trying to grasp ratios in general Question
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Posted by: bobthedog ®

04/18/2007, 08:34:48

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Basically am getting abit confused with the scales and ratios.

One gearing problem had was pinion has minimum number of teeth is 19 and the maximum number of teeth on a wheel is 150 and the velocity ratio is 8:1 so that is 19 x 8 isnt it like someone pointed out to us earlier which is 152 but it says that it should be limited or restricted to 6:1 so thats like 19 x 6 which is 114 teeth.
The next bit is between ratio and scales if a scale on a map is in mm and the scale ratio is 1:2 that is a half scale right? For every one mm on the map is two of the actal value in cms meters or yards etc on the object. So thats a reduced scale an inlarged scale would be 3:1 etc for every 3 mm on drawing is one unit of value yards meters cms of object drawn. Just picked up a dvd and it has 4:2 display ratio so regarding that would would that mean.
What is an equation or quickiest way to work out the velocity ratio of two gears meshing nothing more>

THanks again.





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Re: trying to grasp ratios in general
Re: trying to grasp ratios in general -- bobthedog Post Reply Top of thread Forum
Posted by: bobthedog ®

04/18/2007, 08:40:52

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Ok realise that material boy gave us an equation for v ratios in meshing gears but it dont make sense because


r1 is radius one

T is tip

V is velocity

V ( 15 TEETH) 2xpixr1/T Now material boy put 7.5+tip but in the displayed equation it has / as in divided by tip so which is it please?





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Re: Re: trying to grasp ratios in general
Re: Re: trying to grasp ratios in general -- bobthedog Post Reply Top of thread Forum
Posted by: randykimball ®
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04/18/2007, 09:59:58

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Just divide the number of teeth on the little gear into the number of teeth on the big gear.. forget everything else.

For example:
A 15 tooth little gear, driving a 45 tooth big gear.
45/15=3 ... the ratio is 3 to 1

No matter the diameters, teeth drive teeth!





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Modified by randykimball at Wed, Apr 18, 2007, 10:02:46


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Re: Re: Re: trying to grasp ratios in general Question
Re: Re: Re: trying to grasp ratios in general -- randykimball Post Reply Top of thread Forum
Posted by: bobthedog ®

04/18/2007, 11:15:19

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Thanks randy that made it alot clearer just got confused.

Can be a bit much sometimes thats all.





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why 3;1 Question
Re: Re: Re: Re: trying to grasp ratios in general -- bobthedog Post Reply Top of thread Forum
Posted by: bobthedog ®

04/18/2007, 11:20:01

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3;1 ratio because the wheel with 45 times travels 3 x the rpm of the pinion right????




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Re: why 3;1
Re: why 3;1 -- bobthedog Post Reply Top of thread Forum
Posted by: randykimball ®
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04/18/2007, 22:19:03

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No, because the little gear turns around three times to one time of the bigger gear...




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right got that thanks
Re: Re: why 3;1 -- randykimball Post Reply Top of thread Forum
Posted by: bobthedog ®

04/19/2007, 06:56:08

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thanks again for clearing that up




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