cam for the part of an engine sometimes referred to as a cam see camshaft for the name cam and other uses see cam disambiguation fig 1 animation showing rotating cams and cam followers producing reciprocating motion elliptical disk cam with oscillating follower a cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion it is often a part of a rotating wheel eg an eccentric wheel or shaft eg a cylinder with an irregular shape that strikes a lever at one or more points on its circular path the cam can be a simple tooth as is used to deliver pulses of power to a steam hammer for example or an eccentric disc or other shape that produces a smooth reciprocating back and forth motion in the follower which is a lever making contact with the cam overview the cam can be seen as a device that rotates from circular to reciprocating or sometimes oscillating motion a common example is the camshaft of an automobile which takes the rotary motion of the engine and translates it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders displacement diagram fig 2 basic displacement diagram certain cams can be characterized by their displacement diagrams which reflect the changing position a roller follower a shaft with a rotating wheel at the end would make as the cam rotates about an axis these diagrams relate angular position usually in degrees to the radial displacement experienced at that position displacement diagrams are traditionally presented as graphs with nonnegative values a simple displacement diagram illustrates the follower motion at a constant velocity rise followed by a similar return with a dwell in between as depicted in figure 2 however the most common type is in the valve actuators in internal combustion engines here the cam profile is commonly symmetric and at rotational speeds generally met with very high acceleration forces develop ideally a convex curve between the onset and maximum position of lift reduces acceleration but this requires impractically large shaft diameters relative to lift thus in practice the points at which lift begins and ends mean that a tangent to the base circle appears on the profile this is continuous with a tangent to the tip circle in designing the cam the lift and the dwell angle displaystyle theta are given if the profile is treated as a large base circle and a small tip circle joined by a common tangent giving lift l displaystyle l the relationship can be calculated given the angle displaystyle phi between one tangent and the axis of symmetry displaystyle phi being 2 2 displaystyle pi 2theta 2 while c displaystyle c is the distance between the centres of the circles required and r displaystyle r is the radius of the base given and r displaystyle r that of the tip circle required c l 1 sin displaystyle cl1sin phi and r r l sin 1 sin displaystyle rrlsin phi 1sin phi disc or plate cam fig 3 cam profile the most commonly used cam is the cam plate also known as disc cam or radial cam which is cut out of a piece of flat metal or plate several key terms are relevant in such a construction of plate cams base circle prime circle with radius equal to the sum of the follower radius and the base circle radius pitch curve which is the radial curve traced out by applying the radial displacements away from the prime circle across all angles and the lobe separation angle lsa the angle between two adjacent intake and exhaust cam lobes the base circle is the smallest circle that can be drawn to the cam profile a once common but now outdated application of this type of cam was automatic machine tool programming cams each tool movement or operation was controlled directly by one or more cams instructions for producing programming cams and cam generation data for the most common makes of machine were included in engineering references well into the modern cnc era this type of cam is used in many simple electromechanical appliance controllers such as dishwashers and clothes washing machines to actuate mechanical switches that control the various parts cylindrical cam motorcycle transmission showing cylindrical cam with three followers each follower controls the position of a shift fork constant lead barrel cam in an american pacemaker lathe this cam is used to provide a repeatable cross slide setting when threading with a singlepoint tool a cylindrical cam or barrel cam is a cam in which the follower rides on the surface of a cylinder in the most common type the follower rides in a groove cut into the surface of a cylinder these cams are principally used to convert rotational motion to linear motion parallel to the rotational axis of the cylinder a cylinder may have several grooves cut into the surface and drive several followers cylindrical cams can provide motions that involve more than a single rotation of the cylinder and generally provide positive positioning removing the need for a spring or other provision to keep the follower in contact with the control surface applications include machine tool drives such as reciprocating saws and shift control barrels in sequential transmissions such as on most modern motorcycles a special case of this cam is constant lead where the position of the follower is linear with rotation as in a lead screw the purpose and detail of implementation influence whether this application is called a cam or a screw thread but in some cases the nomenclature may be ambiguous cylindrical cams may also be used to reference an output to two inputs where one input is rotation of the cylinder and the second is position of the follower axially along the cam the output is radial to the cylinder these were once common for special functions in control systems such as fire control mechanisms for guns on naval vessels an example of a cylindrical cam with two inputs is provided by a duplicating lathe an example of which is the klotz axe handle lathe which cuts an axe handle to a form controlled by a pattern acting as a cam for the lathe mechanism face cam a face cam produces motion by using a follower riding on the face of a disk the most common type has the follower ride in a slot so that the captive follower produces radial motion with positive positioning without the need for a spring or other mechanism to keep the follower in contact with the control surface a face cam of this type generally has only one slot for a follower on each face in some applications a single element such as a gear a barrel cam or other rotating element with a flat face may do duty as a face cam in addition to other purposes face cams may provide repetitive motion with a groove that forms a closed curve or may provide function generation with a stopped groove cams used for function generation may have grooves that require several revolutions to cover the complete function and in this case the function generally needs to be invertible so that the groove does not self intersect and the function output value must differ enough at corresponding rotations that there is sufficient material separating the adjacent groove segments a common form is the constant lead cam where displacement of the follower is linear with rotation such as the scroll plate in a scroll chuck noninvertible functions which require the groove to selfintersect can be implemented using special follower designs sash window lock traditional cam style for doublehung sash window a variant of the face cam provides motion parallel to the axis of cam rotation a common example is the traditional sash window lock where the cam is mounted to the top of the lower sash and the follower is the hook on the upper sash in this application the cam is used to provide mechanical advantage in forcing the window shut and also provides a selflocking action like some worm gears due to friction face cams may also be used to reference a single output to two inputs typically where one input is rotation of the cam and the other is radial position of the follower the output is parallel to the axis of the cam these were once common is mechanical analog computation and special functions in control systems a face cam that implements three outputs for a single rotational input is the stereo phonograph where a relatively constant lead groove guides the stylus and tone arm unit acting as either a rockertype tone arm or linear linear tracking turntable follower and the stylus alone acting as the follower for two orthogonal outputs to representing the audio signals these motions are in a plane radial to the rotation of the record and at angles of 45 degrees to the plane of the disk normal to the groove faces the position of the tone arm was used by some turntables as a control input such as to turn the unit off or to load the next disk in a stack but was ignored in simple units heart shaped cam this type of cam in the form of a symmetric heart symbol is used to return a shaft holding the cam to a set position by pressure from a roller they were used for example on early models of post office master clocks to synchronise the clock time with greenwich mean time when the activating follower was pressed onto the cam automatically via a signal from an accurate time source snail drop cam this type of cam was used for example in mechanical time keeping clockingin clocks to drive the day advance mechanism at precisely midnight and consisted of a follower being raised over 24 hours by the cam in a spiral path which terminated at a sharp cut off at which the follower would drop down and activate the day advance where timing accuracy is required as in clockingin clocks these were typically ingeniously arranged to have a roller cam follower to raise the drop weight for most of its journey to near its full height and only for the last portion of its travel for the weight to be taken over and supported by a solid follower with a sharp edge this ensured that the weight dropped at a precise moment enabling accurate timing this was achieved by the use of two snail cams mounted coaxially with the roller initially resting on one cam and the final solid follower on the other but not in contact with its cam profile thus the roller cam was initially carried the weight until at the final portion of the run the profile of the nonroller cam rose more than the other causing the solid follower to take the weight linear cam a linear cam is one in which the cam element moves in a straight line rather than rotates the cam element is often a plate or block but may be any cross section key duplicating machine the original key mounted in the left hand holder acts as a linear cam to control the cut depth for the duplicate a common example of a linear cam is a key for a pin tumbler lock the pins act as the followers this behavior is exemplified when the key is duplicated in a key duplication machine where the original key acts as a control cam for cutting the new key history an early cam was built into hellenistic waterdriven automata from the 3rd century bc reciprocating motion cam engine cam design pages creates animated cams for specified follower motions kinematic models for design digital library kmoddl movies and photos of hundreds of working mechanicalsystems models at cornell university also includes an ebook library of classic texts on mechanical design and engineering introduction to mechanisms cams classification nomenclature motion and design of cams information for the course introduction to mechanisms at carnegie mellon university polynomial cam function with excel vba file to demonstrate its motion vtereciprocating engines and configurationstype bourke orbital sarich piston pistonless wankel radial axial rotary split cycle stelzer tschudi stroke cycles twostroke fourstroke fivestroke sixstroke twoand fourstroke configurations number of cylinderssingle cylinder single two cylinders splitsingle i2 v2 f2 inline straight i2 i3 i4 i5 i6 i7 i8 i9 i10 i12 i14 flat f2 f4 f6 f8 f10 f12 f16 v vee v2 v3 v4 v5 v6 v8 v10 v12 v14 v16 v18 v20 v24 w w8 w12 w16 w18 other inline h u square four vr opposed x x24 junkers jumo 222 componentsvalves cylinder head porting corliss intake exhaust multi overhead piston poppet side sleeve slide rotary valve variable valve timing camless desmodromic hydraulic tappet fuel supplies carburetor gasoline direct injection common rail mechanisms cam camshaft overhead camshaft connecting rod crank crankshaft scotch yoke swashplate rhombic drive linkages peaucellierlipkin watts parallel other hemi recuperator turbocompounding vtekinematic pairlower pairs revolute prismatic cylindrical screw planar spherical ball higher pairs cam gears vteautomotive enginepart of the automobile seriesbasic terminology bore compression ratio crank cylinder dead centre diesel engine dry sump engine balance engine configuration engine displacement engine knocking firing order hydrolock petrol engine power band redline sparkignition engine stroke stroke ratio wet sump main components connecting rod crankcase crankpin crankshaft crossplane cylinder bank cylinder block cylinder head crossflow reverseflow flywheel head gasket hypereutectic piston main bearing piston piston ring starter ring gear sump valvetrain cam cam follower camshaft desmodromic valve hydraulic tappet multivalve overhead camshaft overhead valve pneumatic valve springs poppet valve pushrod rocker arm sleeve valve tappet timing belt timing mark valve float variable valve timing aspiration air filter blowoff valve boost controller butterfly valve centrifugaltype supercharger cold air intake dump valve electronic throttle control forced induction inlet manifold intake intercooler manifold vacuum naturally aspirated engine ramair intake scrolltype supercharger short ram air intake supercharger throttle throttle body turbocharger twinturbo variablegeometry turbocharger variablelength intake manifold warm air intake fuel system carburetor common rail direct injection fuel filter fuel injection fuel pump fuel tank gasoline direct injection indirect injection injection pump leanburn stratified charge engine turbo fuel stratified injection unit injector ignition contact breaker magneto distributor electrical ballast high tension leads ignition coil spark plug wasted spark electrics and enginemanagement airfuel ratio meter alternator automatic performance control car battery leadacid battery crankshaft position sensor dynamo drive by wire electronic control unit engine control unit engine coolant temperature sensor glow plug idle air control actuator map sensor mass flow sensor oxygen sensor starter motor throttle position sensor exhaust system automobile emissions control catalytic converter diesel particulate filter exhaust manifold glasspack muffler engine cooling air cooling antifreeze ethylene glycol core plug electric fan fan belt radiator thermostat water cooling viscous fan fan clutch other components balance shaft block heater combustion chamber cylinder head porting gasket motor oil oil filter oil pump oil sludge pcv valve seal synthetic oil underdrive pulleys portal category authority control ndl 00564826 