As the title says, I know that different shifts mean different gear sizes bein used, but I don’t understand why it makes you unable to start moving the car. I have been able to start a couple of cars on the 2nd shift as an experiment and I understand that I could damage the car and I do it just once for testing purposes but I don’t understand why I cannot do so on other shifts. To clarify, I mean start as in start moving the car and not just turning the car on. Thanks
In: Engineering
To understand this it is probably best to understand what gears do and why. Imagine you have a circle with a radius of 1 unit. It will have a circumference two times the radius multiplied by pi, or ~6.28 units. Now imagine you have a second circle of radius 3 units, which means a circumference of ~18.85 units.
Suppose that our two circles are actually gears that mesh together, so when one turns they cannot slip and the other turns as well. The first, smaller gear has a circumference about 1/3 of that of the larger gear which means it needs to turn about 3 times before the larger gear turns once. This doesn’t just mean we can change the *speed* at which things turn in relation to each other, it also changes other aspects about how they turn. Even though that large gear will be turning more slowly it will be doing so more forcefully.
In the context of a car the car engine only works properly within a certain range of speeds. Usually they will idle between 600 and 1000 rpm, while on the highway they go up to 1500 to 2000 rpm. Car engines tend to have some problems around 5000 rpm. Note the ratio between those speeds is not that high; if you idle at 1000 rpm and go up to 3000 rpm while driving normally, if your car moves at 5 mph while idling then why don’t you top out at 15 mph at 3000 rpm? That is where gears come in.
At low gear your car engine spins a lot compared to how quickly the wheels spin, translating to more torque but lower speed. At high gear the wheels are spinning faster compared to the car engine which translates to more speed but lower torque. This means that when you are trying to start a car in a high gear you are trying to make the car spin the wheels *really fast* while the engine is barely moving itself. It just doesn’t work, the engine doesn’t have the power to do that.
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