I'm undertaking a little project. I am wanting to outfit a cart like this (http://www.northerntool.com/shop/tools/product_200411313_200411313) with RC gear. It will most likely use a hub mounted gear and a motor shaft mounted sprocket to turn the rear axle. I need to know what size of motor and gears I need to purchase to move the load I will put on it. Would like to build an excel spreadsheet so I can compare gear/motor combinations. Here is some relevant information: Mass of trailer and load: 150 lb Maximum speed: 5 mph Maximum needed acceleration: whatever is reasonably close to human acceleraton Tire diameter: 10" Maximum grade: 30 degrees Min/max number of teeth on sprocket: 8-20 Min/max number of teeth on axle gear: 40-114 Maximum motor RPM: don't have an exact number but electric motors (as you probably know) can spin pretty fast I thank you for your help and look forward to learning how to calculate this.