What is Gear ratio: Definition and 54 Discussions

A gear train is a mechanical system formed by mounting gears on a frame so the teeth of the gears engage.
Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission of rotation from one gear to the next. Features of gears and gear trains include:

The ratio of the pitch circles of mating gears defines the speed ratio and the mechanical advantage of the gear set.
A planetary gear train provides high gear reduction in a compact package.
It is possible to design gear teeth for gears that are non-circular, yet still transmit torque smoothly.
The speed ratios of chain and belt drives are computed in the same way as gear ratios. See bicycle gearing.
The transmission of rotation between contacting toothed wheels can be traced back to the Antikythera mechanism of Greece and the south-pointing chariot of China. Illustrations by the Renaissance scientist Georgius Agricola show gear trains with cylindrical teeth. The implementation of the involute tooth yielded a standard gear design that provides a constant speed ratio.

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  1. Leo Liu

    Fixed gear ratio and correction tape

    I recently got a new correction tape. When I was staring at it today (ya I knew I should be studying for calc2), I noticed that the gear ratio between the two gears was notable and fixed. In particular, the bigger gear that unrolls the tape has more teeth than the smaller gear that rolls up the...
  2. M

    I Gearbox Gear ratio: How to get 60 rpm to 3500rpm? help please

    Hello I am trying to achieve 3500 rpm from 60rpm. The gear ratio I have worked out is 58:1. To minimize the size I have divided into 4 levels with the gear ratio of 2:1, 3.1, 3.1, 3,1, which rounds me up to 54:1 ratio is also ideal for me can anyone please help mw find the appropriate solution...
  3. Y

    How to select a stepper motor and gear ratio?

    Hello, I could use some help learning how to properly size stepper motor. Suppose that I want to use a stepper motor to move a load against the force of gravity. It must be able to start, stop, and hold it's position against the static load. I know the maximum torque of the load. In addition, I...
  4. M

    Engineering Two Stage Epicyclic Gear-box - Finding the Gear ratio

    Hi, Just have a question about the method in attempting this two-stage epicyclic gear-box. We are given the following information about the number of teeth: S1 = 48, P1 = 28, S2 = 96, and P2 = 48 My attempt: 1. Work out the number of teeth for the two ring/annulus gears From geometry, we can...
  5. kolleamm

    Higher gear ratio but less torque?

    There's a micro motor with a gear ratio of 298:1 and there's a servo with a ratio of 188:1. The first runs at 12v and the other at 7.4v. How is it that the motor with the bigger gear ratio has only a 70 oz-in torque, while the second motor has a 560 oz-in torque? First motor ...
  6. R

    Calculate the gear ratio for every gear

    Hi, I have Force vs velocity graph. From the graph, I need to calculate the gear ratio of every Gear. This is the formula what I can use to find the gear ratio, V= 2*pi*r.n(1-i)/ε v= vehicle speed m/s ( I consider from the graph lowest speed 3.61 m/s or 13km/h r= radius of drive wheel...
  7. E

    How do I select the right motor and gear ratio for a mid-drive e-Bike?

    Hey all! I am working on my first ebike build and posted a question about friction drives earlier. Now, I have decided to go with a Mid-drive. I made calculations and found out the torque and rpm required for the build. But I am having difficulty find the right motor and gear ratio. I am trying...
  8. Z

    Calculating gear ratio from the motor's graph for an EV?

    Dear community, For my electric vehicle project I want to select a gear ratio (single) of my gear box and send this information to the supplier. In order to calculate this ratio I thought of the following steps but am not sure and want some expert to recheck and answer my queries: 1. Calculate...
  9. F

    Find the gear ratio for maximum angular acceleration

    Homework Statement A constant torque is applied to a pinion which has a moment of inertia of I_m. The pinion(A) drives two gears, one (B) which is connected to a mass which has a moment of inertia = I_m and the other(C) is connected to a mass which has a moment of inertia = 2I_m. The gear...
  10. K

    Help with torque and power required please

    I am looking to build a skateborad like device that i want to power with electric skateboard-like system. However I only want it to go 1.1m/s using 60mm wheels moving a 100kg load for 12 km. I am looking for help determining gear sizes, motor sizes and specs, really anything. I have seen so...
  11. D

    How to calculate the gear ratio of this moonphase watch

    I would like to calculate the gear ratio of this moonphase watch, however i cannot calculate the exact day of its mentioned. What's wrong with my calculation? https://www.ochsundjunior.swiss/watches/moon-phase/tech-specs/ my calculation is 1/(2/12*14/18*14/109)/2=30.03 which is different from...
  12. J

    How can I increase output speed without a significant decrease in torque?

    For a project I am doing I need to increase out put speed to 515 rpm from 1rpm with no more than a 20% decrease in torque, I need help I have been trying a lot of things and can't figure it out.
  13. Gurfin321

    Automotive Electric Longboard Gear Ratio

    I would like to know what gear ratio i would need for my electric longboard. The goal is to run the longboard at 30 - 40 km/h at max power. Me and the longboards weight is approximately 65 kg. The brushless motor i am running has an rpm of approximately 18000 rpm (as it is an airplane engine)...
  14. Gurfin321

    Electric Longboard Gear Ratio

    I would like to know what gear ratio i would need for my electric longboard. The goal is to run the longboard at 30 - 40 km/h at max power. Me and the longboards weight is approximately 65 kg. The brushless motor i am running has an rpm of approximately 18000 rpm (as it is an airplane engine)...
  15. S

    I Effects of lug height on final gear ratio for a snowmobile....

    So, great site. I have a quick question that I think has a simple answer. On a snowmobile forum I visit there has an ongoing debate. The question is, all other factors being the same, does changing the lug height on a track, change the final drive ratio of the snowmobile? I think I know the...
  16. L

    How to show how speed varies with incline, and with Gear ratio

    Hey guys, I'm having difficulty with my university project which is to build an electric bike. My design is to have a friction wheel attached to the shaft of my 800W 2800rpm electric motor which is rated at 2.8Nm. I have two issues with my spreadsheets at the moment. Can someone please help...
  17. B

    SolidWorks worm reducer analysis tutorial needed

    I've calculated my gear ratio to be 1:27 and the most suitable reducer for it would be a worm drive. I couldn't find any descriptive tutorials to do the mesh and perform constructional analysis of the gears on SolidWorks. Can you help me?
  18. E

    Which Gearbox Ratio is Used to Maintain Speed Up an Incline?

    Hi, I don't get the right answer for this question. I don't see where I'm going wrong. I use this equation to get the engine rpm for each gear ratio: engine speed (rpm) = gear ratio X final drive ratio X vehicle speed X 60 / (2*pi*rolling radius) So for first gear I get an engine rpm of...
  19. T

    Optimization of windmill power with use of gears

    < Mentor Note -- thread moved to HH from the technical Engineering forums, so no HH Template is shown > Okay so I'm a freshman BE student and one of our first projects is designing a windmill that can produce a voltage of 5 for 2 seconds or longer. We are having trouble find the optimal gear...
  20. J

    Gear Ratios and Constant Power/Torque: find max velocity?

    I'm trying to determine how exactly gear ratio limits velocity. I know that a high torque configuration is generally regarded as low speed, but my calculations do not seem to support that. Basically, I've written a small problem where we have an input gear with constant torque and an output...
  21. F.Turner

    Reverted Gear Train Design Problem | Get Help Now

    < Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown > I have a design problem that has two predictions that I must make. The constants that I am given is the amount of teeth each gear has, the diameter of the gears, the input torque, speed in...
  22. andyrk

    Gear Ratio in Bicycles using Rotational Motion

    When we change the gears of the bicycle we are riding, we change the the disc we are currently at (which are located at the place where we pedal) to some other disc. This means the radius of the circular disc we were pedaling/rotating changes. So that means if we were rotating the disc with...
  23. S

    Gear Ratio & Voltage/Current Calculation for 24V 1500rpm BLDC Motor on a Tricycle

    I have a 24V, 1500rpm bldc motor.The power output will be around 400W. We are using it to electrically drive a tricycle. How can I calculate the gear ratio to decrease the rpm and increase the torque? The transmission system includes an intermediate shaft with 22 teeth sprocket and 44 teeth...
  24. Karan Dua

    Calculate Top Speed of Car Using Gear Ratio, Torque, Power & RPM

    Hey guys, I am a bit confused while calculating top speed of the car using gear ratio, Torque, Power and Engine Speed(RPM). Can someone help me out with this? Specifications are given as follows: Maximum Torque : 19.2 N-m @ 3800 RPM Maximum Power : 10 Hp @ 2800 RPM Tire Specifications: 25x8...
  25. A

    Calculating Worm Gear & Stepper Motor for Single Axis Solar Tracker

    Dear all, I am trying to build single axis solar tracker using worm gear, I need guide line for calculation of worm gear & stepper motor .he are some relation i taken, But i wanted whether its correct & need to explain with example efficiency= (output Power of Worm gear/ Input Power of...
  26. CJNight15

    Motor that can move possibly up to 4kg

    I'm designing a robot to compete against a friend who is also making a robot based on the Robot Sumo competitions. We decided on the dimensions of our bots and placed a 2kg limit on their weight. I'm having trouble determining what motor to use that will be able to move my own ~2kg robot around...
  27. D

    Does the gear ratio in a differential affect pitching loads

    I'm designing a differential mount and am trying to wrap my head around the pitch loads the mount sees. My question is with a 1000 Ft/lb input torque will the ring and pinion ratio effect the torque that the mount must resolve? The differential is a sub-frame mounted IRS assembly, Nissan R230...
  28. Z

    What gears to use to reduce fan speed from fast moving motor

    hey, I am building a fan, but I need the fan blade to move relatively slow, slow enough to see each panel on the blade. I am expecting to use a gear system with a belt. What gears should I use to active this?
  29. D

    Gear ratio requirement (RPM --> km/h)

    Homework Statement A vehicle having wheels with a diameter of 58cm, is powered by motors that have a maximum speed of 6024 rpm. Each motor is coupled to the wheel using a gear mechanism as shown in figure 2-14. Calculate the required gear ratio if the vehicle's maximum speed is 190.2 km/hr...
  30. T

    Improving Machine Efficiency through Gear Ratio

    Does altering Gear Ratio improve efficiency (loss of energy as heat while converting EE to ME) of a machine? I also read online that having higher gear contact ratio improves the efficiency, but I really don't understand how.
  31. B

    Relating variables: weight, gear ratio, power/torque to make design estimations

    hey all, I'm stumped so I thought I'd try posting here. I am in the early stages of design of a vehicle where we have a rough approximation of weight, no idea what gear ratios or power/torque to use yet, but have an acceleration requirement. I am trying to graphically model the relationship...
  32. J

    Speedometer worm gear ratio changes

    When changing rear end gear ratios, or tire sizes on a vehicle, you can buy different speedometer gears with tooth counts to restore speedometer accuracy. The worm(driver) is inside the transmission and is not changed. It is a 7 or 8 tooth in my application. The speedometer gear(driven) is...
  33. T

    Variable gear ratio [Worm gear - Worm Wheel]

    Hello fellow PF members, This is my first post. I am wondering if there is a mechanism that alters the gear ratio in worm gear-worm wheel setup.. Something like a variable pitch worm gear that can be used instantaneously to alter the gear ratios. If not for worm gear, is there anything in...
  34. N

    Calc Gear Ratio: Helical/Spur Gears

    http://C:\Documents and Settings\design3\Desktop\piccs Hey, I want to know how to calculate the gear ratio of the given arrangement in the picture. I am not sure of how to calculate the gear ratio of two gears on the same shaft. Also the input gear is helical and the output gear is a spur...
  35. N

    Calculate Gear Ratio - Helical/Spur Gears

    Hey, I want to know how to calculate the gear ratio of the given arrangement in the picture. I am not sure of how to calculate the gear ratio of two gears on the same shaft. Also the input gear is helical and the output gear is a spur gear. I have mentioned the number of gear teeth, i hope...
  36. Q

    Need some clarification with torque or force and gear ratio

    Hi guys, I have a question about gear ratio, sprocket or wheel ratio. So let's say I have a motor with connect to a small output sprocket, and I want to use this motor to pull some load, so in order to do this I need to connect the chain with a larger sprocket, let's say 2 time bigger than...
  37. T

    A Gear Ratio Torque Problem

    Hi all... I'm new here... Homework Statement this is not a homework question, I'm just solving practice questions for exam preparation Two wheels with masses M1 = 2 kg and M2 = 4 kg are connected. The ratio is R1 = 5 cm and R2 = 10 cm Considering an angular velocity of ωo = 10rads-1 for the...
  38. A

    Gear ratio - Does it matter how you achieve it?

    Hi all, I always wondered if the combination of gears used to achieve a specific gear ratio mattered. Assuming the desired gear ratio is 3:1, would it matter if the gears used were 10x30 or 9X27? Thanks in advance.
  39. A

    Simple Gear Ratio Problem: Solving for Wheel Rotation with Formula

    Homework Statement In a bicycle, the ratio between the size of the wheel sprocket to the size of the crank sprocket is 2.5 which means... An example of one of the answer choices is: The rear wheel turns ___ times for every full rotation of the pedals. Homework Equations The...
  40. H

    Automotive Torque/hp philosophy (infinant gear ratio)

    I am still trying to visualize horsepower and torque seen on the racetrack, and its hard. Obviously torque is a component of horsepower. Without enough torque, a car would take forever to reach its power-band. With a lot of torque, but merely no horsepower, a car would have a very steady...
  41. O

    Calculating gear ratio for vertical climb

    Homework Statement The problem is that using a human powered bike-like machine we have to climb up a 16 meter long rope. The total weight of the machine + human is 1300N and the theoretical force delivered by the human is 250 Newtons. The crank is 17cm long (that's the length of the arm, the...
  42. L

    Torque and gear ratio help please?

    Hi, I'm new to this forum but I've read over probably a dozen threads so I figured that someone should probably be able to help me; please forgive me if this is the wrong area to post this question as well. Dilemma: So the problem right now is that I'm trying to use a gear reduction system...
  43. C

    Quite a tricky gear ratio question to ponder

    If a 6 speed gear box has a 1st gear ratio of 7:1 and a sixth gear ratio of 1:1 how would you calculate the 2nd,3rd,4th and 5th gear ratio's? If you use the equation for geometric progression which was my first thought - it doesn't work! Any ideas?
  44. B

    Calculating Single Gear Ratio

    Hi. I am designing a model for a vehicle. The power source is solar energy, providing power to a single 12 volt motor of about 1W. Through tests I have calculated the stall torque and max RPM of this motor, and therefore a rated torque of 0.00154 Nm. At this load the motor should ideally spin...
  45. S

    How does the gear ratio affect the power efficiency generated by a wind turbine

    I have a basic question on how the power efficiency of wind turbine affected by the gear ratio. Suppose there is a generator connected with the rotor through a gear enhancer, a higher angular speed of generator is obtained. Since a higher voltage is produced, we may think that the power...
  46. J

    Gear ratio question. ugh i'm confused.

    okay. i recently had a forum asking about gear ratio that has me so confused on the concept of ratio that it hurts. if you have a 40 spline gear and a 20spine gear. and ur power input is on the 40 spline gear. doesn't that mean the 20 spline gear will rotate twice every time the 40 spline...
  47. P

    Gear ratio calculation for a transit bus

    Hi there, I am simulating the hybrid transit bus, Its max speed is at 60 kph, most speed used on road is below 20 kph (more than 60% of its total operation time) The bus follows stop-and-go pattern almost all the time. The bus is to be fuel cell/battery hybrid, therefore it uses an...
  48. A

    Refreshing gear ratio and total inertia

    Suppose we've got the setup as shown in the figure (see attachment). The idea is that the motor transfers its speed and force (rotary) to the actuator force and speed (linear) via some gears and a spindle. Here: R = radius [m] J = inertia [kg m^2] n = rotary to linear transmission [---]...
  49. L

    Gear ratio and power output in a car

    I'm a bit confused about power output and gear ratios. I think it's best to explain by going by my example (imperical units, sorry Americas & Brits): Mass: 1300kg max. power: 128 kW @ 5500 rpm max. torque: 245 Nm Gear ratios (from a slightly different car type, but should be similar): 1st...
  50. G

    Designing a Gearbox for Drum - Finding Gear Ratio

    Hi I have to design a gearbox for a drum, the drum should be brought uniformily to a speed of 7rpm in 8 seconds, I have choosed a motor of 715 rpm output, what's the gear ratio I should use in designing the gearbox? Thanks
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