On Wed, 30 Oct 2013 13:32:45 -0700, Oren wrote:
We talked about how springs use colors, etc., for reasons. When the
spring is tightened, the marks on the coils will off-set ...

This "color" is something else altogether.
There are 5 uses of paint on a spring (only one of which is useful):

1. Color used to denote wire gauge (we covered this in the prior post).
2. Color (usually red) used to denote dangerous bolts (covered prior).
3. Color (usually red) used to denote the wind direction (covered prior).
4. Color (usually a line of #1 above) used to count turns.
5. Color (usually a line added by the homeowner) used to indicate slip.

Since we covered the first three uses of color in the prior post, let's
explain the next two (of which, only the last one is useful).

Here is a picture of the new (larger wire gauge) springs:
http://farm8.staticflickr.com/7442/1...e0f14be0_b.jpg

Here is a picture of the old (smaller wire gauge) springs:
http://farm8.staticflickr.com/7329/1...e2064872_o.gif

Here is a picture of my spring that I put in a year ago on another door:
http://farm6.staticflickr.com/5489/1...29d6a11e_o.gif

It's hard to see in the picture, but last year's spring has both #4 and #5
in my list painted in white paint on it. $4 was painted *before* the spring
was installed (it shows up as 7 spirals); while #5 was painted *after* the
spring was mounted (it shows up as a straight line but it's not really visible
in the photo).

Regarding #4:

It's folly to use the spiral lines to count turns for a whole bunch of reasons,
but, mainly because the better way to count turns is to count from 28 to 30
quarter turns (for a 7-foot door). You couldn't possibly make a full turn
with the winding bars, so, counting quarter turns makes practical sense
(as explained by Dan Musick in all his videos) since that's what you do.

The *reason* for 28 to 30 quarter turns isn't as obvious, but, it's simply
because a drum is "about" a foot in circumference (it's actually about 13
inches, and the diameter actually changes as the wire winds, but, let's not
get picky right now).

So, every full turn is a foot of cable, and since the door is 7 feet tall,
it would take 7 full turns to raise the door the full 7 feet. Since you
can't do full turns, that's 7x4 quarter turns, or 28 quarter turns.

Since you want a slight bit of tension on the door, that would be slightly
more than 28 quarter turns, and, since the drum isn't exactly one foot, nor
do you raise the door exactly 7 feet, you really need an extra quarter turn
or two, so, the typical number of quarter turns is greater than 28, but,
depending on balance, might be 29 or 30.

Regarding #5:
The *only* color on the springs which, in the end, is useful, is a line
painted straight on a spring *after* it has been mounted. Why? Because
if that line isn't straight, then the spring has slipped. This generally
happens over a long period of time, say, 5 years later, as the spring
steel fatigues.

Of course, another way to know whether a spring is fatiguing is simply
to measure (with your hands) the sprung weight of the door at the midpoint,
but, for the price of painting a line, it's still an ok thing to visualize
the slippage, over time, in the spring with that white line.

In summary, there are five uses of color in a torsion spring, and, only one
of them has even the slightest amount of value.