MTHEMTIL SKILLS GERS, GER TRINS ND OMPOUND GERS SSOITED EXMINTION QUESTIONS WORLD SSOITION OF TEHNOLOGY TEHERS DESIGN ND TEHNOLOGY NOT FOR SLE OR REDISTRIUTION THIS MTERIL NNOT E EDITED OR PLED ON NY OTHER FORM OF MEDI, INLUDING POWERPOINTS, INTRNETS, WESITES ET... WORLD SSOITION OF TEHNOLOGY TEHERS
LULTING GER RTIO (VELOITY RTIO) In examinations, one of the first questions will be - to work out the 'gear ratio' (sometimes called velocity ratio). s a guide - always assume that the larger gear revolves one revolution. The number of rotations of the second gear has then to be worked out. 1. 60 TEETH 2. 25 TEETH In the example below, the has 60 and because it is the largest we say that it revolves once. The gear has 0. Simply divide 60 by 0 to work out the number of revolutions of the driven gear. 0 TEETH (LOD) GER RTIO / VELOITY RTIO Distance moved by Effort 60T (GER ) Distance moved by Load 0T (GER ) 1 Input movement 2 Output movement Driver : Driven 1:2 75 TEETH Distance moved by Effort 25T (GER ) Distance moved by Load 75T (GER ) Input movement 1 Output movement (LOD) WORLD SSOITION OF TEHNOLOGY TEHERS. Driver : Driven :1 80 TEETH 20 TEETH Distance moved by Effort 20T (GER ) Distance moved by Load 80T (GER ) 4 Input movement 1 Output movement Driver : Driven 4:1 (LOD)
LULTING GER RTIO (VELOITY RTIO) In examinations, one of the first questions will be - to work out the 'gear ratio' (sometimes called velocity ratio). s a guide - always assume that the larger gear revolves one revolution. The number of rotations of the second gear has then to be worked out. 1. 60 TEETH 0 TEETH GER RTIO / VELOITY RTIO Distance moved by Effort Distance moved by Load Input movement Output movement (LOD) WORLD SSOITION OF TEHNOLOGY TEHERS 2. 25 TEETH Driver : Driven : 75 TEETH Distance moved by Effort Distance moved by Load Input movement Output movement (LOD). Driver : Driven : 80 TEETH 20 TEETH Distance moved by Effort Distance moved by Load Input movement Output movement Driver : Driven : (LOD)
LULTING REVOLUTIONS PER MINUTE (RPM) In the example below, the gear is larger than the gear. The general rule is - large to small gear means 'multiply' the velocity ratio by the rpm of the first gear. Divide 60 by 0 to find the velocity ratio. Multiply this number (2) by the rpm (120). This gives an answer of 240rpm. 60 TEETH 0 TEETH GER GER 60 0 120 rpm (LOD) WORLD SSOITION OF TEHNOLOGY TEHERS 25 TEETH 60 0 120 X 2 2 240 revs/min 75 TEETH GER GER 25 75 60 rpm 75 25 (LOD) 60 20 revs/min GER GER 20 80 80 TEETH 20 TEETH 100 rpm 80 20 100 4 (LOD) 4 25 revs/min
LULTING REVOLUTIONS PER MINUTE (RPM) 60 TEETH 0 TEETH GER GER 60 0 120 rpm (LOD) 25 TEETH revs/min 75 TEETH GER GER 25 75 60 rpm revs/min (LOD) WORLD SSOITION OF TEHNOLOGY TEHERS 80 TEETH 20 TEETH GER GER 20 80 100 rpm revs/min (LOD)
GER TRINS - EXMPLE QUESTIONS ND NSWERS When faced with three gears, the question can be broken down into two parts. First work on Gears and. When this has been solved, work on gears and. 60T 20T 10T The diagram above shows a gear train composed of three gears. Gear revolves at 60 revs/min in a clockwise direction. What is the output in revolutions per minute at Gear In what direction does Gear revolve GER GER GER 20 60 60 rpm 10 60 REVS/MIN WORLD SSOITION OF TEHNOLOGY TEHERS First work out the speed at Gear. 60rpm 60 20 20 revs/min at (Remember is larger than therefore, outputs less revs/min and is slower) Next, take and. is smaller, therefore, revs/minute will increase and rotation will be faster. 60 10 20 REVS X 6 6 120 revs/min at What direction does revolve is clockwise, consequently is anti-clockwise and is therefore clockwise.
GER TRINS - EXMPLE QUESTIONS When faced with three gears the question can be broken down into two parts. First work on Gears and. When this has been solved work on gears and. 60T 20T The diagram above shows a gear train composed of three gears. Gear revolves at 60 revs/min in a clockwise direction. What is the output in revolutions per minute at Gear In what direction does Gear revolve 10T GER GER GER 20 60 10 60 rpm 60 REVS/MIN WORLD SSOITION OF TEHNOLOGY TEHERS First work out the speed at Gear. 60rpm revs/min at (Remember is larger than therefore, outputs less revs/min and is slower) Next, take and. is smaller, therefore, revs/minute will increase and rotation will be faster. REVS X revs/min at What direction does revolve is clockwise, consequently is anti-clockwise and is therefore
GER TRINS - EXMPLE QUESTIONS ND NSWERS When faced with three gears the question can be broken down into two parts. First work on Gears and. When this has been solved work on gears and. The diagram opposite shows a gear train composed of three gears. Gear revolves at 90 revs/min in a clockwise direction. What is the output in revolutions per minute at Gear In what direction does Gear revolve 90T 0T 15T GER GER GER 0 90 90 rpm 15 90 REVS/MIN WORLD SSOITION OF TEHNOLOGY TEHERS First work out the speed at Gear. 90rpm 90 0 0 revs/min at (Remember is larger than therefore, outputs less revs/min and is slower) Next, take and. is smaller, therefore, revs/minute will increase and rotation will be faster. 90 15 0 REVS X 6 6 180 revs/min at What direction does revolve is clockwise, consequently is anti-clockwise and is therefore clockwise.
GER TRINS - EXMPLE QUESTIONS ND NSWERS When faced with three gears the question can be broken down into two parts. First work on Gears and. When this has been solved work on gears and. 90T 0T 15T The diagram opposite shows a gear train composed of three gears. Gear revolves at 90 revs/min in a clockwise direction. What is the output in revolutions per minute at Gear In what direction does Gear revolve GER GER GER 0 90 15 90 rpm 90 REVS/MIN WORLD SSOITION OF TEHNOLOGY TEHERS First work out the speed at Gear. 90rpm revs/min at (Remember is larger than therefore, outputs less revs/min and is slower) Next, take and. is smaller, therefore, revs/minute will increase and rotation will be faster. REVS X revs/min at What direction does revolve is clockwise, consequently is anti-clockwise and is therefore
OMPOUND GERS - EXMPLE QUESTIONS ND NSWERS elow is a question regarding 'compound gears'. Gears and represent a compound gear as they appear 'fixed' together. When drawn with a compass they have the same centre. Two gears 'fixed' together in this way rotate together and at the same RPM. When answering a question like this split it into two parts. Treat gears and as one question ND and D as the second part. GER GER GER D GER WORLD SSOITION OF TEHNOLOGY TEHERS This is an example of a compound gear train. Gear rotates in a clockwise direction at 0 revs/min. What is the output in revs/min at D and what is the direction of rotation GER GER GER GER D 120 40 First find revs/min at Gear. 80 20 120 40 0 rpm X 90 rpm / min is smaller therefore it rotates faster and revs/min increase. is fixed to and therefore, rotates at the same speed. 90 REVS/MIN at Next find revs/min at Gear D. 80 20 D 90 rpm (at ) X 4 4 60 rpm / min D is smaller than, therefore rotates faster (increased revs/min). revolves in a clockwise direction, is therefore anti-clockwise, is fixed to and is also anti-clockwise, which means D revolves in a clockwise direction.
OMPOUND GERS - EXMPLE QUESTIONS ND NSWERS elow is a question regarding 'compound gears'. Gears and represent a compound gear as they appear 'fixed' together. When drawn with a compass they have the same centre. Two gears 'fixed' together in this way rotate together and at the same RPM. When answering a question like this split it into two parts. Treat gears and as one question ND and D as the second part. GER GER GER D GER WORLD SSOITION OF TEHNOLOGY TEHERS This is an example of a compound gear train. Gear rotates in a clockwise direction at 0 revs/min. What is the output in revs/min at D and what is the direction of rotation GER GER GER GER D 120 40 First find revs/min at Gear. 80 20 rpm X rpm / min is smaller therefore it rotates faster and revs/min increase. is fixed to and therefore, rotates at the same speed. REVS/MIN at Next find revs/min at Gear D. D rpm (at ) X rpm / min D is smaller than, therefore rotates faster (increased revs/min). revolves in a clockwise direction, is therefore anti-clockwise, is fixed to and is also anti-clockwise, which means D revolves in a direction.
OMPOUND GERS- EXMPLE QUESTIONS ND NSWERS WORLD SSOITION OF TEHNOLOGY TEHERS Try the following question: GER D GER GER 150T NTI-LOKWISE GER 25T 100 revs/min 100T 50T What is the revs/min at gear D and what is its direction