44 votes

Why are bulldozers so slow?

I wonder why can't we engineer.. We CAN engineer a vehicle which is both fast, and has a lot of torque. (E.g. a tank, as you mentioned yourself) The reason why we don't do this for a bulldozer (I.e. &...
Chris_abc's user avatar
  • 779
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.
Jordon's user avatar
  • 361
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 ...
kamran's user avatar
  • 22.4k
26 votes

Why are bulldozers so slow?

From memory, but pretty much realistic: a tank will use e.g. 1000 liters of diesel fuel just to move 100 km and will probably require a track maintenance afterwards. A truck with the same tank on its ...
fraxinus's user avatar
  • 499
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 ...
NMech's user avatar
  • 24.3k
18 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 ...
Involute's user avatar
  • 1,337
11 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.
jos's user avatar
  • 393
11 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 ...
alephzero's user avatar
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10 votes
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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 ...
NMech's user avatar
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9 votes
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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 ...
niels nielsen's user avatar
9 votes
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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 ...
Viktor Mellgren's user avatar
8 votes
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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. ...
SF.'s user avatar
  • 6,135
8 votes
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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 ...
NMech's user avatar
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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 / ...
Solar Mike's user avatar
  • 15.8k
8 votes

Why are bulldozers so slow?

Because the tracks or tyres and suspension needed for sufficient ground contact when pushing, dozing or grading does not match the suspension etc needed for higher speed situations. Even the ...
Solar Mike's user avatar
  • 15.8k
8 votes

Why are bulldozers so slow?

They need to be heavy for traction, which makes them too heavy for speed. To have enough friction between ground and tracks, the machine needs to be very heavy. The Caterpillar D9 you mention weighs ...
jpa's user avatar
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7 votes
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What mechanism can make a shaft rotate in steps

Geneva drive 3D Printed Geneva Drive Anchor Escapement (Clock Mechanism) 3D Printed Anchor Escapement
ericnutsch's user avatar
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7 votes
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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. ...
fred_dot_u's user avatar
  • 7,090
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. ...
kamran's user avatar
  • 22.4k
6 votes

Is "pitch diameter" the same as the distance between the centers?

Pitch diameter is the diameter of the pitch circle described by the mid point of the length of the teeth around the gear, as shown in this diagram: The pitch circle defines the point where the teeth ...
Greenonline's user avatar
6 votes
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How Much Efficiency is Lost in a Gear Train

Generally gear trains with lower ratios are more efficient due to reduced amount of sliding action between the gear teeth in mesh, so the compound gear train would probably be a better solution. That ...
jko's user avatar
  • 2,347
6 votes

Why does a gear have extra holes?

Also someone may have to pick the machine up and carry it. Reducing weight is not just related to the intrinsic function of the machine, its shafts and so on.
Adrian Midgley's user avatar
6 votes

Why are hydraulic systems widely used to multiply force ? won't a couple of gears do the job?

Power density. Modern hydraulic systems are way better compared to ropes and pulleys, gears, electromagnetic systems or levers. Freedom of geometry. Put a cylinder somewhere, get a rubber hose to it, ...
fraxinus's user avatar
  • 499
6 votes
Accepted

Is it essential for two meshing gears to have even number of teeth?

The recommendation is quite the opposite. The teeth of meshing gears are, where possible, chosen to be odd or, better again, primes so that a bad tooth doesn't keep hitting the same point on the ...
Transistor's user avatar
  • 10.8k
6 votes

Why are bulldozers so slow?

You’d just need a lot of engine power and all the suspension, drivetrain (including tracks), brakes, safety equipment (seatbelts, airbags) etc. would have to be designed for the high speed. Just ...
Michael's user avatar
  • 318
5 votes

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

One solution is to use a system with a ring gear that only has teeth on half of its inner circumference, like conceptually shown in the following image: There are three gears: Ring gear (red) ...
Involute's user avatar
  • 1,337
5 votes
Accepted

Reverse-engineering spur gears - do I have enough data to make a gear that will mesh correctly?

Given these measurements I think these are standard Module 0.5mm (Mod 0.5) gears, and that alone plus a little web search should let you design for them to mesh correctly, and buy, design or ...
user_1818839's user avatar
  • 1,620
5 votes

Is "pitch diameter" the same as the distance between the centers?

As indeed answered by Greenonline, the centre distance is the average of the pitch diameters of the two meshing gears, but this is only strictly true when the gears are operating at standard centre ...
Involute's user avatar
  • 1,337
5 votes
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Involute Gear Calculation

First of all, there should indeed ideally be no backlash between the teeth. There is a slight problem with the code, which stems from the misunderstanding that consecutive points of the involute ...
Involute's user avatar
  • 1,337
5 votes
Accepted

Internal teeth involute gear pitch circles

First of all, yes the pitch circle is the same for an internal gear as it is for the equivalent external gear. Second, note that indeed the addendum refers to how much the teeth extend inward of the ...
Involute's user avatar
  • 1,337

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