Layout Concepts DGC BB145 Back to back Gauge OO/HO

"We too were often frustrated by wheels that were either too close together or too far apart, resulting in awful on-track performance and frequent derailments. At that time, there were a few cottage industries that claimed to offer accurate gauges, so we bought several of them, grabbed my vernier callipers and… were horrified!

Apart from the fact that they simply looked too rough, one was a full 15 thousandths of an inch out—totally inaccurate. Others were around 8 thou out. That is totally unacceptable. So, we reached out to contacts who work in metals to specs for the highest manufacturers on the planet. We asked: can you design us a gauge that’s easy to use, super accurate, and made of high-quality brass so it will last a lifetime?

At one point, we even asked if the back-to-back gauge could be polished to give it a really premium finish. The answer came back, firmly: no. Even polishing these devices, he explained, can be enough to take them out of tolerance and compromise their accuracy. And anyway, he said, the precision of his lathe work is so high that it would appear polished, even though it isn’t.

This wasn’t just any machinist either, but a one-man-band expert who produces components for some of the finest watches in the world—where tolerances are everything.

The result? A super-accurate, high-quality gauge, engineered with absolute precision and built to last a lifetime."

Why does this matter?

It can be perplexing when a brand new loco derails on its "victory lap." 99.9% of the time, the wheels are simply placed on the axles too far apart or too close together. This causes the rolling stock to "hunt," creating pressure that makes wheels catch on every tiny track imperfection or hit the tips of turnout frogs.

Do It Yourself: A Simple Guide

A good quality “Back-to-Back” gauge takes away all the need to worry about measuring. Here is how to fix it in minutes:

1. The Check

Use the gauge to check every wheelset. It should slide smoothly between the backs of the wheels with NO end play. If it doesn't fit, or there is a gap, it needs adjusting.

2. Identify the Insulation

Remove the wheelset. One end of the axle is usually "metal-to-metal," while the other has an insulation collar. It is this insulated end we adjust.

3. Adjusting: The Push/Pull & Twist

• Too Close? Grip the metal-to-metal side firmly and gently "PULL and Twist" the insulated wheel.
• Too Far? Grip the metal-to-metal side and gently "PUSH and Twist" the insulated wheel.

Do it a bit at a time and test with your gauge until the fit is perfect.

Top Tip: If the wheel seems super-tight, pop the wheelset into warm water for a minute. The warmth softens the plastic slightly, making it much easier to move.

Top Tip 2: Make this part of your regular maintenance. Every time you have a loco upside down for cleaning, double-check it with the gauge. Wheels can move gradually over time!

Caution: Do not use force or tap wheels with a hammer. Axles must stay perfectly straight and wheels must stay at 90 degrees.