Ok I go to a diff gym and there's a piece of equipment there I havent seen before. It has a pull up bar with weights on a pulley system. From what it looks like whatever weight you put on it is what it takes from your body weight. For example if I weigh 300 and I put the pin on 150 them get on the pads and pull I'm only pulling up 150. Am I right or off my rocker?
Well, plenty of them dont do the exact weight specified (the cybex's i've tested are about 30 lbs off or so), but you've got the general idea.