So, with that in mind, I had to calculate the difference in size:

**D/W=F**

D = The diameter of the wheel that I am reconfiguring the .sms file for.

W = The wheel diameter that the .sms file originally took into account.

F = Scaling factor

Example:

Intended diameter: 38 Inches, Original Diameter: 40 Inches

38/40 = 0.95

D = The diameter of the wheel that I am reconfiguring the .sms file for.

W = The wheel diameter that the .sms file originally took into account.

F = Scaling factor

Example:

Intended diameter: 38 Inches, Original Diameter: 40 Inches

38/40 = 0.95

Thus, all speed-related parameters in the existing frequency and volume curves have to be multiplied by

**0.95**to get the new values for the new wheel diameter. This also means that steam locomotives would need two or more flange and brake squeal streams, one for the driving wheels and one or more for the idler (non-powered leading/trailing truck/bogie) wheels.

However, when I thought about it more, I realized that even though the wheels of different diameters rotate at different speeds, the treads of the wheels are all moving at the same speed and therefore there is no need for scaling the volume and frequency curve speed variables in such a manner.

However, in the case of steam chuffs, this type of scaling would definitely need to be done for locomotives with different driving wheel diameters to sound "in sync", right?