擂 (léi) is used for heavy, repetitive pounding or banging. When read as 擂 (lèi), it refers to a platform for martial arts contests (擂台, lèitái). The two readings have distinct meanings.
Hand radical on the left fixes the action: 擂 is something done with the hands — pounding, banging, beating. Same radical drives the whole physical-action family: 打 hit, 拉 pull, 推 push, 抓 grab.
Right side supplies sound and a vivid sound-image together: léi → léi (exact match), and thunder's booming rumble matches the drum-beating sense of 擂 perfectly — 擂鼓 'beat the war drum' is essentially making man-made thunder.
