What is Gear: Definition and 399 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. Ranger Mike

    AGMA Gear Questions: Class 16 Tolerance & Grades

    Does anyone here have knowledge of AGMA Gear classification standards relating to classes or grades? I understand the AGMA std was revised in 2015 but many still follow the AGMA 2000 standard. Is Class 16 AGMA the tightest tolerance gear class?
  2. Datt

    Reducing RPM using gears

    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.
  3. FEAnalyst

    Gear teeth force from the rotation angle

    Hi, in books about machine design fundamentals, one may easily find the formulas for forces acting on the teeth of paired spur gears. They require torque as input. For example, for the tangential force: $$F=\frac{2T}{d}$$ where: ##T## - torque applied to the driven gear, ##d## - pitch diameter...
  4. Vossi

    Properties that are important to Worm Wheel functions

    From what I've gather the primary benefits to worm wheels are: - their ability to provide high reduction ratios - self-locking which can be useful for hoisting and lifting applications. - Operates silently and smoothly, which reduces vibrations Feel free to add any important ones I might've...
  5. Euan12345

    Landing gear mechanism design

    Summary:: I am making a landing gear mechanism, and am struggling to mathematically model it, the aim is to find the required properties for the spring for it to work. Hi can you help me with a problem, I am making a landing gear mechanism and am struggling to model it mathematically. The aim...
  6. 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...
  7. 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...
  8. P

    Compound planetary gear problem

    Hi, I need a little help with this problem with compound planetary gears. I don't know how to apply the formulas for this specific type of placement. I need to know the final speed of the engine knowing the number of teeth z1 = -104 ring gear which is internal, z2,3,4 = 22 for small planets...
  9. RichardWattUK

    Automotive Parameters required for a ZK worm gear

    I apologise for cross-posting - I've already posted this question on CrazyEngineers but have had no replies after a few days and I was wondering if someone here could help me: In my current job, I am responsible for maintaining an existing software application that generates a dressing program...
  10. P

    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. O

    Gear Train Design Assistance

    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. E

    3D Printer Stepper Motor Torque Requirements Using Gear Reduction

    I hope to explore mechanical engineering one day so I can answer these kinds of questions on my own, but until then, I appeal to anyone that knows how to do this to help me. I am building a core xy 3D Printer and I want to use a belt driven Z axis. I will have 3 or 4 stepper motors to drive...
  13. 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...
  14. F

    B What is the entire gear reduction ratio of a vehicle?

    As I was looking in the caracteristics of an old tank, I found a number that I could not get anything of on the web. It is called "entire reduction ratio" and was presented just under the gearbox caracteristics. His value is 1:13.4. My question is : is it useful? Does this value have relation...
  15. M

    External Gear Pump: Capacity & Pressure Effects

    Hi everyone, Let's say I have an external gear pump driven by the camshaft of a marine diesel engine. The nominal speed of the engine is 1800 rpm and the capacity of the pump at nominal speed is 8 L/min. Diesel fuel is supplied to the gear pump suction at 0.4 bar g pressure via a 15 mm pipe...
  16. C

    Face width of a spur gear pair

    Dear Physicsforum Mentors, For a pinion and gear wheel, the face width instead of 12mm for both, it should be 14mm and 12mm. The explanation I got is, when there's 0.2mm deviation in axial, then only 11.8mm width will be in meshing. later, when the system be worn out, that 0.2mm will be in...
  17. J

    Energy of translation compared to the energy of rotation

    I use an example with a rack and a pinion. I suppose there is no losses from friction. I suppose the masses very low to simplify the study, and there is no acceleration. I suppose the tooth of the pinion and the rack perfect, I mean there is no gap. There is always the contact between the rack...
  18. S

    Bicycle gear system's Input-Output ratio?

    A person weighing 60 kg exerts 30 kg of thrust on a pedal (crank) x 2 pedals = 60 kg of force per Revolution. Let's say @ 30 RPM. What is the output kg of force per RPM on the back wheel where it meets the tar. I have all the sizes and forces, yet the correct formula eludes me. The ratio per 1...
  19. Richtdow

    Gear Load Factor (Reaction Load) Question

    Using the equation to determine shock stroke I input a gear load factor. For the aircraft landing gear that I am designing, I am assuming a gear load factor of 5 which is what is generally used for Navy fighter aircraft. This is because I am designing landing gear for a STOL aircraft and I want...
  20. I

    Gear ratios for this motorcycle

    Hello guys I have a motorcycle engine in which I know the ratios of the transmission. and given the diagram of Power and rpm I made a function of P(ω) which is a polynomial of 6 order. Then I said that F(friction)*u=P(ω) then I substitute ω=u*r/v v(ratio) and have F(u).Next knowing the Pmax...
  21. 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...
  22. Shubol3D

    Calculate the output power for da Vinci's tank mechanism

    Hello everyone. I'm working on 3D animation about da Vinci tank and why it doesn't work. Please help me find out how to compute: 1: how many men need to move this machine 2: what power on wheel can produce different number of man, like 1, 2, 4, 8.. vehicle mass = 8t men strength = 60kg lever...
  23. Alexanddros81

    Vector Mechanics — Double Gear Rolling on a Rack

    Hi! My first question: How does he get the equation ##\frac {x_A} {2πr_1} = -\frac {θ} {2π}## ?
  24. T

    Gear Ratios: Torque to Teeth

    Hello, I am confused about something. I will take the time to work it out, but right now, I am using it to remember. And I am now confused. Go here: https://www.smlease.com/entries/mechanism/gear-train-gear-ratio-torque-and-speed-calculation/ Scroll down to the section on...
  25. Optymista93

    Locking gear on container doors

    Hi there, I would like to use Your expertise in solving one of the challenges I've faced right now, as an intern. My task is to design steel container doors and its locking system. As it's a light container, locking system should be placed inside of the doors. To visualize, the container and...
  26. 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 ...
  27. P

    Build a Shaker Screen Box: Source Eccentric Drive Gears

    I am hoping to build a shaker screen box, to sort sand from gravel and rocks. Want to use an eccentric drive gear to move the screen creating a vibration that would shift sand through screen mesh and over size rock wold flow off top of screen. Have not been able to find a source of eccentric...
  28. sshanker

    Gear Rotation puzzle is confusing 50:10 GR but 6 rotations

    A gear A has 50 teeth and another B has 10 teeth, how many times does the small gear rotate around the big one? I thought 5 but its 6! Note: The gear is curved like 360 degrees.
  29. N

    Extreme G Protective Gear

    What kind of suit or technology can protect a person from sudden acceleration or extreme Gs and turns that could instantly crush a normal person without protection inside a flying rocket or vehicle?
  30. P

    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...
  31. 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...
  32. F

    What is the consequence of a very low number of teeth on a gear?

    As summarized, I've got these two gear, and another stage of 15:10. I need my gear box as small as possible, and I've never work on this scale with gear (the module is 0,9mm, so this is pretty small). I know that this question is very simple, but I did not find anything relevant on the web, so...
  33. 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...
  34. A

    3D Printed Gear Tooth strength

    HI guys, I am in the middle of a project where i have 3d printed ABS & PLA spur gears, I am looking to do gear teeth strength calculations however I am not sure how to apply the formulas. This is because of the layered structure and the infill % of the prints. Ill appreciate all help. Thank you
  35. L

    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...
  36. S

    Question about gear rotation

    If gear 1 fits into the internal gear and is made to rotate, will the internal gear rotate with gear 1? https://imgur.com/gallery/ELYZoRb
  37. E

    New metal gear 3D model in Blender

    Hi, it's been a long time since I've been on these forums, but here is a new 3D blender model that I spent four weeks of daily work to finish. I'm glad it's done, it wasn't easy. This is metal gear RAY, a 70-foot tall robot from the popular video game franchise metal gear solid.
  38. 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...
  39. Kleinelars1

    Auto/Motor Need help with Gear selection

    Hey Guys, Sorry for my poor englisch, I'am Lars from the Netherlands and currently working on a project. For my motorcycle racer I'm making a "paddock starter" by a 12V car starter from a VW T5 transporter 2.5tdi. No I am having difficulties finding the right gear to match the current starter...
  40. E

    Slowly Rotating Device For a Camera Pan Timelapse

    Hello all! I just discovered PF as I have been searching about a project I have been pondering for a day. The idea is to have a device that I can set my 3lb camera and have the device rotate left-to-right && || right-to-left over the duration of 2 hours for use in a sunset/cloud timelapse...
  41. Nick Amos

    Tabular Method for a Unique Spur Gear Differential System

    Hello everyone, this is my first post here so please excuse me if its in the wrong area. I am looking for the tabular approach to solve a complex gear train based off the spur gear differential design. Attached is a photo of the differential. The requirements of the necessary differential...
  42. A

    Gear Wear Rig Design: Calculating Load for Maximum Durability

    Below I've attached a sketch of the rig designed to wear down the gears.f Firstly my project idea is to test the durability and overall wear of plastic & 3D printed gears however the 3D prints will be electroplated to see what difference it potentially makes. The idea of the rig is to have a...
  43. H

    Design Gearbox #3: Get Help & Expert Advice

    Please help. I am design number 3.
  44. kolleamm

    How to spin a gear at a slower rate without a bigger gear?

    I have a linear wire that moves let's say a distance of 1 inch. I would like this wire to spin a small gear (0.25 in circumference) 90 degrees for every 1 inch it moves. How can I accomplish this without using a bigger gear? Any ideas are appreciated. Thanks in advance
  45. J

    Gear train efficiency help please

    I have been set the following question in my assignment and I have answered all parts with the exception of:- (d) Determine an equation for the efficiency of the gear train in terms of the load (torque) on shaft 2 (all other factors remaining constant). I am struggling here and would appreciate...
  46. Physicsterian

    Extending an aircraft landing gear that has gotten stuck

    Imagine an aircraft of which the its wing is connected to its landing gear by means of a hinge (joint), and then the gear suddenly gets stuck midway. If, subsequently, the aircraft makes a turn around its longitudinal axis (see picture), it seems to hold true that then the angle between the...
  47. B

    How to calculate the weight of a gear?

    I don't know if I have to include the weight of a gear in order to proceed on computing the forces acting on the plane of line shaft. If I have to determine it, how do I calculate the weight of the gear (spur gear)?
  48. A

    200 kilowatt single stage gear

    Hello, I want to design two stage 200 kilowatt helical gear. Ratio that I want is 1:8. Input rpm 1250 with medium shock. Can anyone help me. Or suggest me any free software where I can get gear design.
  49. E

    Question regarding peak torque in first gear

    Hello,I have been trying to wrap my mind around this question for a long time.So I thought it is best the way to share it with you. For a given car speed,the greatest acceleration comes when we are at peak horsepower RPM.This is true for any gear except the first gear.Because in any other...