The gears in the transmission aren’t actually turning, so why does a little gas keep me from rolling back but also not going forward?
In: 3
The gears are turning. At least, those on the engine side are.
They’re applying enough rotational force on the input side to the torque converter to stop the output side gears, and hence the drive wheels, from rotating in reverse.
There’s a special mechanism called a “clutch” that, oversimplified, controls how “tightly” the engine’s rotation is tied to the transmission’s rotation. If the clutch is fully engaged, the engine’s rotation and the transmission’s rotation MUST match, and if the transmission isn’t moving the engine halts. If the clutch isn’t engaged, the engine spins freely with no connection to the transmission. At levels in between, the motor might be spinning more than the transmission.
In a manual transmission, you generally can’t do what you’re saying easily. If you aren’t careful with the clutch, fully engage it, and don’t gain forward movement, the engine stalls. So starting the car moving uphill involves a lot of coordination where you push the gas and *slowly* engage the clutch so the wheels can start turning with only *partial* connection to the engine before you let the clutch fully engage. That way the engine doesn’t stall.
In an automatic transmission, the transmission handles all of that for you so the engine doesn’t stall.
Some drills have clutch mechanisms like that so they don’t strip screws if you’re using them as a screwdriver. When the screw resists the rotational force more than a certain amount, the clutch disengages and disconnects the drill motor from the bit. They make a lot of noise as the clutch engages, meets resistance, disengages, and repeats over and over again.
Same kind of principle in an automatic transmission, it’s letting the engine push *just hard enough* to keep the wheels from spinning backwards but staying *just disengaged enough* the motor can keep spinning.
Your transmission is still engaged if your foot is on the gas peddle, meaning it’s not in neutral. Also, this is a great way to overheat your automatic transmission and increase wear and tear on it. It’s best to let off the gas peddle and apply your break if you are stopped on a hill.
To do that you use an automatic gearbox. On a manual gearbox, you need to use the breaks or slipping the clutch, so you keep the car stationary primary by changing the clutch, not the accelerator.
Between the engine and gearbox, you have a Torque Converter where the connection is not a direct mechanical link but a device filled with oils where the engine rotates a pump and the gearbox is connected to the turbine and there is some other parts. You can learn more at [https://www.youtube.com/watch?v=bRcDvCj_JPs](https://www.youtube.com/watch?v=bRcDvCj_JPs) put what is important is that both sides do not need to rotate at the same speed and the engine can push on the input to the gearbox even if the gearbox do not rotate.
If the car starts to roll back the turbine in the torque converter will rotate backward too , to stop it from rotation there has to be enough pressure on it from the pump that the engine to drive
When you press down the accelerator the engine will increase the RPM and the pump will pump fluid with more force. So the pressure on the turbine is higher. If you press the accelerator just enough the force on the turbine from the car rolling backward will be the same as the force in the other direction from the pump the engine drive and as a result, there is no motion.
Put some light objects on a book and tilt the book until the object starts to slide. You can keep the object stationary at the same angle if you just blow on it with your mouth. You move the object up or let it slowly move down by controlling how hard you blow.
The air you blow is a fluid like the oil in the torque converter. So exactly like of you can keep a object stationary by blowing on it the engine can keep the car stationary even if the wheels are not spinning,
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