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simar kid
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Quote simar kid Replybullet Topic: speed calculations on pulleys
    Posted: 30 Jun 2013 at 7:38pm
without the proper equipment,is there any general guidance to working out pulley speeds given the known speed of the crankshaft ? example ; known crank speed 650 rpm pulley diameter 10 inches what speed is the pulley doing on outer rim.   any suggestions welcome.
Not sure whats wrong. i think we will let it develop
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meadowfield
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Quote meadowfield Replybullet Posted: 30 Jun 2013 at 9:02pm
Divide one pulley diameter by the other...

I.e. crank pulley 5in, gearbox 10in. Therefore 2:1 gearing, so 650 rpm is reduced to 325 rpm.

Does this make sense?
me fatha allus toldus thez three kinds of engineer - them what can add up, an them what can't
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merryman
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Quote merryman Replybullet Posted: 30 Jun 2013 at 9:14pm
Meadowfield’s answer seems more use, but you asked for the speed of the belt. With each rev the distance travelled is the circumference which is 3.142 x D so for a 10” pulley 3.142 x 10/12 = 2.6183 feet. 650 rpm = 650/60 = 10.83 revs /second so in one second the distance travelled is 10.83 x 2.6183 = 28.356 ft or 28.356 ft/sec.
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simar kid
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Quote simar kid Replybullet Posted: 30 Jun 2013 at 9:31pm
Thanks to you both for the calculations have now got to sorce a bigger pulley
Not sure whats wrong. i think we will let it develop
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ranger
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Quote ranger Replybullet Posted: 30 Jun 2013 at 9:34pm
Just about to say the same as merryman,the original question seemed to refer more to surface speed of pulley outer rim which would apply if you were machining the pulley on a lathe,than rpm which would be more use if you were setting up a drive train.
"I`ll be glad when I`ve had enough of this"!
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gardenattwo
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Quote gardenattwo Replybullet Posted: 06 Jul 2013 at 10:29pm
Hi are you looking for the speed of a driven pulley or theperipheral speed. To calculate the rpm of a driven pulley the formular is diameter of drive pulley is F, the driving pulley is D.  Providing that three of the values are known the unknown value can be calculated.
You know the rpm of the driving pulley    
          
                 diameter of D times rpm of D over diameter of F equels speed of the driven pulley.  The pulleys are measured from the middle of the sides of the V pulley. This is called the pitch circle diameter. (PCD) Hope this helps. This formular is correct for calculating the revs of the driven pulley
Measure twice and cut once
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simar kid
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Quote simar kid Replybullet Posted: 07 Jul 2013 at 8:38pm
wow ! its surley complicated. maths was definatly not my preferred subject but I am good at painting.not a lot of good to me with this enquiry. my best bet here is to measure both pulleys and engine known speed and then ask one or so of you maths wizards to work out the nessary.
Not sure whats wrong. i think we will let it develop
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crawler
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Quote crawler Replybullet Posted: 07 Jul 2013 at 10:30pm
Hi simar kid, just Googled speed calculators for pulleys. The first one that came up was this one http://www.culvermotor.com/Engineering-Formulas/Pulley-and-RPM-Calculator.html
Its an American site but the speed calculator will work fine with what you know.
Hope the link works ok.
Rob
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simar kid
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Quote simar kid Replybullet Posted: 15 Oct 2013 at 9:15pm
yes ,and thanks. I found one which I have also informed members by putting in my thread on the lister model a in projects. after all most of us are everything but boffins
Not sure whats wrong. i think we will let it develop
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