What is New From Force Control
Force Control Industries continues to offer new products, or does new applications. This page will keep you up to date with what is happening. Learn about new applications, success stories, and trade shows we are attending..
Current Press Release
Helicopter transmission overhaul
Oil shear technology ensures helicopter transmission test stands operate continuously, without adjustment, while achieving precise positioning for desired percentages of load.
Elizabeth Engler Modic (Edited by)
Professional Aircraft Accessories (PAA) in Titusville, Florida, specializes in the repair and overhaul of landing gear, accessories, instrumentation, pressurization, radio, radar avionics, and airframe components. Already well entrenched in fixed-wing aircraft, expanding into the helicopter market was a natural extension, and the request for quote (RFQ) for overhaul and recertification of OH-58 Kiowa helicopter transmissions provided a perfect opportunity.
There was only one caveat: a very condensed timeframe. PAA officials found that oil shear braking technology helped them meet the technical requirements of the project and the fast response needed for initial certification testing.
Short-fused project takes off
While the system was designed for vertical operation the brake was mounted horizontally to allow direct torque measurement.
With the RFQ approved, PAA officials had four months to design and build a dynamometer test stand and overhaul three transmissions to get their project verification audit from the Army. Given the short timeframe, the project engineering team opted to use non-regenerative technology. Jerry Leach, director of production engineering and planning, led the team designing the system.
“Designing a system to do what we wanted with regenerative technology would have been more efficient, but it would have taken 4x longer and cost at least twice as much,” Leach says. “We contracted out key components of a system we could build in-house and decided to dump power into the system and then load it via braking. This is very effective, but it builds up a lot of heat which must be exhausted.”
Power is supplied via a GE electric motor and variable frequency drive (VFD) combination with 700hp and 3,600rpm. The specification calls for testing at 40%, 60%, 80%, 100%, and 112% of load for various timeframes. Precisely controllable load is supplied by a TB 83 oil shear brake from Fairfield, Ohio-based Force Control Industries. At 112% of load, Leach cites 8,200 lb-ft torque. The test takes about an hour, during which there is very little temperature rise.
HOW OIL SHEAR TECHNOLOGY WORKS
Dry brakes employ a sacrificial surface, usually a disc or pad, to engage the load. With no good way to remove the heat caused from engagement between the disk and plate, these surfaces must absorb the heat. The extremely high temperatures will eventually degrade the friction material. As the friction surface wears away and begins to glaze, the coefficient of friction falls, causing torque fade. This causes positioning errors which require adjustment or replacement of the friction surface.
Oil shear technology plays a major role in ensuring that, in the case of the helicopter transmission test stand, it can operate continuously without adjustment and still achieve precise positioning for the desired percentages of load. A fluid film flows between the friction surfaces and is compressed as the brake is engaged. The fluid particles in shear transmit torque to the other side. Since most of the work is done by the fluid particles in shear, wear is virtually eliminated.
In addition to transmitting torque, the oil dissipates heat due to a fluid recirculation system. Given the size of the system and the temperature rise, a cooling system was also provided.
Along with torque transmission and heat removal, the fluid continually lubricates all components, extending their service life. Oil shear technology provides a cushioned engagement that reduces shock to the drive system – further extending service life. Unlike dry brakes and clutches, the totally “The plumbing required to move that much fluid, at temperatures from 50°F to 175°F to accommodate expansion and contraction, was challenging,” Leach says.
Additionally, 1,200A electrical service had to be put into the facility before everything could be wired and tested. Getting it all in place was the first hurdle, but it wasn’t the last challenge for the project.
For More Information
January 24, 2014
Force Control Industries
Barge Spotting Operation is “Spot On” with Oil Shear Brakes
New Brakes Slash Winch Downtime and Operating Costs
Fairfield, OH – The scene is serene and picturesque. Sunshine reflects off the light chop of the Ohio River, as a barge winds its way into the view afforded through the trees bursting with autumn colors. While those driving along Louisville’s River Road may be inclined to reach for a camera to capture this idyllic scene, the mood at Nugent Sand Company is anything but tranquil. Workers here have a goal to send the deck barge – emptied of its contents – along its way quickly so they can be ready for the next arrival which will doubtless be along shortly. There is no time for downtime for either men or machine. That is why the facility switched from traditional dry friction brakes to MagnaShear Oil Shear Brakes from Force Control Industries.
All day long deck barges loaded with 1100-1200 tons of aggregate arrive at Nugent Sand Company’s Louisville facility. When the barge approaches the unloading zone, lines from a WW Patterson winch are attached fore and aft. Powered by a 7 ½ HP Baldor motor, each line is tightened or loosened to “jog” the barge into place – and position the vessel within reach of the dockside excavator’s 5-yard clamshell bucket. To keep the excavator arm swing to a minimum (and thus speeding the process), each motor and brake is subjected to numerous start/stop cycles for each barge unloaded. However, the motor is only as good as the brakes that stop it – and friction pads on their dry friction brakes were failing all too often - every 6 weeks or so.
When that occurred, crewmembers had to replace the pad – a process which required at least an hour and cost $300 in parts each time. In addition to the raw cost of repair parts, a towboat was launched to replace the winch operation with an alternate means of “jogging” the barge into position.
Although the time required to position the barges with the boat is comparable to positioning with the winch, the cost is much greater. “When we have a boat in the water we have an hourly fuel burn of about $30/hour” said Engineering Director Damon Hughes, “plus maintenance and shipside repairs. The operating cost of the dry brake is just too high.”
Additionally, there are other “soft production deficiencies” when using a towboat rather than the winches. Ideally, the towboat will move other barges into position so that when the vessel currently being unloaded is emptied it can be efficiently sent downstream and replaced with anther full barge. However, devoting all of their time to the barge being unloaded prevents the crew from pre-positioning other barges which slows the process in general. Also, the pilot and deckhand are prevented from doing any of their normal maintenance and cleaning when they are engaged in constantly repositioning the barge being unloaded.
In an industry with razor sharp margins any unintended cost or cost increase can mean the difference between black ink and red. So Hughes began researching alternatives. Luckily, the solution was right under their nose – literally. About 6 years ago, when seeking an alternative to high brake failures and maintenance requirements, they replaced a Stearns dry friction brake on one of the Baldor motors with a MagnaShear MSB6.
“We’ve had that brake for years, and have not had to do anything to it” recalls Hughes. “Other than changing the oil annually, there are no adjustments, no repairs and the operating costs are dramatically lower.”
How Oil Shear Technology Works
Normal dry brakes employ a sacrificial surface – a disc or pad – to engage the load. Having no good way to remove the heat caused from engagement between the disk and plate, this material must absorb the heat. These extremely high temperatures will eventually degrade the friction material. As the friction surface wears away and begins to glaze it causes the ensuing torque fade – and ultimately in pad failure.
Oil-shear technology plays a major role in ensuring that the oil shear brakes at Nugent Sand Company can operate continuously. The MagnaShear MSB6 brake consists of a multiple stack of friction discs and drive plates of a size and number needed to produce the required torque and absorb the energy.
Transmission fluid is pumped through the inner hub pushing the fluid through the friction stack and back into the housing.
As the plates and discs are compressed together the fluid film is put in a state of shear and will transmit torque between the two parts. The torque transmitted isdirectlyrelated to the pressure applied to squeeze the stack together.
In addition to transmitting torque, much of the heat generated is developed within the fluid in shear which is removed from the stack and replaced by cooled fluid. This keeps the friction surfaces cooled eliminating fade and severe friction material degradation due to excessive heat.
Along with torque transmission and heat removal, the fluid also serves to continually lubricate all components such as bearings and splines – thus extending their service life. With elimination of wear comes elimination of repair and rebuild, allowing MagnaShear brakes to operate for years before any repair or parts replacement is required. This means increased “uptime” and availability for barge spotting for Nugent’s Louisville facility – while driving operating costs down since.
Eliminating the $330 out of pocket costs (for repair parts and fuel burn for the positioning vessel) every 6 weeks means that the MagnaShear Oil Shear Brake pays for itself in less than a year. Further, stocking brake pads is a thing of the past, so less cash is tied up in parts inventory. As important to the team at Nugent, is the reliability of the Oil Shear Brakes.
“We never have to worry about the Force Control Brakes” said Hughes. That allows him and his crew to focus on getting the present barge unloaded in a timely fashion in order to make room for another one.