To ensure optimal accuracy AND protect the sensitive electronics inside the gimbals (aka pods, pan-tilt systems) they design, engineers must strike a balance between low friction operation and sealing effectiveness. This presentation explains the relationship between seals and gimbal performance. It also offers tips on how to leverage jacket materials, geometries, and energizer forces to reduce stiction while meeting IPX, MIL-STD, SWaP, and other strict requirements. If you want to build a better gimbal, this deck is really a must-see.

1. Balancing Friction &
Sealing Effectiveness
in Gimbal Design

2. • Housings that contain sensitive
electronic instruments for scanning,
radar detecting, weapons targeting
& other uses
• At work in air, on land, at sea
• Must deliver optimal performance –
failure can impact mission success,
& even cost lives
GIMBALS
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PHOTO: UNITED STATES NAVY

3. • Aircraft
 Fighter/helicopter/UAV
 High vibration, fast moving,
demand for more accuracy
• Shipboard
 Environmental factors such as
moisture & corrosion
• Land-based
 High rotational/speed
requirements
COMMON GIMBAL ENVIRONMENTS
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4. • C4ISR gimbals/pods
• High Energy laser turrets
• LaserComm gimbals
COMMON GIMBAL APPLICATIONS
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5. TOP GIMBAL OPERATING REQUIREMENTS
• Extreme precision
 Perform high-speed bi-
directional rotation with
great accuracy,
consistency
▸ At longer distances,
even tiny pointing
variances = large target
deviations
• Survivability
 Exposed to extreme
temps, pressure
variations
 May be subject to:
▸ IPX standards for air,
sand, dust
▸ MIL-STD for vibration,
other conditions
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• SWaP-readiness
 Rotate with minimal
torque, using smallest
motors to meet strict
size, weight & power
requirements
1 2 3

6. • Protect sensitive
electronics in harsh
environments
• Must not impede
precision targeting,
regardless of conditions
(high speed, high
vibration, adverse
weather)
GIMBAL SEALS: A CRITICAL ELEMENT
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7. Gimbal System Goals Sealing Challenges
Targeting, tracking, acquiring accuracy Stick-slip & dynamic friction
Minimize power consumption Optimize size, weight & agility (SWaP)
Meet ingress protection rating (IPXX)
Sealing ability against
environmental contamination
Survive under extreme conditions Speed, thermal cycling, pressure differentials
Comply w/MIL-STD specs E.g. Mechanical vibrations
GIMBAL SEALING: GOALS VS. CHALLENGES
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8. THE FRICTION FACTOR
• In gimbals, friction …
 Exhibits highly non-linear
behavior
 Is a function of rate
 Is dramatic when transitioning
through zero rate (stiction)
 Can compromise precision
pointing/stability
 Impacts max slew rates and
acceleration
 Is influenced by temp, pressure,
surface finish, condition of
materials
 Affects power consumption
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Model showing irregularities in surface finish

9. • Low friction and low stiction
 Necessary for precision pointing and stability
 Drives the selection of other system components
• Sealing efficiency
 Sealing while still meeting friction requirements is
critical
 Prevention of environmental contamination
 Sealing moisture, dirt, salt, dust, etc.
• Survivability
 Large temperature range (from -40 °C to 60 °C),
vibration conditions, rotation, high speed
• Seal life
 Meet field maintenance requirements
KEY SEAL PERFORMANCE CONSIDERATIONS
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10. • Jacket material choice
 Polymers, such as filled PTFE, with low friction
coefficient
• Energizer choice
 Controllable force for optimal balance of sealing
effectiveness
• Profile/geometry
 Minimal contact without compromising sealing
performance
• Size/diameter
 Low cross-section to diameter ratio
• Additional factors
 Media type (dry, abrasive, lubricating)
 Seal usage after thermal cycling
 Pressure and speed
KEY SEAL DESIGN CONSIDERATIONS
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Seal in naval-based
IRST

11. • Using a canted coil spring
energizer can:
 Promote seal lip contact &
consistency in operation
 Compensate for tolerance
variations, misalignment &
vibration
 Ensure effective sealing force is
maintained under adverse
conditions
▸Weather, speed, elevation,
extreme temperatures
• Controlled force of spring coils
helps balance friction & sealing
performance
THE ENERGIZER: A CLOSER LOOK
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12. CASE STUDY: AIRBORNE LASER-OPTICAL SYSTEM
Features Requirements
Pressurized Yes
Inner diameter 125 mm
Speed 30 to 40 RPM
Service type Rotary, oscillating
Media Nitrogen + air, particles
Temp range -90 to +90 °C
Seal pressure 0 to 1.4 Bars
Back pressure 0 to 1.4 Bars
Ingress protection IP67
Frictional torque 0.9 Nm
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13. SOLUTION: AIRBORNE LASER-OPTICAL SYSTEM SEAL
 Provided in-depth frictional torque analysis
 Met low-friction rate in specification
 Protected optics to specification
Dynamic lip
geometry to
minimize friction
Canted coil spring
applying consistent
light force to minimize
friction
Locking ring to easily
press into hardware
Engineered
polymer material Thin, flexible
hinge point
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14. • To achieve optimal accuracy and durability while meeting SWaP, IPX, and other requirements, look for
these seal characteristics:
SEALING SUCCESS FACTORS
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15. • To eliminate costly mistakes and delays,
consider sealing requirements as part of
overall system design
• In early design stages, collaborate with
Bal Seal Engineering to:
 Custom design a seal that meets all your
system/application requirements
 Produce high-quality seal prototypes
 Perform seal testing to verify performance
▸ Friction testing
▸ Dynamic leak vs. friction testing
▸ Pressure
▸ Spray-down
 Transition successful prototype to full production -
100 to 1M+ units
SUMMARY & RECOMMENDATIONS
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16. RESOURCES & CONTACT INFORMATION
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solutions@balseal.com www.balseal.com +1 949.460.2100 Design request form
May 23 © Copyright, Bal Seal Engineering, LLC. This document contains and/or refers to information that is PROPRIETARY to Bal Seal Engineering, LLC, and may not be reproduced, copied, published,
or distributed in any form or disclosed to a third party, in whole or in part, without the written authorization of an officer of Bal Seal Engineering, LLC. Products are the subject of issued or pending
United States and foreign patents. Products of Bal Seal Engineering, LLC and this document are PROPRIETARY and products may not be manufactured, or caused to be manufactured, by any other
party.
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