Robbe FS 550 BB

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*Spec is estimated from brand data.

Technical Specifications

Last Updated: 2026-11-05

Identity
Brand
Product Number	8521
Category	Hobby
Discontinued	Yes
Performance
Torque	6.0V 41.70 oz-in 4.8V 34.70 oz-in Below Average
Speed	6.0V 0.12 sec/60° 4.8V 0.16 sec/60° Below Average
Physical
Weight	0.64 ozAbove Average
Dimensions	L 1.18 in W 0.51 in H 1.24 in
Drivetrain
Gears	Carbon
Gear Spline/Teeth	25 T estimate
Rotation/Support	Single Bearing
Control & Signal
Modulation	Digital
Control System	PWM
Electrical & Environment
Operating Voltage	4.8–6 V
Temperature	-15–55 °C
Connectivity
Connector	JR (Universal) estimate

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Disclaimer: Most data is sourced from the manufacturer. Some data is sourced from our loyal community and with the help of AI. We aim for accuracy but are not responsible for inaccurate information.

Compatible Hardware

Amazon eBay

*Spec is estimated from brand data.

Class Comparison

Torque	Below Average Stronger than 17% of 290 Digital Mini servos at 4.8V
Speed	Below Average Faster than 19% of 293 Digital Mini servos at 4.8V
Weight	Above Average Lighter than 82% of 505 Digital Mini servos

Performance Analysis

Shaft Power	0.40–0.64 W
Power Density	0.861 W/in³ More power-dense than 12% of 482 Digital Mini servos
Torque Density	1.9066 oz-in/g Stronger than 31% of 286 Digital Mini servos
Torque-to-Volume Ratio	46.50 oz-in/in³ Denser torque than 17% of 288 Digital Mini servos
Speed-to-Weight	0.34341 (1/sec·g) Faster than 56% of 289 Digital Mini servos
Speed-Torque Trade-off	5.55 Better balanced than 36% of 288 Digital Mini servos
Torque Gain per Volt	16.81%/V More voltage-responsive (torque) than 54% of 257 Digital Mini servos
Speed Gain per Volt	27.78%/V More voltage-responsive (speed) than 94% of 262 Digital Mini servos
Voltage Range Width	1.2 V Wider voltage range than 29% of 405 Digital Mini servos