How a Gearless Bike Works? Working of a Scooty

Most of us love riding on bikes and some of us prefer to ride on a gearless bike due to various reasons. Many of us are aware about how transmission in a bike works but only few of us know how power is transmitted in a gearless vehicle and if you are interested to learn that, this is what that happens in the back ground.

When we talk about transmission in vehicles the first thing that strikes our mind is gears. In gearless bikes as the name itself suggests there are no gears in transmission. The gearless vehicle transmission involves CVT.

CVT stands for Continuously Variable Transmission. In this type of transmission we have infinite number of gear ratios between the maximum and minimum values. The maximum and minimum values are determined maximum and minimum pulley diameters which shall be discussed in below.

A CVT consists of following parts:

1. Primary pulley
2. Secondary pulley
3. Belt

Here the word pulley literally doesn't mean a pulley. Each pulley consists of two sheaves one of which is stationary and the other moves far and close to stationary sheave which eventually changes the diameter of pulley on which the belt rotates. The sheaves are conical in shape.

The Primary pulley is also called Driver pulley which is connected to the crankshaft of the engine, the moving sheave in driver pulley is called variator. The Secondary pulley is also called Driven pulley is connected to output shaft. The belt is generally made of steel. Generally centrifugal clutches are used in CVT.

When ever we start our gearless bike engine the crankshaft rotates. At idle speed the clutch is not engaged and the vehicle is stationary, This is like a neutral position in case of bikes with gear transmission. When we rise the acceleration throttle as the clutch engages the vehicle will be in motion.

Once the vehicle is moving and when we want to increase the speed we rise the throttle high as a result the crankshaft rotates even faster and the variator connected to it also rotates at high rpm. The variator consists of weights in it, whenever speed increases the weights move outward due to centrifugal force. As a result of this the variator move closer to stationary sheave thus increasing the pulley diameter.

Because the belt length is fixed, When the diameter of driver pulley increases more length of belt is around it and as a result belt is pulled down to center of driven pulley and the movable sheave moves away from stationary sheave. But when we reduce the speed the movable sheave should return to it's position. This action is taken care by the contra spring present between clutch and movable sheave. 

Goto 1:33

This video demostrates the live working of CVT.

To know each and every part involved it CVT or if you want to self service your gearless bike check this video.

So, this is the mechanism in background that drives a gearless bike.

Notify me about anything you want to know in the comments. Thanks and peace.

References

• http://en.wikipedia.org/wiki/Continuously_variable_transmission
• http://en.wikipedia.org/wiki/Centrifugal_clutch
• http://en.wikipedia.org/wiki/Variator

How a 3D printer works?

Most of us have heard about 3-D Printing in many situations of our life. We know that a 3-D Printer produces a 3-D object, but how many of us know what exactly happens in the background? If you are keen to know check this out.

As a part of learning let us know what exactly is 3-D printing and when it was evolved before going into the working of it. 

3-D printing is previously referred to as Additive Manufacturing(AM). AM is the means of creating an object by adding material to the object layer by layer. AM has various names like Stereolithography, 3-D Layering and 3-D printing. AM was used for rapid prototyping in manufacturing industries to create prototypes of the actual product.

3-D Printing came into existence in early 1980's. In 1981, Hideo Kodama of Nagoya Municipal Industrial Research Institute invented two AM fabricating methods of a three-dimensional plastic model with photo-hardening polymer, where the UV exposure area is controlled by a mask pattern or the scanning fiber transmitter. Then in 1984, Chuck Hull of 3D Systems Corporation, developed a prototype system based on this process known as stereolithography, in which layers are added by curing photopolymers with ultraviolet light lasers. Hull's contribution is the design of STL file format widely accepted by 3-D printing software as well as the digital slicing and infill strategies common to many processes today.

Let us know what kind of processes are there in 3-D Printing.

1) Direct 3-D Printing

      In Direct 3-D printing we have thick waxes and plastic polymers which are extruded (dispensed) from the nozzle to print the object. These printers use inkjet technology. The nozzle can move back and forth to make a layer, it moves up and down to make layer over layer. Once a layer is made the wax or polymer solidfy to form a firm cross-section of the object. Rapid prototyping has been major  factor for growth of direct 3-D printing. Rapid prototyping products use technologies such as multi-jet modeling (MJM), which creates wax prototypes quickly with dozens of nozzles 

2) Binder 3-D Printing

      The Binder printing uses two separate materials that come together to form each printed layer: a fine dry powder plus a liquid glue, or binder. Binder 3-D printers make two passes to form each layer. The first pass rolls out a thin coating of the powder, and the second pass uses the nozzles to apply the binder. The building platform then lowers slightly to accommodate a new layer of powder, and the entire process repeats until the model is finished. This method can incorporate a wider variety of materials in the process, including metals and ceramics, as well as color.

3) Photopolymerization

        Photopolymerization is a 3-D printing technology whereby drops of a liquid plastic are exposed to a laser beam of ultraviolet light. During this exposure, the light converts the liquid into a solid. Stereolithography Apparatus(SLA) uses photopolymerization, directing a laser across a vat of liquid plastic called photopolymer. As with inkjet 3-D printing, the SLA repeats this process layer by layer until the print is finished. 

4) Selective Laser Sintering

       Selective Laser Sintering is an Additive manufacturing process that builds three dimensional parts by using a laser to selectively sinter (heat and fuse) a powdered material, which then solidifies to form the printed layer.

No matter which approach a 3-D printer uses, the overall printing process is generally the same. In their book "Additive Manufacturing Technologies: Rapid Prototyping to Direct Digital Manufacturing," Ian Gibson, David W. Rosen and Brent Stucker list the following eight steps in the generic AM process:

Step 1: CAD -- Produce a 3-D model using computer-aided design (CAD) software. The software may provide some hint as to the structural integrity you can expect in the finished product, too, using scientific data about certain materials to create virtual simulations of how the object will behave under certain conditions.

Step 2: Conversion to STL -- Convert the CAD drawing to the STL format. STL, which is an acronym for standard tessellation language, is a file format developed for 3D Systems in 1987 for use by its stereolithography apparatus (SLA) machines. Most 3-D printers can use STL files in addition to some proprietary file types such as ZPR by Z Corporation and ObjDF by Objet Geometries.

Step 3: Transfer to AM Machine and STL File Manipulation -- A user copies the STL file to the computer that controls the 3-D printer. There, the user can designate the size and orientation for printing. This is similar to the way you would set up a 2-D printout to print 2-sided or in landscape versus portrait orientation.

Step 4: Machine Setup -- Each machine has its own requirements for how to prepare for a new print job. This includes refilling the polymers, binders and other consumables the printer will use. It also covers adding a tray to serve as a foundation or adding the material to build temporary water-soluble supports.

Step 5: Build -- Let the machine do its thing; the build process is mostly automatic. Each layer is usually about 0.1 mm thick, though it can be much thinner or thicker. Depending on the object's size, the machine and the materials used, this process could take hours or even days to complete. Be sure to check on the machine periodically to make sure there are no errors.

Step 6: Removal -- Remove the printed object (or multiple objects in some cases) from the machine. Be sure to take any safety precautions to avoid injury such as wearing gloves to protect yourself from hot surfaces or toxic chemicals.

Step 7: Postprocessing -- Many 3-D printers will require some amount of post-processing for the printed object. This could include brushing off any remaining powder or bathing the printed object to remove water-soluble supports. The new print may be weak during this step since some materials require time to cure, so caution might be necessary to ensure that it doesn't break or fall apart.

Step 8: Application -- Make use of the newly printed object or objects.

The following video illustrates various applications

References

• http://en.wikipedia.org/wiki/3D_printing
• http://en.wikipedia.org/wiki/Photopolymer
• http://en.wikipedia.org/wiki/STL_(file_format)
• http://computer.howstuffworks.com/3-d-printing.htm

How does a bullet get it's speed?

Most of us watch bullets being fired from the guns in many action movies. Ofcourse for us, buying a gun is subjected to the country's federal laws. Whether you own one or not, if you have ever wondered how bullet gets it speed when gun is fired, Then this is what that happens in the background.

There are many sizes of guns right from the smallest Miniature Revolver C1ST to the largest Schwerer Gustav( Railway gun). They all have bullets of corresponding sizes. Let us know in brief how bullets evolved before knowing how bullet gets it's speed.

"Bullet" is derived from the French word boulette which roughly means little ball. Originally, bullets were made out of stone or purpose-made clay balls used as sling ammunition, as weapons and for hunting. Eventually as firearms were developed, these same items were placed in front of a propellant charge of gunpowder at the end of a closed tube. As firearms became more technologically advanced, from 1500 to 1800, bullets changed very little. They remained simple round (spherical)lead balls, called rounds, differing only in their diameter.

The original musket bullet was a spherical lead ball smaller than the bore, wrapped in a loosely fitted paper patch which served to hold the bullet in the barrel firmly upon the powder. Bullets that were not firmly upon the powder, when fired caused the barrel to explode, with the condition known as a short start.

Later Square bullets, invented by James Puckle and Kyle Tunis, were briefly used in one version of the Puckle gun. The use of these was soon discontinued due to irregular and unpredictable flight patterns.

Later the pointed bullets are developed and were resisted to be used at the beginning for various reasons and were later accepted. The next important change in the history of the rifle bullet occurred with invention of the copper-jacketed bullet, which is an elongated bullet with a lead core in a copper jacket. 

The surface of lead bullets fired at high velocity may melt due to hot gases behind and friction with the bore. Because copper has a higher melting point, and greater specific heat capacity and hardness, copper-jacketed bullets allow greater muzzle velocities.

Bullet designs have to solve two primary problems. In the barrel, they must first form a seal with the gun's bore.The bullet must also engage the rifling without damaging or excessively fouling the gun's bore, and without distorting the bullet. These interactions between bullet and bore are termed internal ballistics. Bullets must be produced to a high standard, as surface imperfections can affect firing accuracy.

A bullet generally consist of 5 main parts. They are:

1. Bullet
2. Casing
3. Propellant
4. Rim
5. Primer

The bullet is what that actually hits the target. Propellant is the explosive that gives necessary force to the bullet to hit the target, it occupies about two thirds of a typical bullet's volume. Casing holds all parts together. Primer is like a fuse which ignites the propellant and rim provides the extractor on the firearm a place to grip the casing to remove it from the chamber once fired.

When the trigger is pulled a spring mechanism hammers a metal firing pin into the back end of the bullet, igniting the small explosive charge in the primer. The primer then ignites the propellant, as the propellant chemicals burn, they generate lots of gas very quickly. The gas shoots from the back of the bullet, increasing the pressure behind it, and forcing it down the gun barrel at extremely high speed of around 300 m/s. The speed of bullet depends on various factors. here is video to help you understand better. 

The primer is a metal cup containing a primary explosive inserted into a recess in the center of the base of the cartridge. A primary explosive is an explosive that is extremely sensitive to stimuli such as impact, friction, heat, static electricity, or electromagnetic radiation. A relatively small amount of energy is required for initiation. As a very general rule, primary explosives are considered to be those compounds that are more sensitive than PETN. Upon being struck with sufficient force, a primer reacts chemically to produce heat which ignites the main propellant charge and fires the projectile (bullet).

The propellant chemicals in a handgun bullet are not designed to explode suddenly all at once, that would blow the whole gun open and very likely kill the person firing it. Instead, they are supposed to start burning relatively slowly, so the bullet moves off smoothly down the gun. They burn faster as the bullet accelerates down the barrel, giving it a maximum "kicking" force just as it comes out of the end. As the bullet emerges, the whole gun recoils because of a basic law of physics called "action and reaction" or Newton's third law of motion. When the gas from the explosion shoots the bullet forwards with force, the whole gun jolts backwards with an equal force in the opposite direction. The propellant used could be either gunpowder or cordite.

Previously revolvers used to be the hand guns, now we have semi automatic pistols. The two videos show the animation of how they work.

The recent advancements in technology developed guns with target locking options. More recent developments led to smart bullets which follow the target and takes it down. This saves the rounds and comes handy when the target is surrounded.

Notify me about anything you want to know in the comments. Thanks and peace.

References:

• http://en.wikipedia.org/wiki/Bullet
• http://en.wikipedia.org/wiki/Schwerer_Gustav
• http://en.wikipedia.org/wiki/Primer_(firearm)
• http://en.wikipedia.org/wiki/Centerfire_ammunition#Centerfire_primers
• http://en.wikipedia.org/wiki/Internal_ballistics
• http://en.wikipedia.org/wiki/Explosive_material#Primary_explosive
• http://www.sadefensejournal.com/wp/?p=1241