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Construction & Materials

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What engineers need to know about the construction and materials of Mercotac brushless slip rings.

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Learning Center – Electrical Characteristics

Learning Center – Rotational Characteristics

Frequently Asked Questions

Technical Info.

As an engineer, you understand the critical role reliable electrical connections play in your designs. Mercotac recognizes this and is dedicated to offering innovative solutions that provide superior performance and durability. In this article, we provide valuable details for our engineer and technical customers, including the key benefits and features of our brushless slip rings, internal materials, component details, and installation tips. Whether you're designing a new project or seeking a replacement part, our goal is to equip you with the knowledge necessary to make informed decisions about our products.

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Body Materials Mercotac ImageMercotac® Brushless Slip Ring's outer shells are known as bodies. The bodies are made of using either 2011 aluminum (standard body material) or a 300 series stainless steel (typically a non-standard body material, usually specified with a part number designation). The Versatac™ models use 6063 aluminum as the body material. The model 1500 is an exception, which has a stainless-steel body as its standard construction.

Both 2011 and 6063 aluminum have excellent mechanical properties. Aluminum is lightweight yet durable enough to withstand industrial use. After machining, the aluminum bodies are then color anodized to provide a visually appealing, tougher, and more corrosion resistant surface to the Mercotac bodies. The anodizing process used is of the “regular” sulfuric type.

300 series stainless steel offers good corrosion resistance. For any applications where the unit will be exposed to a corrosive environment, a stainless-steel body, along with a stainless-steel bearing, is highly recommended.

Please note that for single-conductor models the bodies (anodized aluminum or stainless steel) are electrically hot or common to the internal conductor. If electrical isolation is needed, consideration must be given to using an insulating mounting.

Bearing Types & Usage Recommendations Mercotac ImageThe radial ball bearings in Mercotac Brushless Slip Rings are made of either chrome alloyed steel 52100 (a standard bearing material) or are available in 440 stainless steel (a non-standard material, usually specified with a part number designation). For wet or corrosive environments, it is recommended that a Mercotac with a stainless-steel bearing is used since this bearing material is better suited to operate in these types of environments. Please note 440 stainless steel is not as corrosion resistant as the 300 series of stainless steels but is necessary for ball bearings because of its hardening capability. By using the optional boot kit, further protection from internal contamination of the ball bearing from dust and splashing liquids can be had with an increased IP rating of IP51.

The majority of Mercotac ball bearings have rubber seals to prevent dirt and dust accumulation. They are also greased for life, maintenance free, and never need to be re-lubricated. The rubber seals are typically light contact seals which means they have limited rotational torque. Shielded bearings are used in our Low Torque models. For further reduced torque, choose a Low Torque model, which has non-contact shields and is designated with an "L" as a suffix in the part number. Please note the low torque Mercotac models are rated for vertical orientation only, due to internal components with reduced friction.

Note: Mercotac Brushless Slip Rings are not load bearing units, thus they should not have both ends rigidly mounted and should always allow one end to float. Any weight other than the weight of the cables or wires connected to the Mercotac unit should be supported with additional structures to handle the extra load. For long or heavy cables hanging off of the end of the Mercotac, cables need to be supported to reduce the hanging weight of the cable. Also, cables should be loose, preferably with a loop and not taut, which can pull and put a side load on the Mercotac. Any additional weight placed on the Mercotac unit can lead to performance issues and/or premature failure.

The type of conductor and terminal connector(s) varies depending on the model. Mercotac Brushless Slip Rings offer different types of terminal connections, including coaxial, threaded stud, round stud, and blade connection. Versatac models come with terminal screws, pigtail wires, or cables as standard options and can be customized with electrical connectors.

All of our terminals are made of silver-plated copper or brass for low resistance and efficient electrical conductivity. The silver plating may tarnish over time when exposed to air, but this is normal and does not affect the conductivity at the terminals.

Depending on the model, some Mercotac Brushless Slip Rings include electrical connectors, while others require the purchase of additional accessories to connect them to existing wires and cables. Please refer to each model for the specific connection type. For certain models, we also offer plug kits or pre-wired receptacles to facilitate the installation process.

It is important to note that attempting to solder wires directly to a Mercotac Brushless Slip Ring will cause damage to the internal parts, many of which are plastic, and can result in connector failure, as well as void the warranty. For solder receptacles and pre-wired accessories, it is recommended that the accessories are soldered on before connection to the Mercotac unit to avoid heat transfer to the unit.

On either end of Mercotac models which have blade/tab connections there are white plastic insulating bushing made out of an engineering plastic. In addition to insulating the body, they provide an option for mounting. An adapter with a hole or a hole in the end of the shaft is typically used to mount to the white plastic bushing. The Mercotac is held in place with one or two set screws or a split clamp arrangement. It is important not to overtighten the set screws when mounting the Mercotac using the white plastic insulating bushings on either end of models with blade/tab connections. To determine the correct bushing mounting hole size, refer to the dimensional drawing and/or CAD model. Using an appropriately-sized mounting bushing is crucial to ensure proper alignment and prevent damage to the Mercotac.

For certain Mercotac Brushless Slip Ring single-conductor models with threaded stud connections, either standard or metric threads are available. See the chart below for available thread sizes.

Model No. Thread Size
104 6-32
110 6-32
130 M5 x .8
1250 3/8-16
1250-M M10 x 1.5
1500 M16 x 2.0

Each Mercotac Brushless Slip Ring is laser-etched with an UP arrow on the side of the body. For vertical mounting, the Mercotac unit should be positioned with the arrow pointing up. The slip rings can be mounted at any angle between vertical (arrow up) and 90 degrees horizontal (arrow horizontal), providing flexibility in mounting orientation.

When mounting the Mercotac unit vertically, ensure that the arrow on the side of the body is pointing upwards. Depending on the mounting orientation, there are two different options for attaching the unit:

  • If you are mounting the unit to the bottom of a shaft, attach it to the plastic bushing located near the bearing end of the unit (opposite to the body end).
  • If you are mounting the unit to the top of a shaft, you can either attach it to the plastic bushing located near the body end of the unit (opposite to the bearing end) or for a more secure mounting method, attach it to the Mercotac body.

Note that Mercotac units cannot be mounted with the arrow pointing below horizontal or upside down, as this can cause the liquid metal to migrate out of the correct contact areas and lead to performance issues.

More mounting information can be found our Mounting Page.

Mercotac Parts ImageMercotac Brushless Slip Rings are designed for mounting to the end of the rotating axis either in a vertical or horizontal attitude. The mounting method depends upon the Mercotac Brushless Slip Ring model. The larger Mercotac Brushless Slip Ring models are typically mounted into a hollow shaft or collar adapter on the end of the rotating device by either the plastic bushing or the body. The Mercotac unit may be held in place with set screws or a slotted clamp system.

The smaller Mercotac models plug into the electrical receptacle which is used for both mounting and making the electrical connection. These receptacles are knurled and designed to be press fitted into a hole on the end of the rotating device.

Eccentricity of the mounted Mercotac Brushless Slip Ring should be less than .005” (0.127mm) TIR (total indicator reading) or FIM (full indicator movement). The preferable method of mounting the Mercotac is with the black body rotating. Both ends of the Mercotac unit should not be rigidly mounted; one end needs to float free. If needed, a floating torque arm may be used to prevent the stationary end from rotating.

A floating torque arm is a mechanism used to prevent the stationary end of a Mercotac from rotating while still allowing for a certain degree of movement, and is used in special circumstances. Usually, the wires alone are sufficient to keep the stationary end of the Mercotac from rotating. However, in cases where the wires twist up, the floating torque arm connects to the stationary end of the slip ring and rests against a fixed point on the machine or equipment but is not rigidly attached. This provides a flexible connection that keeps the wires from twisting or wrapping around the Mercotac, while allowing the stationary end of the Mercotac to float and avoiding the risk of failure caused by rigid mounting of both ends.

If there are any vibrations, shock, or sudden movements associated with the equipment, it is recommended to use a vibration isolation mounting to separate the Mercotac Brushless Slip Ring from these types of actions. Any vibration or sudden movements can significantly shorten the life of the Mercotac unit or even cause failure. Vibration can move the liquid metal conductor away from the contact area, which can cause open or shorted channels.

More mounting information can be found our Mounting Page.

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