Hi, elise. Found this on Wikipedia and thought it was a pretty good short definition of a curb bit:
According to the article, the curb strap or chain acts as a fulcrum and allow the rider to amplify the pressure exerted on the bars/poll. So you're right - it does sort of keep everything together, in the same way a fulcrum keeps lever and load together.
What don't you like about your broken-mouthed curb bits?
The Action of the Curb Bit
A curb bit works on several parts of a horses mouth.
The bars: applied by the mouthpiece, and directly related to the length of the shank of the bit. The curb chain and a high port can also increase the pressure placed on the bars of the mouth.
The tongue: applied by the mouthpiece, with the pressure related to the thickness and type of mouthpiece.
The roof of the mouth: only applicable if the mouthpiece of the curb bit has a high port.
The poll: severity is directly related to the length of the upper shank in relation to the lower shank. All curb bits apply at least a little pressure on the poll.
The chin groove: pressure applied by the curb chain when the curb rein is used.
Side of the jaws: a curb bit may add some pressure to the sides of the jaw due to its length.
According to the article, the curb strap or chain acts as a fulcrum and allow the rider to amplify the pressure exerted on the bars/poll. So you're right - it does sort of keep everything together, in the same way a fulcrum keeps lever and load together.
What don't you like about your broken-mouthed curb bits?