Category Archives: quality

Detroit Teachers are not paid too much

Detroit is bankrupt financially, but not because the public education teachers have negotiated rich contracts. If anything Detroit teachers are paid too little given the hardship of their work. The education problem in Detroit, I think, is with the quality of education, and of life. Parents leave Detroit, if they can afford it; students who can’t leave the city avoid the Detroit system by transferring to private schools, by commuting to schools in the suburbs, or by staying home. Fewer than half of Detroit students are in the Detroit public schools.

The average salary for a public school teacher in Detroit is (2013) $51,000 per year. That’s 3% less than the national average and $3,020/year less than the Michigan average. While some Detroit teachers are paid over $100,000 per year, a factoid that angers some on the right, that’s a minority of teachers, only those with advanced degrees and many years of seniority. For every one of these, the Detroit system has several assistant teachers, substitute teachers, and early childhood teachers earning $20,000 to $25,000/ year. That’s an awfully low salary given their education and the danger and difficulty of their work. It’s less than janitors are paid on an annual basis (janitors work more hours generally). This is a city with 25 times the murder rate in the rest of the state. If anything, good teachers deserve a higher salary.

Detroit public schools provide among the worst math education in the US. In 2009, showing the lowest math proficiency scores ever recorded in the 21-year history of the national math proficiency test. Attendance and graduation are low too: Friday attendance averages 71.2%, and is never as high as 80% on any day. The high-school graduation rate in Detroit is only 29.4%. Interested parents have responded by shifting their children out of the Detroit system at the rate of 8000/year. Currently, less than half of school age children go to Detroit public schools (51,070 last year); 50,076 go to charter schools, some 9,500 go to schools in the suburbs, and 8,783, those in the 5% in worst-performing schools, are now educated by the state reform district.

Outside a state run reform district school, The state has taken over the 5% worst performing schools.

The state of Michigan has taken over the 5% worst performing schools in Detroit through their “Reform District” system. They provide supplies and emphasize job-skills.

Poor attendance and the departure of interested students makes it hard for any teacher to handle a class. Teachers must try to teach responsibility to kids who don’t show up, in a high crime setting, with only a crooked city council to look up to. This is a city council that oversaw decades of “pay for play,” where you had to bribe the elected officials to bid on projects. Even among officials who don’t directly steal, there is a pattern of giving themselves and their families fancy cars or gambling trips to Canada using taxpayers dollars. The mayor awarded Cadillac Escaldes to his family and friends, and had a 22-man team of police to protect him. On this environment, a teacher has to be a real hero to achieve even modest results.

Student departure means there a surfeit of teachers and schools, but it is hard to see what to do. You’d like to reassign teachers who are on the payroll, but doing little, and fire the worst teachers. Sorry to say, it’s hard to fire anyone, and it’s hard to figure out which are the bad teachers; just because your class can’t read doesn’t mean you are a bad teacher. Recently a teacher of the year was fired because the evaluation formula gave her a low rating.

Making changes involves upending union seniority rules. Further, there is an Americans with Disability Act that protects older teachers, along with the lazy, the thief, and the drug addict — assuming they claim disability by frailty, poor upbringing or mental disease. To speed change along, I would like to see the elected education board replaced by an appointed board with the power to act quickly and the responsibility to deliver quality education within the current budget. Unlike the present system, there must be oversight to keep them from using the money on themselves.

She state could take over more schools into the reform school district, or they could remove entire school districts from Detroit incorporation and make them Michigan townships. A Michigan township has more flexibility in how they run schools, police, and other services. They can run as many schools as they want, and can contract with their neighbors or independent suppliers for the rest. A city has to provide schools for everyone who’s not opted out. Detroit’s population density already matches that of rural areas; rural management might benefit some communities.

I would like to see the curriculum modified to be more financially relevant. Detroit schools could reinstate classes in shop and trade-skills. In effect that’s what’s done at Detroit’s magnet schools, e.g. the Cass Academy and the Edison Academy. It’s also the heart of several charter schools in the state-run reform district. Shop class teaches math, an important basis of science, and responsibility. If your project looks worse than your neighbor’s, you can only blame yourself, not the system. And if you take home your work, there is that reward for doing a good job. As a very last thought, I’d like to see teachers paid more than janitors; this means that the current wage structure has to change. If nothing else, a change would show that there is a monetary value in education.

Robert Buxbaum, August 16, 2013; I live outside Detroit, in one of the school districts that students go to when they flee the city.

What’s the quality of your home insulation

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By Dr. Robert E. Buxbaum, June 3, 2013

It’s common to have companies call during dinner offering to blow extra insulation into the walls and attic of your home. Those who’ve added this insulation find a small decrease in their heating and cooling bills, but generally wonder if they got their money’s worth, or perhaps if they need yet-more insulation to get the full benefit. Here’s a simple approach to comparing your home heat bill to the ideal your home can reasonably reach.

The rate of heat transfer through a wall, Q^w, is proportional to the temperature difference, ∆T, to the area, A, and to the average thermal conductivity of the wall, k; it is inversely proportional to the wall thickness, ∂;

Q^w = ∆T A k /∂.

For home insulation, we re-write this as Q^w = ∆T A/R^w where R^w is the thermal resistance of the wall, measured (in the US) as °F/BTU/hr-ft². R^w = ∂/k.

Lets assume that your home’s outer wall thickness is nominally 6″ thick (0.5 foot). With the best available insulation, perfectly applied, the heat loss will be somewhat higher than if the space was filled with still air, k=.024 BTU/ft^.hr°F, a result based on molecular dynamics. For a 6″ wall, the R value, will always be less than .5/.024 = 20.8 °F/BTU/hr-ft^2.. It will be much less if there are holes or air infiltration, but for practical construction with joists and sills, an R^w value of 15 or 16 is probably about as good as you’ll get with 6″ walls.

To show you how to evaluate your home, I’ll now calculate the R value of my walls based on the size of my ranch-style home (in Michigan) and our heat bills. I’ll first do this in a simplified calculation, ignoring windows, and will then repeat the calculation including the windows. Windows are found to be very important. I strongly suggest window curtains to save heat and air conditioning,

The outer wall of my home is 190 feet long, and extends about 11 feet above ground to the roof. Multiplying these dimensions gives an outer wall area of 2090 ft². I could now add the roof area, 1750 ft² (it’s the same as the area of the house), but since the roof is more heavily insulated than the walls, I’ll estimate that it behaves like 1410 ft² of normal wall. I calculate there are 3500 ft²of effective above-ground area for heat loss. This is the area that companies keep offering to insulate.

Between December 2011 and February 2012, our home was about 72°F inside, and the outside temperature was about 28°F. Thus, the average temperature difference between the inside and outside was about 45°F; I estimate the rate of heat loss from the above-ground part of my house, Q^u = 3500 * 45/R = 157,500/R^w.

Our house has a basement too, something that no one has yet offered to insulate. While the below-ground temperature gradient is smaller, it’s less-well insulated. Our basement walls are cinderblock covered with 2″ of styrofoam plus wall-board. Our basement floor is even less well insulated: it’s just cement poured on pea-gravel. I estimate the below-ground R value is no more than 1/2 of whatever the above ground value is; thus, for calculating Q^B, I’ll assume a resistance of R^w/2.

The below-ground area equals the square footage of our house, 1750 ft² but the walls extend down only about 5 feet below ground. The basement walls are thus 950 ft² in area (5 x 190 = 950). Adding the 1750 ft² floor area, we find a total below-ground area of 2700 ft².

The temperature difference between the basement and the wet dirt is only about 25°F in the winter. Assuming the thermal resistance is R^w/2, I estimate the rate of heat loss from the basement, Q^B = 2700*25*(2/R^w) = 135,000/R^w. It appears that nearly as much heat leaves through the basement as above ground!

Between December and February 2012, our home used an average of 597 cubic feet of gas per day or 25497 BTU/hour (heat value = 1025 BTU/ ft³). Q^U+ Q^B= 292,500/R^w. Ignoring windows, I estimate R^w of my home = 292,500/25497 = 11.47.

We now add the windows. Our house has 230 ft² of windows, most covered by curtains and/or plastic. Because of the curtains and plastic, they would have an R value of 3 except that black-body radiation tends to be very significant. I estimate our windows have an R value of 1.5; the heat loss through the windows is thus Q^W= 230*45/1.5 = 6900 BTU/hr, about 27% of the total. The R value for our walls is now re-estimated to be 292,500/(25497-6900) = 15.7; this is about as good as I can expect given the fixed thickness of our walls and the fact that I can not easily get an insulation conductivity lower than still air. I thus find that there will be little or no benefit to adding more above-ground wall insulation to my house.

To save heat energy, I might want to coat our windows in partially reflective plastic or draw the curtains to follow the sun. Also, since nearly half the heat left from the basement, I may want to lay a thicker carpet, or lay a reflective under-layer (a space blanket) beneath the carpet.

To improve on the above estimate, I could consider our furnace efficiency; it is perhaps only 85-90% efficient, with still-warm air leaving up the chimney. There is also some heat lost through the door being opened, and through hot water being poured down the drain. As a first guess, these heat losses are balanced by the heat added by electric usage, by the body-heat of people in the house, and by solar radiation that entered through the windows (not much for Michigan in winter). I still see no reason to add more above-ground insulation. Now that I’ve analyzed my home, it’s time for you to analyze yours.

Camless valves and the Fiat-500

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One of my favorite automobile engine ideas is the use of camless, electronic valves. It’s an idea whose advantages have been known for 100 years or more, and it’s finally going to be used on a mainstream, commercial car — on this year’s Fiat 500s. Fiat is not going entirely camless, but the plan is to replace the cams on the air intake valves with solenoids. A normal car engine uses cams and lifters to operate the poppet valves used to control the air intake and exhaust. Replacing these cams and lifters saves some weight, and allows the Fiat-500 to operate more efficiently at low power by allowing the engine to use less combustion energy to suck vacuum. The Fiat 500 semi-camless technology is called Multiair: it’s licensed from Valeo (France), and appeared as an option on the 2010 Alfa Romeo.

How this saves mpg is as follows: at low power (idling etc.), the air intake of a normal car engine is restricted creating a fairly high vacuum. The vacuum restriction requires energy to draw and reduces the efficiency of the engine by decreasing the effective compression ratio. It’s needed to insure that the car does not produce too much NOx when idling. In a previous post, I showed that the rate of energy wasted by drawing this vacuum was the vacuum pressure times the engine volume and the rpm rate; I also mentioned some classic ways to reduce this loss (exhaust recycle and adding water).

Valeo’s/Fiat’s semi-camless design does nothing to increase the effective compression ratio at low power, but it reduces the amount of power lost to vacuum by allowing the intake air pressure to be higher, even at low power demand. A computer reduces the amount of air entering the engine by reducing the amount of time that the intake valve is open. The higher air pressure means there is less vacuum penalty, both when the valve is open even when the valve is closed. On the Alfa Romeo, the 1.4 liter Multiair engine option got 8% better gas mileage (39 mpg vs 36 mpg) and 10% more power (168 hp vs 153 hp) than the 1.4 liter cam-driven engine.

David Bowes shows off his latest camless engines at NAMES, April 2013.

Fiat used a similar technology in the 1970s with variable valve timing (VVT), but that involved heavy cams and levers, and proved to be unreliable. In the US, some fine engineers had been working on solenoids, e.g. David Bowes, pictured above with one of his solenoidal engines (he’s a sometime manufacturer for REB Research). Dave has built engines with many cycles that would be impractical without solenoids, and has done particularly nice work reducing the electric use of the solenoid.

Durability may be a problem here too, as there is no other obvious reason that Fiat has not gone completely camless, and has not put a solenoid-controlled valve on the exhaust too. One likely reason Fiat didn’t do this is that solenoidal valves tend to be unreliable at the higher temperatures found in exhaust. If so, perhaps they are unreliable on the intake too. A car operated at 1000-4000 rpm will see on the order of 100,000,000 cycles in 25,000 miles. No solenoid we’ve used has lasted that many cycles, even at low temperatures, but most customers expect their cars to go more than 25,000 miles without needing major engine service.

We use solenoidal pumps in our hydrogen generators too, but increase the operating live by operating the solenoid at only 50 cycles/minute — maximum, rather than 1000- 4000. This should allow our products to work for 10 years at least without needing major service. Performance car customers may be willing to stand for more-frequent service, but the company can’t expect ordinary customers to go back to the days where Fiat stood for “Fix It Again Tony.”

Why the Boeing Dreamliner’s batteries burst into flames

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Boeing’s Dreamliner is currently grounded due to two of their Li-Ion batteries having burst into flames, one in flight, and another on the ground. Two accidents of the same type in a small fleet is no little matter as an airplane fire can be deadly on the ground or at 50,000 feet.

The fires are particularly bad on the Dreamliner because these lithium batteries control virtually everything that goes on aboard the plane. Even without a fire, when they go out so does virtually every control and sensor. So why did they burn and what has Boeing done to take care of it? The simple reason for the fires is that management chose to use Li-Cobalt oxide batteries, the same Li-battery design that every laptop computer maker had already rejected ten years earlier when laptops using them started busting into flames. This is the battery design that caused Dell and HP to recall every computer with it. Boeing decided that they should use a massive version to control everything on their flagship airplane because it has the highest energy density see graphic below. They figured that operational management would insure safety even without the need to install any cooling or sufficient shielding.

All lithium batteries have a negative electrode (anode) that is mostly lithium. The usual chemistry is lithium metal in a graphite matrix. Lithium metal is light and readily gives off electrons; the graphite makes is somewhat less reactive. The positive electrode (cathode) is typically an oxide of some sort, and here there are options. Most current cell-phone and laptop batteries use some version of manganese nickel oxide as the anode. Lithium atoms in the anode give off electrons, become lithium ions and then travel across to the oxide making a mixed ion oxide that absorbs the electron. The process provides about 4 volts of energy differential per electron transferred. With cobalt oxide, the cathode reaction is more or less CoO₂ + Li⁺+ e^–—> LiCoO₂. Sorry to say this chemistry is very unstable; the oxide itself is unstable, more unstable than MnNi or iron oxide, especially when it is fully charged, and especially when it is warm (40 degrees or warmer) 2CoO₂ –> Co₂O₃+1/2O₂. Boeing’s safety idea was to control the charge rate in a way that overheating was not supposed to occur.

Despite the controls, it didn’t work for the two Boeing batteries that burst into flames. Perhaps it would have helped to add cooling to reduce the temperature — that’s what’s done in lap-tops and plug-in automobiles — but even with cooling the batteries might have self-destructed due to local heating effects. These batteries were massive, and there is plenty of room for one spot to get hotter than the rest; this seems to have happened in both fires, either as a cause or result. Once the cobalt oxide gets hot and oxygen is released a lithium-oxygen fire can spread to the whole battery, even if the majority is held at a low temperature. If local heating were the cause, no amount of external cooling would have helped.

Something that would have helped was a polymer interlayer separator to keep the unstable cobalt oxide from fueling the fire; there was none. Another option is to use a more-stable cathode like iron phosphate or lithium manganese nickel. As shown in the graphic above, these stable oxides do not have the high power density of Li-cobalt oxide. When the unstable cobalt oxide decomposed there was oxygen, lithium, and heat in one space and none of the fire extinguishers on the planes could put out the fires.

The solution that Boeing has proposed and that Washington is reviewing is to leave the batteries unchanged, but to shield them in a massive titanium shield with the vapors formed on burning vented outside the airplane. The claim is that this shield will protect the passengers from the fire, if not from the loss of electricity. This does not appear to be the best solution. Airbus had planned to use the same batteries on their newest planes, but has now gone retro and plans to use Ni-Cad batteries. I don’t think that’s the best solution either. Better options, I think, are nickel metal hydride or the very stable Lithium Iron Phosphate batteries that Segway uses. Better yet would be to use fuel cells, an option that appears to be better than even the best batteries. Fuel cells are what the navy uses on submarines and what NASA uses in space. They are both more energy dense and safer than batteries. As a disclaimer, REB Research makes hydrogen generators and purifiers that are used with fuel-cell power.

More on the chemistry of Boeing’s batteries and their problems can be found on Wikipedia. You can also read an interview with the head of Tesla motors regarding his suggestions and offer of help.

Helium leak detector repaired and refurbished in Frankenmuth

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To those who know Frankenmuth, MI, it is generally as “Little Bavaria,” the German-themed vacation town of quaint houses and shops; of cheese, wurst, beer, Christmas ornaments, and Oom Pa Pa bands. I know it in a slightly different way as the only town to get your helium leak detector repaired. There are at least three shops in Frankenmuth that repair helium leak detectors (or make new specialty versions), and this is the source of the reference leaks that most qualified shops use. So I was here yesterday and today, both for the World-class snow sculpture contest, and to get my helium leak detector looked at. It was acting funny; it turns out there was a leak in the leak detector plus a bad potentiometer on a switchover circuit. The leak is already fixed, and I should have it back in my shop next week (Wednesday).

Snow-sculpting in Frankenmuth 2013; I was there to have my helium leak detector fixed.

REB Research Blog

Random thoughts about hydrogen, engineering, business and life by Dr. Robert E. Buxbaum