Scaling Pipe and Pipe Fittings

A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids.

I used that definition of a pipe for my Category page and is as good as any I suppose. Like with many of my models I am concerned with something that looks right, is scaled as best I can within the limits of my own knowledge and simply how well they can be printed.

MicroMimesis Pipe Fittings – Concept

Pipe: In our modeling there is a lot of opportunity to use pipe in one form or another. We have pipe that we are familiar with such as metal and PVC water pipes, PVC sewer pipe, larger welded and flanged industrial pipe

Concept: The basic concept is that I can create fittings such as elbows, tees etc. which can then be fitted to lengths of readily available things such as rods and tubing which represents the pipe in scale. The important thing here is to use materials for our pipe that is readily available and standard dimensions.

Materials: The following come readily to mind …

  • Wire:What wire you use depends on the scale you are modeling in and what size pipe you are trying to replicate in that scale. We are talking about solid wire here. If you look at “Tables of AWG wire sizes” you can easily find a wire diameter close to what you need.

    Hardware Store: NB Cable – “Romex” being a popular brand name. This is available at any hardware store. 14-gauge (15-amp circuits) – White Sheathing and 12-gauge (20-amp circuits) – Yellow Sheathing are common. Since the wire comes in rolls you need to straighten lengths for modeling but that is easy enough as it is copper wire..
    Referring back to the AWG wire sizes we have:
    14-gauge : 0.0641″/1.628 mm – In O scale (1:48) this would be 3″ pipe. In HO this would be 5.6″ pipe.
    12-gauge : 0.0808 “/.053 mm – in O scale (1:48) this would be 3.88″ pipe. In HO this would be 7” pipe.
    … at first thought you may think … “Well .. really! .. 5.6″ pipe?” .. to which I would reply … “Yes. For one thing we are not for the most part engineers and secondly .. this is a model .. and … the Nominal OD for 5″ pipe is 5.563.” The same thing with the 12-gauge. “3.88” pipe?” .. 3″ pipe has a Nominal OD of 3.5″
    (Nominal Pipe Sizes)
    K&S: We can also get wire from K&S. They have Brass Rod ranging from 0.02″ all the way up to .375″ and is straight to boot.
  • Tubing: One important thing about tubing is not only is the OD important but so is the ID. Many of my fittings have a stud that fits the ID of the tubing which means … again .. that the tubing used have a standard dimension.

    K&S: K&S mentioned above has lots of brass tubing ranging from 0.032″ OD/0.020 ID all the way to 1.0625″ OD/1″ ID.
    Evergreen Scale Models: This is my “Go To” source for scale “pipe”. Size ranges from #223 0.093″ OD/0.039″ ID all the way up to #236 0.500″ OD/0.444″ ID.

With the source for the “pipe” identified we can then look at the fittings to convert it into scale pipe.

Except for when working with really small “pipe” I like to use Evergreen tubing. Let’s look at two sizes as an example (and these are the size Evergreen tubing that I have created fittings for)

  • #224 – 0.093″/3,2 mm OD – 0.039″/1,8 mm ID
    • O scale (1:48): 6″ in 1:48 is 0.125″diameter – the OD of #224 tubing. 6′ pipe has a Nominal OD of 6.625″. in 1:48 #224 tubing is 0.625/48 or 0.013″ undersized. For me – this is “Good Nuff” to represent 6″ pipe.
    • O scale (1:43.5): In 1:43.5 #224 tubing’s 0.125″ diameter is 5.4375″ diameter. The Nominal diameter for 5″ pipe is 5.563″ – the #224 tubing in this instance is 1/8″ undersized full scale. Again .. “Good Nuff“.
    • HO scale (1:87.1): In 1:87.1 #224 tubing’s 0.125″ diameter is 10.8875″ diameter. The Nominal diameter for 10″ pipe is 10.75″ – the #224 tubing in this instance is only just over 1/4″ oversize. Again .. “Good Nuff“.
  • #228 – 0.250″/6,3 mm OD – 0.194″/4,9 mm ID
    • O scale (1:48): 12″ in 1:48 is 0.250″ – the diameter of #228 tubing. 12″ pipe has a Nominal OD of 12.75″. In 1:48 #228 tubing is 0.75″ undersized. Scaled down that is 0.016″ .. and might ‘trigger’ someone with OCPD .. it is still “Good Nuff
    • O scale (1:43.5): 0.250″ in 1:43.5 is 10.875″. Nominal 10″ pipe diameter is 10.75″ so we are talking about 1/8″ over the actual pipe size. MORE .. than “Good Nuff“.
    • HO scale (1:87.1): Finally HO. In 1:87.1 this 0.250″ diameter is 21.775″ diameter. Nominal diameter for 22″ pipe is .. wait for it .. 22″. Nominal and actual pipe diameter is the same from 14″ up. Therefore, #228 tubing is about 3/4″ undersized. I give this a final “Good Nuff“.

I have gone over just the two Evergreen tube sizes … #224 and #228 in EXTENSIVE DETAIL to make a point and lay it out as understandable as I can make it. This is NOT rocket science people .. just using some links for pipe sizes in the real world, sizes of Evergreen tubing and a calculator.

For other scales and other sizes of Evergreen tubing simply use the links and a calculator.

A couple of final points:

Flanges and Scale: I did a pretty in-depth look at Pipe Sizing, Flanges, US vs British dimensions etc. on my Deep River Railroad website where I cover all of the above and more. There are two systems of flanged pipe that I looked at – the US ASME B16.5 flange dimensions and British Standard Pipe Flanges. The best I can figure is that the British pipe dimensions are legacy .. current standards allow bolting up to the US pipe (and the rest of the world) there is more .. a great bit of “more” technical “stuff” which I chose to ignore .. this is for modeling after all.

If you take anything away form all of this .. then it is that as pipe size increases or decreases so does the flange. As the flange increases or decreases the number of bolts for the flange also change. The British 10″ elbows and flanges are indistinguishable from the US 12″ elbows. They are after all both made to fit Evergreen #228 tubing. The differences in flange diameter and thickens is so small you need calipers to distinguish between them. The major difference thought is simply that the 1:43.5 elbows has 8 bolts (10″ pipe) and the US 1:48 elbows have 12 bolts (12″ pipel).

This is why a flanged elbow designed for Evergreen #228 tubing but one scale will physically fit but not work visually in another scale is the number of bolts on the flange yousee.

Nominal Evergreen Tubing Dimensions: Just because you are told that Evergreen #224 tubing has an ID of 0.039″/1,8 mm ID or that Evergreen #228 has a 0.194″/4,9 mm ID .. accepting that as ‘Gospel” can lead to breaking the fittings.

I have no real idea how Evergreen tubing is manufactured but I can “suppose” (close cousin to “assume”) that they are made much the same way that noodles are made .. the hot plastic is extruded through a die. What that means is that .. the stated ID is nominal. It MAY be correct ..or it may be undersized. My suggestion is to find a drill bit that is equal to or larger than the nominal tubing ID and ream out the end of the tube where the stud on the fitting will go. This connection is only to help align the tubing and fitting while the cement dries.