It is not possible to draw with a 7824 5A. In addition, it is not possible to regulate with just 1.8 V more. These regulators have a dropout limit of 2 V (typ.). Incidentally, series regulators are the worst choice, as the excess voltage has to be dissipated as heat.

Perhaps you can proceed more skilfully and not regulate the voltage, as this should be sufficiently precise, but the current flow depending on the speed. The back EMF can be evaluated for this purpose.

Depending on the type, motors can be controlled with pulse width modulation. There are also numerous integrated components that can be used.