Modeling Pipe in Scale

A Catch Basin and a pipe

I was working on a Catch Basin .. I am talking about a concrete box that is normally hidden from sight. This one specifically which receives water from a Curb Inlet and routs the water to the Storm Drain system. We see that this example has a 31″ knockout on one side for said pipe. This caused me to pause while I did some research on concrete pipe.

Since the plan was to model this in 1:48, questions about what to use to replicate the pipe, why 31″, what is the diameter of the pipe (chamfered edge of the hole) and so on.

Concrete Pipe

A search brought me to an Oldcastle page showing concrete pipe dimensions. It shows pipe from 16″ to 86″ diameter with the ID, From this I see there is a 30″ pipe (this is the ID .. how the pipe is referred to) which has a 37″ OD. The catch basin knockout is an inch larger at 31″ and the chamfer matches the 37″ OD chamfered end. Here I have copied the information over to a table so I could arrange it like I wanted. For me the important columns are column 1 and 2. The others I included just for fun showing pipe lengths (column 3) which a someone modeling may find useful. Finally I found the average wall thickness (to the pipe OD) which will be useful for my 3D modeling –

Concrete Pipe

Evergreen Tubing

Evergreen tubing is my “go to” for 1/2″ and under. It is readily available, Here we have the Part No  in column one and the OD of the tube in column 2. The size in various scales is shown. Example under 1:48, Evergreen No. 228 (1/4″ tubing) is 12 inches in diameter.

Evergreen Tubing

PVC/CPVC Pipe

This is readily available at a Lowes or other hardware store. You may find it in Schedule 40 or 80 – the OD remains the same but the Schedule 80 has thicker walls. Either PVC or CPVC can be used as the only difference is heat resistance. Given a choice go with the PVC as it is cheaper. Note that the OD of the tube is not the same as the ‘nominal’ size. Example: 1/2″ PVC pipe is actually .84″ diameter. This is because originally (we are talking ‘back in the day’) the ‘nominal’ pie size of 1/2″ was the ID of the pipe and the wall thickness gave the larger actual OD. This was in iron or steel originally but as changes in materials and pressure requirements tit meant that while the OD of 1/2″ pipe remained that .84 inches the ID changed.

I highlighted the pipe that falls within the 16-86 inch range of the concrete pipe (more or less)

PVC Pipe

What to use?

Looing back to the Catch Basin where there was a 31″ knockout with a chamfer .. we can now find something “good nuff” to replicate this in the scale we are modeling in.

• I first look to the “Concrete Pipe” table. That 31″ knockout is for the ID of the pipe connecting with the chamfer to fit the end of the pipe. I run down the second column until I find a pipe with a 30″ diameter ID. Makes sense the hole in the Catch Basin is slightly larger so it doesn’t block any of the flow. Look to the left and the OD of the pipe is 37 inches.
• I jump directly to the PVC Pipe table as I know the largest tubing in the Evergreen line is only 1/2″ but we are going to need something around 3/4″ in 1:48, the scale I model in
• I look down the 1:48 column and find 40.32 inches. Slightly over the 37″ but “good nuff” for modeling. Look to the left and we find that we need 1/2″ PVC pipe to replicate that 37″ Concrete Pipe