Understanding plan notes.

[DaveRC]

Hi All,

I am building a Upsher Vertical Single engine and have the plans and been going through them making sure I understand everything on there along with all the text. I have managed to work out most of it and it's all coming together in my head (slowly) and want to be very clear before I start.

I came across one note in the text about the cam followers I just did not understand.

Note: The axial location of both cams results in a slight offset from there followers to encourage follower rotation.

WHAT....?

As far as I can see the cam followers are directly above the centre of the cam and cam shaft so I do not see what this is referring to, any clues...?

Dave

 

[Deanofid]

Hi Dave; It means the cam lobe itself is not hitting the tappet dead center. The cam shaft and tappets may be in the same plane, but the lobe is set over on the shaft slightly so as it rotates part of the lobe is rubbing more of the radius to one side of the tappet face, making it rotate. I.E. cam lobe hits off C/L of the tappet in relation to the flat face of the tappet.

Sorry if that's hard to understand. Maybe someone else can say it in a clearer way.

 

[Deanofid]

Maybe a pic would help. Crummy drawing, but hope you get the idea.

The left side shows the cam lobe and tappet as seen from the end of the cam shaft.
The right shows them as seen looking at the face of the cam lobe. Being off center on the tappet lets it spin the tappet as the lobe rotates.

 

[DaveRC]

OK Thanks, that actually makes sence.. ;D

All starting to come together now....

Dave