- Thread starter pntdxtr
- Start date

Weigh it.

I have also stopped by the supply house and asked them to measure it for me.

I have also stopped by the supply house and asked them to measure it for me.

You can always pull them off the reels and see how log they then just roll them back up again ,or have your helper roll them up..:lol:Please help , i am trying to figure out some leftover wire on reels i have on the jobsite . The reels are #6 thhn and want to calculate the length to see if i need to order more ..Thanks

You may not even need to get too deep into the math.Weigh a new full reel of the same size and manufacturer, then weigh the used reel. Find the weight to feet ratio and do the math.

A new 500' reel of #8 weighs 31 pounds. So if my partial reel more than fifteen pounds I know I have at least 200' available. That may be all the information I need.

$2200 to $3200 for a Micro ohm meter makes the other options pretty reasonable.:jawdrop:Ohm it out, then divide by .00051 :roll:

Weight or measure once and count the wraps. If we aren't sure, it is cheaper to have new rolls on hand than to come up short on a long pull.

You haven't kept track of what you have pulled in so far?

Yea, I was just throwing that out there for a chuckle. Didn't think it would even be considered...$2200 to $3200 for a Micro ohm meter makes the other options pretty reasonable.:jawdrop:

Weight or measure once and count the wraps. If we aren't sure, it is cheaper to have new rolls on hand than to come up short on a long pull.

You haven't kept track of what you have pulled in so far?

Seriously, I have taken my reels to the supply house and had them spool it off through their counter for the lengths. Usually less than 100 feet though.

Of course, I bought these same reels from them, and they know it.

t=radius of the wire and its insulation

Ri = inner radius of the spool

Ro = outer radius of the spool

First assume that the flanges of the spool are so close together that the wire will look like the way sailors coil rope on the deck of a ship(flat coil). To make such a coil, one would start at the core of the spool (the inner radius Ri) and and make n turns to get to the outer edge of the flange (the outer radius, Ro). Then we can find the number of turns to be

n=(Ro-Ri)/t

The first time around the core requires 2pi(Ri+t) amount of wire, since the radius of the second turn has been increased by t, the second turn will require 2pi(Ro+2t) amount of wire. The last time around will require 2pi(Ri + nt) wire. If all of the turns are added, the formula I get is

Wire on one flat coil = 2n(pi)(Ri + n(n+1)t)

To complete the calculation, you must know how many flat coils are on the spool. If D is the distance between flanges then

m=D/t where m is the number of flat coils.

Therefore, the total length is

Total = m(wire on one flat coil).

Of course, wire does not wrap on a spool exactly like a bunch of flat coils. The second layer on the spool will fall in the space between coils of the first layer, think of three tangent circles. For this and some other reasons, the formula is only an approximation. However, all of the information required can be obtained with a ruler or tape measure.

In applied Murphology, Murphy's Constant is 0.97.

That makes the math simple. You just multiply the amount of spooled material you need by 0.97 and that is how much will be on the spool. So if you need 100 feet, there will only be 97 on the spool.

So Handy10s very fine formula times K8s fudge factor & you got the answer...to short again.

And now the crew is standing around waiting to pull the wire back out and start over. Meanwhile, you could have spent the same amount of money on a meter and had something to show for it....So Handy10s very fine formula times K8s fudge factor & you got the answer...to short again.

Just saying....it doesn't take too many man hours for one of these meters to pay for itself. We used to count wraps, but it doesn't make sense financially, when you figure how much time you spend doing it in say, a year or so. Not to mention a lot more of our spools got used up because we knew what we had on them. When we used to rough guess how much was on it, we'd get scared we'd be short and order new spools instead. You can imagine how many leftover spools end up in inventory this way....we've really trimmed back now using a meter.