Bike Forums > Help me mathletes!
 Register All Albums Elite Membership Forum Rules Calendar Search Today's Posts Mark Forums Read

 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)

 05-18-08, 06:32 PM #1 the pope Senior Member Thread Starter     Join Date: Mar 2005 Location: laramie ! Bikes: Posts: 1,110 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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!
 05-18-08, 06:36 PM #2 sp00ki partly metal, partly real     Join Date: Aug 2005 Location: Philadelphia. Bikes: Hummer H2 Posts: 3,597 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 1) pencil 2) paper 3) ruler 4) protractor surely you have these...
 05-18-08, 06:38 PM #3 the pope Senior Member Thread Starter     Join Date: Mar 2005 Location: laramie ! Bikes: Posts: 1,110 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) What's a protractor?
 05-18-08, 06:44 PM #4 sp00ki partly metal, partly real     Join Date: Aug 2005 Location: Philadelphia. Bikes: Hummer H2 Posts: 3,597 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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.
 05-18-08, 06:45 PM #5 the pope Senior Member Thread Starter     Join Date: Mar 2005 Location: laramie ! Bikes: Posts: 1,110 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Oh, sweet idea. Thanks.
 05-18-08, 06:48 PM #6 Peedtm Tell them I hate them     Join Date: Oct 2006 Location: Boise, ID Bikes: Specialized Allez Epic '91, IRO Mark V Pro, Schwinn Traveler Posts: 939 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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.
 05-18-08, 06:49 PM #7 the pope Senior Member Thread Starter     Join Date: Mar 2005 Location: laramie ! Bikes: Posts: 1,110 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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.
 05-18-08, 07:02 PM #8 Peedtm Tell them I hate them     Join Date: Oct 2006 Location: Boise, ID Bikes: Specialized Allez Epic '91, IRO Mark V Pro, Schwinn Traveler Posts: 939 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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.
 05-18-08, 07:34 PM #9 MIN  big ring     Join Date: Mar 2007 Location: philadelphia Bikes: Posts: 5,838 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) 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.
 05-18-08, 07:40 PM #10 the pope Senior Member Thread Starter     Join Date: Mar 2005 Location: laramie ! Bikes: Posts: 1,110 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Smarties.
 05-18-08, 08:23 PM #11 dervish unofficial   Join Date: Apr 2008 Location: san rafael, CA Bikes: Posts: 1,054 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) dont feel bad, im bad at math too
05-18-08, 11:49 PM   #12
vobopl
re:member

Join Date: Jan 2005
Location: Cracow, Poland
Bikes: unknown make TT bike, fixed; Romet Sport, gone; titanium Pinarello gone;Colnago with Campy C-Record/Super Record,on it's way; Funny Gianni Motta; Buehler track, Polrad track chrome; titanium MTB on 28'', fixed; Tri Wheeler, fixed
Posts: 874
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Quote:
 Originally Posted by the pope 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.

 05-19-08, 01:11 AM #13 raster Heck yes.     Join Date: Jun 2007 Location: Phila-ila-delphia Bikes: Saint Tropez, Shogun Posts: 426 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Wait. Google does math too!?
05-19-08, 01:41 AM   #14
vobopl
re:member

Join Date: Jan 2005
Location: Cracow, Poland
Bikes: unknown make TT bike, fixed; Romet Sport, gone; titanium Pinarello gone;Colnago with Campy C-Record/Super Record,on it's way; Funny Gianni Motta; Buehler track, Polrad track chrome; titanium MTB on 28'', fixed; Tri Wheeler, fixed
Posts: 874
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Quote:
 Originally Posted by raster Wait. Google does math too!?
someone got bored with 80% project

Last edited by vobopl; 05-19-08 at 02:11 AM.

 05-19-08, 08:33 AM #15 kemmer *****es love tarck     Join Date: Apr 2006 Location: Sandy, UT Bikes: so many Posts: 3,303 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) Holy ****, that's amazing. Google is totally going to take over the universe. Maybe this is how the trade federation starts. __________________
 05-19-08, 08:51 AM #16 vobopl re:member   Join Date: Jan 2005 Location: Cracow, Poland Bikes: unknown make TT bike, fixed; Romet Sport, gone; titanium Pinarello gone;Colnago with Campy C-Record/Super Record,on it's way; Funny Gianni Motta; Buehler track, Polrad track chrome; titanium MTB on 28'', fixed; Tri Wheeler, fixed Posts: 874 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) How about unit conversions (inches to metric etc.) paste that: 20 inches in cm and mouse over
 05-19-08, 10:50 AM #17 Yoshi Senior Member   Join Date: Nov 2004 Bikes: Posts: 2,544 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) But can google do Gauss-Jordan elimination?
05-19-08, 11:20 AM   #18
MIN
big ring

Join Date: Mar 2007
Bikes:
Posts: 5,838
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Quote:
 Originally Posted by Yoshi But can google do Gauss-Jordan elimination?
No but it finds online calculators for linear algebra!

 05-19-08, 01:23 PM #19 tx_what_it_do SWAAAAAAAAAAAT   Join Date: Apr 2008 Location: alief houston texas Bikes: masi speciale fixed (urrringe), haro f1 (black), haro x2 (red) Posts: 336 Mentioned: 0 Post(s) Tagged: 0 Thread(s) Quoted: 0 Post(s) can google do statics? not statistics, statics