ecentrics calcalations

[wmf138]

Hi All
just wondering if Ive got this right
the ecentrics Ive made are 10mm from the centre of the hole to the furtherest part
putting two of the ecentrics together gives me the maxamiam distance is 20mm
so does that give me a stroke of 20mm because it doesnt look like it does
or am i wrong

Cheers
Wayne

 

[Captain Jerry]

Wayne

You need to measure the distance from the shaft center to the maximum AND to the minimum offsets of the eccentric. The stroke or throw of the ecc is the difference between the two. Putting two together as in a
Stephenson reversing gear does not change the throw, it only changes the timing.

Jerry

 

[SandyC]

Hi Wayne,

The total travel of an eccentric is 2 x the eccentric centre (throw)offset from the crank shaft centre.

Think of it as a crank having a crankpin offset of (X).

If you offset the eccentric centre (X) from the crankshaft centre by 10mm (throw) then the total travel will be 20mm.

The outside diam. of the eccentric (a circle having it's centre at point X) is chosen such that when the eccentric strap is fitted it clears the crankshaft and eccentric hub with no binding/interference and that sufficient material remains around the crankshaft at the eccentrics closest point to ensure sufficient strength and to permit a hub of sufficient diameter to accomodate the grub screw/fixing.... the eccentric's OD has no bearing on the total throw.

Hope that helps.

Best regards.

SandyC ;D

 

[wmf138]

cool thanks for that my mind isnt what it used to be
and Im only 42

cheers Wayne