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Nie, dziękuję Przekieruj mnie tamrazlika me motorjrm rs 987 in rs985
Key points
• Diameter: ≈ 49 mm (RS-987) vs ≈ 45 mm (RS-985)
• Rated voltage range: 24–48 V vs 12–24 V
• Typical continuous power: 300–800 W vs 150–350 W
• Stall current: 150–250 A vs 80–150 A (at max rated V)
• Bearings/cooling: RS-987 almost always dual ball bearings + internal fan; RS-985 often sleeve or single ball, fan optional.
Mechanical envelope
• RS-987 “49 mm can” (Ø 49 ± 0.2 mm, length 80–90 mm without shaft).
• RS-985 “45 mm can” (Ø 45 ± 0.2 mm, length 70–80 mm).
• Shaft: both 5 mm Ø, 13–20 mm stick-out; keyway/pin‐hole optional.
• Mounting face: 2-M4 on 29 mm PCD, same as 775/895 series ⇒ partial interchangeability.
Electrical characteristics (typical catalogue values, 20 °C)
| Parameter | RS-985 (12 V coil) | RS-987 (24 V coil) | Comment |
|---|---|---|---|
| Nominal voltage | 12 V (also 24 V winding offered) | 24 V (36/48 V windings common) | |
| No-load speed | 9 000 rpm @ 12 V | 12 000 rpm @ 24 V | kv ≈ 750 rpm/V both types |
| No-load current | 1.0 A | 1.8 A | larger iron & magnets → higher eddy + bearing loss |
| Stall current | 80–120 A @ 12 V | 160–220 A @ 24 V | twice the copper section |
| Stall torque | 1.8–2.5 N·m | 3.0–4.0 N·m | τ ≈ kT·Istall |
| Output power (max eff.) | 150–350 W | 300–800 W | \(P≈0.25·V·I_{stall}\) (brushed theory) |
| Efficiency peak | 70–74 % | 70–75 % | similar copper loss ratio |
(Values consolidated from Kinmore, RIC-Motor, Greartisan, and Johnson Electric data sheets; tolerance ±15 % between vendors.)
Internal construction
• Armature: RS-987 uses longer stack, thicker wire; turns per coil adjusted for ~same rpm/V.
• Magnets: both use sintered ferrite; high-end RS-987 options offer Nd-Fe-B for +20 % torque.
• Bearings: RS-987 almost exclusively dual 608-type ball bearings; RS-985 base variants may use oil-impregnated bronze at commutator end.
• Cooling: RS-987 can integrates a seven-blade centrifugal fan; RS-985 only in “H” (high-speed) sub-variant.
System impact
• Controller/ESC: RS-987 requires MOSFET/H-bridge with 200–250 A peak, 60 V FETs; gate-drive layout and copper pours become critical.
• Supply: 6-10 mΩ battery + wiring impedance advisable → typically 6 S–12 S Li-ion or 12 S Li-Po.
• Thermal: RS-987 reaches 120 °C winding temp within 3–4 min at 80 % rated load without forced airflow; base plate heat-sinking or ducted air strongly recommended.
Application mapping
• RS-985: cordless demolition hammers, 9-inch fan blowers, mid-size CNC spindles (<400 W), planetary-gear winches.
• RS-987: electric go-karts, 30–40 kg combat robots, concrete cutters, high-power vacuum pumps.
• Chinese vendors (Kinmore, RIC-Motor, Dong-Hui) have begun shipping RS-987 with neodymium magnets and silver-graphite brushes, pushing continuous power toward 1 kW at 48 V.
• Brushless drop-in upgrades (outer rotor BLDC, same 49 mm flange) are emerging, offering 90 % efficiency and sensorless operation; expect gradual replacement of brushed RS-987 in e-mobility kits.
• Automotive 48 V mild-hybrid auxiliaries are a key growth driver for this frame size.
Power scaling: For geometrically similar DC machines, torque \( \tau \propto D^{2}L \cdot I \). RS-987’s 49 mm diameter and extra stack length give ~35 % larger magnetic air-gap area than RS-985, enabling ~40 % more torque at the same ampere-turns. Running it at twice the voltage doubles current headroom (if copper fill increased), explaining the factor-of-two power step.
Analogy: Think of RS-985 as a 1.3-litre turbo engine, RS-987 as a 2.0-litre tuned engine—same mounting rails, but larger displacement, higher boost, bigger radiator.
• CE/UL compliance: Many low-cost imports lack EMC and thermal-runaway certification. Adding an external PCB filter and thermal cutoff can keep the final product compliant.
• Safety: Stall currents >200 A can weld relays and ignite undersized wiring. Use 200–250 A MIDI-fuses or ANL fuses close to the battery.
• Environmental: Brushed motors shed copper/graphite dust—consider BLDC alternatives where cleanliness or long lifetime (>1 000 h) is required.
Potential challenges & mitigation
• Commutation brush arcing at >36 V → add RC snubber 0.1 µF + 100 Ω across terminals.
• Vibration at ≥12 krpm → dynamic balance rotor to <3 g·cm.
• “RS” numbers are marketing shorthand, not an IEC frame-size: two suppliers’ RS-987 may differ by ±10 % in length, coil resistance, and idle speed. Always re-characterise critical parameters for volume production.
• Data above is consolidated from 2022–2024 catalogues; earlier versions of RS-985 (pre-2018) had weaker ferrite magnets and lower currents.
• Compare with 50-mm outer-rotor BLDC (e.g., 5065-400 kv) to evaluate efficiency gains.
• Investigate Ti-brushes or brush-holder spring upgrades to extend RS-987 life in continuous-duty tools.
• Explore sensor retro-fit (Hall or encoder on rear cap) if precise closed-loop speed control is required.
Relevant resources
• Kinmore Motor RS-987/RS-985 datasheets (2023 edition)
• Johnson Electric application note “Thermal modelling of high-current brushed DC motors”, 2022
• IEC 60034-1 (rating & insulation limits)
RS-987 is the physically larger, higher-voltage, higher-torque evolution of the RS-985. Expect roughly double the power but also double the current, heat, and control-system demands. Select RS-985 for 12–24 V, moderate-load applications where space and cost matter; choose RS-987 when 24–48 V supplies, very high peak torque, and robust cooling are available. Always verify the exact datasheet from your supplier and engineer the power electronics, wiring, and thermal management accordingly.
