Why do heavy vehicles like busses and trucks make that hisss/ sushhh sound when they stop/ during braking ?

Why do heavy vehicles like busses and trucks make that hisss/ sushhh sound when they stop/ during braking ? (Try to hear it today when you board a bus )?



They have Pneumatic brake system which uses compressed air to apply brakes on their heavy and big wheels not like conventional car brakes which uses brake oil to do the job.
In big vehicles along with engine a air compressors is installed which stores compressed air in cylindrical tanks.
It's just like the Tyre shop air compressor tank and compressor but small. So when ever driver applies brake compressed air is sent to brake shoe of wheels which forces brake pads against brake drums to stop the vehicle. After he releases the brake pedal that compressed air on brakes cannot be sent back to the cylinders, that's why it is released into atmosphere and that creates the Phuss sound while releasing air from valves.

Comments

  1. Anonymous21 June 2020 at 07:40

    I cannot thank Mr Benjamin service enough and letting people know how grateful I am for all the assistance that you and your team staff have provided and I look forward to recommending friends and family should they need financial advice or assistance @ 1,9% Rate for Business Loan .Via Contact : .  lfdsloans@outlook.com. WhatsApp...+ 19893943740. Keep up the great work.
    Thanks, Busarakham.

    ReplyDelete

Post a Comment

Popular posts from this blog

Mechanical engineering all text books pdf

Download pdf format of all text books links click here HEAT AND MASS TRANSFER      I NCRO P E R A -  h tt ps : // d ri ve . g oo g l e . co m / open? i d = 0 B 9 b ps T Y X P 4 ce U E g z V H V Q LWF D d2s      YUNU S  C E N G E L -  h tt p s : // d ri v e. g oo g l e.co m / open ? i d = 0 B 9bp s T Y X P 4c e WHlD W W l H dEx 6 aFE      R .  K .  R A J P U T -  h tt p s : / / d r i v e. g oo g l e.co m / open? i d =0B 9 bp s T Y X P 4 ceb kg 2WF91b 2 5 D V FE      P.  K .  NAG -  h tt ps : / / d r i v e. g o o g l e.co m / ope n ? i d=0B9 b p s T Y X P4c ea T J o N F p K S0 F zb l U      K O T ANDARA MA N -  h tt ps : / / d ri v e. g oo g l e.co m / open ? i d=0B 7 J W d K w _ 4 Q 07dnh 5 b X k 5 X 0 t RV 0E      F RAN K  K R E I T H-  h tt ps : / / d ri v e. g oo g l e.co m / open ? i d = 0 B 7 J W d K w ...
Read more

What are the reasons for bending / bulking of connecting rods?

Image
The connecting rod connects the pistons to the crankshaft. It converts the linear motion of the pistons to the rotary motion of the crankshaft. On every stroke, the connecting rod is stretched and compressed. This pressure, plus other factors, can cause the connecting rod to bend. Some of the reasons for bending or bulking of connecting rod Hydrolock Hydrolock is a deformation of the connecting rod caused when water gets into the piston chamber. This usually happens after the car has been driven through deep water such as a flooded street.  Liquid will not compress like a fuel and air mixture so the only thing that can happen is the rod will bend as the piston is stopped prematurely at the top of the stroke.  If only a little water gets into the cylinder the car makes a knocking or tapping sound and it can be repaired (have the water taken out and the gaskets replaced), but if enough water gets in the cylinder that it takes up all the space available at spark...
Read more

Why do trains (Locomotives) does not have differential ?

Image
Differential gear , in automotive mechanics,  gear  arrangement that permits power from the engine to be transmitted to a pair of driving wheels, dividing the force equally between them but permitting them to follow paths of different lengths, as when turning a corner or  traversing  an uneven road. On a straight road the wheels rotate at the same speed; when turning a corner the outside  wheel  has farther to go and will turn faster than the inner wheel if unrestrained. Take a look at these wheels: ​ If you throw these two pictures at someone and ask them which part of the wheel keeps the train on the tracks, they would probably tell you that the flange is what keeps the wheels on tracks. That's only a half-told story at best.   Flanges are only a fail-safe mechanism. Main Mechanism Here is the main mechanism and it is brilliant. ​ Suppose the track turns left. The train’s right wheels now have to travel more tha...
Read more

Why I - Section used for connecting rods and railway rails?

Image
What is an I-beam? An I-beam, also known as H-beam, W-beam (for "wide flange"), Universal Beam (UB), Rolled Steel Joist (RSJ), or double-T (especially in Polish, Bulgarian, Spanish, Italian and German), is a beam with an I or H-shaped cross-section. The horizontal elements of the "I" are known as flanges, while the vertical element is termed the web. I-beams are usually made of structural steel and are used in construction and civil engineering. Why do we use I Beam, instead of rectangular beam? On the left side we have a simple rectangular beam, whereas on the left hand side on the above image, we have an I section beam. The question that is most commonly asked as to why do I section beam most frequently used in construction as compared to simple rectangular beam. And also why only I beam is used and not a beam of any other shape. When a beam is subjected to stresses, the outer layer is compressed, with the inner one undergo tension. The m...
Read more

Why can't we use a single big cylinder instead of multiple cylinders in an Engine?

Image
          Pic Credits: Smart Mechanicals                            Some of the probable Reasons to avoid single cylinder.. 1. Unbalance and vibrations are produced due to high inertia caused when a larger mass is reciprocating at high speeds. 2. The power obtained is intermittent , since there is only one power cycle outof four strokes in the entire engine. In case of Mutli cylinder engine the power produced is continuous since there is atleast one power cycle in one cylinder out of multi cylinder. 3. A heavy flywheel is required to store the energy and  supply it to next 3 cycles, since power is produced in only single cycle. 4. Single cylinder occupy more space to produce same power of that multi cylinders. 5. More starting torque is required to start the engine. 6.  Engine Speed : lesser the reciprocating mass - the engine can operate at high...
Read more

Why most of the propeller shafts are hollow? Does hollow shaft have more strength than solid shaft?

Image
A hollow shaft has greater strength and stiffness than a solid shaft of equal weight. So most of the propeller shafts are hollow. The strength of a shaft implies the maximum torque it can transmit. It depends on Torsional rigidity of the shaft since it renders the stiffness to the shaft. Torsional rigidity is defined as the torque required to produce a twist of one radian per unit length of the shaft. and by torsional formula: T/(θ/L)=GJ=Torsional rigidity. So, Stiffness and hence strength is proportional to J which is: by maths, less for solid shaft. Stress distribution of solid vs hollow shaft. Hollow shafts are much better to take torsional loads compared to solid shafts. As shown in the figure, shear stress in a “shaft subjected to torsion” varies linearly from zero at the center to the maximum at the boundary. But Inside a solid shaft, most of the material experiences / carries a shear stress whose value is much below the maximum shear stress [Interior...
Read more

How balls of ball point pen is manufactured?

Image
Most of the times steel wires are used as raw material which is fed to forming machine which has spherical shaped dies. Step followed for manufacturing 1. Forming by Heading 2. Flashing 3. Heat treatment 4. Grinding 5. Lapping 6. Washing 7.Precision and NDT testing This wire is fed from a roll into a machine that cuts off a short piece, and then smashes both ends in toward the middle. This process is called cold heading. Process is explained through following figures          The steel wire is fed into spherical shaped dies                             And a spherical ball is produced Flashing is a process of removing uneven burrs and surfaces  Heat treatment is done to increase the hardness of the steel balls. Precision grinding is done to improve surface finish further Then lapping is performed to produce mirror like surface fi...
Read more

What is the use of parallel lines on rear glass of car?

Image
 It is called as  defroster . Usually there’s a switch on the dash to turn on the system and it will run for a specified time then turn off automatically.  There may be an icon on the dash or the switch itself illuminates when the rear window defroster is operating. The amount of heat produced by the grid is relatively low …just enough to raise the temperature to evaporate any dew or melt any ice …so it’s not like you’re gonna burn your hand if you touch the glass while the system is working. It is just same as the Defogger used by us when there is mist on the windshield. The grid lines are made up of resistive conductors in or on the glass, generally they are very fine wires that are baked or sometimes embedded onto the inside of glass surface. In these lines when current is passed, due to resistance the glass heats up and removes the mist so that the driver get a clear view in the rear view mirror .
Read more

Why stones are layed in switchyard or in power stations?

Image
Reasons for using Stones in Switchboard Yard / Substation : Power Transformers installed in the substations will have oil as cooling and insulating medium.Oil leakage takes place during operation or when changing the oil in the transformer. ... So Stones is provided to protect from fire when oil spillage takes place. View of Technical :  1.To avoid rain water to stand on ground, to prevent the growth of grasses & plants,growth of plants & grass near the yard cause will create the short circuit . 2.The most important point to avoid step potential and touch potential to rise.where step potential is potential between human body & touch is potential between human body & equipments.  3. keep the moisture always bottom  of the stone to reduce the earth  resistance
Read more