with body weight exercises, your body adapts to a certain range of motion and resistance (your body weight) in your case it has adapted itself to us the machine because that is what it is used to. You may also do cheat sets, pull yourself all the way up and go down about half way and go back up. its...

the machine that you use is a crutch, your body has adapted to that movement and knows that is the easiest way to get the job done. when doing either exercise, pull your self up as high as you can for 10 reps of 3 sets, only go high enough so you can complete 10 reps, over time, each time you to do ...

If you are trying to gain mass in your triceps or anywere else for that matter, you need to progress overload for about 35-50 seconds of continus stress on that muslce. lay off the cario a little, only do about 3 exercises for your triceps, 4 sets of 8-12 reps and add more weight on each set.