Mr. Baker - Cam math question

[mshultz]

A quick question for Gary of anyone who can find the right issue of the Hook Magazine 2-3 issues back....

Could you post the formula that you use to determine the camshaft key offset? I can find intake centerline okay, but my trial and error method of filing keys till I get one "close enough" isn't cutting it anymore. (plus as an Ag teacher I might be able do a math lesson with it and impress my math teacher friends

It makes me smile to see my kids wanting to look through my Hooks even though the covers do get ripped.... there's only about 30 of them in the house so its no big deal. But do you think I can find the one I'm actually looking for? I knew I should have put that one up on my closet shelf!

Thanks for your time.

Mike

 

[puller1]

On farmalls the keys I had made I got thicker larger keys and milled them down with an offset.What I found was that .005" offset would change the degree on the camshaft 1 degree..020" changed it 4 degrees.I've had to use as much as .025" to get cam to recommended centerline. Hope this helps.Tim

 

[north puller]

Someone else may have the correct formula, but this may help.

The cam turns at half crank speed. Therefore, 1 degree of cam offset equals 2 degrees of centerline change.

I believe that you find the diameter of the inside of your cam gear, divide that by 360 degrees (full circle) and that will give you the distance to offset for 1 degree of cam change, or 2 degrees of crank centerline change.

Not sure if that tech article is available on the hook website?

 

[mshultz]

The article is on the website - thanks for the tip.

Bryan - are you okay with it if I print copies of that article and circulate it to my students? Some of them think they're real gear heads and that their math classes won't get them anywhere.......

I honestly never thought to look there as the last I looked on the website there wasn't much info there other than how to subscribe, etc. It does look like it is becoming more useful to those who are alreay subscribed and looking for some information. I don't mean for that to be derogatory - just noting what I'm seeing. Hook is definitely been improving with each edition and that edition with the cam article was sort of a turning point if I remember right.

 

[Bryan Lively]

Print it out! Share it! I was an Ag teacher in a former life myself anything I can do to help Im all for it. Look for more Ag teacher (and student) friendly stuff in the future.

 

[Anonymous-0]

Puller 1 you are correct in that .005" offset is 1 deg. The formula I use is: Take the radius of the camshaft (.562") x the sine of the Degree offset you need (1)=9.808 divide x 2 = .0049 I use a scientific calculator with the sine function. Gary

 

[mshultz]

Thanks. Wonder if I took 2 cams from briggs and stratton and turned the cam gear off of one and the center out of the other and put a keyway in if I could simulate this on a briggs? Might be interesting....

 

[Red D]

On a Briggs cam, make a fixture to hold the cam then heat the cam with a torch and twist the cam to split the lobes to give it more overlap between the lobes, or cam advance on the gear drive end.