The Yamato LR-500A is a digital overhead (top-driven) laboratory stirrer tuned for high-torque, low-speed mixing of viscous samples. Its gearless direct-drive design turns a ø10 mm shaft at 34–340 rpm with a peak torque of 1.96 N·m (20 kgf·cm) — the highest-torque, lowest-speed member of the LR-500 pair. A brushless DC motor (no brushes to spark, no brush replacement) and speed-feedback control hold the set rate as viscosity changes mid-stir. Ships as the main body including a stainless shaft and 75 mm propeller; the LR-500AA adds the stand and rod as a complete set.
Key Specifications
| SKU | LR-500A |
| Type | Overhead (top-drive) digital laboratory stirrer — main body |
| Speed range | 34–340 rpm (no load) |
| Max torque | 1.96 N·m (20 kgf·cm) |
| Motor | Brushless DC, 70 W |
| Drive | Gearless direct-drive |
| Shaft diameter | ø10 mm |
| Speed control | Speed feedback control (holds set rate under changing load) |
| Display | Digital 3-digit speed / green-LED torque, 2 steps + overload display |
| Safety | Stops automatically when overloaded |
| Power source | AC 100–125V, 3A, 50/60 Hz |
| Included | Stirring shaft (ø10 x 500 mm), 75 mm 4-blade propeller, clamp |
| Speed twin | LR-500B (100–1000 rpm, 0.98 N·m) |
| Complete set SKU | LR-500AA (adds stand + rod) |
| List price | $2,695.00 |
Application Profile
- High-viscosity mixing — thick solutions, gels, slurries, polymers and resins where torque, not speed, is the limiting factor.
- Overhead stirring of large / open vessels — top-driven stirring reaches volumes and geometries a magnetic stir bar cannot couple to.
- Homogenization and blending — controlled low-speed shear for suspensions and emulsions.
- Continuous / long-run stirring — the maintenance-free brushless motor and feedback control suit extended unattended runs.
Overhead vs magnetic — when to pick the LR-500A: choose an overhead stirrer when the sample is too viscous for a magnetic stir bar to hold coupling, when the vessel is large or non-flat-bottomed, or when defined mechanical shear is required. The LR-500A's high torque and low top speed target the most viscous end of that range; for lower-viscosity work at higher rpm, see the LR-500B.
Design Architecture
The LR-500A uses a gearless direct-drive layout: the ø10 mm shaft is driven directly by a 70 W brushless DC motor, eliminating gear noise and gear wear while delivering the full 1.96 N·m to the sample. The brochure calls out the brushless motor's safety advantage — no brushes means no sparks and no brush replacement — well suited to solvent-exposed benches.
Speed feedback control monitors load and maintains the set rate despite viscosity changes during a stir, a behavior the brochure notes is especially valuable for high-viscosity samples. Load is shown on a green-LED, two-step + overload torque display alongside a 3-digit digital tachometer; when load exceeds the maximum, an overload lamp turns on and the motor stops automatically.
Frequently Asked Questions
What speed range does the LR-500A cover? The LR-500A runs at 34–340 rpm (no load) — the low-speed, high-torque member of the LR-500 pair. For higher-speed work, the LR-500B covers 100–1000 rpm.
What is the maximum torque of the LR-500A? 1.96 N·m (20 kgf·cm), the highest torque in the LR-500 pair, driven directly by a 70 W brushless DC motor through a gearless direct-drive.
Does the LR-500A come with a stand? No. The LR-500A is the main body only — it ships with a stirring shaft (ø10 x 500 mm), a 75 mm 4-blade propeller, and a clamp. A stand and rod are required to mount it; order the LR-500AA complete set to include them, or add a stand/rod set separately.
LR-500A vs LR-500B — which should I choose? Choose the LR-500A for the most viscous samples, where torque (1.96 N·m at 34–340 rpm) is the limiting factor. Choose the LR-500B for lower-viscosity work at higher speed (0.98 N·m at 100–1000 rpm).
Is the LR-500A suitable for viscous samples? Yes. Its high torque, low top speed, and speed-feedback control (which holds the set rate as viscosity changes mid-stir) target thick solutions, gels, slurries, polymers, and resins that a magnetic stir bar cannot couple to.
Ordering & Configuration
In the box: LR-500A main body, stirring shaft (ø10 x 500 mm), 75 mm 4-blade propeller, and clamp. A stand and rod are required to mount the unit and are operational accessories — order the LR-500AA set to include them, or add a stand/rod set (e.g. LR-41-124) separately.
Optional accessories: propellers in various types/sizes, vacuum adapter, extra-long stirring shaft (ø10 x 800 mm), glass stirring shaft.
At $2,695.00 the LR-500A is quoted rather than added directly to cart. Confirm at quote:
- Main body vs complete set — LR-500A (this SKU, needs a stand) vs LR-500AA (with stand + rod).
- Speed/viscosity fit — 34–340 rpm / 1.96 N·m (this SKU) vs LR-500B's 100–1000 rpm / 0.98 N·m.
- Shaft and propeller — the 500 mm shaft and 75 mm propeller against vessel depth; long shaft / alternate propellers as needed.
Warranty: per Yamato standard terms — confirm at quote.
LR-500 family: LR-500A (34–340 rpm, high torque, this product) · LR-500B (100–1000 rpm) · LR-500AA / LR-500BA (complete sets with stand + rod).
