|Intermission – Crunching Numbers|
So .. got to looking at the Version 1 gate valves .. and took a closer look at the minimums in FUD (Frosted Ultra Detail). Minimum detail thickness is 0.1mm (0.004in) and minimum wall thickness is 0.3mm (.012in). That means I could model bolt heads about 9/16″ across the flats. Heck. I decided to re-work the Version 1.
The original design, as I said, was scaled from a drawing of a gate valve in a book published in 1907. Since that was before standards were in effect I happily modeled away. When I started to re-work that design though, I found that in 1927 they started standardization so I took time to adapt my model to those standards.
The flange is based on – Cast Iron Flanges – ASME/ANSI Class 125 [The maximum allowable pressuretemperature ratings for these flanges range from 50 psi to 200 psi]
Pipe dia is based on nominal pipe size of 6″. 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.
6″ pipe has an outside diameter of 6.625″. The inside dia varies .. but Standard (STD) has a 0.280″ wall thickness. My assumption is that the AcmE pipe, fittings and valves are Standard.
In O scale ..
This is where I varied slightly from prototype. Evergreen tubing #224 is 0.125″ OD / 0.069″ ID. Using this to represent 6″ pipe will mean it would be 5/8″ smaller in OD full size. In O scale this would be 0.013″. I can live with that. If anyone wants to get picky .. I will simply say that the gate valves and piping used were made prior to the 1927 standardization. The important thing for me is the ability to use easily obtainable Evergreen tubing for the pipe.
Cast Iron Flanges – ASME/ANSI Class 125
Pipe Size 6″
Number of Bolt Holes = 8
These measurements posed no problem. I just used the Class 125 flange dimensions and where necessary modify for the Evergreen #224 tubing.
|With those numbers in hand then, I modified the original design and came up with Version 2 (next page)|