Hot answers tagged

36 votes

How do bike wheels keep turning when the rider stops pedalling?

The soft clicking sound you hear when coasting is the pawl going over the ratchet as in the picture below.
user avatar
  • 361
28 votes

Is it possible for a bicycle chainwheel to have a fractional number of teeth?

Gear ratio This is a Roller Chain drive system, and as such it's a timed system. The ratio between the two connected pieces depends entirely on the number of teeth on either end. Even if you ...
user avatar
  • 1,106
26 votes

How do bike wheels keep turning when the rider stops pedalling?

it is called a freewheel. Inside the sprocket gear, there is a mechanism that lets the chain engage the rear wheel only when it is moving faster than the wheel is turning; else the wheel will turn ...
user avatar
  • 20.9k
23 votes
Accepted

Why does a gear have extra holes?

Different gears have different drivers for having holes. One way you can categorize gears is by whether they are used primarily for transferring: motion: transferring angular position and angular ...
user avatar
  • 22.6k
21 votes

Effective ways to drive a single shaft with multiple motors?

A differential is a mechanical device designed to do exactly what you propose. It will allow the two motors to spin at slightly different rates while still combining the power. The most common use ...
user avatar
20 votes

Effective ways to drive a single shaft with multiple motors?

While a mechanical differential does what you ask, you don't really need it. You can connect two identical electric motors together on the same shaft. There is no "slipping out of sync" because ...
user avatar
  • 11.2k
18 votes
Accepted

Is it possible for a bicycle chainwheel to have a fractional number of teeth?

I suspect that the answer to this is that, ultimately the gear ratio comes from the ratio of diameters of the gears rather than the number of teeth, although in most circumstances practicality ...
user avatar
15 votes
Accepted

What is the mechanical element that holds a worm gear shaft in place called?

Anything that holds a shaft and allows it to rotate is called a "bearing". It could be a simple metal bushing or a complete assembly with inner and outer races holding balls or rollers. A bearing ...
user avatar
  • 6,719
13 votes
Accepted

Involute gear curve when root diameter falls below base diameter

In general, each tooth of an involute gear is made up of two curves: the involute curve and the root fillet. The involute curve is essential for gears to operate properly, and allows power to be ...
user avatar
  • 1,262
12 votes
Accepted

Why do tower cranes have gear shifts?

You need very slow speeds to make precise movements of the load. At high speed, the cables will stretch as the load accelerates and decelerates and then oscillate longitudinally, "bouncing" the load ...
user avatar
  • 12.5k
10 votes
Accepted

Is there a mechanism that can turn circular motion into alternating circular motion?

What about a crank-rocker mechanism? (source: udec.cl) When I am looking for inspiration for mechanisms, I have a look in the book Mechanisms and mechanical devices, by Neil Sclater.
user avatar
  • 373
10 votes
Accepted

How to fix this gear

Oddly enough, this problem can be fixed using a set of car keys and your wallet. Here are the steps to follow: 1) put the keys in the ignition of your car, start it, and drive to the motorcycle ...
user avatar
10 votes
Accepted

How does a (pulley based) continuous variable transmission (CVT) work?

Review of geared transmissions In general, the idea of a geared transmission is depended on the gear ratio. The gear ratio $i$ affects many aspects of a gear transmission, and the following equations ...
user avatar
  • 22.6k
9 votes

Mechanism of gear rotation

There are many examples of low input speed to high output speed gearing: kitchen "salad spinner" old-fashioned hand-cranked siren electrical generator attached to a tractor PTO (power takeoff) —...
user avatar
  • 6,719
9 votes
Accepted

How do bike wheels keep turning when the rider stops pedalling?

Basically several ratchets, below animation shows when you are not pedalling. In the other direction the ratchet will engage and provide force. If you lift a bike and get the wheel spinning or just ...
user avatar
8 votes
Accepted

What does "tol" mean in a gear box?

Oh, I get it. The typo is a missing space. It's supposed to mean "23 to 1".
user avatar
8 votes
Accepted

Mechanism of gear rotation

Two meshed gears are used to transfer rotational drive between two shafts. The relative speeds of rotation are inversely proportional to the number of teeth on each gear. That is - $$\text{Input}_{\...
user avatar
8 votes
Accepted

How are high gear ratios achieved in a small space?

One simple way is to do the gearing in a number of stages in a gear train. Such a system uses gears which have two different gear sizes on the same wheel. In the example shown in the image below (...
user avatar
8 votes

Is it possible for a bicycle chainwheel to have a fractional number of teeth?

A "44.2 tooth" gear still can only push 44 links of chain per revolution, which pushes a 16 tooth cog around 2.75 times. There's no getting around that. I think that is the question that has everyone'...
user avatar
8 votes
Accepted

How to reverse the direction of rotational movement on the same axis?

Option 1 - just reverse direction without affecting the speed: Bevel gears in differential gear setup, with the carrier (the axle on which the intermediate gears are located) fixed to the chassis. ...
user avatar
  • 6,113
8 votes

Why does a gear have extra holes?

In addition to the other answers such as weight reduction and inertia, there are other possibilities: Often there can be a precision machined hole for timing purposes. A common solution for some / ...
user avatar
  • 13.6k
7 votes
Accepted

What mechanism can make a shaft rotate in steps

Geneva drive 3D Printed Geneva Drive Anchor Escapement (Clock Mechanism) 3D Printed Anchor Escapement
user avatar
  • 7,444
7 votes
Accepted

Meaning of O-slash in data sheet about gear diameter?

In the lower right corner of the document/drawing, you can see four (or five) lines of text upward: UNIT: mm Another piece of useful information in the data panel is the scale, shown there as 3:1. ...
user avatar
  • 6,117
7 votes
Accepted

Does a gear retain its mechanical advantage in a 1 2 1 ratio?

if you have them in line like the following picture then NO. The first and the last gear will have the same speed and the same torque (actually slightly less due to losses). if you wanted to retain a ...
user avatar
  • 22.6k
7 votes

Why does a gear have extra holes?

It could be for combination of reasons. lubrication: the holes will both pump and let the lubricant pass through. Reduced angular momentum reduces backlash and adds to gearbox responsiveness. ...
user avatar
  • 20.9k
6 votes

How do I calculate the gear ratio to lift a weight at a constant speed?

If I understand correctly the problem is like this The velocity of the load is $R\omega=0.5=R\underbrace{\frac{\pi}{30}\frac{15000}{n}}_\omega$ Solving for $n$ we get $$n=1000 \pi R$$
user avatar
  • 273
6 votes

What is the use of gears in a device with a fixed gear ratio?

Electric motors typically only operate well at high speeds, and compared to something like an internal combustion engine, relatively low torque. Fixed gear ratios are used to cope with this inherent ...
user avatar
  • 81
6 votes

What is the mechanical element that holds a worm gear shaft in place called?

Not only does the shaft have a "bearing" surface but the ends of the shaft also need something to "bear" against due to the "thrust" of the shaft in either direction. So I would add the term "thrust ...
user avatar
6 votes

What is the use of gears in a device with a fixed gear ratio?

A given mass of copper and iron can only produce so much torque : increasing torque further would require more current which means (a) the increased magnetic flux saturates the iron and (b) the I^2R ...
user avatar
  • 1,570
6 votes
Accepted

Transform/change/convert rotation axis

The go-to solution is bevel gears. They are used when the shafts would intersect and allow the same ratios as normal gears. You can also make one of the gears a crown gear so the other gear can be a ...
user avatar

Only top scored, non community-wiki answers of a minimum length are eligible