Homemade Roots Blower: Second revision of the rotor profiles

Hopefully This will be the final designs of the Roots lobes before I start making it.

I decided to design a 3 lobe and 2 lobe rotor that would be compatible with supercharger case I designed, I will see which works out best by testing it in use. I will most likely make the 3 lobe first since I feel that the 3 lobe design is better.

I do not have any keyway broaches, for now I will just have drilled holes for the keyways. I plan on using a 1/8 round nose endmill to cut grooves into the shaft so that i can insert a 1/8 inch metal rod to lock together the rotor and the drive shaft. No idea how well that would work out though.

This 3 lobe is significantly smaller than what I had originally planned mostly due to the size restrictions of my small mill. The entire assembly is much smaller too.

Some advantages I see with the 2 lobe rotors is using less raw materials to make one and less machining required. Unlike the 3 lobe above, the centers of radii is different between the male and female lobes. I designed it this way because when they are equal, the center section becomes too thin to properly support the rotor.


I also made a rotor profile that just looked like an oval blob, was surprised that it actually works but the swept volume was very low so it's not very practical.

Next I will probably try to make a lysholm style rotor.

Rotor profile fail...

Apparently having symmetrical and perfectly round lobes does not work as the lobes will not mesh correctly. I will try to design a simple to make lobe profile in Autocad before I try again to make another set of roots rotors.

Making a DIY homemade Supercharger

Originally I wanted to make my own small engine supercharger. Or at least find out how difficult it is to make one. There are other alternatives for small engine superchargers such as smog pumps, crankcase vacuum pumps, and the chevy oil pumps. But all of those would have trouble supplying a decent amount of pressurized airflow to a small engine.

I think a small roots type supercharger would work out nicely for a small motor, but the thing is that there does not exist any. So i decided to make my own.

After some planning and drawing diagrams on random pieces of scrap paper i realized that it isn't as difficult as originally planned. the rotors are actually quite easily made. The only hard part is attaching the gears to the thing, because currently i have no ability to make gears.

I decided to mock up some blower rotors in wood first as an experiment to see how easily i can get it to somewhat resemble an supercharger.



Making that was surprisingly easy, all i needed was 2 hole saws for the inside and outside diameters. I cut out cylinders with one hole saw and used the other hole saw to notch the center part for the rotors to be attached to, basically 6 equidistant notches in a circle made the center part. Looking at this design i realized i could just use a hole saw to cut out the center part from a plate of metal and then weld/solder/braze/glue cylinders of tubing onto the center, and i would have some easily made roots supercharger rotors.
I could extend this step to make rotors as long and big as my drill press could handle, could be an interesting project later on when i start making them for bigger and bigger engines.

Now the next step is making some gears to prevent the rotors from constantly grinding each other. The rotor case should be easy enough to make, using a fly cutter to bore a hole. Making gears is the hardest thing for this project. I will try to make some gears from wood as soon as i get some gear tooth cutters.

My emphasis here isn't really on precision, mostly the bang for buck rating. If I can make boost on a wood roots blower i would use a wood supercharger hehe. Of course if the wood one doesn't last as long as expected then i would try to remake everything in some other cheap material such as plastic or mild steel.