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Lab News -- April 29, 2005

April 29 , 2005

LabNews 04/29/2005PDF (650KB)

Sandia assists with project to maintain vehicles’ tire pressure automatically

By Michael Padilla

Dale Petty was tired of maintaining his old farm tires and dealing with blowouts caused by low tire pressure.
Petty, owner of Petty Farm and Ranch in Clovis, N.M., wanted to develop a gadget that would automatically check tires for the recommended pressure and add or release air.

Now the idea is a reality and is being marketed to various companies.

Petty received assistance from Sandia’s Small Business Assistance Program and was partnered with John Browning (5919), principal investigator for the project.

John, a member of the Systems Research Department, came up with various ideas for maintaining the manufacturer’s recommended tire pressure without having to do it manually. He suggested three engineering concepts to Dale: an air compressor system, a high-pressure bottle, and a gas generator.

The air compressor concept is similar to systems that operate tools powered by compressed air. A centrally located air compressor would call for tire inflation pressure to come through the air channel of a rotary union mounted on the wheel. John says this concept would work well in semi tractor trailers, for example, but could not be easily implemented on the majority of passenger vehicles that use constant-velocity joints. A more expensive system could put an air compressor on each wheel, and would require power to be provided through a slip connection on the axles.

The high-pressure bottle concept is similar to systems used to inflate life rafts and aircraft emergency slides. A high-pressure bottle with a pressure regulator can be placed on each wheel of almost any vehicle. Product pricing issues, however, include costs of the high-pressure-rated parts and possible regulatory maintenance requirements such as periodic testing of the system components.

The gas generator concept would use materials already in use in automobiles today to inflate airbags. A series of small, hot-wire-ignited pellets (e.g., sodium azide) could provide nitrogen gas for periodically replacing lost tire pressure. The pellets could be mounted on a flex circuit board, which would be strapped around the tire rim inside the tire volume, along with a battery, pressure sensor, microcontroller, and igniter electronics. John says the gas generator concept is potentially the lowest cost manufacturing solution, but because of the relatively high development cost was not pursued under the small business assistance project.

Air compressor

The air compressor concept was chosen in the preliminary design of an automatic tire pressure maintenance system. A prototype system was built under the small business assistance project to address the safety and economic issues of under-inflated automobile tires frequently driven on American’s roadways.
A portable prototype has been created to hand-carry to trade shows and potential customers. The portable system is designed for demonstrations, and may be powered either by a portable 12-volt, sealed lead-acid battery (with a 110-volt AC battery charger), or by a 12-volt DC output, 110-volt AC power converter. The system features a mounted tire and wheel, attached to a pedestal by a bearing, with a handle for manually rotating the tire. A carrying case is included. The pedestal contains an air compressor, pressure switch, and vent valve, with associated tubing and wired connections to a control box with an internal pressure sensor.

The prototype has some features similar to the Dana Corporation’s central tire inflation systems (CTIS) which have found utility in the trucking industry, particularly in off-road vehicles, and have been employed with both trailer axle vehicles and tractor drive axle vehicles. The CTIS is currently available on some models of the Hummer, but, says Petty, “Hopefully someday all vehicles will be equipped with a device that will help save lives.”

High pressure bottle

With the assistance of John’s brother David, an automotive technician at Galles Chevrolet in Albuquerque, Dale also created an automatic tire pressure maintenance system using wheel-mounted high-pressure nitrogen bottles.

The system has been installed on all four wheels of a 1966 Ford Mustang.

Testing of the system included tire balance check and various bottle road tests. The bottle road tests test rim and tire assemblies, shock and vibration from various highway speeds, and the structural integrity of the system. In addition, tests were conducted to detect leaks and simulation of proper functioning of the automatic tire pressure maintenance system.

Small idea, big concept

Petty says the idea for the system came after his son came home with a homework assignment. The assignment was to not to reinvent the wheel but to make it better. Petty sat on the idea for a year and soon contacted Sandia’s Small Business Assistance Center.

Besides being tired of changing flats and dealing with blowouts, Petty says the idea was also based on safety.

Petty was alarmed with the 2000 recall of Bridgestone/Firestone’s 6.5 million tires. Close to 300 complaints had been received by the National Highway Traffic Safety Administration about the tires. Several hundred lawsuits were filed because of fatal accidents due to the faulty tires.

After meeting with Mariann Johnston (13021), the Small Business Assistance Program team leader, he knew his idea would soon be developed.
“I am pleased with all the assistance Sandia provided,” Petty says. “Sandia took the lead and helped out tremendously.” -- Michael Padilla

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Working to make New Mexico’s chile industry high-tech and healthy

By Will Keener

Across southern New Mexico and into Texas and Arizona, a major effort is under way to modernize the harvesting and production of a product near and dear to many lovers of Southwestern cuisine — chile.

Mechanization is coming gradually to an industry that has been synonymous with handpicking and hand-cleaning for many decades. Survival is now at stake.

Mechanization of this valuable crop ($300 million in New Mexico alone) is a critical step toward success, says Roy Pennock, a Cooperative Extension research specialist at New Mexico State University who has spent his life in the industry. As labor costs and availability fluctuate and availability of red chile powder from Peru, Africa, India, and China increases, the industry has come together to fight back. The New Mexico Chile Task Force combines growers, processors, crop consultants, university extension experts, and others “. . . to get everyone working on the same page,” says Pennock.

Add Sandia Labs to that mix, as Chris Wilson, Maritza Muguira, David Novick, Jon Salton, and Jesse Schwebach, all of Intelligent Systems Controls Dept. 15234, are working hard to play a contributing role. Now moving into the fourth year of a project with the task force, Chris and his team took their high-tech contribution to the effort on the road for last year’s harvest.

New machines

Working with Pennock, New Mexico State University Extension Engineer Ed Eaton, and others, Chris and the Sandia team have developed an imaging system that can measure the effectiveness of mechanical harvesters, cleaners, and sorters for chile producers. “We looked at the mechanical devices under development and decided we could help most with a measuring system,” says Chris. The system measures chile on a conveyor belt and quantifies the percentages of chile and “field trash,” which generally consists of sticks, leaves, and other natural debris.

The system was used in connection with a two-stage mechanical chile cleaner developed by Eaton during last year’s harvest. But it may also be of use to processors in the future, Pennock believes. “Mechanically harvested chile isn’t always perfect. You get pods, but you get leaves, branches, and maybe a few other things,” Pennock says. Without the “vision device” developed by Chris and this team, laborious before-and-after sampling is needed to gauge success.

“I think the system has tremendous potential for processing plants. You could have it at the beginning and at different stages of the system and it would tell you quantity and quality of the chile during processing,” says Pennock, who operated the system last year as part of the evaluation process.

The original idea of how Sandia might help the task force has evolved over the past three years, Chris says. He started out with the goal of doing a survey to provide some factual information on which methods of mechanical cleaning work and which do not. Originally, he thought Sandia’s robotics talents might be brought to bear on developing machines, but others, including researchers at NMSU, were ahead of the curve in this area, so Chris found another niche. He continues to consult with Eaton on design issues but has focused on measurement.

Cleaning chile fresh from the field is complicated by the fact that the peppers change throughout harvesting season. Early in the season the plants are green and fresh and there’s little field trash. Later as the plants turn red, mature, and endure frost, mechanical harvesters tend to pull up large amounts of brittle branches and leaves with the pods.

“Chris has been a good sounding board for me,” says Eaton. “He’s someone I can talk to who listens and is very helpful.” Eaton plans to take a new version of his cleaner, mounted on a conventional chile harvester, into the field this year. “We need investment to help us go forward to the commercial stage,” he says.

Examining different imaging technologies, Chris and his team developed a system that analyzes the chile and debris on a conveyor belt based on color differences. A digital camera connected to a portable computer takes still images of cleaned product on the conveyor belt. Software then analyzes the image, segmenting it according to color into product, trash, or background. Then the system counts pixels and provides feedback to the operator on percentages of product and waste. The operator can then adjust the cleaner and recheck the output plots to see the effect.

More variables

The project has thrown problems at Chris that he hadn’t seen before. “There are a lot more variables out in the field than there are in a controlled laboratory space,” he says. Given the variety of difficulties, Chris believes the task force, led by NMSU’s Rich Phillips, is doing a good job. “They’ve reduced the scope of the problem significantly. Part of what we do involves educating customers as well as trying to listen to them.”

Right now, most measurements are made by “eyeball,” says Chris. “There is no standard for estimating the amount of product. An objective metric system is needed.”

To achieve segmentation or determine what part of the image is actually the conveyor belt, debris, or chile, the system operator must “train” the software. The operator can develop appropriate masks to screen the images, based on hue and saturation values plotted as histograms. “This makes it easy to move from one conveyor belt to another with different color belts, or to measure differences in chile color based on the variety being harvested,” says Chris. “We should be able to work with our customers to make changes as necessary.”

“This work builds on and adds to what we are doing at Sandia. Here, I work on a lot of 3-D imaging, and this is a switch to 2-D. We are stretching ourselves in some different directions, but I think it will make us stronger.” -- Will Keener

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Innovative Kansas City Plant process yields lubricant of unprecedented thinness — with help of Sandia

By Monta Morris, Kansas City Plant

This story, reprinted from the Kansas City Plant’s internal newsletter, Connections, offers a vivid account of a collaboration between Sandia and the Kansas City Plant to solve a sticky friction challenge. — Editor

Mark Smith doesn’t like to say no. So when customers at Sandia National Laboratories came to him with a requirement that — as far as any of them knew — had never been met, he considered it a challenge.

The requirement was for an extremely thin layer of lubricant — thinner than has ever been achieved either within the weapons complex or in industry — to be applied to small bearings and parts for the W76 and W80.

“Oil can’t be used on these parts because oil flows and could eventually spread to parts of the system where it might interfere with performance,” said Smith, principal engineer in materials engineering at the Kansas City Plant. “Also, for systems that are likely to remain in stockpile for years at a time, oil can settle, leaving parts unprotected by lubrication.”

What the lab asked for was a layer of lubricant to be applied at a maximum thickness of .05 mils, or 50 microinches.

For comparison, typical paints and coatings go on at 1.0 to 3.0 mils thick. Bonded solid film lubricants, which are applied as a solid lubricant powder mixed with a liquid adhesive, are generally thinner, at 0.6 to 0.9 mils; but that’s still more than 10 times too thick. The Kansas City Plant’s production paint department, using their expert techniques, can apply those adhesively bound lubricants at 0.1 to 0.3 mils, but that’s also too thick to meet the new requirement.

“We were trying to solve a ‘micro’ problem with a ‘macro’ solution,” said Smith. Faced with these impediments, he determined that an entirely new approach was called for.

Initially, Smith, who has extensive expertise in spray coating with powder, considered incorporating the lubricant into a powder coating that could be sprayed onto the substrate. But because the goal was thinness, and lubricant by itself is as thin as you can get, Smith tried something unusual — spraying the solid lubricant directly onto the substrate without using an adhesive.

The lubricant he used, molybdenum disulfide (MoS2), is a dry powder in the form of microscopic flakes or plates. Senior engineering technologist Mike Hester dry-blasted the MoS2 at high pressure onto clean substrates in a dry nitrogen atmosphere. When the dust settled, and the loose material was washed away, Smith and Hester were greeted by a pleasing sight: the substrate had a smooth, even, and very thin layer of MoS2 embedded into its surface.

It was Mike Dugger, Ph.D., distinguished staff member at Sandia Albuquerque, who had initially suggested to Smith the possibility of blasting the lubricant directly onto the substrate. Dugger is a tribologist — an expert in friction and lubrication — with years of experience analyzing lubricants and their properties.

And he’s frankly impressed with the Kansas City Plant’s success. “This process generates a film of unprecedented thinness and excellent friction behavior,” said Dugger.

Lubricant is measured using a coefficient of friction: the lower the coefficient, the less friction exists. “This process provides an excellent fiction coefficient,” said Dugger. “Typically, for the kinds of products we build in the weapons complex, we get friction coefficients of 0.15 to 0.12. This process is significantly lower. The lowest we’ve measured with the new process is .03, which is so low it is getting hard to measure.”

The thinness of the MoS2 lubricant is what pleases Smith most about the process. “That’s what we were after,” he said. “It’s a good lubricant, and it’s as thin as you can get. Adhesive and binder are what make the lubricant thicker, and we’ve eliminated them.”

He’s also extremely pleased with the simplicity of the process. It’s easy and inexpensive to perform and, unlike many other methods of applying lubricant, it uses no hazardous solvents or other pollutants.

“This process can be easily applied to production throughout the nuclear weapons complex,” said Smith. “It will lend itself to new weapon designs that require or can make good use of extremely thin permanent lubricants.”

The Air Force is highly interested in the new lubricating process and has asked the Kansas City Plant to consider reprocessing 2,000 gyroscopes — containing 20,000 individual parts — for them. The MoS2 dry-blast coating will allow the gyros to remain in long-term storage without losing lubrication protection.

“What we really need is a material that can be applied with a thickness so small that we don’t have to allow for it in the dimension of the part,” said Dugger, “and this lubricant is providing that. I’ve looked at a lot of solid lubricants over the years, and this is one of the best I’ve seen.”

An ‘interesting challenge:’ Make the thinnest-film lubricant ever

The Lab News asked Mike Dugger (1824) for some additional Sandia context to the ultra-thin lubricant achievement. Here’s his story:

Our colleagues in component design presented us with an interesting challenge last fiscal year. New stronglinks (safety and security components) for the W76 and W80 life extension program would use designs with tolerances down to 2.5 microns on some dimensions.

The solid lubricant films typically used in these mechanisms to minimize wear and ensure consistent friction performance over the life of the component would require that parts be left undersized to allow for the thickness of the lubricant. A lubricant layer so thin that it can be ignored in the design, and yet produce low and consistent friction behavior, was needed. Commercial sputtered solid lubricant films would meet this requirement, but a process external to the weapon complex presents some challenges in terms of lead times, inspection, and qualification for the stockpile.

Metal dichalcogenide lubricants used in stronglinks operate by “transfer film” formation. Shear occurs between weak c-axis bonds in the crystal, forming an atomically thin layer of the lubricant on both sliding bodies even if initially placed on only one. We reasoned that a particle of MoS2 blasted at a metal surface in a stream of nitrogen (to minimize oxidation) would fracture and form the transfer film. Based a fundamental understanding of how these materials work, the process should also be quite robust since additional lubricant will not tend to stick to the sulfur-terminated surface that forms. In other words, the lubricant thickness should be self-limiting.

The staff at Honeywell have done a great job implementing this idea, and our measurements show that we get friction coefficients around 0.03 in nitrogen, where these films will operate. The previous resin-bonded lubricant gave a friction coefficient of about 0.10 under the same conditions.

We have examined this film on complex mechanism parts as well as bearings, and it appears to perform well. This process should be amenable to any surface that can be reached with a line-of-sight gas stream. We are also working under an LDRD on other approaches for forming thin films conformally on hidden interfaces. -- For information, contact Bill Murphy

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