

0.15mm at 50mm/s for most parts.

All the parts were printed with PLA or PLA+ except for the tourbillon which works better in PETG. It’s also important that all the parts are cleaned of stringing and printing artifacts.

Case

The ‘’whistle’’ part of the case should be printed flat on the bed with the filament of your choice.
The main case should be printed vertically with the smallest section on the bed. You may need to force supports only under the first bearing casing. The holes on top of the case for the sliders may need some rounding with a knife.

Gears
All of the gears were printed flat on the bed with PLA+. If you’re having trouble with the Big one, try printing it at 99% scale. If you do so, don’t forget to scale the crank-rod as well.

Shaft
The shaft must be printed upright and with a big brim to prevent it from moving.

Bearings

OK, so this one is a bit tricky, I really wanted to create a model which was all 3d printed. So I tried this model for the bearings.

https://www.printables.com/model/154655-bearing-608

They work fine for the shaft, but they don’t scale much. So I’ve used three 15mm bearings for the gears. Make sure you follow Kamil K instructions on how to print functional bearings. For a smoother spins you can use regular 608 bearings.

Assembly

I admit that this is a hard finicky assembly, but once everything is in place it spins smoothly. The hardest part of the assembly is to put the smallest gears in their spots. Start with the gears in the bearings. Insert the rod and the slider on the gears. Then, insert the assemble in the bearing casing, starting with the smallest one. The biggest gear can be mounted directly on the end support with the rod and slider on. The propeller is attached to the shaft with the small part called fit to shaft. This part is what goes in the bearing once the propeller is attached to it. TOLERANCE ARE TIGHT, most of the parts need a good firm press. Make sure everything is rolling and sliding before assembling it. A bit of oil goes a long way.

Easy assembly
If you have trouble with the assembly, you can take the easy way. Don’t use any of the gears, use only the two end support with the 608 bearings and the shaft. Insert the Tourbillon on the hex shaped part of the end of the shaft and fixed it to the end support. Make sur the spiral is starting from the same side as you blow! Voilà