Succesful taketowns?

In my jujitsu class i train with men which are alot heavier than me and i cant seem to take them down without them landing on top of me. How do i succesfully take them down?

avoid shooting in under them. If they're that much bigger than you, it will usually end poorly, especially if you're not experienced with shooting in. Work on tying up with their upper body and use movement. Try to get to the side of them with say a russian 2 on 1 or anything so that you're not coming in directly at them. Also having a good front headlock and sprawl can help to negate their shooting in on you. Just an idea, but that's why I never do double or single legs on big guys.

You can shoot on them, you just have to use a sweep single or the like.

i recently worked on this with my coach and some points to keep
in mind are (especially when shooting from the outside), try to
always initiate your shot from an angle and if you feel their weight
coming down on you, immediately turn the corner.

if you do end up getting sprawled on do not give up. keep driving
and turning.

there are some really great tips in the Wrestling forum's saved
threads which can give you all the info you need.

i'm still a takedown novice so hopefully i'm not giving incorrect