Calculate the gear ratio for every gear

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Discussion Overview

The discussion revolves around calculating the gear ratio for various gears based on a Force vs velocity graph. Participants explore the necessary formulas and parameters required for the calculation, including vehicle speed, engine speed, and overall gear ratio, while addressing the challenge of an unknown variable, the radius of the drive wheel.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant presents a formula for calculating gear ratio but expresses uncertainty about the radius of the drive wheel needed for the calculation.
  • Another participant requests additional context for the problem, suggesting that relative gear ratios might suffice.
  • A third participant provides a response in German, indicating that the calculation should focus on vehicle speeds rather than pulling forces, and lists specific gear ratios for various gears.
  • Another participant mentions having contacted a teacher, who advised that the task should be solved using the diagram, noting that different gear ratios yield varying pulling forces at the same engine torque.
  • A later reply questions whether the minimal speed for the gears is indeed required and emphasizes the need for the wheel diameter to use the graph's velocity as an absolute reference.

Areas of Agreement / Disagreement

Participants express differing views on the necessary parameters for calculating gear ratios, particularly regarding the importance of the wheel diameter and whether to use minimal speeds or other reference points. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

There are limitations regarding the assumptions made about the wheel diameter and the specific context of the problem, which may affect the calculations. The discussion also includes references to different methods of determining gear ratios based on vehicle speeds and engine torque.

robax25
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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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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?
 
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:
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.
 
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.
 

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