What are some things that mechanical engineers know and others don't?

  1. We know , why water droplets are formed around a cool water bottle ? ( Take that frozen bottle from fridge and observe it today :) )
Image source: Google
The outer air which is hotter when touches the colder surface of bottle then the air molecules are getting colder and thus getting heavier and after it they extract the moisture present in atmosphere and when capacity of molecules is full then the condensation takes place and we see water droplets on water bottles same phenomenon happens in a air conditioned car.
Credits: Yashohit Shukla
2. Ever thought that, why there are projections (fins) on a bike engine or on a electric motor? ( Today while starting your bike see that once ;)
Image source: Google
During the operation of engine heat is generated, that heat has to be rejected, so that engine would not damage. This fins increase the surface area of the engine, more the surface area, the more heat transfer takes pace.
Think about a tea cup and saucer, when tea is pored into saucer it cools down quickly, because here we increased the surface area by using saucer so that more area is exposed to air. This fins acts as a saucer for the engine cylinder.
3. How bottles are manufactured? (Have a look at that bottle in your room, this how it made :) )
Blow moulding process
Image source: Google
4. 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 )
Image source: Google
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.
5. Why this parts are present between every railway wagon? ( Observe when you see a train)
Image source: Google
Those parts are called buffer springs.
It absorbs the vibrations/shocks that created during brakes or stopping.
6. What is Anti locking Braking System (ABS)? ( Ride below two vehicles and observe the difference)
Image source: Google
When you press hard on the normal brake pedal, the disc/drum brakes are engaged and they slow you down. But at the risk of locking up the wheels. This means they do not have any circular movement left and due to the inertia of the car, they will just keep skidding along the road surface. Turning the steering wheel will have no effect as the wheels have very little grip left.
What the ABS does is monitor the wheels under braking. If the system senses that the wheels are about to stop moving, it releases the brake even if you are pressing the brake pedal. When the wheels are moving, you have enough grip on the road so you can turn the steering to give direction to your car.
7. Why there are holes on the disc brake? ( See those disc on your bike, making it beautiful to look)
For example try to hold or stop a high speed rotating wheel or disc with your hand, your hand would get heated within 2 to 3 seconds and you would remove your hand immedietly.
Similary, in Disc Brakes,
Calipers, holds the rotating disc when you apply the breaks.
Though, the calipers inner lining is made up of some kind of asbestos to develop friction required to stop the wheel disc, at some point of time the caliper or disc would melt due to heat developed by friction.
If the holes are provided on the disc wheel, then heat would dissipate through holes, hence the disc and caliper are safe from overheating.
Short Answer
The holes are provided in disc wheel of disc breaks to dissipate the generated heat due to friction.
8. What happens when Petrol is used in diesel engine and diesel in Petrol engine? (Don't try :))
️The compression ratio in petrol engine is in the range of 1:7 to 1:10, whereas the compression ratio in diesel engine is in the range of 1:18 to 1:21.
️The fire and flash points for petrol (very low) and diesel (very high) are totally different. Under these conditions:
Diesel in petrol engine
Result:- Combustion process will not take place. 1. Diesel is more viscous and it is non volatile than the petrol. The air fuel mixture is a homogenous mixture. also Diesel fuel requires an high higher compression ratio so
If you will use Diesel in petrol it will not Start combustion process. If maybe it started then also you are able to achieve the required speed. It will rotate very slowly. That power is not sufficient to drive the vehicle.
If we add diesel in petrol engine (because the compression ratio is very less, and fire and flash points of diesel is very high) combustion can not happen. And therefore it becomes a failure.
Petrol in Diesel engine
Result:- It will cause Abnormal Combustion.
⚠️ 1. The combustion process will work normally until the temperature of cylinder will increase more than its normal set values, then due to detonation phenomenon, the mixture will start firing before the top dead centre. It will cause the abnormal Combustion and Ash particles, carbon particles will damange the piston and they can stuck the piston.
❌If piston got stucked then there is only one option of complete overhauling to repair the engine.
If we add petrol in diesel engine (because the compression ratio is very high,and fire and flash points of petrol is very low) combustion happens halfway through the compression stroke. Lot of variations/fluctuations are expected and therefore, this also becomes a failure.
There are many other things that Mechanical Engineers know. Most of them are mentioned by other writers.


I don't think these are known only to Mechanical Engineers. I hope everyone knows, about everything something.
ARAVIND REDDY

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