# What is Gears: Definition and 178 Discussions

A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth (called cogs), which mesh with another toothed part to transmit torque. A gear may also be known informally as a cog. Geared devices can change the speed, torque, and direction of a power source. Gears of different sizes produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a simple machine. The rotational speeds, and the torques, of two meshing gears differ in proportion to their diameters. The teeth on the two meshing gears all have the same shape.Two or more meshing gears, working in a sequence, are called a gear train or a transmission. The gears in a transmission are analogous to the wheels in a crossed, belt pulley system. An advantage of gears is that the teeth of a gear prevent slippage. In transmissions with multiple gear ratios—such as bicycles, motorcycles, and cars—the term "gear" (e.g., "first gear") refers to a gear ratio rather than an actual physical gear. The term describes similar devices, even when the gear ratio is continuous rather than discrete, or when the device does not actually contain gears, as in a continuously variable transmission.Furthermore, a gear can mesh with a linear toothed part, called a rack, producing translation instead of rotation.

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1. ### B How does mechanical motion start at the deepest, smallest level?

The first molecular motions of gears and levers in a machine. I can make an educated guess about how a seemingly unrelated type of motion starts... how a magnet's magnetic fields can cause a metal to move: first you move the magnet nearer, and its magnetic field will touch the electrons of a...
2. ### I Why is the driven gear's torque's direction clockwise?

We have two gears A and B (left and right). Gear A is driven with a clockwise torque. Why is gear B's torque also clockwise? I would say that if gear B is driven to turn counterclockwise, the torque should be in the counterclockwise direction.
3. ### How Does Gear Count Affect the Efficiency and Size of Gearboxes?

I have a question what is a difference or advantage for using two gears with high gear ratio or using three gears with lower gear ratio.Is there any advantage.

5. ### Designing a Geneva Mechanism: Overcoming Challenges

(note: I never studied engineering, but I think I have a good math (and slight physics) background. I'm mentioning this not so you'll go easy on me - if I don't understand something, I'm sure I'll figure it out or find someone to help me decode what you're saying. I'm mentioning this in the...
6. ### Simple kinematics question -- Riding a bicycle race in two different gears

I calculated average velocity but obviously it helps nothing with this problem. I hope to get me going with these exercises once I break the ice. Thank you in advance!
7. ### Spur Gear Ratio: Optimal Ratio Explained

What is an optimal spur gear ratio?
8. ### My weird geneva mechanism doesn't work. Looking for suggestions

Two things that I think I should say before I describe what I did: First, I do not have any physics-related background (but I have a degree in CS, and I'd like to think I have a good enough grasp on math to be able to understand equations describing motion of objects). So please forgive me if...
9. ### Rack and Pinion motor selection

Summary:: I want to design a mechanism consisting in 4 rack driven pinions , like an elevator and i need help in choosing the right motor. Hello!I want to design a mechanism consisting in 4 rack driven pinions , connected to each other via shafts, used for a positioning system , a moving up...
10. ### Kinematic diagram of a gear mechanism

Can anyone help me with a kinematic analysis for the mechanism attached below? I need the outline of the mechanism, its notes and the necessary formulas to find out the transmission ratio and the rest of the values.
11. ### How can I design a gear train to meet specific torque and RPM requirements?

Hello, I'm after some advice/ clarification on some gear train design. This may just be a simple clarification Requirements I have a lead screw which needs to be supplied power by a Motor. This Lead screw must have 140Nm Torque to raise and lower the load, and must turn at 200RPM. The motors I...
12. ### Angular momentum conserved with multiple gears?

Say we have a motor attached to the Earth with gear A, that drives identically sized gear B. Gear B spins on its own axis and but is also attached to ground. Torque between gears is equal. Technically each gear has equal but opposite AM right, but If I take Earth into account, how is Ang...
13. ### If two gears are connected by a shaft do they have the same torque?

1 axle. 2 gears on the same axle fixed in place. Does the larger gear with 48 teeth have the same amount of (force/strength) as the smaller gear of 12 teeth. IE: if I attached a chain to the 12 tooth gear and it could lift a max load of 10 kg, would the 48 tooth gear be able to lift 10 kg as...
14. ### Problem with gears — One geared wheel spins up another

By third Newton's law, i would imagine that fa = -fb, so and assuming f to be the average value torque in A -ra*f*t = Waf - Wao torque in b rb*f*t = Wbf and Ia*wo² = Ib*wbf² + Ia*waf² it Looks right to you? I really appreciate this method that i thought, but the answers don't match, and i...
15. ### Increasing the output torque of a DC motor with gears

Hello everyone, I see videos showing the output torque can be increased by using gears and this is usually demonstrated with DC motors (simple DC motors can be removed from toys). I understand the general logic: * The DC rotates in a high speed. * The gear system reduces the output speed. * If...
16. ### Find the Right Motor for a Vertical Load Torque

If I'm to choose a motor to suit a vertical load (torque)-see the attached picture for more illustration-. What is the criteria should i follow? After i have done the math for the weight of the object to be rotated, the torque to rotate the load is to be horizontal, and i only have the weight...
17. ### Possibility of turning a threaded rod with spur gears using a motor

So I'm a college student currently doing A-Level Physics, I am attempting to build a type 4 double arm barn door tracker and although it has been a complicated project, I believe I've got all the planning done, however, I have a 2Rpm motor, a PWM motor controller, 2 9v batteries, an M8 threaded...
18. ### Planet Gear System: Sun Gear Input, Same Torque in Ring & Carrier?

Hello all, In a planetary gear system, there is: sun gear planet gear Ring gear Carrier Suppose the SUN gear delivers the input torque to the system. (I do not care about the planet gears in this system.= There are two torques that can result. The ring can deliver a torque and the carrier...
19. ### Where can I find pinion gears?

So I have a broken plastic pinion gear that belongs to my microscope and I'm wondering if there are standard sizes or how am I supposed to get a replacement? How do you guys find the gears you need? Seems like a pretty hard thing to find online. It's an helical pinion gear. I have the...
20. ### Living gears in the insect Issus Coleoptratus

There is an insect called the Issus Coleoptratus that has biological mechanical gears that is uses to use its legs.
21. ### Gears create more torque? Prove it

Hi guys, I was sizing up a servo motor the other day and started thinking. While we all know gear ratios will effectively "convert" speed into torque. I couldn't help wondering about the initial starting conditions.. The problem below... Lets say I have a motor with a max load of 1Kg...
22. ### Why the explanation of wormholes using paper grinds my gears

Hey, This is more of a discussion rather than a question. A lot of movies (e.g. interstellar, Event Horizon), have a go at trying to explain how the Warp/Alcubierre drive could work, and usually, the argument goes like this: They take a point A and a point B, connect them with a line on the...
23. ### Velocity Ratio in Gears & Wheels Systems: Inverting?

Hi, if the velocity ratio is equal to the distance traveled by the effort divided by the distance traveled by the load, in a gears and wheels system, do you invert that in the case or gears? Making it number of teeth on driven gear divided by number of teeth on driving gear? Thanks
24. ### What is the best material for making gears?

For making gears as light and strong as possible, what is the best material to use?
25. ### Planetary gearbox speed calculation - Simultaneous equations

I'm looking to calculate the ratio of a planetary gear train. With the ultimate goal of producing a spreadsheet/calculator to show the state of the gearbox (i.e. all shaft speeds) based on applied constraints. A gear set consists of Ring Gear, Planet Gear, Sun Gear. The sick diagram is the...
26. ### What SI Gear Standards Do You Use?

I am an American author, working on a revision for my Theory of Machines textbook. In the past, I used only US Customary units, but now see a need to introduce SI units. This is particularly a problem with regard to gear standards. An internet search shows that there are dozens of SI-based gear...
27. ### Find the angular speed of the smaller gear

1.Why does the angular speed of small gear depend only on larger gear only? 2.Why does the length of linkage connecting two gears does not have any influence on the angular speed of smaller gear? The first question can be answered by looking at slack and tightening of chain caused by rotation...
28. ### How is the moment of inertia of gears calculated?

If two gears are joined to together, how are their moment of inertia calculated? Separately or combined?
29. ### Why do bicycle gears make pedaling easier or harder?

Hello, I'm trying to get a conceptual understanding of why switching gears makes pedaling easier or harder. I think I understand what's happening with the rear gears, but I'm not sure I understand what's going on with the front gears. I will outline my thinking: Let's suppose our bicycle has...
30. ### B Explaining forces acting on gears

Hi all In respect to a simple gear system, two cogs are linked together, Cog A and Cog B. You apply a force to cog A, and cog A transmits this force to cog B through contact of the teeth on each cog (third law pair?) If cog A pushes on cog B, does cog B not push back on cog A? Does this not...
31. ### Viscocity sensor for grease levele measurment for gears

Hi, I want to know about viscocity sensor working principle to find the level of grease available in a gear system? Any inputs ?
32. ### Understanding Gears & Machines: Force & Distance

Homework Statement I am really struggling to understand gears and how they can multiply force or speed. I was reading over this physics link (http://www.tutorvista.com/content/physics/physics-i/power-energy-machines/gears.php). Homework EquationsThe Attempt at a Solution I'm confused about the...
33. ### How to calculate the maximum RPM of a motor?

Hello all, Just wondering if there is a mathematical formula that calculates the maximum rpm. If I have a fan that puts out 3 pounds of rotational force at stall speed(completely still) at the end point of a 1.5 ft blade what would be the maximum rpm of this fan with the blade attached. What...
34. ### Automotive Engine Torque Control: A Guide to Automatics & DCTs

Hi guys, I have a question about engine torque control in automatic transmissions and dual clutch transmissions. I've seen cases where the engine torque is decreased on an up-shift and increased during a downshift. Why is this done?
35. ### Understanding Failure in Helical Gears: The Role of Rolling and Sliding Contact

Hi everyone. I'm a college student, and I need help of experts with gears. What I know is that there are two dynamics in gear : rolling and sliding. And I heard that the main cause of failure (wear) of spur gear is rolling. Then... how about the cause of failure in the case of helical gear...
36. ### Should I avoid using high ratio spur gears?

So I have been looking into efficiency, My system is high radius with the motor located outside. This motor is small, and thus the gear being driven by the motor, is also small for space requirements. I have wanted to use a ratio of about 22:1 to make this system, and everything seems to work...
37. ### Is this zero backlash or am I missing something?

Hello guys, I am quite unsure if this application I have will be zero backlash using the solution in the attached image. I don't really have any means to test this so asking around sounds like a good feedback chance. I haven't decided yet on the preloading solution but it will be done so that...
38. ### Sprockets, chains, and gears question

hello. I'm tring to find a compatible sprocket for my chain. I need to know what these abbreviations mean here: http://www.ebay.com/sch/i.html?_odkw=sprocket+40&_sop=15&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xsprocket+40+3%2F4.TRS0&_nkw=sprocket+40+3%2F4&_sacat=0 For...
39. ### B Why do gear forces need to be balanced at the pitch circle radius?

Imagine we have two simple gears with different radii that are connected, with each gear on its own axis. If we fix the smaller gear so that it cannot rotate, then apply a force to the edge of the larger gear (perpendicular to its radius), the force applied to the smaller gear by the larger gear...
40. ### Angular momentum for these strange nonplanar gears?

I wonder what would the angular momentum vector look like for these gears. As it rotates, there is no clear direction on where the angular momentum vector is pointing. This object is symmetric. Here's the video about these.
41. ### Magnetic Gears For Power Transmission

This thread is an attempt to better understand the pseudo direct drive, or PDD, gear. What I do know is it's made up of a set of magnets which can serve the function of a reducer- a basic diagram of it as well as a video can be seen below. In this mechanism, the inner rotor is the input while...
42. ### Gears: when Base circle less than the root circle/dedendum

Hey guys, Trying to design a spur gear but I am very confused as the root circle/dedendum ends up being greater than the base circle. What do I do in this case? The gear I'm trying to design has a 68.33mm pitch diameter, 60 teeth, the pressure angle a standard 20 degrees. What am I doing...
43. ### What is the Angular Velocity of Gear 5 in a Differential Gear System?

Homework Statement Gear 2 in the figure below is driven at a speed of 80 rpm in the CCW direction viewed from the right end. Gear 4 meshes with a fixed ring gear (gear 7) and with gear 5. Find the angular velocity of gear 5. N2= 16 T, N3= 32 T, N4= 30 T, N5= 22 T and N7= 77 T. Homework...
44. ### For gear teeth to linear shaft, what's the center point?

I used to know this back when i worked with Flash animation, but I'm working on a 3D printer now and I've forgotten, when you have a set of teeth, on a linear shaft and a gear, do you base the unrolling of the gear, for the spacing, on the inside of the teeth, the outside of the teeth, or the...
45. ### Design of Spur Gears for a Gearbox

I need to design and find suitable specifications for spur gears for a two stage reduction gearbox. The gearbox has to transmit 5kW at an output rotational speed of approximately 125 rev/min. The gearbox will be driven by a separate mains 4 pole synchronous electric motor . The required...
46. ### How pick gears that will hold for given torque?

Hello, I was wondering if anybody could recommend a simple method to pick gears for a given task. I need to make a rough estimation to see if I'm off by more or less a factor of ten. The only method I have access to is very complex and hard to understand. Cheers
47. ### Calculations - some fundamentals

Hi, that's my first post here.First of all – I do not want to ask someone to calculate something for me. I did my best (I hope correctly) – can you briefly check it and answer my additional questions? I am especially interested in these questions – I always have some doubts during calculations...
48. ### Biking up a hill in different gears

Homework Statement Hi there, I am doing a project for my physics class where I am attempting to calculate the amount of force and work required to go up a 10% grade hill in a variety of different gears and I am running into a lot of issues. I have already collected my data and have calculated...
49. ### What is the Proper Involute Profile for Worm Gear Drive Teeth Design?

Hello i am having trouble figuring out the proper profile to use for the worm and the gear. I need to model it in solidworks and everything i am finding online is for spur gears. I need to get the worm and gear to mesh correctly so i can do some finite element analysis on it. I have calculated...
50. ### Understanding Gear Ratios and Torque in Torsional Problems

Hi, this is a question from a previous past paper that I am having trouble with. Am I meant to just use the number of teeth from each gear to find a ratio and use this to find the effective inertia at point C. Then use this to find a torque and take away the torque of the constant load. My exam...