I have a Eureka “Boss Excalibur” upright vacuum cleaner and I need to change the belt on it. (That’s what my mother says at any rate and since it’s ma, I believe her.)
How do I do this?
And perhaps more importantly how do I know what kind of belt I need and where can I buy one?
Steps to changing a vacuum belt
My hardware store has them, about a dollar or two each. thee package says what model its for. Or an appliance store. I dont know your model but usually just turn the thing upsidedown, take off the screws on the bottom, pull the base off & there you should find a belt. It probably slipped off & you can take that to the store for a match. Just fit a new one back on, easier said then done.
The classic Kirby™ vacuum (that was copied in one form or another by several competitors), has a faceplate on the sweeper assembly that rotates. (In old machines, it was a circle with a handle on it; in new machines it is 3-D rectangular plastic.)
As that is being rotated out of position, a curved flange inside pulls the belt away from the driveshaft connected to the motor.
A latch at the top of the sweeper assembly unlocks to allow the sweeper to fall away from the vacuum. The sweeper can then be lifted off pins to be handled separately.
Turning over the sweeper, two thumb-latches can be turned to release the metal grille that holds the roller in place.
(Watch for the “right” and “left” sides to the roller to allow easier replacement, later.)
Rotate the faceplate back to the “Normal” (vacuuming) position, thus releasing the belt from the flange.
Remove the roller. Remove the belt from the roller. (Remove the 1,000 yards of string and thread that caused the roller to jam, wearing out the belt.)
Place the new belt over the roller, holding it in the middle during the next step.
Insert the roller back into its place in the sweeper. (Watch for the “right” and “left” sides to insert it correctly.)
Rotate the faceplate back to the “Remove” position, forcing the belt to be held in place with an opening where the driveshaft will poke through.
Place the grille back on the sweeper, hooking two small tabs on the front of the sweeper into two small slots in the grille. Pivot the grille back into place. Reclamp the thumb-latches.
Place the sweeper on the front of the vacuum, placing the “C” shaped hinge units over the pins that look like the ends of an axle on the front of the vacuum and rotating the sweeper back up onto the face, latching it at the top.
Crank the face-plate back around to the upright position: this will cause the curved flange, inside, to grab the belt and pull it over the driveshaft.
If the Eureka™ looks nothing like a Kirby™, you’re on your own.
Lots of companies now have their Owner’s Manuals online. Unfortunately, Eureka isn’t one of them.
However, they give a number on their Web site to call about getting one, in case you run into more serious problems with the machine after changing the belt. Always good to have manuals around, so you can be extra cool and fix things yourself and then call mom and tell her something is FIXED, not BROKEN 
Here’s the #, by the way: 1-800-438-7352
I find once you unscrew the bottom plate covering the works by the rotating brush, it’s fairly easy to figure out where the belt goes.
However, getting a new belt on our Panasonic takes superhuman strength. I thought I’d never get that rat bastard stretched over the right parts. I live in fear of the belt snapping again. It was such a headache.
Thanks all. I’m off to the hardware store on the morrow. Perhaps I’ll only have to make one trip. 
ZipperJJ I did have the owners manual for all my stuff, until I moved. They were all in a box together and wouldn’t you know it, that’s the box that didn’t make it. Along with a couple of boxes of my favorite books. Still not quite over that. Thanks much for the number.
And I did fix the toilet all by myself earlier this week. I feel like such a big girl.
As for the physical strength to stretch the belt thing CrankyAsAnOldMan mentions, we’ll see how that goes. I’m moderately strong but not super-humanly so.
They take strength alright but you can use a tool to make it easier. I bet those appliance guys have something special to use.
You forgot the most important part…
First put on your space suit. Go into the airlock. Decompress the airlock. Go outside into the vacuum of space.
What?
Oh … ON a vacuum.
<blush> I’ll be going now.
Open the pod bay doors, HAL.