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Posted:
Fri Mar 20, 2009 3:56 pmby bruce
This is a project that has sat in my shop long enough now that I finally want to get it running or find out it will be a total failure.
I purchased an old Van Norman piston grinder to convert to a small engine camshaft grinder. It features a rocking table and I know of a few other shops using this machine for this application although nobody will "share" any info.
What I am working on now is an indexing fixture so I can use the same cam lobe pattern to grind various lobe center angles from one pattern by indexing my cam blank in my machine.
My plan is to use a plate with indexing holes spaced every degree, bolt a plate to my blank with a hole at lobe center and index my blank to mate with the indexing hole. I will also need a separate plate that will be a .5 degree offset.
My blanks will be the same design so I do not have to setup to machine other style cams. I am doing this for my own designs and have no desire to grind cams for others' in my sports venue. Down the road I might look at other cams but for now this is for my own playing.
I'm attaching a layout that shows what I am planning on doing. The drawing actually shows the two plates as one. The holes in the array are actually under the first plate which sits on top, you can see the indexing holes at the top. There are two sets of holes one for odd numbers and one for even. I only have a 6" diameter to work with so the holes would not all fit on the same bolt circle. The other holes are locating holes for my blank and are for reference. As I get my design more refined I'll layout a 3D drawing showing more details.
Any thoughts?
Posted:
Fri Mar 20, 2009 4:13 pmby bruce
This might make it clearer:
Posted:
Fri Mar 20, 2009 4:16 pmby bruce
The cam lobe master loads on the opposite end of a shaft that runs through the headstock. The pattern is indexed off the shaft which matches the indexing plate on the cam end. This keeps the master and indexing plate in time.
Posted:
Fri Mar 20, 2009 4:33 pmby bruce
I'm on a roll . . . here is a picture showing my idea for an exhaust lobe or intake lobe. This does not take into account an advanced cam. My cam gear is slotted so the cam can be degreed in.
Posted:
Fri Mar 20, 2009 6:08 pmby Tony
Those holes look rather small and close together Bruce.
Why not spread them out right around the disc ?
Have two full discs, one with holes maybe ten degrees apart, and the other with holes eleven degrees apart. For every single full degree of displacement, a pair of holes will line up around the disc.
That means the holes and pin can be made larger (and more robust), and there will then be sufficient room between holes to mark each individual hole on the upper disc with the displacement angle.
The same holes can be used for inlet or exhaust lobes, by moving the 10 degree disc around by eleven holes , to provide the basic 110 lobe angle separation.
So the basic idea might be one disc drilled with 36 holes at ten degrees, and the other disc drilled with eleven holes spaced at eleven degree intervals, marked between -5 to 0 to +5 degrees.
Any angle over the full 360 could then be pretty quickly set. But in practice that would never be required.
This is pretty basic, and obviously more closer spaced holes would offer finer divisions.
Posted:
Fri Mar 20, 2009 7:16 pmby bruce
I located the holes to match up with lobe centerline each hole is spaced 2 degree from each other on one circle (even degrees) and another circle (odd degrees) By making up another plate offset by .5 degree I get the half-degree. This saves making a whole indexing plate and trying to find which holes line up on which sector.
I'm sure I'll end up changing the design after I grind something so nothing is firm on the machine except the spindle which I have already machined for 5C collet dimensions.
The unfortunate thing with my questions posted here is you all can't see the machine and how it operates. Trust me as you already know I'm open for brainstorms! Hence the reason I'm looking for input from the forum "brain collective" . . .
Posted:
Fri Mar 20, 2009 8:15 pmby bruce
This shows the relationship of all the parts, the arbor goes through the spindle which is power driven to rotate the blank as it's being ground:
Posted:
Fri Mar 20, 2009 8:35 pmby Tony
Yes Bruce, all you need are two index plates, or an index plate and sector (same thing) that need to be accurately displaced by a known angle and then rigidly locked.
Posted:
Sat Mar 21, 2009 7:09 amby bruce
Did you ever think about all the great stuff we could design and build if we all had a big ole shop we all worked out of?
I think I just needed to make this post to free some of the creative juices in my brain on this project.
Posted:
Sat Mar 21, 2009 10:08 amby 49-1183904562
Bruce,
On your setup how are you establising TDC/BDC datams on your patern ?
Rick
Posted:
Sat Mar 21, 2009 10:28 amby bruce
Pattern is setup so my datum (index) of my lobe profile is center of the lobe design. My cam gear is adjustable so any degreeing required can be set on engine build. Lobe separation is in the cam grinder indexing (shown above), so for the cam profile you posted the cam blank would be offset ICL 54.5 (109/2) and ECL 56 (112/2).
I haven't worked out all the details of my pattern design just yet . . . gotten remember it's all done the old manual way on my mill and rotary table.
If I required a cam to be ground 2,5 10 etc degree advanced I could always make an indexing fixture to move the pattern by that much and still set my lobe centerline with the blank. But, for my cams as I said above it can be done with the adjustment in the gear or course adjustment of gear tooth offset.
Edited By bruce on 1237645775
Posted:
Sat Mar 21, 2009 10:57 amby 49-1183904562
Bruce
My question is more about thinking through the machining setup process. I/E i want to grind a split lift duration cam. In your setup I see how i can grind symmetrical cam but once i take the pattern off to grind the second lobe how do ensure index between patterns? as not to effect your intended LSA. In other words all of your patterns will need to be exactly indexed to its own CL.
This is I great mind puzzle, I might suggest you think about putting a good quality camshaft degree wheel in your fixture maybe on the spindle as a visual reference.
Rick
Posted:
Sat Mar 21, 2009 11:13 amby bruce
The pattern is indexed to the machine arbor which is indexed to the lobe angle index plate, so just remove the first pattern, install the second pattern and re-index the blank for desired lobe angle. Only problem might be if you are grinding something that needs a 1/2 degree then you would have to remove the blank and install the 1/2 degree selector and re-install the blank.
Blanks all have an index hole for what would be center lobe separation angle.