So, I came to the conclusion in the previous post that otoshi is a dropping forward motion that happens right on the footfall, and that guruma is a turning and rising motion that happens an instant after the footfall. So, timing plays a role - otoshi is on-time and guruma is late (wrt the footfall).
The idea is that on or around the footfall, you do something to uke (or something happens to uke if you want to say it that way). You are pushing or pulling him - applying a force. This suggests that there is a proper and improper direction to put force onto uke. This direction thing plays into the otoshi-guruma concept.
- otoshi happens on the footfall as you put force onto uke in line with (or parallel to) his feet.
- guruma happens slightly later as you put force onto uke perpendicular to the line of his feet.
This is not absolute. It is possible to otoshi uke perpendicular or guruma him parallel to his feet, but for the most part and in a general sense, this rule holds - otoshi is related to the parallel offbalance line and guruma is related to the perpendicular line.
Patrick Parker, is a Christian, husband, father, judo and aikido teacher, Program Director for a Cardiac Rehab, and a Ph.D. Contact: firstname.lastname@example.org or phone 601.248.7282