# Gear Definition and 29 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. ### 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...
2. ### 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...
3. ### 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...
4. ### 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...
5. ### 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...
6. ### 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...
7. ### 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...
8. ### 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...
9. ### How To lock My gear?

SO, here is the case guys. I have a mechanism to turn plate by a motor. Both motor and plate was connected through 2 spur gears. But here is the problem, when wind strike the plate, the plate start to rotate even without the power of the motor. What is the best way so i can prevent the plate...
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### Calculating the load on planetary gear from driving torque

Hello, I am very new to gears I am fairly confused about planetary gears. I want to know the load on the gears contact point between the sun and the planets and the planets and the ring, assuming the ring not moving. Given I have the solid works file ,the pressure angle, and the gear ratios, I...
11. ### 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...
12. ### Calculating gear ratios for a drivetrain

I'm trying to calculate the required gear sizes for the system shown below: The driven wheel is connected to a 600mm diameter bicycle wheel and the driver wheel connected to a 580 mm long lever arm which has a forward driving force of 40 N. I want to calculate the most efficient sizing of...
13. ### 4DOF Spur Gear System - Eigenvalues not corresponding with the Eqns?

Hi there, I am modelling a four degree of freedom system which is the dynamics of two spur gears in mesh, having two rotational and two translation degrees of freedom, respectively, a diagram exhibiting the system can be seen below. I have derived the equations of motion (EOM) and...
14. ### How to calculate the required specifications of a motor?

I am planning to design a reciprocating rack and pinion, as shown in this figure I plan to attach a cutter to this setup to cut anything.I need to know how to calculate the motor specifications for the given mass of the gear, cutter and cutter velocity I plan to make it with a plywood
15. ### Spur gear transmission

Hello. I need to calculate spur gear transmissions. I need a bit of guidance for the first steps. The data is the next: n= 1000 rev/min Mt torque= 28.65 Nm i transmission ratio= 4 P load in the shaft= 3kW I am a bit lost to star selecting the material (depending the load and work...
16. ### Why is the addendum of the gear kept equal to the module?

In general calculations of gear design, addendum is taken as a factor of the module of the gear such as equal to module or 0.8 times the module and dedendum is taken as 1.25 times the module. Why are both these defined in terms of module? How did we reach to this conclusion?
17. ### Gear ration

Hello I am using two motor which are coupled with the mechanical coupling. The coupling has moment of inertia. The gear ratio of both motors is same 26:1. I want to know i also need to divide the coupling moment of inertia with the gear ratio? Thany
18. ### One way clutch for motorized cable reel?

I am newbie in the area of clutches. I am making a motorized cable reel (DC motor) which I needed to make it easy for anyone to pull the cable reel out manually without much effort. Only pulling the cable out is manual. The retraction of the cord is done automatically via the DC motor. So, based...
19. ### 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...
20. ### Gear RPM "img attached"

Hey Guys, So in the attached image I'm trying to determine what the rpm of the 60 tooth gear will be given the 8.4" tire will be rotating at .68 rpm, everything else is just an assumption on my part. I'm assuming the following which is probably wong: The tire being rotated at .68 rpm will...
21. ### Automotive Why is an FFT done after a noise signal is captured?

Presently there is a gear whine noise issue in a vehicle transmission. Our NVH team captured the noise signal using a microphone and then did an FFT of the signal and gave us a frequency plot. What exactly can I take out of it? Can I assume every harmonic belongs to a noise generated by a gear...
22. ### System for turning Rotational into Linear movement

Hey Everyone, I want to build a Laser cutter for myself from scratch (sort of). I need some way of turning the rotational energy of the servo into a linear movement. I want something fairly cheap, so nothing to pricey. I thought of the classic Lego style thing, with a gear on the servo, with a...
23. ### Expandable Gear CVT

Hi there, I started working on an idea for an expandable gear CVT about 3 years ago, while out of work for a few months. I had some exciting progress on an idea that I think might be worth pursuing more, but I now have 2 kids, 2 jobs, and no time. I have brought up the project idea with a few...
24. ### Torque & Force required to slide a gate

Greetings all, I am trying to build a sliding gate operator. I have this wiper motor which says, 24v dc, 64rpm, nominal torque- 4Nm. Max weight of gate to be 400kg, sliding on a steel rail (Not sure how to consider rolling resistance or Co-eff of friction) . Max pull force to be achieved by...
25. ### Looking for mechanical clutch solution

Hi, I made an electronics project but I'm having some mechanical problems. Particularly, I'm having issues finding a good clutch for my problem. What I'm trying to do: A motor is connected to shaft 1, a human can manually rotate shaft 2. I want that when the motor isn't doing anything, a...
26. ### Mechanism that only rotates when driven from one side

I have a geared DC motor taken from a hand drill. When I manually turn the internal motor, the drill bit rotates. This can be done in both directions. However If I try and turn the drill bit it does not rotate. What is the mechanism called that achieves this? My friend says it is a sprag...
27. ### 3 gears and the torque on the support

Homework Statement I need to find if there is a torque on the support with 3 gears: http://imageshack.com/a/img901/8954/mFzBas.png [Broken] The Gear1 is forced to turn at 3w by an external device. Gear2 and Gear3 must follow. Homework Equations None The Attempt at a Solution I drawn all...
28. ### Worm gear enveloping argument

I wanted to exchange some opinions about worm gear enveloping. I am designing a worm gear 3d model and, putting the appropriate amount of thought in it, some interesting points arise. One may either: 1) Envelop (is that right?) the worm gear helix, so that its radius increases from the gear's...
29. ### Motor displacement reduction

I have a little project, I am building a simple lift that is moved with cable by a 3-phase motor which has it's speed controlled by variable frequency drive. I am going to be implementing PID control into the VFD via PLC that will be based off of a distance reading from an ultrasonic sensor for...