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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 05-18-08, 06:32 PM   #1
the pope
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Help me mathletes!

Question from the back of the class:

Word problem.

A flat bar, 46 centimeters long with a 5 degree sweep, will sweep back how many centimeters from the center to an end. I realize that the sweep in a flat bar does not start in the center but I've shortened the measuring distance to (hopefully reasonably accurately) compensate for this.

I'm pitiful. Please help.

Thanks!
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Old 05-18-08, 06:36 PM   #2
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1) pencil
2) paper
3) ruler
4) protractor

surely you have these...
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Old 05-18-08, 06:38 PM   #3
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What's a protractor?
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Old 05-18-08, 06:44 PM   #4
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it's a simple tool which allows you to draw angles.

if you have a printer:
1) type pdf protractor into google
2) print it out
3) make a dot where the anchor point is
4) make a dot where the 5 is and another where 0 is
5) draw a line from the anchor dot to the 5 dot; another from the anchor to 0

the line from anchor to the 5 dot is a 5 degree sweep. draw a 46mm (or whatever) line from the anchor through the 5 with a ruler. that's half the length of your bar. the rest should work itself out as you go.
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Old 05-18-08, 06:45 PM   #5
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Oh, sweet idea. Thanks.
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Old 05-18-08, 06:48 PM   #6
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Put the flat part against a wall and measure from the wall to whatever part you're curious about

Edit: Or solve tan(x/23)= pi/36 (5 degrees in radians)

Last edited by Peedtm; 05-18-08 at 06:52 PM.
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Old 05-18-08, 06:49 PM   #7
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I don't have the part yet. Wondering if I'll need a longer stem - and how much longer.

Measured. At 25 cm length I get a rise of 2 cm. That's a ballpark.
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Old 05-18-08, 07:02 PM   #8
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If you consider the slope (from math, 'member?) is pi/36, this is ~.087 cm of rise per cm of run. If you extend that for 25 cm (25 X .087), that equals 2.175cm. So I concur, sir. Go to it.
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Old 05-18-08, 07:34 PM   #9
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sin(5)*(46/2)=~2cm of backsweep

this translates to about 1.5cm in extra stem reach requirement because in reality hand placement is not at the end of the bar but about 5cm from the end.
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Old 05-18-08, 07:40 PM   #10
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Smarties.
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Old 05-18-08, 08:23 PM   #11
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dont feel bad, im bad at math too
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Old 05-18-08, 11:49 PM   #12
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Quote:
Originally Posted by the pope View Post
Question from the back of the class:

Word problem.

A flat bar, 46 centimeters long with a 5 degree sweep, will sweep back how many centimeters from the center to an end. I realize that the sweep in a flat bar does not start in the center but I've shortened the measuring distance to (hopefully reasonably accurately) compensate for this.

I'm pitiful. Please help.

Thanks!
Type this: 23*sin(2*pi*5/360) to google search box and mouse over to get 2 cm and a change.
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Old 05-19-08, 01:11 AM   #13
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Wait. Google does math too!?
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Old 05-19-08, 01:41 AM   #14
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Wait. Google does math too!?
someone got bored with 80% project

Last edited by vobopl; 05-19-08 at 02:11 AM.
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Old 05-19-08, 08:33 AM   #15
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Holy ****, that's amazing. Google is totally going to take over the universe. Maybe this is how the trade federation starts.
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Old 05-19-08, 08:51 AM   #16
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How about unit conversions (inches to metric etc.) paste that: 20 inches in cm and mouse over
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Old 05-19-08, 10:50 AM   #17
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But can google do Gauss-Jordan elimination?
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Old 05-19-08, 11:20 AM   #18
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But can google do Gauss-Jordan elimination?
No but it finds online calculators for linear algebra!
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Old 05-19-08, 01:23 PM   #19
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can google do statics? not statistics, statics
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