## Drive calculation for vehicles

### 1. motor speed: n, RPM

**v** _{km – vehicle speed, km/h;}

**v** _{ml – vehicle speed, mil/h;}

**R**_{m – rolling radius wheel, m;}

**R**_{in – rolling radius wheel, in;}

**i** – transmission factor from motor to drive wheels. Without transmission gear, i=1.

### 2. rolling resistance: RR, daN [lbs]

Resistance force, which results from the contact of the wheels on different surfaces:

RR=G x ρ

**G**– total weight of the vehicle load, daN [lbs]

**ρ**– coefficient of rolling resistance (Table 1)

### 3. gradient resistance: GR, daN [lbs]

GR=G x (sinα + ρ x cosα)

**α** – inclination angle (Table 2)

### 4. acceleration force: FA, daN [lbs]

The force **FA,** required to achieve acceleration from 0 to a maximum velocity **v** in time **t**, is calculated using the following formula:

**FA** – acceleration force, daN [lbs]

**t** – time, [s].

### 5. tensile force: DP, daN [lbs]

Tractive force DP is the additional tractive force required to move the trailer. This value is calculated as follows:

- according to the designer’s assessment
- by calculating the forces according to points 2, 3 and 4 for the trailer; the calculated sum corresponds to the tractive force sought

### 6. total tensile force: TE, daN [lbs]

The total tractive force TE is the tractive force needed to move the vehicle; this is equal to the sum of the forces calculated according to points 2 to 5 with a increase of 10% due to air resistance.

TE=1,1 x (RR + GR + FA + DP)

**RR** – force needed to overcome rolling resistance;

**GR** – force needed to overcome the slope;

**FA** – force needed for acceleration (acceleration force);

**DP** – additional traction effort (trailer).

### 7. torque of the motor: M, daNm [in-lb]

Required torque for each hydraulic motor:

**N** – number of motors;

**η _{m}**-mechanical efficiency of the gearbox (if any).

### 8. wheel adhesion: M_{W}, daNm [in-lb]

To avoid wheel slip, **M _{W}** should be larger than

**M.**

**f**– Coefficient of friction;

**G _{W}**– total weight over wheels, daN [lbs]

**9. radial load of the motor: P _{rad} [daN] [lbs]**

If the motor is used to drive vehicles with wheels mounted directly on the motor shaft, the total radial load on the motor shaft **P _{rad}** is equal to the sum of the driving and load force acting on one wheel.

**G _{W}** – Gewicht, getragen vom Rad

**P**– Total radial load on the motor shaft

_{rad}**M/R**– Driving force

Gemäß den berechneten Belastungen kann der passende Motor aus diesem Katalog ausgewählt werden.