VALICALC / MECHANICAL ENGINEERING SUITE / DS08

Timing Belt Drive & Engagement Sheet

Enter pulley teeth and a matching pitch convention. Compare theoretical belt teeth with your physical selection and recalculate the complete pitch-line geometry and engagement.

Verified mathematical models with explicit assumptions. Component capacity and applicability are shown as separate checks.

Labeled example inputs • SI calculations • Project revision 0 • No account or cloud upload

01 / ENGINEERING INPUTS

Define the operating point

Matching pitch geometryPitch geometry only. Equal pitch does not make tooth profiles interchangeable.

Driver pulley teeth

Driven pulley teeth

Preliminary center distance

Selected belt teeth

Actual available belt; nearest theoretical integer is not necessarily a catalog size.

Driver RPM

rpm

Transmitted mechanical power

Operating slack-span tension

Required engaged teeth (0 = unspecified)

Use the selected manufacturer's rating/engagement method.

02 / CALCULATE → SELECT → RECALCULATE

Calculation & checks

Actual center distance

199.36439 mm

Actual pitch/datum length

550 mm

Theoretical length at preliminary center

551.26718 mm

Center adjustment

-0.63561 mm

Actual reduction ratio

Driven RPM

750 rpm

Belt speed

2.5 m/s

Small-pulley wrap

170.84228 deg

Effective pull · total

200 N

Tight tension · per belt/rib

300 N

Slack tension · per belt/rib

100 N

Estimated span load on each shaft

399.0429 N

Theoretical belt teeth

110.25344

Selected belt teeth

110

Driver pitch diameter

31.83099 mm

Driven pitch diameter

63.66198 mm

Small-pulley teeth in mesh · geometric

9.49124

Schematic authored for this worksheet; not a manufacturing drawing. Numerical pitch/datum dimensions and checks control the calculation.

Intermediate values and comparisons - SI units
State	Center (m)	Exact length (m)	Legacy approximate length (m)	Small wrap (rad)
Preliminary	0.2	0.551267	0.551267	2.982269
Actual / recalculated	0.199364	0.55	0.549999	2.98176

Criterion-specific verification

PASSED · Pitch/datum circle geometry
Positive, non-overlapping pitch/datum circles. Outside diameters, take-up and installation clearances remain unverified.
PASSED · Selected-length recalculation
Exact pitch-line residual 1.11e-16 m.
BLOCKED · Tooth load, width and torque capacity
No current applicable product rating dataset. Operating load calculations do not establish allowable capacity.
UNKNOWN · Entered engagement criterion
Required engagement is unspecified; consult product guidance.

Method and calculation trace

Actual dimensions control all downstream results. Ratio uses integer pulley teeth / circular pitch.

Exact tangent geometry solves length and center; the established approximate ValiCalc kernel is retained in the comparison table.

P/v gives total effective pull. 1 equal load-sharing belt/rib path(s); operating slack tension is entered rather than inferred from installation pretension.

Matching profile htd5; pitch 0.005 m. Selected 110 teeth gives 0.55 m pitch length.

Span-force vector estimate excludes weight and transient loads. No overall safety/capacity approval.

Assumptions & scope

Open two-pulley drive with no idler. Enter consistent actual datum/pitch diameters and lengths. Outside diameters, alignment and take-up travel still need checking.

Tensions are operating values; equal sharing across entered belts/ribs is an assumption. Shaft span-force estimate excludes pulley weight, bearing reactions and transient loading.

Capacity, fatigue, installation pretension and allowable speed require current product-specific evidence. No catalog dimensions or ratings are inferred.

HTD 3M/5M pitch conventions are supported by SDP/SI product documentation; catalog belt availability, tooth shape, width, torque capacity and tooth-jump resistance are not validated.

Teeth in mesh is fractional geometric contact, not a count of fully load-bearing teeth. Required engagement is user supplied. No automatic tooth-width or allowable load selection.

Worked example

20/40 teeth at 5 mm pitch gives pitch diameters 31.831/63.662 mm and 2:1 reduction. Selecting a 110-tooth belt fixes pitch length at 550 mm; the physical center and engagement are solved again.

Calculation methods and sources

d pitch = zp/π; L pitch = N belt p; teeth in mesh = z small θ small/(2π)

Circular pulley pitch convention for selected matching profile. Engagement is fractional geometric contact; entered required engagement is a separate user criterion.

SDP/SI timing profiles and technical section 22

L = 2√(C²−δ²) + π(D+d)/2 + 2δ asin(δ/C); δ=|D−d|/2

Exact ideal tangent pitch-line geometry. A bounded bisection solves selected pitch length → physical center distance. No tooth deformation or installation tension correction.

Independent tangent geometry; SDP/SI equation 22-11

ΔT = P/v; T tight = T slack + ΔT; R = √((Tt+Ts)²cos²α + (Tt−Ts)²sin²α)

α = asin(|D−d|/(2C)). Steady span-force estimate using entered slack tension or operating tension ratio. Equal belt/rib sharing is an explicit assumption; no rated belt count is inferred.

Gates Heavy Duty V-Belt Drive Design Manual, tension ratio D18; independent vector sum

Textbook references identify the method context. Historical numerical catalog, material and service-factor tables have not been copied or treated as current product ratings.

Related calculators and references

Existing component-selection Jobs → · All mechanical worksheets →

Common questions

Does this approve a real component?

No. The worksheet separates mathematical results from criterion-specific checks. Actual motor, belt, sprocket and chain capacity need applicable current manufacturer data and installation review.

What changes after choosing a physical size?

The worksheet recalculates the outputs and geometry from the entered actual dimensions or discrete tooth/link count. Dependent checks are reevaluated; previously saved results are not restored as approvals.