Okay so. Let’s begin by the weight of the human part of a centaur.
A quick research gave me access to a list of different human body parts relative to total weights on this site. Summing it up, I found that for a 150 lbs (68 kgs) human the torso + head + arms is about 110 lbs (50 kgs).
I looked up the same things for horses but only found guides to weigh your horse, and a scientific paper that may have the answer, but it’s behind a paywall and I’m not coughing up 15€ to maybe get the answer I need.
Then I remembered I have a Facebook friend who’s passionate about horses, and has access to a lot of scientific literature. I asked her. I presented the question as something pretty weird, as I don’t know if people other than I are interested by strange scientific inquiries.
- If we take in account the center of gravity of a horse, behind the shoulders, we know that its position varies a lot based on the position of the head + neck block (the higher the head gets, the more the gravity center moves towards the rump), so – laws of physics – the head + neck block is an important part of the weigh of the horse, with a leverage effect.
- Also, the position of the center of gravity tells us that 50 % of the horse’s weigh is before that point : head, neck, shoulders, front legs. Even when comparing a strong torso + arms and a slender neck, it means that for a 1,000 lbs (450 kgs) horse the “front block” is about 500 lbs (225 kgs).
This doesn’t give us the weigh of the neck + head block, but it tells us that with the shoulders and front legs (that a centaur keeps) it’s nearly five times the weigh of the human part. And I doubt the front legs of a horse weigh that heavy (to give a vague idea, both legs of a 150 lbs human weigh about 52 lbs – 23 kgs).
Another thing about centaur anatomy (from the same trusted source) : in a centaur, the torso is (most of the time) held straight, so the center of gravity is closer to the rump than for a horse and the distribution of the weigh on the four legs is probably more even (for a horse about two thirds of the weigh is borne by the front legs). However back pathologies like kissing spines could happen more often, since equine anatomy means that horses need to lower their neck to limit the risk of back wounds.
That’s all folks, I hope my translation to English isn’t too bad!