I have probably been washing clothes in this hand-powered washing machine for over 25 years. It has two funnels inside the tank that serve as plungers, agitating the water every time the handle is pumped. The inside dimensions of the tank are: 15" tall, 33" long, 14" wide.
The idea was originally for construction in wood. It came from a village technology handbook. I built mine out of iron and cement, and came up with the funnel plunger idea. The rectangular tank uses a special sheet metal with holes for plastering called Hi-rib. It is sealed with a cement-base sealer.
My method is to soak the clothes in detergent and water overnight, pump them for about 5 minutes in the morning, rinse them twice and hang them up on the clothesline.
It's good exercise, and it consumes no electricity.
Step 1: Inside the Washer
The funnels go up and down. Shape-wise, the funnel is streamlined and cuts the water as it moves upward. Coming down, it creates more churning action because of the less streamlined bottom.
The funnels can be easily replaced if they eventually break, but they hold up quite well. The bright red funnel was recently replaced.