About three hours after I took the castor oil, the effects kicked in. I spent a goodly amount of time in the bathroom.
But all in all, not nearly as bad as I had feared.
After that phase, I had about ?40 minutes of contractions about three minutes apart.
Alas, they have seemed to died down.
Now I am having twinges of contractions, and it's hard to bend over even a tiny bit... but that's about it.