Hey I am building a butler bot. To start off what type of motors should i use after i have the butler bot built it will weigh in about 100lbs what type of DC motors should use? how do i pick? how do i tell which motors will work? im think of going with car window motors since they push and pull about 25lbs of weight and four of toughs should give me all together 100lbs of push / pull. but idk any help in the right direction would be grate.
Those will probably do. You could also consider DC motors used for pulling heavy loads (like you see on some fishing boats), but these might be a little pricier.
Golf carts or old/fat people's scooter things are apparently a good source for really powerful motors, but probably overkill for this application (especially if battery life and cost are important)...
Power Wheels ride-on toy gearmotors can easily move that kind of weight, and they are cheap - you can't buy them direct, though, so you'll either have to salvage them from a Power Wheels toy, or get them off ebay.
Try to get the same type, in pairs (different models have different gear ratios); some of the ride-on toys have two motors (generally the 12V ride-ons with two speeds, the Hummer H2).
They are noisy, though (spur gears)...