Grinding a 20/30/50 visx cam

[alantani]

thanks to christina for helping with the video!!!!

[Gfish]

Another great video Boss. What comes odda a 4 degree grind down? More gradual drag ramp-up?

[alantani]

Yeah,  nice, smooth and even.

[Donnyboat]

Thanks Alan, great idea, if you wished to finnish it of a bit smoother, one of the bright boy discs, would vertually pollish it, cheers Don.

[pitchinwedge]

Alan,

I worked on three cams freehanded for my 12VISX, 16VISX, and 30VISX. The 12VISX works perfect.  On the other hand, I'm having major loss of freespool and handle binding issues with 16VISX and 30VISX.  Was hoping you might have some insight into this. 

What I have now is similar (but worse) to 1min:40sec in your 50VISX video:

Appreciate any advice. 

[alantani]

Any time that the handle binds as you increase the drag, it's almost always the pinion bearing.  Once that is replaced,  then look at the cam. It should be cut to degrees. For both reels, make sure that the bellevilles are 0.038". For the 16 visx,  add another belleville to make the stack "(()". For the 30 visx 30, you will likely have thinner bellevilles.  Switch the thicker bellevilles from the visx 20/50 and see.

[alantani]

https://m.facebook.com/story.php?story_fbid=328672862736987&id=100067828264550

[pitchinwedge]

Really appreciate the suggestions, Alan.  I was also thinking it might be something along the lines of spacers/washers/bellvilles.  Good news is I have a bunch of new parts arriving tomorrow.  Will give em a try and report back. 

[Robert Janssen]

We need to look at something. I have been a bit reluctant to get involved, but I started making cams around twenty-five years ago.

When striving to achieve an even rotary to linear movement, as in this case,
the cam needs to be truly helical. What is being accomplished here, is not a helix. This is only a simplified straight-line approximation of what a helix should be. The resultant total rise of the cam may be similar -after all, the line goes from a to b- but, the progression of the axial movement is not linear.
Now, there is nothing inherently wrong about this form of cam in itself; i have used it myself on occasion, depending on the type of cam and not leastly depending on the type of cam follower.
In this case, the cam follower is designed to ride the planar surfaces of the cam lobes, distributing load evenly across their width.
However, the straight-line approximation, cut-across-a-cylinder technique also alters the geometry of the planar surfaces, so that the cam follower no longer properly follows them or distributes load and wear evenly. The cam followers now choose to concentrate on a path from the inside radius to the outside, with a small section in the middle of the arc where full contact is made. This effect can be seen by looking at the wear tracks in the pic below.




This is a rig i sometimes use to grind cams. The cylinder you see is internally threaded over on the right hand side, and will when rotated thusly follow the axial movement as dictated by the thread, which in this case happens to have a pitch of 3 mm. Over at the left-hand end of the cylinder, there is a pocket in which to place the cam to be ground. Above this, there is a high-speed spindle with the milling ttol or grindstone mounted at 90 degrees to the surface to be worked. The chuck at the extreme right of the picture can be rotaded 180 degrees, alternating as needed to cut the facets, or ramps, of the cam. The entirety of this rig is mounted to the table of a horizontal milling machine, which means that the cam-to-be can be advanced towards the cutting tool a few hundreths of a mm at a time, until reaching a predetermined dead stop, thusly ensuring that both facets of the cam are cut equally, and are truly helical.



So, another look... here we have a cam-to-be, on the milling machine, with the freespool notches already cut, and the cam ramps having been milled at at an angle, resulting in the straight-line, cut-across-a-cylinder form desribed above.



We then color it with marking blue, and move it over to the grinding jig. As we begin grinding, we clearly see the pattern described above.



As the grinding process continues, truly planar helical cam ramps will develop. 



 I was going to clarify the difference in cam shape  by documenting how the curve progresses, but decided that i had other things to do.



The sum total rise of active portion of the cam, excluding the freespool groove, should not exceed 75% of the sum total of available belleville spring travel. Otherwise, the belleville springs will bottom out, resulting in an immediate and drastic spike in drag pressure. (75% of spring travel is a general recommended engineering parameter used in such situations)
 This happens to be a favorite sore spot of mine. For years it has seemed perfectly obvious to me, that a reel should be able to achieve a full range of drag across the range of its lever.
Everol has achieved this for six decades. Why is it so difficult for others?

[jurelometer]

Interesting!

I was curious as to how much actual difference there would be for the equivalent rise  helical cut compared to a 4 degree flat cut.

I used a CAD program to draw up both, and superimposed the helical (yellow) on the flat cut (red)



Came out to be a bit more than I would have guessed.   As to whether it matters or not, dunno. If the lever operates smoothly, the only other issue should be wear over time. If the follower is hard enough and has enough contact surface area, the assembly might wear toward the proper shape.
 
-J

[alantani]

yeah, straight line was the best i can do.   

[Keta]

Too bad manufactures can not provide improved cams.

[MarkT]

Shimano offered a bunch of different cams for the Torsa's.

[pitchinwedge]

This happens to be a favorite sore spot of mine. For years it has seemed perfectly obvious to me, that a reel should be able to achieve a full range of drag across the range of its lever.
Everol has achieved this for six decades. Why is it so difficult for others?

Nailed it on the head.  Totally agree!

[jurelometer]

My diagram shows a full 180 degree of travel, but in real life, it looks like sunset is more like 150 degrees or so from the freespool notch.   Where there is actual significant  clamping load and frequent use in the 60 to 120 degree range, the difference between helical and flat is not that huge.  I am wondering if flat cut is that much worse.  In a piece of machinery that is in constant motion, we would want a real helical cut cam, but in a reel, this is not a very demanding application.  Mostly from freespool to strike  a couple dozen times a day at low speed, with the occasional swing into sunset if you get lucky.

Another thought:

I presume that all lever drag cam ramps are linearly progressive.  Belleville springs are pretty much linearly progressive as well, as long as we keep below the 75% of maximum compression that Doc mentioned.  So the combo should also progress linearly  unless you bottom out the bellevilles.

By using  stronger (i.e., thicker)  bellevilles, you get more clamping load increase per degree of lever swing, and vice versa.  Same effect as changing the cam rise.  So theoretically, in a hypothetical reel with a ton of room for bellevilles, and with a big selection of bellevilles to choose from, you could tune just the belllevile stack in place of tuning the cam.

Back in the real world, it seems that cam swapping/grinding is easier than belleville tuning, and you don't have to worry about space for extra bellevilles.  But you can't totally disregard belleville tuning, and getting the bellevilles sized right means a wider range of drag strike settings without a sudden ramp up.

As to why they never bothered to sort this out in the stock reels, dunno.  The problem might not have been as big with the original settings used with mono by the average angler?

I think that I may be  repeating a bit of what Alan and Doc have already posted, but I am working my way though this whole cam thing.  Never thought about it much until now. Appreciate any corrections if I got something wrong here.


-J