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Belt Drive Simulator

v1

Exact ideal timing-belt ratios and pitch geometry for the Parallax drive—and any three-stage variation.

Parallax presetGT2 · 2 mm pitch · upper + lower outputs
Accuracy boundary

Rotation ratios, elapsed angles, and ideal open-belt pitch geometry are calculated exactly from the entered values. This does not model torque, acceleration, friction, elasticity, shaft binding, vibration, tension, or tooth skipping.

Belt length does not change RPM. It changes center distance, wrap, and required idler take-up.

Playback
Exact pitch geometry

Pulley + belt view

Pitch circles and natural center distances share one scale.

20T driver20T driven60 mm natural centerFast12 RPM20T driver40T driven59.66 mm natural centerMedium6 RPM20T driver60T driven58.61 mm natural centerSlow4 RPM
Synchronized face view

Six output discs

Disc diameters are adjustable placeholders until measured.

UPPERLOWERUpper Fast discLower Fast discFast · Ø120 mm*Upper Medium discLower Medium discMedium · Ø180 mm*Upper Slow discLower Slow discSlow · Ø240 mm** placeholder visual diameters · lower row shown from the same face
Calculated from your inputs

Stage readout

Negative RPM and angle indicate the selected reverse direction.

Fast

12 RPM
Speed ratio
1×
Period
5 s
Elapsed angle
0°
Revolutions
0
Belt-line speed
8 mm/s
Natural center
60 mm
Small-pulley wrap
180°
Engaged teeth
10
Shared-center surplus
2.777 mm

Medium

6 RPM
Speed ratio
0.5×
Period
10 s
Elapsed angle
0°
Revolutions
0
Belt-line speed
8 mm/s
Natural center
59.66 mm
Small-pulley wrap
167.75°
Engaged teeth
9.32
Shared-center surplus
2.085 mm

Slow

4 RPM
Speed ratio
0.3333×
Period
15 s
Elapsed angle
0°
Revolutions
0
Belt-line speed
8 mm/s
Natural center
58.612 mm
Small-pulley wrap
154.91°
Engaged teeth
8.61
Shared-center surplus
0 mm