Even aerospace engineers will make small models to support their calculations and assumptions before building something really expensive. Practical uses for even these models of moving props could be for the actors trophies or other appreciation awards or locking them up like a secret receipe.
Then chose hardware that has known pre engineered loads and safety factors that are known. Use wooden links to mock up what you want then convert it to metal with proper bearings and such. Even poster board cut outs become useful with pins like childrens pocket puppets. With little marks it is a ruler of something larger.
Center of gravity and weights of materials require a little research. You could also befriend an Engineering student of even a whole class to check your work and suggest improvements. They like to show off.
Industrial manufacturers of cylinders love handing out engineering data as it means you might buy their products. Some of the best basic charts come from manufacturers of materials and devices and are way more specific and worked out compared to any text book.
You can become and immediate genius just by reading the instructions.
Another fabulous post from the U.S.Department of Wild Imaginings, now in spectaclar stereo, sponsored by the Adhesives and Sealants Council, suggesting ways to stick things together since the 1800s. Not fabulous in a gay way. Your results may vary. Illinois residents add 8% sales tax. These posts have been made by professional post makers, do not try this type of posting on your own without extensive training, lovely assistants and a trusty clown horn.