Here are some exercises to help improve bass drum co-ordination while
playing triplets. We will layer triplets with the hands over a gradually
busier pyramid of patterns with the bass drum. The hi-hat will keep time
playing a straight quarter note pulse with the foot.
Play the eighth note triplets with ALTERNATE SINGLE STROKES. If it helps, put a light accent on the first note of each triplet. This will define the pulse against the bass drum part. Note that measure #6 contains the polyrhythm "3 against 2" (between the snare and bass drum). This is quite difficult to play when using hand to hand triplets.
Next, try the exercise using the same foot patterns, but produce a double stroke roll with the hands using the eighth note triplet "base" or wrist motion. Because the wrist motion is still the same, the physical coordination is the same.