Questions tagged [gears]
412 questions
46
votes
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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18
votes
5 answers
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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17
votes
3 answers
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
votes
6 answers
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
votes
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
votes
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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9
votes
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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8
votes
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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8
votes
1 answer
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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8
votes
1 answer
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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8
votes
1 answer
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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7
votes
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
votes
2 answers
How to mount a load-bearing gear shaft through a wooden plate
I don't have experience in mechanical engineering so I came here to ask for help. Here is sketch of one simple construction I want to realize:
Here we have 5 cm thick wooden plate, 50 cm long and 35 cm wide. I will drill a hole through the plate…
etf
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7
votes
1 answer
Internal teeth involute gear pitch circles
I'm having some trouble figuring out how to design the corresponding internal gear for any particular spur gear. With spur gears, meshing is accomplished by having two gears with the same modulus (MOD) or, in the US, the same diametral pitch. The…
carveone
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