Re: [ATM] [atm_free] RE: Ronchi profile technique

["Jerry" <wa4guu@verizon.net>]

That is right. Hence the option of which way you look at it. But when you
choose one when you get to the other end you have to reverse the last slope.


Here is a good place for an example.  Scroll down to the single line Ronchis
on the first page.

http://johnspics.com/a/spot3.html


This makes it where we know we are looking at the same line.
The first one is inside COC. 

The line is the glass. And let's just look at the top half of the line.
The apparent ambiguity of my method is resolved by the fact that you should
know what you are trying to do to the curve. From the center out you can see
the center is somewhat spherical, ever so slightly oblate. Then there is a
moderately abrupt start to the change to a longer radius at about 30 % that
continues to increase radius to about the 80% and then decreases somewhat
the rate of change of the downward slope until the turn down at the edge
starts.

To fix this shape near the edge we might do it two different ways.


1
We could look at the right side of the line as the surface and the tde looks
turned down. You could wear the crest of the turn down which looks to be
about 5 or 10 % wide. We try to push this crest down to make the band curve
more uniform. Doing this makes the crest inward a longer radius to be closer
to the radius of the turn down. It makes the crest outward shorter radius
and closer to the radius farther inward on the mirror. We all hate to have
to do this so near the edge, don't we.


2
We could look at the left side as the surface but now the edge looks to be
turned up. Now the crest is farther in and when we push this in to the
desired band curve we are shortening the radius of the crest to make to
increase the curve of the band to match the stronger curve nearer the edge.
But we better not try to push what appears on this side of the line into the
curve of the band or you will really do the opposite and make the turn down
worse. This one isn't much fun either. I think it is easier. But it is
easily overdone making an over corrected outer zone a worry. 

With method 1 if we also wanted to fix farther in we could work the hump in
the line at 30% by pushing it into the curve. That would smooth the curve
but the correction would not increase. 

With method 2 We would see the middle as a hump and push it outward to match
the curve farther out. This would increase correction. 


By method 1 the center looks like a low area. We reverse our interpretation
in this case. It is a raised area.

By method 2 it looks high but the edge looks turned up. We reverse the
interpretation to a down turn.

Depending on our desired shape relative to the reality of what we have we
can choose either way but must remember to reverse our interpretation of the
last slope change. Naturally I think we would all agree that the edge is the
one that you don't want a misinterpretation to guide our work. We don't want
to in the center either but a mistake there is easier to erase.  Usually.

Jerry

 






-----Original Message-----
From: atm_free@yahoogroups.com [mailto:atm_free@yahoogroups.com] On Behalf
Of Mel Bartels
 
> Make it look right and wear the highs. You can see exactly where and how
> much (relatively speaking) you need to work and even judge the feathering
> you need to do to blend the zone.


I'm not sure where the confusion is, but depending on RoC, a high can be a
low, and visa versa.  One should consider picking the best relative RoC in
order to achieve the result.  For instance, TDE can be attacked by
concentrating inside the turning zone and it can be attacked by
concentrating on outside the turning zone.


> If you start at the edge and look at the right side of the line as the
> surface the edge looks turned down as it really is. The high now becomes


For instance, the above comment is relative to a particular RoC.  From
another RoC's vantage point, that TDE is actually turned up.


Mel Bartels



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