Originally Posted by Skiddins
No they aren't.
I understand that the voltage sags when a load is applied.
I wasn't talking about the 'drop' while the cells are in use but the supply voltage, 7.2 v's 6V.
Take a DC motor, put it on a Dyno and increase it above the rated voltage, the Amps will increase, which means so does the power output.
This effect was used a lot in Robot Wars, take a 12V motor then supply it with 24V, the current will change in proportion to the voltage doubles, so the overall power QUADRUPLES
and of course it's life expectancy plummets.
But the reverse is true, if you reduce the volatge to the motors, the current will decrease aswell which means a drop in power.
As I said before, electric motors do not have the same rules as most electronics.
Skiddins you are not correct. I do not want to take this too long.
The power you use in a RC car is pulled by the motor from the batteries. Is not pushed by the batteries to the motor. So this is not a questions to put a motor on a dino and aply diferent voltages.
I will just put this simple. In a RC car you have an installed power supply lets say 7,2v and 4200mah.
With a 27t motor with no pinion on it and you can full throtle the radio and you will be there for 2 hours until the batteries go flat. It will long because the motor has no load and so is pulling just a few amps from the batteries.
If you put in the car a pinion of let's say 20T then you will be able to drive the car not very fast but for lets say only 30 minutes. You easily understand this and it happens because now you have "loaded" the motor and it is taking more amps from the batteries.
But if you mount now a 30T pinion your car will be like a bullet(Ok a small one) but you will able to drive it for only 10 minutes, and that is because now you "loaded" even more the motor. It is taking now a lot of amps from batteries and as the motor converts those into work it will drive faster because it will have more power-Watts.
this is why you concluded right that with gearing up comes less time to drive.
But now you can understand that if you do this with a more powerful motor (less turns) you will be able to do every thing like before but all the runs will be shorter, because the motor will use more amps from the batteries to convert those into watts, you will drive faster but less time.
Then come the situation where instead of using the 7,2v ans 4200mah you will using 6v 4200mah. You do all the same and everything will happen as before but you will notice that the same 27T motor will now drive the car slower but problably the same time.
But if you take for example a 19T motor with those 6v you will notice that if you gear it high you will be able to drive as fast as the 27T with 7,2v that is because you would be able to match the power-watts. Now you will understand that you have done that pulling more amps from the batteries and so you will drive as fast but less time.
This is what happens with 5 and 6 cells and mod motors,taking the right motor you will be able to drive as fast but always less time. It is physics.
My calculations just show this.
Sorry to bother the rest of you with the long text