What a Collector and a Contact Shoe Actually Are
In the arm-and-shoe systems covered here, the collector mounts to the crane bridge or trolley and travels along the conductor bar, maintaining electrical contact as the crane moves. SAF-T-BAR collectors, for example, use an insulated spring-arm linkage made of aluminum alloy and injection-molded, high-impact plastic. The linkage clamps to a mounting bar and pivots at shoe-contact height, allowing the shoe to glide along the conductor and maintain full-face contact throughout its stroke. The spring applies constant pressure to the shoe as the linkage flexes.
The contact shoe is the specific wear part within that assembly: a self-lubricating conductive shoe — typically copper-graphite, sometimes carbon — typically clamped into an insulating housing (the collector head) and held against the conductor bar by the collector's spring linkage. It's the part most commonly replaced as routine maintenance, meant to be swapped out periodically without replacing the collector arm, head, or linkage underneath it, though arms, spring linkages, and connection cables are also wear items on some systems and are worth inspecting on the same schedule.
Collector Arm Styles
Collectors aren't one-size-fits-all. The arm style determines how much vertical motion the collector can accommodate and how it behaves at circuit interruptions. SAF-T-BAR's naming and dimensions below illustrate these distinctions clearly, but they're specific to SAF-T-BAR's Series C line. Other brands offer their own configurations for similar applications under different names and dimensions, and Vahle's brush-based systems (covered later) don't use an arm-and-shoe design at all:
| Arm Style | What It's For | SAF-T-BAR Example |
|---|---|---|
| Standard Arm | General use on cranes and stable monorails; a 2" vertical stroke | 70E, 100E, 150E |
| Long Arm | Excessive vertical or horizontal motion — a swaying hoist, or high-speed travel; accommodates a 3" total vertical stroke | 70L, 100L, 150L |
| Self-Centering | Discontinuous circuits where the collector leaves the conductor and must be realigned on return (such as bridge controls or runway circuits at fire doors) | 70C, 100C |
| Tandem | Maintaining full shoe contact through expansion gaps, or where a higher amperage is needed than a single collector provides; mounted on 2" centers minimum | 70LL, 100W, 150LL |
A dedicated 35-amp collector also exists as a lighter-weight option, built with lighter shoe pressure for long wear on control circuits, light hoists, hand-pulled equipment, and standby duty rather than continuous main-hoist service.
Matching a Shoe to a Collector
Contact shoes must be matched to the collector's specific system, series, and applicable current rating; the exact identification method varies by brand. On SAF-T-BAR's Series C line specifically, shoe size varies by rating: the 35S and 70S are 0.188" thick, the 100S is 0.225", and the 150S and 150S-1 are 0.200", with the 150S and 150S-1 the longest at 5.00". Shoes aren't universally interchangeable between amperage families even within one brand: a 70S shoe is matched to the 70E/70L/70C/70LL collector family, not to the 100 or 150 families, each of which has its own shoe. Other brands size and construct their shoes differently, so this dimension pattern shouldn't be assumed to carry over.
Some substitutions are possible but come with restrictions. SAF-T-BAR's 150-amp collector head, for instance, can be used in place of a 70 Amp head for extra current draw, heat capacity or as a replacement. It uses the longer 5.00" 150S-1 shoe and cannot be used with pickup guides, transfer guides, or on curves. Curve radius is itself a sizing factor: Series C bar can be factory curved to a minimum 18" radius with 35-amp collectors. The 70- and 100-amp collectors need a minimum 36" radius, and 150-amp collectors are for straight runs only.
Shoe Material and Contact Design
Copper-graphite is a common contact material among the arm-and-shoe brands in this lineup — SAF-T-BAR, Insul-8, Duct-O-Bar, and Wampfler — chosen for its self-lubricating, low-friction wear characteristics. Carbon is also used on some collector lines. Wear rates depend on travel speed, duty cycle, alignment, contact pressure, electrical loading, and operating environment, which is why a shoe is treated as a routine wear item rather than a fixed-life part. It's designed to be swapped out as it wears, without disturbing the collector arm or head underneath it.
Not every brand relies on a spring-arm-and-shoe design to maintain contact. Insul-8's Safe-Lec 2 and Hevi-Bar II use V-contact or V-groove conductor profiles that help keep the collector shoe mechanically centered in the rail channel, working alongside the arm's spring pressure rather than replacing the need for it — and Hevi-Bar II pairs its shoe with a stainless steel V contact surface. Vahle's KBH and KSL products use carbon brushes as the contact component rather than the shoe arrangements described above. The terms brush and shoe are often used interchangeably in the industry, so Vahle's collector-related parts on Crane-Controls.com are listed as brushes.
What Crane-Controls.com Offers, by Brand
| Brand | Contact Design | Naming Convention | Notes |
|---|---|---|---|
| SAF-T-BAR | Spring-arm collector with copper-graphite shoe | Arm-style suffix (E/L/C/W) plus an S-suffix shoe, e.g. 70E, 70L, 70LL, 70S | Standard, long-arm, self-centering, and tandem configurations; Series C collectors run from 35A to 150A, with separate higher-amperage collectors for the heavier series |
| Insul-8 | Spring-arm collector with copper-graphite shoe; V-groove rail profile on Safe-Lec 2 and Hevi-Bar II | M Head / L Base plus amperage, e.g. 80 Amp M Head L Base Collector | Standard, self-centering, and tandem variants; ratings vary significantly by product line — the Hevi-Bar I line alone includes collectors rated up to 600A at 7,500V |
| Wampfler | Collector heads and shoes, collector cables, and complete current-collector assemblies | Numeric part families, e.g. 081001, 081002, 081007 | Shoes, cables, and full collector assemblies are specified individually by conductor-rail series, amperage, and Phase/Earth configuration |
| Duct-O-Bar | Contact shoe on a Figure Eight collector | Series C and P shoe designations, e.g. C-40-B3, C-100-B5 | Replacement shoes are specified by series, current rating, physical dimensions, and collector configuration for Duct-O-Bar's Figure Eight conductor bar line, including vertical-mount configurations |
| Vahle | Spring-loaded carbon brush collector, rather than a copper-graphite shoe | Brand plus system plus brush code, e.g. 600 088 for KBH | A narrower product line on Crane-Controls.com than the other four brands, built around Vahle's KBH and KSL conductor bar systems specifically |
Terminology
- Collector
- The complete assembly — arm, spring linkage, and head — that mounts to the crane and maintains sliding contact with the conductor bar.
- Contact Shoe
- The replaceable conductive wear part, usually copper-graphite, held against the conductor bar by the collector's spring linkage.
- Collector Head
- The part of the collector assembly that holds the contact shoe in position.
- Self-Centering Collector
- A collector with centering attachments for discontinuous circuits. Used with pickup guides, which let the collector leave the conductor and be realigned on return.
- Tandem Collector
- Two collectors mounted together to maintain full contact through an expansion gap or to reach a higher amperage than a single collector provides; SAF-T-BAR, for example, specifies 2" centers minimum for this configuration.
- Pickup Guide
- A guide for discontinuous circuits, such as bridge controls or runway circuits at fire doors, that lets the collector leave the conductor and be realigned on return. Used with self-centering collectors only.
- Transfer Guide
- A guide that tracks the collector through lateral bar misalignments of 1/8" to 1/2" at conductor transfers. Tandem collectors are required if a power interruption can't be tolerated.
- Carbon Brush
- The contact component used on Vahle's KBH and KSL systems. Also known as carbon shoes.
Frequently Asked Questions
What's the difference between a collector and a contact shoe?
The collector is the whole assembly — arm, spring linkage, and head — that mounts to the crane and rides the conductor bar. The contact shoe is the specific replaceable part within that assembly that actually touches the conductor and wears down over time. Shoes are routinely replaced as wear items; the collector assembly generally has a longer service life, although its other components should also be inspected and replaced when necessary.
How do I know which shoe fits my collector?
Shoes are matched to a collector by brand, series, and amperage. A shoe built for one amperage family isn't sized for another, even within the same brand. SAF-T-BAR's own shoe line, for example, varies in thickness and length by rating, from 0.19" thick at 35A and 70A to 0.225" at 100A. Confirm the exact collector model before ordering a replacement shoe rather than assuming a shoe from a different rating or brand will fit.
Can a higher-amperage collector head be substituted for a lower one?
Sometimes, with restrictions. SAF-T-BAR's 150-amp collector head can substitute for a 70 Amp head for extra heat capacity or as a replacement, but it uses a longer 5.00" shoe and can’t be used with pickup guides, transfer guides, or on curves. Substitutions like this are specific to the brand and series involved and should be confirmed before mixing collector heads across ratings.
Why do some conductor bar systems use carbon brushes instead of collector shoes?
It comes down to a different mechanical approach to the same job. The SAF-T-BAR, Insul-8, Duct-O-Bar, and Wampfler products discussed here use collector/shoe arrangements to maintain sliding contact with the conductor rail. Vahle's KBH and KSL systems instead use a carbon brush for that sliding contact. Both approaches maintain continuous electrical contact as the crane travels; they just do it with different hardware.
How often should a collector shoe be replaced?
There's no single fixed interval — a shoe is a wear item, and how quickly it wears depends on travel speed, duty cycle, and environment. Because shoes are designed to be swapped out without disturbing the rest of the collector, periodic visual inspection, together with the manufacturer's wear indicators and maintenance instructions where provided, is the practical way to catch a worn shoe before it affects contact quality.
Can a self-centering collector be used anywhere a standard arm collector is used?
Not necessarily. Self-centering collectors are built for discontinuous circuits, where the collector leaves the conductor and must be realigned on return through a pickup guide, such as bridge controls or runway circuits at fire doors. They are also used where a swaying hoist or high-speed travel calls for added centering. Standard arm collectors are recommended for general, continuous-contact use on cranes and stable monorails where the collector never leaves the bar.
Application Support
Crane-Controls.com's technical support team can help match a replacement contact shoe or collector to your existing conductor bar system, confirm amperage and mounting compatibility, and identify the correct part across SAF-T-BAR, Insul-8, Duct-O-Bar, Wampfler, and Vahle. Systems can be specified to support installations designed in accordance with OSHA 1910.179, CMAA, and applicable ASME B30 standards. and final electrical design and code compliance should be confirmed by the installing electrical contractor or engineer of record for the specific jurisdiction.
Contact: +1 888-822-2024 · info@crane-controls.com