It looked like dad was in a race riding a horse and he needed to win at any cost. The speed was so fast with two opposing motions. Dad's thrusting his hips as fast as he could and also moving my mom's hips back an forth with his hands grabbing her by the waist. It was well over 120 rpm by the end of the race when dad let out a loud whisper 'AAAHHHHH'. Then "phaarrrrrrrr sluurrp prlp", the exact sound of diarrhea. Like somebody pooped loose motion but it didn't smell like shit, it smelled like pussy juice and cum mixed and rubbing against one another and drying up and becoming more concentrated, more sour, more salty over the passing night.
He then turned over mom like a piece of meat, pulled up her nightgown till her neck exposing her firm but slightly dangling boobs.
Spreading mom's legs on both side he was grinding upright at first, but leaned more and more forward over time. Putting my mom's legs over his shoulders, he was drilling mom top down, his own legs straight behind. It was a spectacle to watch, like a tunnel being bored between mom's legs using a high-power machine. This too went for about an hour. Mom's legs were turned 135 degrees towards the wall behind her head. Dad was panting hard digging mom at maybe 150 rpm this time and he finally finished with few hard thuds, I could hear their bone smashing and dad struggling to catch his breath like after running hard to save his life.
Lastly, the finisher. I named it the flying chariot. Dad will order mom to get totally naked pulling out her nightgown, put mom on her knees again, enter from behind like a gorilla, but this time he pulls mom's both hands behind her until mom's head is in the air pointing ahead like a bird flying with her wings spread. Dad pumps in hands-behind-back-doggystyle. This was more brutal than the hardest hardcore porn I ever watched. It was pure BDSM without whips or handcuffs.
Dad was riding the flying chariot at a perhaps world record breaking speed, moving the whole mattress over the floor, sweating, panting but not giving up another orgasm. Dad was literally risking killing mom. I could hear mom's muted moans, sobbing and sniffing. It was easily over three hours since dad started the torture. It was like being in the center of an earthquake and thunderstorm and dad riding a coal powered steam engine to save the last of humanity. Pushing the coal as fast as he could behind the engine which was mom running at it's max speed.
To be continued.