Jackshaft stage combinations
Compare second-stage reductions while keeping the first chain stage fixed. Change an input to explore the relationship.
Input parameters
Set your values below. The table updates automatically.
Comparison results
Two fixed, non-slipping stages. A free idler does not create an additional reduction.
| Second-stage reduction | Overall reduction | Axle RPM |
|---|---|---|
| 2.00 | 3.00 | 1,200 |
| 3.00 | 4.50 | 800 |
| 4.00 | 6.00 | 600 |
| 5.00 | 7.50 | 480 |
| 6.00 | 9.00 | 400 |
| 7.00 | 10.50 | 342.86 |
| 8.00 | 12.00 | 300 |
How this table is calculated
overall = first-stage reduction × second-stage reductionRows use the same assumptions while varying the value in the first column. Input-unit controls change the units used to enter values; column headers always state the output units.
How to read this comparison
The first stage remains fixed while the second-stage reduction varies by row. Multiply the two stages for total reduction, then divide input RPM by that product to find axle RPM.
A worked example with the initial inputs
At the initial 1.5:1 first stage and 3,600 input rpm, the 5:1 second-stage row gives 7.5:1 overall. Axle speed is 3,600/7.5 = 480 rpm; the jackshaft itself turns at 2,400 rpm.
The live table changes when you edit its controls.
Use the interactive calculator to explore more scenarios, units and relevant inputs.
Frequently asked questions
Does a routing idler count as another reduction?
No. These rows represent compound stages, with an input and output sprocket fixed to an intermediate shaft. A free idler on one chain does not multiply the tooth-count reduction.
Why do input controls and column headers show different units?
The unit toggle changes how you enter dimensional inputs. Each output column keeps its stated unit so you can compare values consistently. Read the column header before copying a result.
Understand the method in more detail
How to read a go-kart gear ratio chartA gearing chart compares front and rear sprocket combinations at a common operating point. Read the row and column labels before interpreting either reduction or speed.Go-kart jackshaft gearing explainedFor a compound jackshaft, multiply the engine-to-jackshaft reduction by the jackshaft-to-axle reduction. Two sprockets fixed to one shaft share RPM.Source and assumptions
Angular speed and tangential speed. Gear reductions follow tooth engagement and conservation of rotation count.
OpenStax — University Physics: rotation with constant angular accelerationRead the calculation methodology for model scope, unit conventions and review status.