For me, it probably has something to do with the "fixed interest" characteristic of Asperger's Syndrome. ANYTHING that is mechanical or has something to do with water fascinates me (the "switchitis" that Glenn referred to comes to mind), from cars to vacuums to power tools to air compressors to mixers, and I am always interested in seeing how things work. Had one of those "Real Power Tool Shop" toys when I was 7 and used the hell out of it. I spent a LOT of time disassembling broken electrical items around the house and playing with them, seeing what I could make. Such as the time I ran an old hair dryer motor off of a DC transformer, took a blower nozzle and put it over the end, and made a leaf-shredder out of it. Ran MANY little motors off of DC, and also made a "pencil eraser lathe" out of a paper shredder motor when I was 10.
I remember faintly when I was little, my mom picking me up and putting me in front of the White-Westinghouse washer so I could watch it wash. Then, when I could stand tall enough to see inside the washer, I did this on my own, often watching it from fill, to wash, watching the water action and taking in the smells of the detergent and Clorox bleach on some cycles. Then when the spin came and the lid locked, I pulled up hard on it so I could still see the tub spin through the small gap. Turned the WCI/Montgomery Ward dryer on with the door open and wondered why, with clothes in it, they would fall out. Also liked to start the Jenn-Air dishwasher and feel the steam come out of the vent during the wash cycle.
As for the vacuums, you've seen the pictures, LOL. Yet another mechanical fascination from day one. We had 2 1970's-vintage Eureka uprights for each floor of the house, one red, and the other blue. Of course they were called the "red vacuum" and the "blue vacuum". I LOVED the sound they made and of course was hooked on vacs instantly. One of the many reasons why I love those "blender-motor" Eurekas; each time I use my red-orange 664A it brings back a lot of memories, though I wish we had kept the two I grew up with. Of course when I was 2 years old, that vacuum didn't feel as lightweight as it does now!
I normally keep quiet about my obsession when it comes to others (both people my age I know in school and adults) unless they end up asking what my interests/hobbies are (then I end up spilling the beans of course), or in the case of relatives or family friends, they come over to visit and of course end up seeing the collection. I get a lot of strange looks when I do tell, but then I explain to them about my mechanical fixation and the fact that seeing how the transmission drives the agitator or watching the water splash around in a front-loader fascinates me...then they usually understand where I'm coming from. Most of the time they ask more questions, and I answer them! A few who I have talked more "in-depth" with about my obsession found out my strong appreciation for vintage everything, mainly because what is made now is nothing compared to what came out of the factory 50 years ago. I then mention about that the vintage machines are much more fun to use and watch compared to what they have now, and are much more stylish as well...then comes the part about the different types agitators and mechanisms and what makes them fun, etc. As long as they can get me talking I don't mind!
--Austin