Calculate the gear ratio for every gear

In summary, the conversation is about calculating the gear ratio of every gear from a Force vs Velocity graph. The formula given is V=2*pi*r.n(1-i)/ε, where v is the vehicle speed, r is the radius of the drive wheel, n is the engine speed, ε is the overall gear ratio, and i is the slippage of the drive axle. The problem is that the radius of the drive wheel is unknown and the speaker is unsure which formula to use. Some context is provided, mentioning a course in Fahrzeugtechnik and an email exchange with a teacher. The teacher suggests using the minimal speed for the gears, but the speaker believes that the wheel diameter is still needed for accurate calculations.
  • #1
robax25
238
3
Hi, I have Force vs velocity graph. From the graph, I need to calculate the gear ratio of every Gear.
This is the formula what I can use to find the gear ratio,

V= 2*pi*r.n(1-i)/ε

v= vehicle speed m/s ( I consider from the graph lowest speed 3.61 m/s or 13km/h
r= radius of drive wheel
n=Engine speed ( From the graph, 5500 rev/min or 91.667 rev/s)
ε= overall gear ration( In this case, it is 0,85)
i= slippage of drive axle.

The problem is that I don't know the radius of the drive wheel. Can anybody tell me please which formula should be fit for the problem?
 

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  • #2
Where does this problem come from? Some context would help (ideally translated, but German is better than nothing - I'm German, I can read it).
Maybe you only need the relative gear ratios?
 
  • #3
Fahrzeugtechnik (3. aktualisierte) Werner klement

Sie sind richtig. .

Es gibt erläturungen.

Da I am Diagramm unterschiedliche Wirkungsgrade angeben sind, so sollte die Ermittlung nicht über die zugkrafte erfolgen, sondern nur über die Fahrgeschwindigkeiten.Hier kann mann entweder den punkt der Abregelung nehmen order die kleinste fahrbare Geschwindigkeit, da die Mindestmotordrehzahl unabhängig vom geschalteten Gang ist. Es ergibt sich dann:
Lösungen sind Gang 1. 3,9 Gang 2: 2.3, Gang 4: 1.44 Gang 5. .81
 
Last edited:
  • #4
Ich habe schon der lehrer einen email geschreiben und Sie haben schon geantwortet. Die Antwort ist

Die Aufgabe 1.6 müssen Sie mit Hilfe des Diagrammes lösen. Die Übersetzungen ergeben unterschiedliche Zugkräfte bei identischem Motormoment.
 
  • #5
To summarize: You are expected to use the minimal speed for the gears? I think you still need the wheel diameter, otherwise you can't use the velocity (x axis) of the graph as absolute reference.
Maybe the course expects some standard wheel diameter, I don't know.
 

What is the gear ratio?

The gear ratio is the ratio of the number of rotations of the input gear to the number of rotations of the output gear in a gear system. It determines how much the output gear will rotate in relation to the input gear.

How is the gear ratio calculated?

The gear ratio is calculated by dividing the number of teeth on the output gear by the number of teeth on the input gear. For example, if the output gear has 20 teeth and the input gear has 10 teeth, the gear ratio would be 20/10 or 2:1.

Why is knowing the gear ratio important?

Knowing the gear ratio is important because it helps determine the speed and torque of a gear system. A higher gear ratio means the output gear will rotate more times than the input gear, resulting in a slower speed but higher torque. A lower gear ratio means the output gear will rotate fewer times, resulting in a higher speed but lower torque.

How does the gear ratio affect the performance of a machine?

The gear ratio can greatly impact the performance of a machine. A higher gear ratio can provide more power and strength, making it suitable for heavy-duty tasks. A lower gear ratio can provide more speed and precision, making it suitable for tasks that require more accuracy.

How can the gear ratio be adjusted?

The gear ratio can be adjusted by changing the number of teeth on the gears. A larger gear with more teeth will result in a higher gear ratio, while a smaller gear with fewer teeth will result in a lower gear ratio. The gear ratio can also be adjusted by changing the size of the gears, as larger gears will have a higher gear ratio than smaller gears.

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