Technical Studies

I would like to extend my most sincere gratitude to Prof. K.Muru-gan, Department of Fashion and Lifestyle Accessories, NIFT, New Delhi for his scholarly guidance and constant constructive criti-cism which has been instrumental in developing this report. I would also like to thank my friends and family for their constant support. I hope that this report does justice to the time and ener-gy that everybody has put in.Thank you.

Shalvi SharmaFashion and Lifestyle AccessoriesSemester V2012-2016NIFT, New Delhi

Introduction........................................................Springs.................................................................Bearings...............................................................Gears.....................................................................Hinges..................................................................Cams.....................................................................Levers....................................................................

010206091 11 31 5

Screws........................................................................Light Emitting Diode (LEDs)...........................Product: Kawad......................................................Bag Construction..................................................Learning Outcome...............................................References...............................................................

010206091 11 31 5

1 61 820232627

Technology is the collection of tools, including machinery, modifications, arrangements and procedures used by humans. Technologies significantly affect human as well as other animal species’ ability to control and adapt to their natural environments. The term can either be applied generally or to specific areas: ex-amples include construction technology, medical technology and information technology. The term ‘technical’ refers to- having special and ususally practical knowledge especially of a mechani-cal or scientific subject.Under the head ‘technical studies’, we studied about springs, gears, cams, pulley systems, hardwares (screws, hinges, bearings), how some of the objects like refrigerators, clocks, television sets etc. worked.It was an enriching and a splendid experience in learning and applying it in the laboratory.

01

A bike engine

A pulley system

A spring is a device that changes its shape in response to an external force and stores energy, returning to its original shape by releasing energy, when the force is removed. It is an elastic object used to store mechanical energy. Springs are usually made out of spring steel. There are a large number of spring designs; in everyday usage the term often refers to coil springs.Small springs can be wound from pre-hardened stock, while larg-er ones are made from annealed steel and hardened after fabrica-tion. Some non-ferrous metals are also used including phosphor bronze and titanium for parts requiring corrosion resistance and beryllium copper for springs carrying electrical current (because of its low electrical resistance). When a coil spring is compressed or stretched slightly from rest, the force it exerts is approximately proportional to its change in length (this approximation breaks down for larger deflections). The rate or spring constant of a

spring is the change in the force it exerts, divided by the change in deflection of the spring. That is, it is the gradient of the force versus deflection curve. An extension or compression spring has units of force divided by distance, for example lbf/in or N/m. Torsion springs have units of torque divided by angle, such as N·m/rad or ft·lbf/degree. The inverse of spring rate is compliance, that is: if a spring has a rate of 10 N/mm, it has a compliance of 0.1 mm/N. The stiffness (or rate) of springs in parallel is additive, as is the compliance of springs in series. Depending on the design and required operating environment, any material can be used to construct a spring, so long as the material has the required combination of rigidity and elasticity: technically, a wooden bow is a form of spring.Springs can be classified depending on how the load force is applied to them:

02

- Tension/extension spring – the spring is designed to operate with a tension load, so the spring stretches as the load is applied to it.- Compression spring – is designed to operate with a compres-sion load, so the spring gets shorter as the load is applied to it.- Torsion spring – unlike the above types in which the load is an axial force, the load applied to a torsion spring is a torque or twisting force, and the end of the spring rotates through an angle as the load is applied.- Constant spring - supported load will remain the same through-out deflection cycle.- Variable spring - resistance of the coil to load varies during compression.

They can also be classified based on their shape:* Coil spring – this type is made of a coil or helix of wire.* Flat spring – this type is made of a flat or conical shaped piece of metal.* Machined spring – this type of spring is manufactured by machining bar stock with a lathe and/or milling operation rather than coiling wire. Since it is machined, the spring may incorpo-rate features in addition to the elastic element. Machined springs can be made in the typical load cases of compression/extension, torsion, etc.

The most common types of spring are:* Cantilever spring – a spring which is fixed only at one end.* Coil spring or helical spring – a spring (made by winding a wire around a cylinder) and the conical spring. These are in turn of two types:* Compression springs are designed to become shorter when loaded. Their turns (loops) are not touching in the unloaded posi-tion, and they need no attachment points.* A volute spring is a compression spring in the form of a cone, designed so that under compression the coils are not forced against each other, thus permitting longer travel.* Tension or extension springs are designed to become longer under load. Their turns (loops) are normally touching in the un-loaded position, and they have a hook, eye or some other means of attachment at each end.* Hairspring or balance spring – a delicate spiral torsion spring used in watches, galvanometers, and places where electricity must be carried to partially rotating devices such as steering wheels without hindering the rotation.* Leaf spring – a flat spring used in vehicle suspensions, electrical switches, and bows.* V-spring – used in antique firearm mechanisms such as the wheellock, flintlock and percussion cap locks.

(1)(2)(From top-left, clockwise):closed coil helical spring, open coil helical spring, coil spring, (1) concial disc spring, (2) wire spring

Other types include :- Belleville washer or Belleville spring – a disc shaped spring com-monly used to apply tension to a bolt (and also in the initiation mechanism of pressure-activated landmines).- Constant-force spring — a tightly rolled ribbon that exerts a nearly constant force as it is unrolled.- Gas spring – a volume of gas which is compressed.- Ideal Spring – the notional spring used in physics: it has no weight, mass, or damping losses.- Mainspring – a spiral ribbon shaped spring used as a power source in watches, clocks, music boxes, windup toys, and mechan-ically powered flashlights.- Negator spring – a thin metal band slightly concave in cross-section. When coiled it adopts a flat cross-section but when unrolled it returns to its former curve, thus producing a constant force throughout the displacement and negating any tendency to re-wind. The commonest application is the retracting steel tape rule.- Progressive rate coil springs – A coil spring with a variable rate, usually achieved by having unequal pitch so that as the spring is compressed one or more coils rests against its neighbour.- Rubber band – a tension spring where energy is stored by stretching the material.

- Spring washer – used to apply a constant tensile force along the axis of a fastener.- Torsion spring – any spring designed to be twisted rather than compressed or extended. Used in torsion bar vehicle suspension systems.- Wave spring – a thin spring-washer into which waves have been pressed.

USES OF SPRINGS:-to absorb or store energy and to reduceshock and vibration (eg. buffers, shockabsorbers)-to apply a definite force or torque (eg.valves, governors)-to indicate or control load or torque (eg.spring balance, weighing machine)-to supply motive power to mechanisms (eg.clocks, cameras)

(From top, clockwise): helical torsion spring, flat spring/leaf spring, close-up of helical torsion

MATERIALS USED FOR MAKING SPRINGS:

-High carbon steel-Silicon-manganese steel-Chromium-vanadium steel-Stainless steel-Phosphor bronze-Hand-drawn copper-Titanium alloy

SPRINGS AND THEIR APPLICATION:

1. WIRE SPRING: Used to retain covers where it is necessary for the cover to be removed separately.2. HELICAL COMPRESSION SPRING: Resist compressive loads used in shock absorbers.3. FLAT/ LEAF SPRING: Absorb energy by means of bending- used in hairclips, paper clips, spring clips, circlips, etc.4. CONICAL DISC SPRING: Suitable where high loads are required and limited space is available.5. HELICAL TENSION SPRING: Resist tensile load applied by means of a suitable end form, normally a hook or a loop.6. HELICAL TORSION SPRING: Used to resist torque when the ends are subjected to an angular displacement. Used in manufac-ture of cycle carriers, pad clips, etc.

06A mechanical element which supports another element and at the same time constrains the relative motion of the part with minimum friction is called a bearing. It is typically used in rota-tion or linear movement. The basic parts of a bearing are:-an outer ring-an inner ring-a cage or retainer-rolling element (ball or rollers)-boreAll bearings might not have all the necessary parts.

Races:The inner and outer races are provided with grooves or face-ways which guide the rolling elements. They are made of high gradechromium steel or chrome-nickel steel. They are hardened, ground and polished.

Cage:Each rolling element is separated from the other by means of a cage and it keeps the rolling elements from bunching up. The cage and rolling elements are retained between the inner and outer races. The rolling elements are retained between the cages to ensure proper fits and equal spacing between the rollingelements. They are made out of brass, steel or plastics.

Rolling elements:They are available in a variety of shapes such as balls, parallel

rollers, taper rollers, barrels and needles. They are made of chro-mium or chrome-nickel steel with a ground or polished surface.The load of the rotating member is carried by the rolling ele-ments.

TYPES OF BEARINGS:

BALL-BEARINGS:They are the most widely used of all thebearings. Although, principally, they are to carry journal loads, the deep groove type of ball races are capable of withstanding the axial thrust.

SELF-ALIGNING BALL-BEARINGS:This type of bearing has a spherical bore on the outer race. This

Parts of a bearing

bearing can carry journal loads which are slightly inclined due to shaft misalignment.

ROLLER BEARINGS:Roller bearings are available with the grooved race in the outer and inner members. Selection of this depends on which race is required to be locked. Roller bearings are intended to carry radial (journal) loads and can carry greater radial loads than ball-bear-ings of the same size.

SELF-ALIGNING ROLLER BEARINGS:Self aligning roller bearings have barrel-shaped rollers and spher-ical bores in the outer race. For very heavy radial loads, double row roller bearings are also available.

NEEDLE-BEARINGS:Rollers of very small diameter, called needle rollers, are used where outer diameter of the bearing is severely restricted be-cause of the limited bearing space in the housing.

ANGULAR CONTACT BALL-BEARING:These bearings are designed to take an axial thrust as well as radial loads.

TAPERED ROLLER-BEARINGS:These are used for taking high axial thrust loads. Tapered roller bearings with slow tapered cones are used where the axial thrustis more than the radial load. These bearings are made to take thrust from one direction only. Where there is an opposingthrust, then the bearings must be mounted as pairs in opposition.

THRUST BALL-BEARING:These bearings are useful for taking vertical thrust loads but cannot take any radial load. Special thrust bearings are available which can also take horizontal end thrusts.

BEARINGS AND THEIR APPLICATIONS:

1. BALL BEARING: -they are to carry general load -the deep groove type of ball races are capable of withstanding the axial thrust.

(From left, clockwise) : ball bearing, tapered roller bearing, self aligning ball bearing, roller bearings, needle bearing, angular contact ball bear-ing, self aligning roller bearing

2. SELF ALIGNING BALL BEARING: can carry journal loads whichare slightly inclined due to shaft mis-alignment.3. ROLLER BEARING: carry radial (journal) loads and can carry greater radial loads than ball-bearings of the same size.4. SELF ALIGNING ROLLER BEARING: For very heavy radial loads.5. NEEDLE BEARING: used where outer diameter of the bearing is severely restricted because of the limited bearing space in thehousing.6. ANGULAR CONTACT BEARING: designed to take an axial thrust as well as radial loads.7. TAPERED ROLLER BEARING: used for taking high axial thrust loads. Tapered roller bearings with slow tapered cones are used where the axial thrust is more than the radial load.8. THRUST BALL BEARING: useful for taking vertical thrust loads but cannot take any radial load.

(Top and Bottom): Types of thrust-ball bearing

Ball and roller bearing

Parts of a bearing

09

Bevel gear

Gear is a mechanical device that transmits power and motion be-tween axes in a variety of commercial and industrial applications. Gears or toothed gearing is often used in places where moder-ate or large amount of power is to be transmitted at a constant velocity ratio. They are used to -transmit torque/ motion from the driving shaft to the driven/ follower shaft, -to change the velocity ratio, -to change the direction of rotation, -to get a positive drive.They are made from cast iron, steel, non-ferrous, plastic or fibre material.

TERMINOLOGY USED:

PITCH CIRCLE – It is an imaginary circle which by pure rolling action, would give the same motion as the actual gear.PITCH POINT – It is a common point of contact between two pitch circles.PRESSURE ANGLE – It is the angle between the common normal to two gear teeth at the point of contact and the common tan-gent at the pitch point. It is often termed as angle of obliquity.

ADDENDUM – It is the radial distance of the tooth from the pitch circle to the top of the tooth.DEDEDUM CIRCLE – It is the circle drawn from the bottom of the teeth. It is also known as the root circle.MODULE – It is the ratio of the pitch diameter in millimeter to the number of teeth.CLEARANCE – It is the radial distance from the top of the tooth to the bottom of the tooth in the meshing gear.TOOTH THICKNESS – It is the width of the tooth measured along the pitch circle.BLACKLASH- It is the difference between the tooth space and tooth thickness, as measured along the pitch circle.PATH OF CONTACT –It is the path traced by the point of contact of two teeth from the beginning to the end of engagement.ARC OF CONTACT –It is the path traced by a point on the pitch circle from the beginning to the end of engagement of a given pair of teeth. The arc of contact consists of two parts; Arc of approach Arc of recess

TYPES:SPUR GEAR:The teeth are cut parallel to the axis of rotation. The spur gears are used to transmit power between two parallel shafts. Spur gears are used in the centre lathe to transmit motion from the main spindle to the lead screw.HELICAL GEAR:In a helical gear, the teeth are cut at an angle to the axis of rotation. It may be used to transmit power between two parallel shafts. Helical gears run more silently than spur gear. They are widely used in automobile vehicles. The end thrust is exerted by the driving and the driven gears in the case of helical gears and the thrust may be eliminated by using double helical gears called HERRING-BONE GEARS.BEVEL GEAR:The bevel gears are used to transmit motion between shafts at various angles to each other. In a hand driller, the bevel gears transmit motion when the shafts are at right angles to each other.MITRE GEARS:If two bevel gears are symmetrical to each other and transmit motion at right angles, such gears are called mitre gears..

WORM SHAFT AND WORM GEAR:The worm shaft has spiral teeth cut on the shaft and the worm wheel is a special form of gear teeth cut to mesh with the worm shaft. They are widely used for speed reduction purposes.RACK AND PINION:The rack and pinion can change rotatory into linear movement and vice-versa. This mechanism is used in drilling machines. The rack and pinion mechanism is also used in lathe traverse mecha-nism.HYPOID GEARS:The hypoid gears are used in automotive differential gearboxes. A pair of hypoid gears is similar to the spiral bevel gear but with shafts offset. The tooth action between each gear is a combina-tion of rolling and sliding action along a straight line. The pitch surfaces are hyperboloids of revolution which is why they areknown as hypoid gears.VELOCITY RATIO OF GEAR TRAIN:The gear train transmits motion without slip. Different speeds can be obtained by shifting gear position in the gear- box.LUBRICATION OF GEAR TRAIN:The low speed gears which are visible may be lubricated with an oil can or brush. The drop oil method of lubrication may be used.Gears can be packed in grease or run in an oil bath.

Hypoid gear

11Hinges are flexible joint mechanisms that provide support and allow for the turning or swinging movement of the object to which they are attached. It consists of two leaves attached to the object and to the frame of the object. A set of knuckles rests between the two leaves. The knuckles connect the leaves to one another. A pin is inserted through the knuckle to secure the hinge in place.

DOOR HINGEButt Hinge-It is normally used for doors, cabinets, boxes doors-Materials: brass, stainless steel, iron-Sizes from 1/2” x 1.5mm upto 8”

Spring HingeSpring hinge is used for automatic closing of doors. Spring is attached to the two leaves. -They are available in various sizes: 2”, 3” 4” & 5”-Material: brass, iron-Cost of spring hinge varies depending upon the size; the cost of 5” spring hinge is Rs 75

No-MortiseThe advantage of a “no-mortise” hinge is that because the one leaf is set inside the other installation, the hinge leaves only a small gap between the door and the frame -Used in bi-fold doors

Piano hinge It is ideal where a long hinge is required such as a desk top or a cupboard door. Small countersink screws are normally used to fix it in position.-Material : Brass, steel, iron.-Size : 6 feet Tee Hinge-For wood, metal or vinyl gates -Adjustable self closing gate hinge -Internal stainless steel torsion spring -Cost: Rs 150 per piece-Material: Made of iron

(From right, clockwise): butt hinge, piano hinge, no mortise, spring hinge, tee, hinge keeping the door together

FURNITURE HINGESButler Tray Hinge-Folds to 90 degree-Stop holds hinge flat in horizontal position

Pivot HingesThey provide openings in the floor and the top of the door frame. -Also referred to as a double-acting floor hinge-Mounts at the top and bottom of the door leaving, a small wafer of metal exposed-Commonly used on furniture doors or where doors are intended to be inconspicuous

Hinges are available in various materials like plastics and metals, such as stainless steel and aluminum. Other materials include acrylic, aluminum & brass. Costing depends on the kind of mate-rial, size and finish of the hinge.

Used in :Double sided photo framesBelt bucklesFolding LampsBraceletsWatches

(From left, clcokwise): a hinge having an antique finish, pivot hinge, stainless steel hinge

13The cam and follower is a device which can convert rotary mo-tion (circular motion) into linear motion (movement in a straight line). The cam and the follower have a line/surface contact. It is a convenient means of transforming one form of motion to another. A cam can have various shapes. These are know as cam profiles. The ‘bumps’ on a cam are called lobes. The square cam illustrated below has four lobes, and lifts the follower four times each revolution.Cam systems can replace relatively complicated linkages in achieving desirable motion cycles. In all cam systems it is import-ant that the follower is always incontact and following the motion of the cam. This is achieved in a number of ways including the following.-Gravity -Using a mechanical constraint system i.e. groove -Using a spring force -Using a pneumatic or hydraulic force

CLASSIFICATION OF FOLLOWERS

According to the surface contact:

KNIFE- EDGE FOLLOWER-When the contacting end of the follower has a sharp knife edge -It is seldom used in practice because the small area of contact-ing surface results in excessive wear-There is a considerable side thrust between follower and guide

ROLLER FOLLOWER -When the contacting end of the follower is a roller-Rate of wearing is less then that in knife edge follower-They are used where more space is available-Used in engines ( stationary gas and oil ) and aircraft engines

FLAT- FACED FOLLOWER-When the contacting end of the follower, is a perfectly flat faced-The side thrust between the follower and the guide is much less-The relative motion between the surfaces is of sliding nature-They are used where space is limited-Used in cams which operate the valves of automobile engines

Pear Heart Circular Drop

Square cam

Follower

(From top left, clcokwise): the square cam having four lobes, rotary cam profiles, knife-edge follower, roller follower, a toy having pear shaped cams, different cam profiles

SPHERICAL FACED FOLLOWER-When the contacting end of the follower is of spherical shape-It is used to minimize the high surface stresses produced in cams

APPLICATIONS OF CAMS:

-Cams are used in the wipers of the cars-Automatic locking is one of its applications-Cams have a wide application in textile industry like the sewing machine, offset printing etc.-Internal combustion machines also uses cams-Cam is used in position control and indicating mechanism-It is used in precision stepping devices-Cams have a wide application in automobiles too

(From top left, clcokwise): flat-faced follower, dif-ferent types of cams according to path of motion of follower, spherical-faced follower

15A lever is one of the FIVE simple machine elements. It is a rigid object resting over a pivot joint known as fulcrum. It helps to multiply the mechanical force that can be applied to lift or move an object. Thus, it allows us to lift heavy loads by applying less force. Its theory of operation states “equal weights at equal dis-tances are in equilibrium, and equal weights at unequal distances are not in equilibrium but incline towards the weight which is at the greater distance.” (Load arm) X (Load force) = (Effort arm) X (Effort force) F1 X D1 = F2 X D2

There are three classes of levers namely:First class leverSecond class leverThird class leverThis classification represents variations in the location of the fulcrum and the input and output forces.

FIRST CLASS LEVER The fulcrum is located in between the input effort and the output load. This supports the effort arm and the load. Force is applied

(by pulling or pushing) to a section of the bar, which causes the lever to swing about the fulcrum, overcoming the resistance force on the opposite side. Examples are scissors, crow bar, engine valves, bicycle brakes ets.

SECOND CLASS LEVERThe input effort is located at one end of the bar and the fulcrum is located at the other end of the bar, opposite to the input, with the output load at a point between these two forces. This supports the effort arm and the load. Examples are wheel barrow, nut cracker etc.

THIRD CLASS LEVEREffort is applied between the output load on one end and the fulcrum on the opposite end. The input effort is higher than the output. The distance moved by the resistance (load) is greater than the distance moved by the effort. Thus, it still has its uses in making certain tasks easier to do. Examples are fishing rod, stapler etc.

CURVED LEVERS:Because of its name, a lever which is bent, is known as curved lever. In this type of levers, both the arms are bent between 0 to 180 degrees. Best example of curved lever is Bell cranked lever, in which arms are usually bent at 90 degrees.

16

(Bottom-right, anti-clockwise): Self-tapping screws, thread cutting, thread forming

A screw, or bolt, is a type of fastener characterized by a helical ridge, known as a male thread (external thread) or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as a female thread (in-ternal thread), often in the form of a nut or an object that has the internal thread formed into it. Other screw threads are designed to cut a helical groove in a softer material as the screw is inserted. The most common uses of screws are to hold objects together and to position objects.A screw will almost always have a head on one end which contains a specially formed shape that allows it to be turned, or driven. Common tools for driving screws include screwdrivers and wrenches. The head is usually larger than the body of the screw, which keeps the screw from being driven deeper than the length of the screw and to provide a bearing surface. There are excep-tions; for instance, carriage bolts have a domed head that is not designed to be driven; set screws often have a head smaller than the outer diameter of the screw; J-bolts have a J-shaped head which is not designed to be driven, but rather is usually sunk into concrete allowing it to be used as an anchor bolt. The cylindrical portion of the screw from the underside of the head to the tip is known as the shank; it may be fully threaded or partially threaded.The distance between each thread is called the “pitch”.The majority of screws are tightened by clockwise rotation, which is termed a right-hand thread; a common mnemonic device for remembering this when working with screws or bolts is “righty-tighty, lefty-loosey.” Screws with left-hand threads are used in exceptional cases.

SELF-TAPPING SCREWS:They are used in assembly where thin section metal sheets are used. Joints made using these screws are vibration resistant and can be assembled and dismantled many times.Designation:Self tapping screws are designated by the nomenclature, type, screw size number, nominal length and the number of the IndianStandard. eg. A slotted raised countersink (oval) tappingscrew of type AB, screw size number 10, nominal length 25 mm shall be designated as -Tapping screw, oval head AB 10x25. The size of the screw (diame-ter) is indicated by the size number which ranges from 0 to 16.

TYPES OF SELF-TAPPING SCREWS:1. Thread forming type:This type of metal screws produces the mating thread by displac-ing the material. These are useful for softer and thinner materials.2. Thread cutting type:This type cuts the mating thread in the hole in the same way as a thread cutting tap. These screws will have projected ridges in the shape of thread for the cutting action. These are useful for self-tapping on hard or brittle materials with thin wall sections.3. Self-piercing and self- tapping:These screws have a special piercing point and twin start thread. These screws are used along with a special gun. In a single opera-tion, the hole is pierced and the screw is also driven in.

Self-tapping screws are available in a variety of head shapes. They are either with cross-recessed or slotted heads. The ends of self-tapping screws are of two types as per Indian Standard; Types AB and B. Type AB is the self-piercing type B is a threadforming type.

HAMMER-DRIVE SCREWS:They are used for fixing thin plates like nameplates, etc. on cast iron machine body. These screws have multi-start threads. For fixing this screw, a hole is drilled on the machine casting to the size of the pilot. The screw pilot is then placed in the hole anddriven in by a hammer.Designation:Eg. A hammer drive screw with screw number 4 having a length of 9.5 mm can be designated as Hammer-drive screw No.4x9.5.-IS 5957. The I.S.I. specification number and the type ofcoating can be included at the end.

The threads are formed on screws in a helix. When a single helix is making a screw, it is called SINGLE START thread. In a single start thread, the lead and pitch are the same (Fig 1). In case ofDOUBLE START threads, one thread is wound within the other exactly in the middle. This enables the lead of the helix to be increased without increasing the pitch (Fig 2).

MULTI-START SCREW THREADS:A screw thread may have any number of starts, the general term for such threads other than single start is MULTI-START. Applica

tion of multi-start threads can be found in fly press, pen cap, etc. (Fig 3). Multi-start thread allows the depth of the thread to be less and provides for rapid axial movement of the screws.

RIGHT HAND AND LEFT HAND SCREW THREADS:The threads found on bolts and screws are generally right hand. In this case, when the bolt is rotated clockwise, it advances into the nut. A left hand thread bolt screws into the nut whenit is rotated anticlockwise.

18A light-emitting diode (LED) is a semiconductor diode that emits light when an electrical current is applied in the forward di-rection of the device, as in the simple LED circuit. LEDs are widely used as indicator lights on electronic devices and increasingly in higherpower applications such as flashlights and area lighting. An LED is usually a small area (less than 1 mm2)light source, often with optics added to the chip to shape its radiation pattern and assist in reflection. The color of the emitted light depends on thecomposition and condition of the semiconducting material used, and can be infrared, visible, or ultraviolet. Besides lighting, interesting applications include using UV-LEDs for sterilization of water and disinfection of devices, and as grow light to enhance photosynthesis in plants.

ADVANTAGES:

* LEDs produce more light per watt than incandescent bulbs; this is useful in battery powered or energy-saving devices.* LEDs can emit light of an intended color without the use of color filters that traditiona lighting methods require. This is more efficient and can lower initial costs.

* The solid package of the LED can be designed to focus its light.* LEDs are ideal for use in applications that are subject to fre-quent on-off cycling.* LEDs can very easily be dimmed either by pulse-width modula-tion or lowering the forward current.* LEDs light up very quickly. A typical red indicator LED will achieve full brightness in microseconds.* LEDs mostly fail by dimming over time, rather than the abrupt burn-out of incandescent bulbs.* LEDs can have a relatively long useful life.* LEDs, being solid state components, are difficult to damage with external shock.* LEDs can be very small and are easily populated onto printed circuit boards.* LEDs do not contain mercury.* Due to the human eye’s visual persistence, LEDs can be pulse width or duty cycle modulated in order to save power or achieve an apparent higher brightness for a given powerinput.

20The Kawad or the story-telling boxes come from Bassi, 24 km from Chittorgarh. They are sometimes called travelling altars. Although made in Bassi, the boxes were traditionally carried by singer-storytellers from the desert areas, who performed house to house, telling the stories of the Ramayana, the Mahabharata or other religious and epic tales painted on the boxes. According to one Kawad performer interviewed in the Hindu, these performers once used scrolls, but the scrolls were easily destroyed in bad weather or by bugs, so they began using these wooden boxes.As with other traditional Indian forms that involve the use of ob-jects in storytelling or performance, performers and performanc-es have become rare as the traditional context for performance has dissolved. However, the objects that are part of the tradition have found a new economic niche, being sold to tourists and collectors. Their status as performing objects has dwindled while their status as art objects has grown.In Bassi about 5 or 6 families of carvers continue to make these boxes, almost entirely for the tourist market. They have expanded their subject matter to capture the interests of new customers. Boxes now display not just traditional Hindu tales, but also the story of Jesus Christ or the English Alphabet. A box devoted to Ganesh is also popular as are some with contemporary images. At first they are compact, beautifully painted boxes. But they slowly unfold, revealing all the treasures painted inside. Each image prompts a well-known story or episode. One side of this particular box has images and episodes from the Ramayana. The other has images and episodes from the life of Krishna. The style of the painting is said to be related to that of the Pabuji ke phad scrolls that come from the town of Bilwara, which is not far away.The idea to make this for my ‘Technical Studies’ module came to me when I visited Jodhpur as a part of our Craft Cluster Pro-gramme in college. These little pieces of art were seen as one to two pieces in shops of Jodhpur and Jaisalmer. However, the tricky part was to combine gears with it. Materials used were teak wood of thickness 6 mm, cylindrical saagwaan rods, hinges, glue and other adhesives, all the ma-chines and tools used for wood-work, composite spur gears and basic stationery. Time taken to finish the product was approxi-mately fifteen days. The process involved cutting wood accurately according to the required dimensions and putting it all together. Once the altar was ready, then came the gears. The eight gears were put beside each other, four with the temple doors and the others acting as idle gears. The mechanism was brought about by rotating any of the idle gears. While placing the gears, take note, that the distance between two gears should be such that their teeth do not tightly fit into each other. Hence, the doors open with the help of gears and a traditional handicraft item gets a contemporary touch.

Reference picture

Cut the pieces according to dimension

Put it together

‘Primer’ it

Grrove it to gear

‘Gear’ it

Paint it accordingly

Product

23Any mechanical or electromechanical device used for fastening of cloth, leather, furs, and other flexible materials, using needle and thread is a sewing machine. Some of the tools required for sti-tiching would be measuring tapes, needles, thread, seam guage, pin cushion, thimble, shears, sewing needle threader, pinking shears, embroidery scissors, seam ripper, rotary cutter, pressing tools like hams, press cloth, sleeve rolls, iron and iron board, drawstring threader, fabric marking tools, tracing paper, tracing wheel, hem tape, bias tape, elastic etc.

The basic machine stitches are:• Straight: You use the straight stitchfor basting, seaming, and topstitching.• Zigzag: The machine adds width to the straight stitch to make the zigzag stitch. You use the zigzag stitch for stitching around

(From extreme left, clockwise) : Types of sewing

machine needles, seam ripper, nee-

dles, measuring tape, pin cushion,

stitching in progress, double

needle

Sewing is the craft of fastening or attaching objects using stitches made with a needle and thread. Sewing is one of the oldest of the textile arts, arising in the Paleolithic era. Before the invention of spinning yarn or weaving fabric, archaeologists believe Stone Age people across Europe and Asia sewed fur and skin clothing using bone, antler or ivory needles and “thread” made of various animal body parts including sinew, catgut, and veins.For thousands of years, all sewing was done by hand. The inven-tion of the sewing machine in the 19th century and the rise of computerization in the later 20th century led to mass produc-tion of sewn objects, but hand sewing is still practised around the world. Fine hand sewing is a characteristic of high-quality tailoring, haute couture fashion, and custom dressmaking, and is pursued by both textile artists and hobbyists as a means of creative expression.

appliqués, making buttonholes, sewing on buttons, and embroi-dering. The zigzag stitch is as practical as it is fun.• Three-step zigzag: When used on the widest width, the ordi-nary zigzag stitch pulls the fabric into a tunnel and the fabric rolls under the stitch — not very desirable. To eliminate this problem, the sewing gods handed down the three-step zigzag stitch. The needle takes three stitches to one side and then three stitches to the other side, keeping the fabric flat and tunnel-free. Use the three-step zigzag for finishing raw edges, sewing on elastic, mending tears, and making decorative effects.• Blind hem and stretch blind hem: The blind hem stitch is designed to hem woven fabrics so that the stitches are almost invisible when looked at from the right side of the garment. The stretch blind hem stitch has an extra zigzag or two that stretches to invisibly hem knit fabrics. Both stitches have decorative appli-cations, too.

• Overlock: Many of the overlock-type stitches on today’s sewing machines are designed to stitch and finish seams in one step, simulating the serger stitches that you see on ready-to-wear gar-ments. Some of these stitches work well on woven fabrics; some work better on knits.• Decorative: Decorative stitches fall into two basic categories: closed, satin-type stitches (such as the ball and diamond) and open, tracery-type stitches (such as the daisy and honeycomb). Many newer machines can be programmed to combine these stitches with other stitches, elongate the designs for a bolder decorative effect, and even stitch someone’s name.SELECTING A STITCH TYPE:If the sewing machine does more than straight stitch and zigzag, it must give you some way to select the stitch you want to use.

(From bottom left: Different types of sew-ing machines, emroidery scissors, different

stitches

Older machines have dials, levers, buttons, or drop-in cams as stitch selectors. Newer, computerized models have keys or touch pads that not only select the stitch but also can automatically set the stitch length and width. We must consult the Operating Manual that comes with your sewing machine to get the specifics on how to select a stitch type.

SELECTING THE LENGTH OF THE STITCH:The length of the stitch determines the stitch’s durability. Short stitches (1 to 3 mm, 13 to 60 spi) are very strong and are meant to be permanent. Longer stitches are usually temporary or are used as a decorative topstitch. Stitch length isdetermined by the distance the feed dogs move the fabric under the needle. When the feed dogs move with shorter strokes, stitches are short. When they move with longer strokes, stitches are longer. Feed dogs, sometimes referred to as “feed teeth,” are teeth or pads that move the fabric through the machine. The fabric is sandwiched between the presser foot and the feed dogs, and as the needle

stitches up and down, the feed dogs grab the fabric and move it under the foot. Stitch length is measured two different ways — in millimeters (mm) and in stitches per inch (spi). The setting used depends on the brand and model of your machine. Topstitching is an extra line of stitching sewn on the right side of the fabric that parallels a seamline or is used to sew a hem. Top-stitching is usually visible on a project, so it needs to look good.

For our class assignment we made patterns for T-base and square base bags. We were also taught running gusset and round base patterns. There is always a minimum of 1 cm allowance left at the edges to stitch.

Running Gusset

Round Base

Square Base T-Base

Allowance is required to stitch the sides together

Height can be ‘x’

Length is 2*pi*r which is also the circumference of the circle

x

x

The sides are stitched together to close it

Identical patterns for front and back and a ‘gusset’ to stitch the three sides (top remains open)

The patterns of the assignment done bags

26The ‘Technical Studies’ module was full of great fun and learn-ing. It was an insightful experience. My professor, Mr.K.Murugan is very patient and possesses a great amount of knowledge of machines and materials. I gained invaluable experience under his guidance. The module involved putting the theoretical learn-ing into practise by develpoing a product from cams and gears. The process was enjoyable as I got more and more aware of the machines and tools required for wood work. It is a whole lot of effort that goes in from the ‘idea phase’ to the ‘final product phase’. The classroom learning was implemented at every step, that being the best take-away from the module.

27Screwfix Direct Ltd, 2014. Screws. [online] Available at: < http://www.screwfix.com/c/screws-nails-fixings/screws/cat840008 > [Accessed 29 November 2014].

Wikimedia. Cams. [online] (29 October 2014) Available at: <http://en.wikipedia.org/wiki/Cam> [Accessed 29 November 2014].

Bown, Deni, 1996. The Complete Book of Sewing: A practical step-by-step guide to sewing techniques. Chester: Dorling Kindersley Limited.

Hettich Holding GmbH & Co.. A good turn. [online] Available at: < http://www.hettich.com/in_EN/products/hinges.html> [Ac-cessed 29 November 2014].

InfoSpace LLC, 1998-2014. How gears work. [online] (2014) Avaialble at: < http://science.howstuffworks.com/transport/en-gines-equipment/gear.htm> [Accessed 29 November 2014].

Shanavas S., 2013. Stress Analysis of Composite Spur Gear. [on-line] India: International Journal of Engineering Research & Tech-nology. Available at: < http://www.ijert.org/view.php?id=6740&ti-tle=stress-analysis-of-composite-spur-gear##tab1> [Accessed 29 November 2014].

Boots Group Plc., 2003. Hinges. [online] Boots Group Plc. Avail-able at: <http://www.Boots-Plc.Com/Information/Info.Asp?Lev-el1id=447&Level 2id=0> [Accessed 29 November 2014].

Defoe, D., 1999. How stuff works. [online] Champaign, Illinois: Project Gutenberg. Available at: <http://www.gutenberg.org/etext/370> [Accessed 18 November 2014].