Gear ratio calculation for a transit bus

In summary, the type of transmission to use for a hybrid transit bus should be based on its specific power requirements, with automatic transmissions being best for high torque needs, and manual or CVT transmissions being more suitable for low torque needs. A single gear transmission can also be used, but may not be as efficient as a multi-gear transmission.
  • #1
pchoopanya
25
0
Hi there,

I am simulating the hybrid transit bus,

Its max speed is at 60 kph, most speed used on road is below 20 kph (more than 60% of its total operation time)

The bus follows stop-and-go pattern almost all the time.

The bus is to be fuel cell/battery hybrid, therefore it uses an electric motor as a traction motor

I need to specify its transmission and not sure if whether I should go for

1. Manual transmission
2. Automatic transmission
3. CVT

For a transit bus, how do I determine what type of transmission it should be?

Also, some texts suggest that the traction motor is capable of achieving ideal torque curve therefore a SINGLE gear transmission would suit this. How's this?

Should I go for a single gear for simplicity or multigear? What is the advantage and disadvantage of single gear?


Thank you
 
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  • #2
for your question. For a transit bus, the best type of transmission to use would depend on the power requirements of the bus. If the bus requires a lot of torque, such as when it is accelerating from a standing start, then an automatic transmission would be the most suitable option. This is because an automatic transmission can provide a wide range of ratios which allow the engine to operate at its most efficient regime. If the bus does not require a lot of torque and operates mainly in urban areas, then a manual transmission or Continuously Variable Transmission (CVT) may be more suitable. Manual transmissions are simpler, more reliable and cheaper than an automatic transmission and CVTs can also provide a wide range of ratios which allows the engine to operate at its most efficient regime. A single gear transmission would be suitable for a hybrid transit bus, but there are some drawbacks. A single gear transmission does not provide a wide range of ratios and the engine will not be able to operate at its most efficient regime. Furthermore, a single gear transmission is less economical than a multi-gear transmission as the engine must always run at the same speed regardless of the load on the vehicle. Ultimately, the decision on which type of transmission to use should be based on the power requirements of the bus. An automatic transmission is the best option if the bus needs a lot of torque, while a manual transmission or CVT is more suitable for applications that do not need a lot of torque. A single gear transmission is suitable for hybrid transit bus, but should only be used if the power requirements are low and the engine can operate efficiently.
 

1. How is gear ratio calculated for a transit bus?

The gear ratio for a transit bus is calculated by dividing the number of teeth on the driven gear (usually the rear axle) by the number of teeth on the driving gear (usually the engine's crankshaft gear). This gives you the overall gear ratio, which determines how many times the engine must rotate in order to turn the wheels once.

2. What is the purpose of gear ratio in a transit bus?

Gear ratio is important in a transit bus because it allows the engine to operate at its most efficient speed while still providing enough power to move the heavy vehicle. It also allows the bus to achieve different speeds and torque levels by changing gears.

3. How does gear ratio affect fuel efficiency in a transit bus?

The gear ratio has a direct impact on fuel efficiency in a transit bus. If the gear ratio is too high, the engine will have to work harder and use more fuel to turn the wheels. On the other hand, if the gear ratio is too low, the engine may not have enough power to move the vehicle, also resulting in poor fuel efficiency. Finding the optimal gear ratio is crucial for achieving the best fuel economy.

4. Can gear ratio be changed in a transit bus?

Yes, gear ratio can be changed in a transit bus by replacing the gears in the transmission or axle with ones that have a different number of teeth. This is often done to improve performance or fuel efficiency, but it can also be necessary if the bus is operating in different terrains or carrying different loads.

5. How do other factors, such as tire size, affect gear ratio calculation for a transit bus?

Other factors, such as tire size, can affect the gear ratio calculation for a transit bus. If larger or smaller tires are used, the overall gear ratio will change, which can impact the vehicle's performance and fuel efficiency. It's important to take all of these factors into consideration when calculating the gear ratio for a transit bus.

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