Strain-wave (harmonic) gear
Laifual Drive FSG (FS high-torque) strain-wave (harmonic) gear
High-torque cup-type strain-wave gear, sizes 14 to 40 and ratios 50–160, rated up to 382 Nm with 841 Nm start/stop peak and 1,510 Nm momentary (size 40), backlash 20 arcsec or less; listed as the CSG-equivalent type.
Key specifications
| Rated torque | 7–382 Nm |
|---|---|
| Peak torque (max) | 841 Nm |
| Ratio | 50–160:1 |
| Backlash (max) | 0.33 arcmin |
| Sizes | 14, 17, 20, 25, 32, 40 |
| Rated life | 15,000 h |
| Momentary torque max | 1,510 |
| Max input | 8,500 |
| Backlash | ≤20 arcsec |
| Structure | cup-type flexspline |
Summarised in our own words from Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952)'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Notes on this data
Size 14 row carries an FSS label on the page; confirm. Life 10,000 h at ratio 50, 15,000 h at 80 and above.
Specify Motion is not affiliated with Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952). Laifual Drive and FSG (FS high-torque) are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a Laifual Drive part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These 3 series from our supply network are the closest match on published figures.
Cup-type strain-wave gear component sets for building your own joint; the LCSG high-torque version lifts capacity by around 30% over the standard LCS.
| Published maximum | FSG (FS high-torque) | LCS / LCSG |
|---|---|---|
| Rated torque | 382 Nm | — |
| Peak torque | 841 Nm | — |
| Ratio (max) | 160:1 | 500:1 meets or exceeds |
| Backlash (lower is better) | 0.33 arcmin | — |
Hollow-shaft strain-wave gear units with a large central bore for routing cables and services; LHSG is the high-torque version (over 30% more torque).
| Published maximum | FSG (FS high-torque) | LHS / LHSG |
|---|---|---|
| Rated torque | 382 Nm | — |
| Peak torque | 841 Nm | — |
| Ratio (max) | 160:1 | 500:1 meets or exceeds |
| Backlash (lower is better) | 0.33 arcmin | — |
Ultra-flat cup-type strain-wave gear with a very short axial length, light weight and high stiffness for its size.
| Published maximum | FSG (FS high-torque) | LCD |
|---|---|---|
| Rated torque | 382 Nm | — |
| Peak torque | 841 Nm | — |
| Ratio (max) | 160:1 | 500:1 meets or exceeds |
| Backlash (lower is better) | 0.33 arcmin | — |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What a strain-wave (harmonic) gear is
A strain-wave gear, often called a harmonic gear, reduces speed using three parts: an elliptical wave generator, a thin flexible toothed cup or hat called the flexspline, and a rigid circular spline with internal teeth. The wave generator deforms the flexspline so its teeth engage the circular spline at two points. Because the flexspline has typically two fewer teeth, each input turn advances it slightly, giving ratios of about 30:1 to 160:1 in one stage, with near-zero backlash.
When engineers choose a strain-wave (harmonic) gear
Choose a strain-wave gear for compact, lightweight, high-ratio reduction with near-zero backlash, such as robot joints, cobots, medical robots, aerospace and optics. Hollow versions allow cables through the centre. The trade-offs are torsional stiffness at low load, which is lower than some alternatives, limited input speed and the risk of tooth ratcheting under overload. For shock loads and heavy base joints, cycloidal reducers are often preferred.
How to specify the Laifual Drive FSG (FS high-torque)
Send these with your enquiry and an engineer can confirm the right FSG (FS high-torque) variant or an equivalent:
- Ratio (:1)
- Rated, peak and momentary torque (Nm)
- Input speed limits (rpm)
- Torsional stiffness (Nm/arcmin)
- Hysteresis and accuracy (arcmin)
- Component set or housed unit
- Hollow shaft diameter and output bearing loads
Common mistakes to avoid
- Exceeding momentary torque and ratcheting the teeth
- Ignoring low-load stiffness in precision control
- Poor housing tolerances for component sets
- Using the wrong lubricant or quantity
Laifual Drive FSG (FS high-torque): frequently asked questions
What is the Laifual Drive FSG (FS high-torque)?
High-torque cup-type strain-wave gear, sizes 14 to 40 and ratios 50–160, rated up to 382 Nm with 841 Nm start/stop peak and 1,510 Nm momentary (size 40), backlash 20 arcsec or less; listed as the CSG-equivalent type. Published series figures include rated torque 7 Nm, rated torque 382 Nm, peak torque 841 Nm, ratio 50:1. It is made by Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952); Specify Motion can help source it or propose an equivalent.
Who makes the Laifual Drive FSG (FS high-torque)?
The Laifual Drive FSG (FS high-torque) is made by Laifual Drive (Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952)) and is listed here for engineers comparing options. Specify Motion is not affiliated with Zhejiang Laifual Harmonic Drive Co., Ltd. (HKEX: 03952); brand names are used only to identify the product.
What is the rated torque of the Laifual Drive FSG (FS high-torque)?
The published series minimum rated torque is 7 Nm. Individual models and sizes in the FSG (FS high-torque) range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the Laifual Drive FSG (FS high-torque)?
Yes. On published figures, LeaderDrive LCS / LCSG and LeaderDrive LHS / LHSG are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
Why do strain-wave gears have near-zero backlash?
The flexspline teeth are preloaded into the circular spline teeth by the elliptical wave generator, and many teeth engage at once. There is no clearance between teeth at the engagement zones, so backlash is close to zero. Lost motion comes mainly from elastic deflection.
What is the difference between a strain-wave component set and a housed unit?
A component set is the wave generator, flexspline and circular spline, which the machine builder mounts in its own housing with bearings. A housed unit adds a housing, output bearing and seals. Component sets save weight and space; housed units are easier to integrate.
Further reading: Harmonic vs planetary vs cycloidal · How to select a gearbox · Gearboxes and harmonic drives
Other strain-wave (harmonic) gear series
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