three million Torque-Arm speed reducers already working in the field, new Dodge
Torque-Arm designs are expanding the available options by using a motorized,
beltless version of the product for rugged, harsh-duty applications. And now a
redesign of the Motorized Torque Arm (MTA) is targeting applications from 3 to
75 hp where customers were forced to put a traditional gear-motor-drive package
into a harsh environment and didn't achieve long life.
"In 2007, Baldor introduced two sizes of the Motorized Torque-Arm (MTA) to test the market. The current release is a complete redesign which provides three sizes and higher torques up to 65,000 pound inch," says Rick Stewart, product manager for Torque Arm & Renewal Parts at Baldor Electric. "The MTA has the same ratings, bore sizes and accessories as the Torque Arm II, but also provides a direct drive solution for harsh-duty environments,"
The Torque-Arm brand started with Dodge in 1949 and, over the last 60 years, the company has developed different variations and innovations. It is mostly used in harsh-duty environments such as cement, aggregate and grain handling.
The MTA is a beltless version of the Torque-Arm II product and uses the exact same technology, gear geometry, features and sealing systems. It is in full compliance with American Gear Manufacturers Assn. (AGMA) guidelines.
"AGMA has developed engineering criteria for gear life expectancy, minimum bearing life, and overload capacities that are required for engineers to use when rating a product for applying the AGMA stamp," says Stewart. "Only a handful of companies follow the guidelines and no other gearing manufacturer that we know of follows the guidelines for a gear-motor or NEMA C-face right angle product."
The unit is a complete drop-in replacement and interchangeable with the current Torque Arm product. It has the same torque ratings and uses the same accessories such as bushings, so that from an engineering perspective the motorized version provides a drop-in beltless solution.
The new MTA product offers a dual seal system featuring both an oil seal and dust seal which is identical to the Torque-Arm II. It exclusively uses tapered roller bearings, and doesn't use ball bearings or light-duty bearing support mechanisms found in competitive right-angle products.
The product design also uses center "straddle mount" input pinion to provide maximum torque transmission. Stewart says that almost all gear motors use an overhung shank pinion, which is lower cost but less resilient when it comes to intense shock loads or overload conditions which the straddle mount design handles more effectively.
Another unique feature is an integral backstop. Most gear motors have a non-reversing clutch mechanism inside of the reducer to keep the unit from back driving. If the application is an incline belt conveyor which stops, for example, the user doesn't want the load to move backward down the conveyor. With other gear motors, that requirement needs to be specified upfront as a required feature along with the direction of rotation. With a motorized torque arm, the backstop can be installed in the field, and users can also reverse the direction of the backstop in the field.
"The motorized torque arm is also a modern design relative to lubrication capabilities," says Stewart. "Both the Torque Arm II and MTA are fully compatible with most synthetic lubricants on the market, and can also handle extreme pressure additives. It is very rare for a gear manufacturer to be able to use synthetics and EP additives without affecting the performance of the sealing system or backstop."
Because the motorized design uses Torque Arm II accessories, it can be easily applied to a screw conveyor drive, mixer drive or a traditional shaft mounted conveyor drive. The unit uses the same bushings, both metric and imperial, screw conveyor adapter and the same exact accessories that are readily available all around the world. The motorized torque arm is designed for NEMA motors, as well as metric IEC motors which means it can fit on both imperial and metric shafts.
For the connection between a motor and gear reducer, quill mounts are commonly used in worm gear boxes to drive light continuous loads. A slightly more robust connection is called a clamp collar which is used for material handling in warehouses where there is moderate loads and active start/stopping.
The most robust connection is a three-piece coupling method which features a rubberized coupling mechanism between the gearbox and the motor to absorb heavy shock loads. The MTA is designed with three-piece couplings throughout the product, and offers a rubberized element jaw style coupling that is designed specifically for high shock environments.
"We see the new MTA going into similar applications where Torque Arm is used today but where a direct drive is now required. The MTA gives the engineer an option to use a beltless solution with an inverter duty motor or premium efficient motor in very harsh environments and offer a longer life, heavy-duty product," says Stewart. "For an engineer to move to an inverter drive motor or premium efficient solution, they were previously forced to go with a ball bearing unit with a light-duty sealing system that was designed for traditional unit-handling applications."
CON-E-CO, a manufacturer of stationary and portable concrete equipment plants, has been using Torque Arms for many years. Due to space restrictions on their portable concrete plants, they have now standardized on the MTA.
The design of the MTA saves overhead space, so when a folding conveyor is being collapsed into position to drive down the highway, the gearbox motor fits right into the conveyor section. When the conveyor unit is extended in the field, the MTA rotates up with the conveyor and doesn't require additional space normally used for the v-beltdriven units where the motor mounts on top the reducer. CON-E-CO also still utilizes the Torque Arm II product but have specific applications where the MTA gives them all of the ratings and sealing performance of the industry-leading Torque-Arm product line.
"Most customers have similar needs where 80 to 90 percent of their needs are addressed by the belted Torque Arm but there are some applications with a unique user specification or space constraints that require a direct drive," says Stewart.
During a market survey for the product, Baldor identified a target market for equipment where there are either space constraints or international requirements. In portable equipment where there is folding, plus hauling and width limitations, the MTA is much narrower than a traditional gearbox in that torque class. And many international customers often don't want a v-belt on their product or an integral gearmotor because of power consumption.
Globalization is starting to move the market toward direct drive solutions, a trend that is starting to move into the U.S. primarily due to mergers and acquisitions.
The v-belt does provide the reducer and entire path, even the customer's equipment, some protection from uncertain shock loads because the v-belt will slip. One of the reasons it is popular is its mechanical shock resistance, plus it provides a low-cost way to change speeds. V-belts have been around for years but we are seeing some trends toward the beltless product even though they are no companies with a severe duty beltless product in this size range.
Stewart says the MTA product is a logical move for Baldor-Dodge to provide longer life and durability for auxiliary or secondary drives. Most primary drives will continue to be traditional shaft mounted units, with torque requirements as high as 500,000 lb inch and drives in the 1 to 200 hp range. The motorized drives are focused on requirements for 3 to 75 hp range where there is strong demand.