SCALE RULES
Manufacturer: CTT, Inc., 109 Medallion Center, Dallas, TX 75214. Price: Plastic rules in any of ten scales, $2.89 each suggested list.
THE GREAT CLARINETIST, Artie Shaw, once said the problem with a lot of newer music (and, for that matter, any number of other things) has been a lack of precision. Well, it looks as though CTT is here to try to set things right in model railroading.
They have used a clear, engineering plastic similar to what they use in their well-known track planning templates to produce high quality rules in the following popular modeling scales: 1:22.5, 1:24, 1:25, 1:32, 1:35, 1:48, 1:64, 1:72, 1:87, and 1:160.
At first glance you might think only one or two would be appropriate to our hobby but glance again. Sure, if you're scratchbuilding a model from a full-scale prototype you might only need one rule. But what if you want to build a 1:22.5 scale model from a published plan and that plan happens to be in N Scale (1:160) or, as was the case of our D&RGW caboose plan in the last issue, S Scale (1:64)? You'll need a rule for that scale, too.
Each CTT rule is one actual foot long. The clear, flexible plastic offers three advantages. First, you can see what you are measuring through the rule. Second, since the rule flexes, you can measure curved objects. Finally, since the plastic CTT uses for the rule is relatively soft, you are less likely to scratch or nick delicate paint jobs or other plastics.
The rules use one edge for the scale itself, the opposite edge to show actual inches and millimeters, and the center to provide a decimal and metric conversion table. Our samples were very convenient to use.
Compared with an etched, stainless steel rule we used as a standard, CTT's 1:22.5 scale rule appeared to gain about a third of a scale inch after 22 scale feet. The 1:32 scale also gained a very slight amount at the end of the scale just under half a scale inch. The 1:24 scale measured out exactly the same as the metal rule.
Then we checked CTT's HO scale rule (1:87) against a stainless rule. This time the CTT rule checked out two scale inches short at the far end of the scale.
Just for comparison, we compared the two stainless rules. The quarter-inch-to-the-foot and the half-inch-to-the-foot scales also failed to line up exactly, exhibiting a percentage of error the same as that between the metal and plastic rules.
I wish I could tell you what rule is correct. Either way, at least in the case of the larger scales, the variations are slight enough to be negligible for most applications.
Two changes I would like to see, though. First, the CTT rule shows markings only in three inch increments. It then becomes a matter of estimation when you try to measure something down to the inch. A nitpick? Not with regard to a scale rule. Its sole function is precision because some measurements in modelmaking must be exact. Marking every inch would be more appropriate.
The second suggestion is similar. CTT's markings are a little heavy. What you gain in readability you lose in precision. Lighter lines would seem more appropriate.
As a result of this review CTT plans to make changes in future runs of their rules.
For most applications, though, CTT's rules would be adequate as they now come. For some, such as checking the dimensions of actual models where metal could damage the finish, a plastic rule is preferable. And for everyday model building they should do fine.
No hobbyist should be without rules in the common scales. The combination of reasonable prices and high quality should make CTT's rules very popular. RR
