You don't know this?
4 in a row: 1927, 1928, 1929 and 1930 by Collingwood. We lost the first 3 of those Grand Finals, and 1931, but came back to win 1932 and 1934, just a pity we stuffed up against South Melbourne foreign legion in 1933.
As for Richmond, hard to go past the 8 years 1967 to 1974 - 4 flags and 5 Grand Finals, 3 GFs in a row from 1972 to 1974 and out in the Preliminary Final in 1975.
Not sure 4 in a row is still possible.
DS
1927 Collingwood beats Richmond in freezing wet conditions 2:13 to 1:7. The lowest winning and losing scores in history.
1928 Collingwood draws the Semi and Richmond has to wait two weeks to play them in the GF and loses 13:18 to 9:9
1929 Richmond wins the grand final, but under the rules Collingwood who finished top of the ladder had the right to challenge and won the replay the next week.
1930 Geelong wins the grand final and again Collingwood challenged and won the replay. Coll d Rich by 3 points in the semi final.
The softest fourpeat ever, and if you want more pain.
1919 Richmond beats Coll in the GF and Coll as minor premier challenges and wins the replay.
1924 There is no grandfinal, just three weeks of round robin matches for the top four. Rich beats Ess in the last round and Ess and wins the premiership on percentage!