They say necessity is the mother of all invention. I think that's a load, and the mother of invention is really laziness. Now-a-days, most inventions don't make tasks possible, they make them easier. The truth is probably somewhere in between. Either way, I still love coming up with ideas, and being able to put those ideas into motion.
I had one such "need" for an invention recently. I guess it's not so much an invention really, but a DIY version of something that is currently available on the market, just for more money than I am willing/able to pay. What I needed was a commercial blower unit to suck blown in insulation out of attics. They are available for purchase, at a price point somewhere around $5000. So I figured, I'm a smart dude, I went to engineering school, this is my jam. So I got to it, and what follows is my method.
Step 1: Design
I started out the same way I always do when planning out a build, build a model. I modelled all my parts and assemblies in Inventor, according to what I had available to me as par as parts, and made sure the concept wasn't completely off the wall. Being that I was able to research actual versions of the real machine it was much easier than if I were starting from scratch. I did a bit of research as far as general impeller size, benefits of different types of impellers, materials to avoid, etc. I could have gone further and used impeller curves to determine exactly what size of impeller would generate what kind of displacement ant certain speeds, as well as what sizes of input and outputs would be optimal. I did not do that, and I know that my machine could be more efficient because of that, but I'm ok with it.
I went with a 14 inch impeller, backwards curved blades, mostly determined by what raw materials I already had available to me for the impeller. I went with five blades, also just because. The impeller works in counter-clockwise rotation, based on the shaft rotation of the motor I was going to use.
I will try and add some Inventor screen caps later on.
I am in the process of a redesign right now. Instead of a direct drive, it will be a belt drive with a centrifugal clutch. This has many advantages over the original design, and all of this will be explained after I complete the project, again. I should be done the project by the end of the week, and the updated instructable will follow shortly.