delete all backups of all machines and reset time machine drive Delete all backups of all machines and reset time machine drive. 

As you can see I just want to start over. There are some great discussions on deleting one backup at a time. I have 30 or so. I am changing mac and I would like to just reset time machine. 

Please note the drive I have is external. So I can do it through disk utility by directly plugging in but I remember reading somewhere that it's not a good idea.
Just wipe the drive clean using Disk Utility and then have Time Machine start it all over again. I'm not sure what kind of issues you are going to run into because I've done that probably 50 times in my life and never had an issue besides falling asleep while I wait for an entire Time Machine backup to finish.