* Shell: The "e" at the end of "shell" is silent. The word is pronounced "shel." It is not a short "e" sound.
* Belt: The "e" at the end of "belt" is also silent. The word is pronounced "belt." It is not a short "e" sound.
Short "e" sounds are usually spelled with the letter "e" in a one-syllable word, like "bed," "get," and "pen."
Therefore, neither "shell" nor "belt" have short "e" sounds.