Monster guts and Wiper motors are cheep and simple but you can run a monster guts motor in a 4 arm but i agree with kid 2 arms are pretty good and easy to make. I have monster guts running 8 arms but that's a lot of work to make so it doesn't break. If you want more arms i would go with a bigger motor. The big ones that turn the f fliers use big real motors but they are a lot more $$ thats why they charge so much. You could build them for basically half of what they charge. Its not rocket science. I have built tons of circus toys and if I was going to start over I would build 2 arm cheep rotaries and if I want more I'd pony up the bucks and get big motors and build what ever you want. But find a group of friends to deploy all of it.