Tuesday, March 1, 2011

CrazyEngineers Forum - Mechanical & Civil Engineering

CrazyEngineers Forum - Mechanical & Civil Engineering

Bloodhound SSC Engine Discussions

Posted: 01 Mar 2011 12:35 AM PST

We published our Small Talk with the Chief Engineer of Bloodhound SSC Project : Mark Chapman - Bloodhound SSC: The 1000mph Engineering Adventure - CrazyEngineers

I'm so impressed by the extreme engineering the team is putting into this car. I'd like to see a discussion on the engine of Bloodhound SSC. I'm sure Automobile and Mechanical engineers would have lots of interesting insights.

if i want to localize a CAD mechnical software in india, how should i do?

Posted: 27 Feb 2011 11:34 PM PST

Now i hava a Chinese CAD mechnical software , i want to make it use in India, how should i do? if someone know this please tell me, thanks in advance

couple of questions

Posted: 27 Feb 2011 07:54 AM PST

Hello everyone, I have a couple of questions for you
1- I'm working on a back-filling of a causeway in the sea, can I use salt water in watering for compaction or is it necessary to use fresh one, form a scientific point of view?
2- The consultant always asks me to remove stones bigger than 1/3rd the thickness, what is its effect scientifically on compaction? and is this proportion a rule of thumb ?
thanks

need help for my project work

Posted: 26 Feb 2011 11:53 AM PST

i am doing bearing cup using cold forging i.e backward extrusion process
the initial billet height is 13mm and dia 20mm my question is in how many stages i.e sequence of operations can we do this to get 14mm inner dia and 14mm depth

Valves

Posted: 25 Feb 2011 04:06 AM PST

Hello friends,
Many a times you must have heard of valves many times. ever wondered what a valve is?Let us talk what a valve is with reference to an engine.
Each engine by default is provided with two valves.The intake and the exhaust valve.
The intake valve is the passage for air fuel mixture to enter the cylinder.
While the exhaust valve opens at the end of exhaust valve.

So there are basically four types of engine valves and the engines are named accordingly.The valves can be arranged in various ways in the cylinder block.

1.L-head engine:
The valves and camshaft are located in the cylinder block.Ever seen a lawn mower? you have a high probability to see this type of arrangement there.
Disadvantages:
1.Cannot be designed for high compression ratio
2.It has excessive exhaust emissions.
This arrangement was popular in 1950's but now out of service.

2.Overhead valve engines:
These valves have high compression ratios.The valves are located directly above the piston.This also provides clearance volume.It has got more engine torque and power.

3.Overhead-camshaft engines:
Here the camshaft is placed over cylinder head.These are called OHC engines.
In this type pushrods and rocker-arm have got inertia.This resists changing speed and direction.So these push rods bend slightly before they open the valve.This bending has little effect at lower speed. But increases as the speed increases.This causes increasing lag in valve action that tends to limit speed.

4.Multivalve engines:
This engine has many valve per cylinder.but to increase power output mostly 4 valves are used per cylinder.

Acrylic or ABS Plastic ??

Posted: 23 Feb 2011 09:54 PM PST

Just trying to get ideas for a project and was wondering what materials i could use to build the body that would attach to a frame like body panels of a car. I am deciding between ABS plastic or Acylic Sheets. Are these good choices or are there better ones that are cheaper and stronger.

Welding

Posted: 20 Feb 2011 05:25 AM PST

Hi friends,
Ever wondered about solid state welding?
Well there are in principle three types of solid state weldings:

1.DIFFUSION WELDING:
In this process,the two surfaces are made to come in intimate contact of each other.Later a good amount of pressure is applied on them.It sometimes take hours to get the two surfaces welded.
Also heating is not required in it.However if we apply heat,the matter of time can be cut to minutes.
By this process we can join metal-metal,ceramic-metal, metal-metal with intermediate layer of other materials etc.
(Next time ask a Gold smith what is the actual process.:mrgreen:)

2.ULTRASONIC WELDING:
This technique joins similar or dissimilar metals by high frequency vibratory energy.May be about 20000-60000 Hz.
The advantage includes we don't require any flux material for welding.
The parts to be joined are clamped together and then high frequency energy is transmitted in it.
We can weld to a thickness of 0.38mm to 2.5mm.


3.FRICTION WELDING:
To surfaces which have high relative velocity are made to slide against each other.
So that due to high friction a large amount of heat is generated.And ultimately the surface material melts and joins with each other.
Advantage is that the heat affected region is very small and dissimilar metals can be easily joined.
e.g;mild steel tool shanks are fastened to high speed steel tool shanks.

All about oils

Posted: 19 Feb 2011 04:42 AM PST

Hello everyone ever wonder about oils?
Oils are gift of nature to mankind.We sometimes use oils as lotions.But I am talking about lubricating oils.Don't try to use them as lotions.:mrgreen:
Anyways jokes apart.Actually I want to discuss the various properties of lubricating oils and their general types.
1.Viscosity
Viscosity is the property of flow of any liquid to flow.Simply speaking,
A low viscosity oil is very thin and flows readily.
A high viscosity oil is very thick and resists flow.
So it is actually difficult to define a good lubricating oil.It depends under what conditions you use it.To be more scientific there are two types of viscosities

a) Dynamic viscosity : also called as absolute viscosity, the more usual one (typical units Pa·s, Poise, P); and

b) Kinematic viscosity: is the dynamic viscosity divided by the density (typical units m2/s, Stokes, St).

2.Viscosity index:
This is the rate of change of viscosity with respect to temperature.So a single viscosity oil is very thick at low temperatures and very thin at high temperatures.

3.Viscosity numbers:
As any other things oils also have various grades.As the oils used in winter conditions are thick hence the two grades
1.winter
2.Other than winter
the various grades are SAE 0W, SAE 5W, SAE 10W...and so on.As you can easily guess W stands for winter.

4.Multiple-Viscosity oils:
In many applications the changing of viscosity with respect to temperature is undesirable.So we have viscosity index improver.Most automotive manufacturers recommend multi viscosity oils for automobiles.

5.Resistance to carbon formation and oil oxidations:
When the temperature increases,we may face this problem so we need the resistance to it.

6.Corrosion and rust inhibitors:
Additives are put in oils so that oils should protect the parts from rusting in case they come in contact of water.

7.Foaming resistance:
Whenever the moving part moves, it may churn the oil so that it will foam.This reduces the lubricating property of oil.To prevent it we may have the following
1.Additives or
2.A baffle in oil pan and
3.A windage tray between pan and cylinder.

8.Detergent-Dispersants:
These additives act as a soap and they carry dirt and carbon away from oil.

9.Extreme pressure resistance:
The oils also prevent the parts from extreme pressure.As in case of bearings and valves.

10.Energy conserving oils:
These oils reduce fuel consumption when compared to engine operation with a specified engine oil.
There are two types.
EC1 and EC2.EC2 oils provide much better fuel economy than EC1 oils.

11.Synthetic oils:
As modern sciences are advancing we have better oils which are artificially obtained.They are made from certain Carbon compounds and alcohols.
The advantages include
a)They tolerate heat better
b)Produce less sludge
c)Less carbon deposits

So it was all I could do for you.Everything rests with you people.Please correct me wherever I am wrong.

Carburetors

Posted: 19 Feb 2011 03:43 AM PST

The device which mixes air and fuel and supplies the engine with this air-fuel mixture is called a carburettors.It is connected before the engine.A simple carburettor consists of three basic parts.
1.Air horn
2.Float bowl and
3.A throttle body
Now, there is one type of carburettor called as fixed-venturi carburettor.The so called venturi is nothing but the partial vacuum produced due to air flow in carburettor.The region where this partial vacuum is produced is called venturi.The venturi is a small and restricted space.
The air flows in carburettor because the pressure outside is atmospheric while that inside is below atmospheric pressure.
The fuel tank supplies fuel to float bowl with the help of a pump.
Because of the pressure difference the fuel is pushed through the nozzle.The fuel then mixes with the incoming air.
The throttle valve is a component which allows the air to enter in the carburettor.
The more the vacuum generated the more air flows inside.
There is also a type of carburettor called as variable venturi carburettor.So by the name can you guess its working???
:cean:

Crank Shaft

Posted: 18 Feb 2011 05:30 AM PST

Hi friends,
Ever wondered of a crank shaft?
Well this is a single one piece casting or a forged part.The material is heat treated alloy steel.The crankshafts may be unbalanced.So to balance them we usually place dead weights also called as counter weights.The crankshafts of some V6 engines have crank pins which have spread out.It is also called as a splayed crank pin.This crank pin is split in two parts.To balance out-balance conditions each rod is provided with its own crank pin.
The front end is connected with Gear or sprocket which drive
1.Camshaft
2.The pulley which is actually belt driven and
3.Vibration Damper.
While the output side is as usual attached with a flywheel.
Usually an engine which is accommodated with electronic engine control or simply EEC has a timing disc mounted on crankshaft.
I think I have already explained the use of sensors as to how the ignition system knows about piston positions
So great studying.And please do correct me wherever I am wrong.Ciao
:cean:

Variable compression ratio

Posted: 17 Feb 2011 06:30 PM PST

I found this video while surfing.http://video.i.ua/user/1791221/35590/186762/

Mechanical to Electronics and design

Posted: 17 Feb 2011 09:32 AM PST

Hi everyone. I completed my b.tech mechanical engineering from VIT University. But now i want to learn electrical/electronics and become a solution provider and entrepreneur or a product designer (products that are not restricted to mechanical but involves electronics also. Like a robot, washing machine, speed detectors etc). Right now i am planning to take up M.Des which has a lot of compitition in india so i put mechatronics as my second option but im not very sure these couse willfulfill my inteests. Please suggest me a caree plan based on my intrests mentioned above..

Machined Cubesat Chassis (10x10x10 cm^3) made of aluminum

Posted: 17 Feb 2011 02:20 AM PST

I have to realize a cubical rigid aluminum structure, roughly 10 cm x 10 cm x10 cm like this cubesat chassis. For PCBs, I know that there are manufacturers where you can order a number of boards designed by you in ORCAD or Eagle. About aluminum structures manufacturers I have no idea. Is it possible to order a structure like that cubesat chassis, I have wrote about, for a total cost of less than $500? Has anybody, on this forum, made or had it made a rigid aluminum structures like the one I want to build? I have no idea how difficult is to machine such a chassis.

Crank-shaft sensor

Posted: 16 Feb 2011 02:29 AM PST

In case of a petrol engine,it is important to achieve a correct timing between piston and ignition system.So basically we require a sensor.
It is called as:
Crank-shaft sensor :
This sensor reports the crank-shaft speed and piston position to ignition system.The ignition system should know as to when to ignite spark.In other words it must be able to calculate the instant when piston reaches TDC in compression stroke.
It consists of a pulse ring which rotates with the crankshaft.Whenever a notch in the disc aligns with sensor,it produces a voltage pulse.Hence the spark ignites.

There are two such types of sensors.
1.Pick up coil crankshaft sensor:
This arrangement consists of a reluctor i.e; a slotted disc which rotates with crankshaft.As each shaft passes through magnetic field at the end of pickup coil, a voltage is induced in it.
So even if you increase or decrease the speed,The ignition system will know the position of piston as the voltage will also vary.

2.Hall effect crankshaft sensor:
It uses HALL effect:
Def:
The Hall effect is the production of a voltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current.(source of definition is wikipedia)
This crank sensor uses a Hall effect switch to turn voltage on or off.

Please contribute more to this article.:cean:

Joints

Posted: 15 Feb 2011 08:22 AM PST

As we all know joints form an important component of an automobile.Joints are needed to hold parts together,to transmit power and various reasons as we all aware.
So directly coming to point,let us now discuss various types of joints.

But before discussing joints let us talk about:
Drive Lines:
A drive line is actually an assembly of various joints like universal joints,slip joints and drive shafts.A propeller shaft is a simple example if I am not wrong.
Vehicles with front wheel drive usually have trans-axle assembly mounted transversely.Also short drive shafts extend from trans-axle to front wheels.

Universal joints:
Whenever two shafts are inclined at an angle we can easily transmit power from one shaft to another by using a Universal joint.(For reference see an image of Cardan universal joint).
In this joint to Y shaped objects called yoke are connected to each other with the help of a cross shaped part also called as 'spider'.The driving and yoke force the spider to rotate.When two shafts are at an angle with each other,the needle bearings permits the yokes to swing around the trunnions with each revolution.
Eg: Spider and two yoke universal joint.

Slip Joints:
A slip joint has splines on its outer part and matching internal splines in a mating hollow Yoke.When this assembly is assembled these splines cause the shaft to rotate together while they can move back and forth.Hence the length of drive shaft changes.

CV joints
Actually the full form of this joint is constant velocity universal joint.A common example of CV joint is double cardan joint.It is nothing but two universal joints put together.They are linked by ball and socket joint which splits the angle between two shafts.This causes both the shaft to rotate at same speed.
The various other types of CV joints are:
1.Outer CV joints
2.Inner CV joints
3.Double-Offset CV joints
4.Plunging-Tripod CV joints

Can any one add value to this article?
Waiting for your replies...
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