Questions tagged [gears]
479 questions
47
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9 answers
Is it possible for a bicycle chainwheel to have a fractional number of teeth?
Background
In the world of bicycle motocross, also known as BMX racing, gearing is a hotly-debated topic.
Since the bikes are all single-speed, gear ratio is a fixed number defined as chainwheel / cog (front gear divided by rear gear). Altering your…
eckza
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20
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Effective ways to drive a single shaft with multiple motors?
To head off the "why not use a bigger motor" question, I'm a high school mentor for an FTC (First Tech Challenge) robotics team, with a bit of a soft mechanical / hardware background. They're somewhat limited in what they're allowed to use, motors…
trycatch
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How do bike wheels keep turning when the rider stops pedalling?
I am very confused with something regarding bikes...
How is it that a bike wheel continues to spin (either from momentum or from going downhill) when the rider is not pedalling, without also spinning the pedal?
Similarly, what mechanism allows the…
Ankit
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13
votes
1 answer
How does a (pulley based) continuous variable transmission (CVT) work?
How does the (pulley based) CVT achieve the following?
no requirement for a clutch
fuel economy
smooth gear transition
NMech
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12
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Why does a gear have extra holes?
In a gear you normally have a center hole for the shaft to be put into. Why do some gears have holes surrounding that center hole?
Is it for weight reasons? Does it add stability? Is it so you can add special parts?
Mat NX
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11
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2 answers
What is the mechanical element that holds a worm gear shaft in place called?
Here is an image of a worm gear. What is english word for mechanical element (two of them will be necessary for a worm gear) in which the worm shaft will "lie" and rotate?
Here is one photo of the element where it is part of a housing; I need it as…
etf
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10
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4 answers
How are high gear ratios achieved in a small space?
I have a very basic understanding of how gears work, and while trying to learn more, I've run into a small point of confusion.
If a 2:1 gear ratio is achieved by having twice as many teeth on one gear than the other, then how are 250:1 ratios…
Soviero
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10
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7 answers
Why are bulldozers so slow?
Tracked-type tractors and bulldozers are very slow engineering vehicles. Their top speed is less than 15 km/h and when pushing it is even lower (< 5 km/h). For example: the Caterpillar D9's top speed in forward gear is 11.0 km/h while in reverse…
Triceratops
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9
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What is the benefit of additional planetary gears?
A planetary gear is a gear that rotates not around an axle but around another gear known as a sun gear, or star gear. I have designed prototype systems in the past that used a single planetary gear rotating around a rotating gear. However since then…
Sam Weston
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9
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3 answers
Mechanism of gear rotation
Is the smaller gear (pinion) always mounted to the input shaft when meshed with a bigger gear that is mounted on the output shaft? Are there places where the bigger gear drives the smaller gear?
Debanshu Thakur
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9
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Involute gear curve when root diameter falls below base diameter
The answer to a question on involute gear curve calculations shows how the gear tooth curve proceeds as an involute calculation from the base diameter.
If the pitch diameter is D = m.N where N is the number of teeth and m is the modulus (for metric…
carveone
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8
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5 answers
How can I get a stepper motor to engage with a freely spinning wheel?
I'm working on a project that uses a strong stepper motor to power a wheel that needs to be able to "coast" freely at times. The motor is too stiff when not engaged, and along with my gearing ratio, makes it impossible to get the free-spinning…
nonlinearmind
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What does "tol" mean in a gear box?
In this NASA document, it is mentioned on page 221 (239 of the pdf) that a "23 tol gear box" was used. What does that mean?
A google search for "23 tol gear box" (with quotes) comes up completely empty, and "tol gear box" shows only irrelevant…
Rikki-Tikki-Tavi
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7
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3 answers
Compound gear system ratio
This might be a stupid question, but I'm new to mechanics, so please bear with me. Suppose I have a compound gearing system defined in the image below (not to scale).
The green gear is the driving gear, and the blue gear is a compound gear.…
Tom
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7
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How does this gearbox work?
EE here; I need help!
This gearbox takes rotational motion from a single DC motor and turns one gear when the DC motor spins in one direction and another gear when the DC motor spins in another direction. Can you help me understand how it…
webhunt
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