Weighing Your Motor Options, Advice for Auto Shredders

Choosing the right motor for your auto shredder can significantly impact the efficiency and longevity of your operations. With numerous factors to weigh, how can you ensure that your decision-making process is thorough? Here are insights from industry professionals.

By Eileen Zagone

Eileen Zagone is Editorial Associate of Scrap Processing and Recycling.

When it comes to most scrap processing machinery, the provided motor is standard. However, auto shredders are unique; they can be equipped with a variety of engine types regardless of the shredder's make or model. This flexibility allows operators to replace one motor type with another without any major modifications to existing shredders.

This range of options enables operators to select motors tailored to their operational needs. While this is beneficial, it also raises a critical question: how do you determine which motor is appropriate for your setup? This question can be complex as industry experts often have differing opinions on the merits of various motor types. Acknowledgement of the particular challenges presented by each shredding application is essential. Factors such as the type and quantity of scrap material, energy availability, environmental issues, and financial strategies must all be considered in your decision.

What Are Your Options?

To make an informed decision, familiarize yourself with the different motor types that are currently available.

Generally, auto shredder motors can be categorized into two main groups: internal combustion engines and electric motors. The internal combustion engines may utilize natural gas or diesel fuel, whereas electric motors can operate using alternating current (AC) or direct current (DC). Within AC motors, you’ll also find squirrel-cage and wound-rotor motors, each employing energy in a slightly different manner due to their design differences.

The variety of options has expanded over the years. Keith Elkins, plant manager for Sims-LMC Recyclers in Redwood City, California, notes that early models used squirrel-cage AC motors repurposed from WWII Merchant Marine vessels and diesel engines from submarines. Wound-rotor AC motors and natural gas engines emerged more recently, and the introduction of DC motors into the market occurred only about six years ago with advancements in technology.

Even though all motor types can be adapted to modern auto shredders, the availability of energy at your site's location can influence your choices, especially concerning electric motors. Therefore, a sensible first step is to consult with your electric utility provider to ensure they can meet your electricity needs for operating a shredder.

Ted Lipman, president of Denbo Scrap Materials in Pulaski, Tennessee, recounts his company’s experience: when they installed a shredder in 2010, the local electric company advised that transitioning to an electric motor would require significant upgrades, including a new substation and an extensive rewiring. The high costs associated with electricity made the option unappealing, especially as petroleum shortages elevated diesel prices, thereby making natural gas a more viable option.

L. Gordon Iron & Metal Co. encountered similar electricity-related hurdles during their 2012 auto shredder purchase, deciding to opt for diesel as their internal combustion engine due to a scarcity of natural gas in their area.

Your location could lead to entirely different considerations regarding energy availability.

Narrowing Down Choices

If you have sufficient electricity accessible, manufacturers suggest that an electric motor may be your best option since they are typically viewed as more efficient than internal combustion engines. Electric motors are also easier to maintain as they do not require oil or filter changes, nor do they need to be pre-warmed before operating. Moreover, increasingly stringent environmental regulations make internal combustion engines, particularly diesel, less preferable in many circumstances.

Some early adopters of internal combustion engines express dissatisfaction today and are considering a shift toward electric motors. A clear example is Steiner-Liff Iron & Metal Co. in Nashville, Tennessee, which transitioned from a natural gas engine to an electric motor. President Adam Liff cites improved efficiency and better environmental performance as reasons for the change.

Electric motors also benefit from the ability to negotiate more favorable electricity rates. Scrap recyclers can arrange to run energy-intensive shredders during off-peak hours, or agree to temporarily halt operations at the request of their electric company to help manage peak demand.

Now, if you decide to concentrate your search on electric motors, it’s worth noting that even within this category, options have become more narrowed, with squirrel-cage motors losing favor due to perceived inefficiencies compared with DC and wound-rotor motors. Elkins points out that squirrel-cage motors tend to struggle to reach optimal speed and maintain consistency during operation, while wound-rotor motors are better suited for managing the loading conditions associated with shredding.

To mitigate these concerns, Lindemann Recycling Equipment Inc. offers a "turbo coupler" attachment that helps control the acceleration and peak performance of squirrel-cage motors. While this functionality has seen success in European markets, it remains less common in the U.S.

The Electric Factor

Contact us to discuss your requirements for Automotive Parts Shredders. Our knowledgeable sales team can assist you in identifying options that will effectively meet your needs.

As you sift through these various motor types, current discussions primarily center around two classes: AC wound-rotor motors and DC motors.

The notable distinction between these types lies in their speed control capabilities. DC motors allow for adjustments in speed, which may be necessary when dealing with different types of scrap loads. In contrast, AC motors provide automatic acceleration in response to particular demands, without user intervention.

Proponents of DC motors argue that their adjustable speeds help manage electricity demand, thereby lowering associated costs. Utilities often charge industrial clients based on their highest electricity usage during a billing period, which can lead to inflated costs when unexpected power spikes occur.

On the other hand, AC motor supporters claim that the ability of their motors to self-regulate can lead to performance advantages such as consistent shredding force, even if it may result in occasional spikes in electricity demand.

Scott Newell, president of Newell Industries Inc. in San Antonio, explains that these power spikes typically arise when shredding dense materials, requiring additional horsepower to maintain consistent operation. While a DC motor may slow during these instances, resulting in less effective shredding, an AC motor would handle the situation more dynamically.

Assessing Cost vs. Longevity

Beyond electricity considerations, the conversation about motors inevitably shifts to cost and performance reliability. Most DC shredder motors are reconditioned units, previously used in more intensive applications. Consequently, they often come with a more affordable price in comparison to new AC motors, which are typically imported and can be considerably more expensive.

Some experts question the longevity of these reconditioned motors, while proponents assert that the proven durability of AC motors justifies their cost. Schorch motors, for example, are renowned for their longevity and are specifically designed for shredding tasks.

Purchasers of rebuilt DC motors are advised to scrutinize their specifications to ensure they can withstand the rigorous conditions associated with shredding operations.

Evaluating Expectations

While consensus exists around the effectiveness of AC wound-rotor motors and DC motors for shredder applications, opinions on their long-term viability remain varied. Individuals like Ralph "Bud" Murray of Universal Engineering have noted a trend toward DC motors, while others warn against this move based on misconceptions. Over time, only market performance will reveal the prevailing choices trusted by operators.

Given the wealth of opinions on motor types, it may be prudent to consult with an expert in shredding machinery—particularly one well-versed in electrical components—to closely assess the options available for your specific circumstances. Indeed, almost all seasoned shredding professionals advocate for seeking an independent consultant to help navigate this complex decision.