Centre Spur Gear (CS) = 46 Tooth

Clutch Bell (CB) = 15 Tooth

Diff Spur (DS) = 40 Tooth

Diff Pinion (DP) = 10 Tooth

Engine Speed for this Calculation (ES) = 30,000 RPM

Diameter of buggy wheel = 110mm

The abbreviations in brackets above will be used in the calculations below.

Firstly we need to calculate the ratio of the clutch bell / centre gear.

CS / CB = 46 / 15 = 3.07

Ratio = 3.07 : 1

So you need to divide the Engine Speed by the Ratio.

ES / 3.07 = 30,000 / 3.07 = 9,772 RPM (this is the speed of the centre diff and centre drivetrain)

Now we need to calculate the speed of the wheels after the ratio of the diffs.

DS / DP = 40 / 10 = 4 (Ratio is 4 : 1)

9,772 / 4 = 2,443 RPM (this is the speed of the diff outdrives, driveshafts and wheels)

Now we need to calculate the Circumference of the tyres, we know that the diameter is 110cm.

Circumference = Diameter X Π

110mm X 3.14 = 345.4 = 34.5cm = .345 metres = 0.000345 km

The wheel is rotating at 2,443 RPM (revolutions per minute) 60 minutes in an hour so:

2,443 X 60 = 146,580 Revolutions Per Hour

Now to calculate KM/H

146,580 X 0.000345 = 50.57 Km/h

There are other things to take into account such as tyre inflation, but for this exercise 50km/h is what I was expecting to see if an engine is at 30,000 RPM.