Dimension of a commercial vehicle plays a very important role. The application as well as performance of a vehicle changes drastically with respect to it's overall dimension. There are plenty of dimension related laws too. All the automotive manufacturers in India are required to adhere to the laws mentioned under CMVR (Central Motor Vehicle Rules).The sections below would help us in understanding the different dimension related terminologies as well as their impact on overall performance of the vehicle.
Q. What is wheelbase?
A. The wheelbase is the measurement of distance between the centre of the front axle to the centre of the rear axle for a two-axle vehicle. In case of a multi-axle vehicle, the wheelbase is measured from the centre of the front axle to the middle point of drive & the tandem axle.
Q. What is the importance of wheelbase ?
A. "Wheelbase of a vehicle not only impacts its dimension, but also influences the overall performance of the vehicle in terms of-
-Turning circle diameter
-Efficiency of power transmission
-Stability
-Tyre life
A vehicle with shorter wheelbase would most likely going to have a shorter deck length, whereas a longer wheelbase vehicle is going to have a longer deck length.
A shorter wheelbase vehicle will have shorter turning circle diameter as well as better power transmission. A longer wheelbase vehicle would tend to have better stability.
"
Q. Why there are multiple wheelbases for a single GVW vehicle ?
A. There could be multiple wheelbases for a particular tonnage segment of vehicle. Different length of wheelbase allows accommodation of different types of items based on their density or specific gravity. For example, a shorter wheelbase is suitable for higher density goods such as agri, cement, construction aggregates, etc. An Intermediate wheelbase is suitable for medium density goods such tanker, LPG cylinders, reefer, etc. Whereas a longer wheelbase is suitable for lower density goods such as FMCG, white goods, E- commerce, automobiles, etc.
Q. What is the meaning of overall length of a vehicle ?
A. Overall length of a vehicle is the measurement of distance between the front most part of the vehicle to the rear most part of the vehicle.
Q. Is there any law related to maximum permissible length for a truck ?
A. Maximum permissible length for a rigid trucks in India is 12 meters. In case of tractor trailers, the maximum permissible length is 18.75 meters.
| Haulage Truck | Tractor Trailer | |||||||||
| General carrier | Container Body | ISO standards shipping containers | Motor vehicle/ Construction equipments | General carrier | ISO standards shipping containers | Motor vehicle/ Construction equipments | ||||
| Length | 12 m (39.4 ft) | 12 m (39.4 ft) | 18 m (59 ft) | 18.75 m (61.5 ft) | ||||||
Q. What is the importance of overall length of a truck ?
A. "Length of a truck plays a very important role for the transporters. Selecting correct length of a truck is quite crucial as it impacts payload, tyre life, power transmission efficiency, stability & manoeuvrability. A high density product for example boulder, may not require a longer loading deck. At the same time, high volume consignment such as a refrigerator would need a longer loading span. "
Q. How different overall length of a vehicle affect its applications?
A. "There are multiple length of a truck for a particular tonnage vehicle which allows loading of different items based on their density or specific gravity.
A shorter overall length deck is :
• Suitable for carrying high density loads.
• Suitable for intracity movement for better manoeuvrability.
Example- Sand, Cement etc.
A Longer overall deck length is:
• Suitable for carrying intermediate/ low density goods
• Preferred for highway movements.
Example- Consumer durables, Cars, FMCG etc."
Q. How deck length of a vehicle is measured?
A. It is the loading area available on any commercial vehicle, which measured between the rear of the cabin to the rear end of the chassis frame.
Q. What are the implications of deck length?
A. Application of the truck changes with deck length. A shorter deck length is suitable for carrying high density goods like sand & cement. A longer deck length on the other hand is required for carrying intermediate to low density goods like coal & consumer durable products.
Q. How different deck length of a vehicle affect the applications?
A. "There are multiple loading deck length for a particular tonnage vehicle which allows loading of different items based on their density or specific gravity.
A shorter overall length deck is :
• Suitable for carrying high density loads.
• Suitable for intracity movement for better manoeuvrability.
Example- Sand, Cement etc.
A Longer overall deck length is:
• Suitable for carrying intermediate/ low density goods
• Preferred for highway movements.
Example- Consumer durables, Cars, FMCG etc."
Q. How is overall height of a vehicle measured?
A. Overall height of a commercial vehicle is measured from the surface to the uppermost part of the vehicle such as cabin/ load body/ container/ tipper canopy, etc. In case the cargo height is higher than the truck, then the height of the cargo from the ground is taken into consideration for the measurement of height.
Q. Is there any law related to maximum permissible height of a commercial vehicle ?
A. Yes, there are laws related to maximum permissible overall height of commercial vehicle in India, please refer to the table below.
| Haulage Truck | Tractor Trailer | ||||||||
| General carrier | Container Body | ISO standards shipping containers | Motor vehicle/ Construction equipments | General carrier | ISO standards shipping containers | Motor vehicle/ Construction equipments | |||
| Height | 4 m (13.12 ft) | 4.52 m (14.83 ft) | 4.75 m (15.6 ft) | 4 m (13.12 ft) | 4.52 m (14.8 ft) | 4.75 m (15.6 ft) | |||
Q. What are the impact of overall height?
A. Longer overall height though allows larger volume to stuff material but they also lead to higher centre of gravity which means lower vehicle stability and higher drag while the vehicle is on the move. A shorter overall height on the other hand will offer higher stability, but at the cost of load volume capacity.
Q. How overall width of a vehicle is measured?
A. Overall width of a vehicle measured from the one side of the vehicle to the other side, excluding outside rear view mirrors.
Q. Is there any law related to maximum permissible width of a commercial vehicle ?
A. Yes, there are laws related to maximum permissible overall width of commercial vehicle in India, please refer to the table below.
| Haulage Truck | Tractor Trailer | ||||||||
| General carrier | Container Body | ISO standards shipping containers | Motor vehicle/ Construction equipments | General carrier | ISO standards shipping containers | Motor vehicle/ Construction equipments | |||
| Width | 2.6 m (8.5 ft) | ||||||||
Q. What is the implication of the width of a truck ?
A. Usually the commercial vehicle manufacturers & the fabricators go for maximum permissible width for ensuring accommodation of goods in larger quantities. Excess wider structure however may lead to higher instability, higher drag and poor manoeuvrability of the truck.
Q. What is front & rear overhang ?
A. Front & rear overhangs are the length of a vehicle extending beyond it's wheelbase at front and rear end respectively.
Q. I s there any law related to maximum length of front & rear overhang ?
A. Maximum permissible length of front overhang is 40% of the wheelbase of the vehicle, whereas maximum permissible length of rear overhang is 60% of the wheelbase length.
Q. What are the implications of overhang?
A. Longer overhangs lead to longer chassis length thereby offering longer loading span. However longer overhangs may also lead to vehicle instability, lower tyre life, longer clearance circle diameter and lower approach & departure angles.
Q. What is wheel track?
A. For an axle mounted with two tyres, the wheel track is the measurement of distance between the centre line of one tyre tread to the centre line of the tyre tread on the opposite side. In case the axle is mounted with two tyres on each side, the distance is measured between the mid point of the centre line of both the tyres on one side to the mid point of both the tyres on the opposite side.
Q. What are the implications of wheel track?
A. "Both shorter as well wider wheel track have their own advantage & disadvantages.
Shorter wheel track:
• Advantage- Lower TCD (Turning circle diameter)
• Disadvantage- Lesser vehicle stability
Wider wheel track:
• Advantage- Higher vehicle stability.
• Disadvantage- Longer TCD"
Q. How the ground clearance of a vehicle is measured?
A. Ground clearance is the distance between ground and the lowest fixed portion (typically the axle/differential) of the vehicle.
Q. What are the implications of ground clearance?
A. Off roading capability increases with higher ground clearance. A vehicle with higher ground clearance will have lesser chances of underbody damages. Too high ground clearance however may lead to vehicle instability as well.
Q. What is approach angle & departure angles?
A. Approach angle is the maximum angle of the ramp which a vehicle is able to climb from a horizonal ground without any underbody interface. Departure angle is the maximum angle of a ramp which a vehicle is able to descend on to a horizontal ground without any underbody interface.
Q. How these angles affect the movement of a vehicle?
A. Higher the approach & departure angles are, better the off roading capabilities of the vehicle would be.
Q. What is a tanker truck?
A. A tanker truck is a specialised fabricated tank which is mounted on a truck chassis for transportation of liquid or gas in bulk. There are various categories of tankers such as- Petroleum, Oil & Lubricant (POL) tankers, chemical tankers, water tankers, milk & gas tankers etc.
Q. Do all tankers have same design or different designs ?
A. "Tankers are specifically designed for carrying different type of fluids or gases. A water tanker may have quite a simple design whereas a tanker carrying hazardous chemical will have far more sophisticated design considering all the factors related to safety of the consignment. Such tankers must be having CCOE ( Chief Comptroller of Explosives) or the PESO ( Petroleum & Explosives Safety Organisation) approvals. "
Q. How is volume of a tanker decided for a particular tonnage of vehicle?
A. "If one is supposed to transport water then the calculation is simple. A 10 KL ( 10,000 L) tanker will accommodate water which will weigh 10 tons. However for petroleum & diesel to be carried, there are some basic
calculations one needs to understand.
Usually tanker size in M&HCV segment starts from 12 KL & goes up to 40 KL. Given below is some basic calculation to understand how the weight of fluid can be calculated w.r.t the volume of tankers.
Formula:
Weight of fluid (Tons) = Tanker size (KL) X Specific gravity of the fluid (Ton/KL) X Ullage (%)
Lets calculate the weight of different fluids carried on a 20 KL tanker
Calculation:
• Petrol = 20 KL X 0.745 Ton/KL X 95% = 14.155 Ton
• Diesel = 20 KL X 0.85 Ton/KL X 95% = 16.15 Ton
• Edible Oil = 20 KL X 0.93 Ton/KL X 95% = 17.67 Ton
• Water = 20 KL X 1 Ton/ KL X 100% = 20 Ton
Ullage= The volume of tanker (in %) which is not filled
"
Q. What is a tipper?
A. "A tipper is a truck which has self unloading capability. Typically a tipper is mounted with an open-box bed, which is hinged at the rear end & equipped with hydraulic tipping kit to lift the body from front, allowing the material to be dumped onto the ground. A tipper, is used for carrying materials such as sand, gravel, stone, coal, etc for mining & construction. "
Q. On what basis the volume of a tipper body is decided ?
A. "Multiple GVWs are fitted with multiple boxes & rock body sizes . Its is obvious that body sizes will keep on increasing with the increase in GVW. So what is the basis on which those box sizes are kept for
different tonnage tippers?
Body should be of such a volume that once it is filled at its maximum capacity, the weight of the consignment should be equal to the payload available. Refer calculations below to ascertain the weight of the consignment w.r.t size of the body
:
Weight of material (Tons) = Body size (m³) X Density of the material (Ton/ m³) X Fill Rate (%)
Lets calculate the weight of different materials carried on a 16 m³ box.
Calculation:
• Coal -
16 m³ X 0.83 Ton/m³ X 90% = 11.95 Ton
• Wet Sand -
16 CuM X 1.9 Ton/m³ X 100% = 30.4 Ton
• Boulder -
16 CuM X 2.6 Ton/m³ X 70% = 29.12 Ton"
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