I am making a life-size robotic dog, and i am having trouble with getting it to walk as it is too heavy for my 4 micro sg servos. Can i make the servos more powerful with more power? If not i can just see if i can make the dog lighter. Many thanks
If by 'Can i make the servos more powerful with more power?' you mean, if you use a higher voltage, will the device be more powerful, the answer is generally yes, but within limits.
Model servos typically have a fairly wide range of acceptable voltages, and are typiclaly run at voltages from 4.8V (i.e. nominally four NiMh/NiCd cells) to 7.4V (i.e. nominally two lipo cells). Typically, the higher the voltage, the greater torque and the greater speed you get from the servo, potentially at the cost of more heat and somewhat shorter life.
For example, this page shows differing performance for a range of (rather more expensive than the one illustrated above) servos, at variously 4.8V to 7.4V. Futaba USA servo chart. In the chart 'TQ' is torque and 'speed' is actually the time it takes to traverse, so smaller value is faster.
However, four micro servos are not going to have enough power to operate a lifesize dog, regardless of what voltage you apply.