The last entry in this series was about barbells. For barbells to be useful, you need plates for them.
As discussed in that post, there are two types of straight barbell bars: standard and Olympic. The bar ends have a significant difference in diameter. The standard bar stays the same (around 1 inch) while the Olympic bar gets much larger: about 2 inches (50 millimeters). Thus, each bar uses different plates: the standard bar uses plates with holes around 1 inch while the Olympic bar plates have holes around 2 inches.
While all plates can come in various heights depending on the weight, the standardized height of Olympic plates for competition is about 18 inches (450 millimeters). This is the height of a 45-pound plate. However, lighter plates can also be of this same height by using "bumper plates." These are coated in solid rubber to allow the bar to be dropped from a considerable height, as happens during Olympic lifts (the snatch and the clean-and-jerk). Bumper plates also allow you to raise the bar off the floor the same height as a 45-pound plate but with a smaller load which is helpful for people who aren't yet strong enough to deadlift a 135-pound load (two 45-pound plates plus the 45-pound bar). But this comes at a price: bumper plates are much more expensive than the usual cast iron.
When you have weight plates, the question arises: where do I keep them? One option is to just set them on the floor, but a better choice--if you have the space and money---is to use a plate tree. They can be a bit pricey (they have to be very sturdy, after all) but they're darn handy. There are DIY options available for adventurous, handy folks. (Search on diy weight plate tree. )
I use a purchased tree for most of my Olympic plates. Some plates I leave on the bars, some I leave on my power rack (more on that in a future post). I set the tree on a small platform to raise it up a bit: bending over with heavy plates at the end of a workout can be less than fun.
While weight plates are for use on barbells, they can also be used alone for some exercises such as plate halos or 90-degree vertical plate presses.
If you use barbells (and everyone should...really), you need plates. They're not just for dinner anymore. (At least I waited to the end for that one.)
Be seeing you.
-gary