Modeling Pipe

History
The following was taken from “Nominal Pipe Size” (Wikipedia)

In March 1927, the American Standards Association authorized a committee to standardize the dimensions of wrought steel and wrought iron pipe and tubing. At that time only a small selection of wall thicknesses were in use: standard weight (STD), extra-strong (XS), and double extra-strong (XXS), based on the iron pipe size (IPS) system of the day. However these three sizes did not fit all applications. The committee surveyed the industry and created a system of schedule numbers that designated wall thicknesses based on smaller steps between sizes, although IPS and NPS numbers remain equivalent.

The original intent was that each schedule would relate to a given pressure rating, however the numbers deviated so far from wall thicknesses in common use that this original intent could not be accomplished. Also, in 1939, it was hoped that the designations of STD, XS, and XXS would be phased out by schedule numbers, however those original terms are still in common use today (although sometimes referred to as standard, extra-heavy (XH), and double extra-heavy (XXH), respectively). Since the original schedules were created, there have been many revisions and additions to the tables of pipe sizes based on industry use and on standards from API, ASTM, and others.

If you have ever done any plumbing then you recognize the term – Schedule – as PVC pipe can be bought in Schedule 40 and Schedule 80 (at Lowes for example). Interestingly, we can take a look at 1 in. (Nominal) PVC/CPVC pipe. The O.D. is 1.315 in. with the I.D. different. For Schedule 40 the I.D. is 1.049 in. with a 0.133 wall thickness while the Schedule 80 is 0.957 I.D. with the walls 0.179 in. thick.

The important thing to take from this (as far as modeling is concerned) is that the 1.315 O.D. .. this is the NPS (Nominal Pipe Size) and is the same whether we are talking about a plastic PVC pipe or one made of cast iron.

Materials etc.
supplies_1200Simply .. solid copper wire with insulation. I rummaged around a bit and found various sizes at hand – as shown in the photo to the left .. and other things needed.

So .. what does this mean for modeling? Just that we need to pick the appropriate wire for the scale we are modeling. Let’s look at the four wire sizes that I found rummaging around. Remember .. what you can do is figure what size you need for YOUR modeling and then purchase that size. Easy enough. The following is from the American Wire Gauge (AWG) and Nominal Pipe Size (NPS) charts on Wikipedia. With this in hand we can determine what pipe we can create in various scales.

  • 12-2 NM w/ground – this is the yellow jacketed wire and is used for 20-amp house circuits (such as for your microwave). The conductor is #12 AWG. The chart shows this is 0.0808 in. dia.
  • 14-2 NM w/ground – this is the wire jacketed wire and is used for 15-amp house circuits (lighting and ‘common’ outlets). The conductor is #14 AWG. The chart shows this is 0.0641 in. dia.
  • #18-2 Bell Wire – this is the twisted red and white wire and is used for low voltage circuits .. door bells for example (as the name suggests). #18 AWG is 0.0403 in. dia.
  • #30 Wrapping Wire – this is the spool of blue wire. It comes in various colors. It is used in a method of constructing electronic circuit boards. I purchased my spool at Radio Shack. The #30 AWG has a 0.010 in. dia.
  • Razor blade for cutting the insulation, a hammer with a plastic/rubber face to straighten the wire, CA (cyanoacrylate adhesive – aka – ‘Super Glue’), a CA Applicatormake your own via this article. I don’t show diagonal pliers to cut the wire .. well excuse me if I reply to that – DUH!
Size as relates to scales
Okie Dokie. What does that mean for modeling then? I’ll do some calculation and stick the numbers into a chart for O, HO and N (I’m nice like that!) – Example: #18 AWG (Bell Wire) is 0.0403 dia. In O scale this equals 1.9344 in. 1-1/2 in. pipe as an O.D. of 1.9 in.

Wire

O.D.

Scales

   

O (1:48)

HO (1:87)

N (1:160)

   

Exact
DIA

Nearest
OD

NPS

Exact
DIA

Nearest
OD

NPS

Exact
DIA

Nearest
OD

NPS

#12/2 NM 0.0808 3.8784 3.500/4.000 3/3.5 7.0296 6.625/7.625 6/7 12.928 12.75/14 12/14
#14/2 NM 0.0641 3.0768 2.875 2.5 5.767 5.563 5 10.256 10.75 10
#18/2 Bell Wire 0.0403 1.9344 1.9 1.5 3.5061 3.5 3 6.448 6.625 6
#30 Wrapping Wire 0.010 .48 .405/.540 .125/.25 .87 .84 .5 1.6 1.66 1.25
Wire and Doughnuts
wireandinsu_1200I used the plastic face hammer to straighten the wire. For the ebow simply make a nice right angle bend. The insulation for the 12 and 14 AWG wires are covered with a clear plastic film that needs to be removed. With that done, I used the single-edge razor blade to slice off thin doughnuts from the insulation. Since I can’t reliably make even slices, I made a bunch and then chose the best ones.

Leave a Reply

Your email address will not be published. Required fields are marked *

I'm not a spammer This plugin created by Alexei91

Heads up! You are attempting to upload an invalid image. If saved, this image will not display with your comment.