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).
