verbs

[black cat]

please i want to ask question about the verb tense when we change a verb in the present and it ends with one vowel and one consonant but not w or y to past tense we double the consonant and then we add ed such the verb ( commit - committed ) but why the verb happen is different why don't we double the consonant. what is the rule

[Anglika]

Two-syllable words:
ED = If the stress is on the first syllable, the word only gets one consonant + ED.
ING = If the stress is on the first syllable, the word only gets one consonant + ING.

Examples: visit > visited, open > opened
happen > happening, enter > entering

ED = If the stress is on the second syllable, the word gets a double consonant + ED.
ING = If the stress is on the second syllable, the word gets a double consonant + ING.

Examples: refer > referred, admit > admitted
begin > beginning, permit > permitting

[black cat]

Two-syllable words:
ED = If the stress is on the first syllable, the word only gets one consonant + ED.

ING = If the stress is on the first syllable, the word only gets one consonant + ING.

Examples: visit > visited, open > opened

happen > happening, enter > entering

ED = If the stress is on the second syllable, the word gets a double consonant + ED.

ING = If the stress is on the second syllable, the word gets a double consonant + ING.

Examples: refer > referred, admit > admitted

begin > beginning, permit > permitting

but wahat about the verb ( invent ) it is with two syllables and the stress on the second syllable but we don't double the consonant..