Hello everyone. I'm new to this site and I am not an engineer. I'm more of a backyard tinkerer. Anyway, I have been reading many sites and came up with a design for a soil sifter. Everything looks good on paper but I am having difficulty with the sifting mechanism. Since I don't have a photo posted, I give a brief description of the project. I have a base which is 30" x 36" sitting on my lawn trailer. Inside the base I have rails which support a 28"x30" sifter which has 1/4" screen on the bottom. Initially I had this powered by a jigsaw. It was working well until the jigsaw died 20 minutes later. The sifter was mounted on casters and there wasn't any friction. It moved back and forth smoothly. Searching around the house and online. I came up with plan B. With plan B I am using a 1/4 horse washing machine motor with a 2" pulley. The 2" pulley turns a 10" pulley via 1/2" belt. The motor is mounted below the 10" pulley and I am using a 40" belt. I then built a crank and slider mechanism to give me the reciprocal motion. It works but man is it rough. I tried to research crank and sliders but most of what I found is way over my head with the math. So here is my question, is there a simple way to design or calculate the proper diameter of the crank, slider and connecting rod? Currently I have a bolt going through one of the spokes on the crank connecting it to a 1"x1"16". The connect is loose enough to allow the shaft to move freely. The other end of the shaft is attached to the sifter tray and can move freely. Does this make any sense to you guys? Any ideas or suggestions on how to make a crank and slider that isn't so rough? Maybe you can recommend another method to provide the reciprocal motion I need? I'll try to post pictures tomorrow. Thanks.