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Can you explain gearing to me?

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Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Can you explain gearing to me?

Old 08-31-12, 01:11 PM
  #26  
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Originally Posted by RaleighSport
With the other answers already in this thread, the other information outputs and also including the GI are useful. Thanks for 41ing me though.
Whether or not you find it useful, it's in no way, shape or form the answer to the question that was asked, which makes it decidedly useless to the person asking the question.
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Old 08-31-12, 01:20 PM
  #27  
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Originally Posted by WhyFi
Whether or not you find it useful, it's in no way, shape or form the answer to the question that was asked, which makes it decidedly useless to the person asking the question.
Actually I personally think that in relation with say your first answer in this thread there's tons of useful info in this link. Now stop 41ing me.
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Old 08-31-12, 01:26 PM
  #28  
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Originally Posted by WhyFi
His statement is still more accurate. Your statement makes a couple of assumptions that aren't always true: it assumes that there are no missing teeth (like some of the previous SRAM cassettes) and it assumes circular (Q-rings are not circular hence the 'easy' and 'hard' parts of the stroke).
Not to be argumentative, but I will be. First, missing tooth doesn't affect PD for the balance of teeth. They still have to be in the correct chordal relationship as if the tooth was there. Second, non-circular paths still require the same effective PD for gear ratio determination (they have the same total chordal circumference), they vary the torque required based on the lever arm changing, but for rpm to rpm, it is still total number of links moved in a rotation.

The only time PD becomes essential is when using double pitch chain with mixed sprockets. Using a 2040 chain with a 40 cassette and a 2040 crank would alter PD on the crank enough that you would not use a tooth comparison. Usually this only comes up in implement and conveyor chain applications.
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Old 08-31-12, 01:28 PM
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Originally Posted by RaleighSport
Actually I personally think that in relation with say your first answer in this thread there's tons of useful info in this link. Now stop 41ing me.
Yes, the person that's pleased to see non-relevant info being presented as an answer in a thread is the victim of being 41d.
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Old 08-31-12, 01:37 PM
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Ya'll are making this harder than necessary.... break it down.

-------

"work"
"torque" crank vs rear wheel
"leverage."

------

the work is the rotation of the rear wheel

the torque is your legs/feet pressing on the pedals

the levers are the cranks

---

the crank torque is only as strong as your legs

the levers are a fixed length

the rear wheel is a fixed size

--

ease of turning the rear wheel is through "mechanical advantage" in gearing

this controls the torque of the rear wheel.

more torque is needed to accelerate; as you accelerate in a given gear you lose torque and approach a stall of the crank, but increase mechanical advantage as you approach stall. (spin out of gear)

In order to accelerate more you need more mechanical advantage, therefore you shift to have a greater advantage of the front gear over the rear gear..... this can be express in many ways, typically as a ratio or percentage.

----

Some people are strong and can "turn big gears" accomplishing lots of "work" , others are weak/frail excuses for human beings relying on the lightest bicycle/rider combination and "high spin rate" in order ride on flat ground or climb hills.

Just like a motorcycle consumes more gas at high RPMs, so does the human body consume fuel.

Also, like a motorcycle, the greatest mechanical advantage occurs just before stall, but this is not the most efficient fuel usage. Shift UP, grab "more gear", lower your cadence and heart rate and conserve fuel for long endurance.

---

Don't be a weak/frail excuse for a human being, get strong and PUSH BIG GEARS.

Last edited by BigJeff; 08-31-12 at 01:40 PM.
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Old 08-31-12, 01:38 PM
  #31  
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Originally Posted by RollCNY
Not to be argumentative, but I will be. First, missing tooth doesn't affect PD for the balance of teeth. They still have to be in the correct chordal relationship as if the tooth was there.
Translation: the radius/circumference is unchanged, despite the missing tooth (teeth). That was exactly the point - it's not the teeth, it's the circumference. Correct.

Originally Posted by RollCNY
Second, non-circular paths still require the same effective PD for gear ratio determination (they have the same total chordal circumference), they vary the torque required based on the lever arm changing, but for rpm to rpm, it is still total number of links moved in a rotation.
Sure, but the OP was asking why is was easier or harder, he wasn't asking for gear ratio calculations.

I'm not saying that you're wrong - I'm just saying that the other answer is more right.
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Old 08-31-12, 01:49 PM
  #32  
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Originally Posted by WhyFi
Yes, the person that's pleased to see non-relevant info being presented as an answer in a thread is the victim of being 41d.
This thread was resolved how many posts ago? And your irritated people are supplying more info besides the already answered question specifically.. or answering in a way you don't like.

BigJeff I personally like that answer. Hopefully the OP does too.
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Old 08-31-12, 01:53 PM
  #33  
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Originally Posted by WhyFi
I'm not saying that you're wrong - I'm just saying that the other answer is more right.
You are clearly saying I'm wrong, and it deeply, deeply upsets me. I may have to start a thread on it.
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Old 08-31-12, 01:57 PM
  #34  
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Originally Posted by RaleighSport
This thread was resolved how many posts ago?
If Bianchi10 was a noob OP, I would agree. But 1,588 posts indicate that he anticipated tangents, secants, rants, rebuttals, and the general free for all that any and all posts can garnish.
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Old 08-31-12, 03:35 PM
  #35  
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lol, tangets are expected and encouraged! I have a better understanding but am still trying to wrap my head around it all. thank you everyone for the info.

Let the rants and secants continue ;-)
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Old 08-31-12, 03:41 PM
  #36  
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Forget the explanation. Take a simpler approach...if the pedaling gets too difficult, shift...if it gets too easy, shift! If it gets way too difficult HTFU!
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Old 08-31-12, 03:48 PM
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Originally Posted by WhyFi
The closer to the hub (hinge) you apply your effort (the pulling chain) the harder it is, but the farther the outside (rim/door knob) travels.
Okay, but why does that not apply for the front gears? Would your analogy then be that it would be a larger or smaller door being swung?
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Old 08-31-12, 03:57 PM
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It's simple.

The ratio of chainring teeth in the front and cog teeth in the rear create an imaginary wheel. This wheel circumference is calculated by whatever diameter of the rear wheel times (front chainring teeth / rear cog teeth)

So if you have a rear wheel of 27" in diameter you times this by the ratio of front and rear teeth say 46/17 and you get a imaginary wheel with a circumference of 73 inches.

If you kept the same wheel diameter and changed the gearing to 46/16 the imaginary wheel would now have a circumference of 77 inches.

Larger wheels require more effort to turn because you keep the pedal revolution as constant (1) as the wheel gets larger so more work has to be done.

https://en.wikipedia.org/wiki/Gear_inches
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Old 08-31-12, 04:29 PM
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Originally Posted by RaleighSport
And your irritated people are supplying more info besides the already answered question specifically.. or answering in a way you don't like.
No, I'm not irritated that people are supplying more info, I'm pointing out that people are providing info that's not germane and that it may be irrelevant at best or confusing matters at worst.

Originally Posted by RaleighSport
BigJeff I personally like that answer. Hopefully the OP does too.
That was a friggin' horrible answer, but I can see how you would appreciate it as you don't understand the subject. Am I "41ing" you again?

Originally Posted by DGoeder
Okay, but why does that not apply for the front gears? Would your analogy then be that it would be a larger or smaller door being swung?
Well, no. There are three different types of levers and it has to do with the arrangement of three elements: the fulcrum (pivot point), where the resistance is and where the force is applied. With the rear wheel, you're essentially talking about a lever with a fulcrum at one end, the resistance at the other end and the force being applied someplace in between. With the front gears, the fulcrum is at one end (the bottom bracket), but the force is being applied at the other end (pedal) and the resistance is in the middle (at the engaged chainring). In this instance, a more apt analogy would be a plank with a weight on it, some place in the middle. One end of the plank would rest on the ground, you'd be lifting at the other end. If the weight is close to the far end (BB/fulcrum), it doesn't take much force to lift off of the ground, but the weight will only travel a fraction of the height that you lift the other end of the plank. If the weight is closer to your end, it would take more force on your part, but the weight would travel further (higher off of the ground) than in the previous position closer to the fulcrum.
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Old 09-01-12, 08:20 AM
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Originally Posted by bianchi10
lol, tangets are expected and encouraged! I have a better understanding but am still trying to wrap my head around it all. thank you everyone for the info.

Let the rants and secants continue ;-)
There's really nothing to wrap your head around. A lower gear simply spreads the work you have to do over a longer period of time. Power is the rate at which you do work (expend energy), so in a lower gear your are using less power and it is, thus, "easier".
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Old 09-01-12, 11:06 AM
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Originally Posted by WhyFi
. If the weight is closer to your end, it would take more force on your part, but the weight would travel further (higher off of the ground) than in the previous position closer to the fulcrum.

got it. I vaguely remember all this from high school. But who really thought they'd use it in life after all.

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Old 09-01-12, 11:18 AM
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Originally Posted by whyfi
it has to do with the number (ratio) of teeth when comparing the chainring and the cog. To make things easy, let's say that you had a 48 tooth chainring and (implausibly) a 48 tooth rear cog. For every revolution of the crankset/pedals, the rear cog would go around once, too (because there's an equal number of teeth). Make it a 24-tooth cog (while keeping the 48t chainring), and the rear will go around twice for every revolution of the crankset/pedals - you gain speed, but it's at the cost of using more effort. With a 12-tooth cog, the rear wheel would revolve 4 times for every revolution of the crankset, but it would take even more effort. Make sense?
<-------- this
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Old 09-01-12, 01:38 PM
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Another way to think about it is developement. Chainring teeth/cog teeth x wheel circumference = distance travelled for one revolution of the crankset.
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Old 09-02-12, 12:58 PM
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I'm buying a bushel of apples and chucking them at every roadie's head I see....How fast do I need to throw it if I'm traveling 5 MPH faster than...
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