My throwing form is bad, but I can’t point out my errors. Additionally, I throw 70 mph and I experience elbow pain after pitching.
This may help some.
Ride that back leg longer and delay your throwing arm more. Everybody has different cues and drills for the back hip/leg but for the arm delay I’d just try to break your hands later. This is just to try and separate your hips and shoulders more at foot strike which should lead to more power/whip in your throws. Your shoulders open simultaneously with your hips right now so you’re using very little torque in your throws. I struggle with the same stuff.
I agree with Seth on separation between your hips and shoulders and front foot strike. This could be a mobility issue with your hips or because you are not strong enough to hold torsion between your lower half and upper body. Somthing that may help is hip lead. When you start you motion and go into leg drive, you have no momentum toward home plate. You need to have you body moving toward home plate before you even load your leg. Watch any professional in slow motion. You will see at the top of their leg kick they are starting to move toward home plate to help gain momentum and speed toward their target. This will even help you be less rotation with your upper half at the end of your delivery. The reason this momentum is critical is because it sets up your back leg angle to drive off of. When looking at how you drive your back leg, you drive with it straight up and down. You want your back leg to be at and angle to where you are forceing energy to home plate, not up. If you think about it you want all of your energy going in a straight line to home. You are loosing power by your drive leg being straight up and down upon drive. See if some of these things help mechanical wise, but one of the best ways to throw harder is get bigger. Hope this helps!
Ben (from your YouTube account name),
When I watched your video in slow motion, your pitching arm appeared to be “dragging”.
Since you mentioned that your elbow hurt after pitching, it signaled stress on the elbow.
I observed your elbow bend too quickly for you to produce your “whip” motion like a catapult launching. Ideally, you should form your “L” shape with the Ball points away from you, which will be the farthest point for the ball to be away from you. Your elbow went ahead of your shoulder turn. It means you are pitching more with your arms/elbow instead of generating the torque from the body turn.
My advice is to work with a good pitching coach to break down your mechanics first. Record yourself and watch in slow motion.
Good luck and enjoy baseball always!