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Comment Re:what? no battery assist? (Score 2) 100 100

Do a bit of research and you should get the price down.

I have a friend who is a type I diabetic with a number of complications (occasional dizzy spells) which rules out being able to drive a car or ride a regular bike.

I was able to source a kit adult tricycle for about AUD$300 and a bike conversion kit from http://dillengerelectricbikes.... for AUD$700 (replace the front hub). There are some shipping costs which I haven't included, assembly took about a day and a half (one day for the trike, 4 hours for the conversion kit). I have come across adult trikes are used by the maintenance crews on industrial sites.

In hindsight given that it was a trike I could of gone sealed lead acid battery conversion kit (AUD$360 - includes electric hub, battery, controller and all the components). Providing that you are moderately competent with hand tools such as a spanner and hex keys you could replicate what I did for AUD$800 / USD$600.

Comment Nuclear plants don't like sudden shutdowns (Score 3, Informative) 311 311

Sounds like this is a "preventative measure".

Normally there is some time between neutron capture and actual nuclear fission (I have heard a figure of 15 minutes). This means that even if the control rods are slammed in when the power transmission lines were cut the previous heat load would still be generated for a period of time. Often this means resorting to drastic measures to reduce the neutron flux to zero ASAP (certain salts are added to cooling loops which achieve this but requires a good flush to get rid of).

Controlled shutdown means the reactor can be restarted in "a couple of hours"
Emergency shutdown means the reactor can be restarted in "a couple of weeks"

Burnt once, twice shy...

Comment Nice in principle but fails at higher temperatures (Score 5, Interesting) 183 183

There is a chart which shows the optimal temperature for an office is around 23'C (Google "HVAC comfort chart"), this is the temperature which has the widest acceptable range for humidity that people find comfortable.

Evaporative cooling brings the air temperature down by increasing the humidity of the air. The issue is that to achieve sufficient cooling the humidity increases beyond the comfort zone without bringing the temperature down sufficiently.

What would be interesting is a two stage evaporative cooling that does not require mechanical assistance. In a two stage system the first stage provides net cooling without humidifying the air used by the second stage. It results in cooler air with less humidity.

ZombieEngineer

Comment At 44'C ambient a lot of air conditioners fail (Score 2, Informative) 103 103

Depending on the refrigerant used it is possible that the condenser temperature (the bit exposed to the outside air) exceeded the critical point of the gas at which point it is impossible to tell the difference between liquid or gas. The trouble is phase change cooling works best (most efficient) the closer to the critical point you can go but not past it.

The second problem is the condenser pressure would increase with increasing ambient air temperature. In the past this was enough to stall the compressor motors on a hot day.

My guess is they went for a system with a high efficiency that should work for 99.9% of the time, that last 0.1% is the 8 hours of the year when the temperature is above 42'C (normally for Perth it is normally only an hours before the sea breeze kicks in and drops the temperature by at least 5'C). This time the temperature went up and stayed up for a period of time.

Comment Building codes and other methods (Score 1) 34 34

First issue is will this material be suitable for wind speeds of 100 miles per hour?
I live in a coastal city where wind gusts reach that speed and that is "a bad winter storm".

Did they think to look at the mechanical ventilators used on glass houses? These are driven by the thermal expansion of wax (incompressible fluids can exert a very large force)

For the cost of the proposed surface perhaps they should be looking at optimal spacing of solar panels (solar panels have a higher initial cost but have a long term financial benefit as opposed to the alternative roof material). On a tile roof the installation requires an air gap between the panels and the roof, this gap has cooling benefits however panels are often placed edge-to-edge preventing any hot air trapped from escaping.

Comment Re:Price is key... (Score 1) 207 207

You are not alone in that view...

Link to referenced study report:
http://www.nhtsa.gov/DOT/NHTSA/NRD/Multimedia/PDFs/Crash%20Avoidance/2008/811060.pdf

Page 41:
In 1999, the Commonwealth of Virginia tasked the Virginia Department of State Police to study the need for State standards for recapped vehicle tires. The occurrence of tire debris along Virginia’s highways gave rise to the perception that retread truck tires were to blame. The study would determine whether there was any substance to the perception.

Page 43:
The primary conclusion from the Virginia study “revealed that the quality of materials and methods of producing retreaded tires are not major factors in the problem of tire debris along the highways” (Commonwealth of Virginia, 2000). The primary study objective was not proved through the evidence collected and analyzed. Of the tire debris items analyzed, only one case was directly linked to manufacturing error in the retread process.

Another interesting bit of information can be found on page 48, that a survey of unservicable tires that 31% were original with the remainder being retreads (mostly one or two retreads).

The perverse bit is the more times a tire can be retreaded the more likely the road debris is going to be from a retread tire however the overall amount of road debris should drop.

Comment Re:Price is key... (Score 1) 207 207

This will probably come down to whether this feature can squeeze another retread out of the tire casing - that is where the savings are going to be.

The 1% extra saving in fuel will be lost in the noise (that is - too difficult to measure).

I was reading a DOT report on "Commercial Medium Tire Debris Study" (DOT HS 811 060) and an inference that approximately 50% of tire failures are due to belt separation and that 50% of the probable cause is due to under inflation (both refer to "all tire failures").

Quoting the report:
This scenario is confirmed by Kreeb et al. (2003) who noted “The act of tire pressure maintenance is labor- and time-intensive. An 18-wheeled vehicle can take from 20 to 30 minutes to check all of the tires and inflate perhaps 2 or 3 tires that may be low on air. To complete this task once each week on every tractor and trailer becomes a challenge for many fleet operators. As a result, tires are often improperly inflated.”

ZombieEngineer

Comment Re:Would stop a lot of development (Score 1) 550 550

Not really - you would need professional indemnity insurance.

The insurance is based on risk of a claim (more copies sold / bigger the premium, could be priced on a fixed price per copy), the impact of damage (just make sure that the license terms exclude indirect consequental damages).

The risk side of the equation can be reduced by using appropriate development structures (code reviews, etc).

This could improve the quality of the industry long term but there will be some pain getting there...

Comment Bad Analogy (Score 4, Informative) 550 550

You can not sue a door or window manufacturer for failure of your action (leaving the door / window open).

You should be able to successfully able to sue a door / window manufacturer for failing to provide the request product (i.e. seal the opening).

That then hits the ugly question of what is "reasonable". Did the manufacturer provide a reasonable product that provided the expected level of security?

Comment Not the only swinging float wave system (Score 4, Interesting) 103 103

Another system just off the coast of Fremantle, Australia (west coast of Australia) http://www.carnegiewave.com/index.php?url=/ceto/ceto-overview Does not produce electricity directly but very high pressure sea water which can then be used directly in a desalination plant and the waste run through a hydraulic turbine to generate mechanical / electrical energy. Given that wave energy is nearly constant around the clock, generating fresh water rather than electricity does have its advantages, doubly so in a very dry part of the world. ZombieEngineer

Comment Abnormal Situation Management (Score 2, Insightful) 421 421

The chemical processing industry have been working together for at least 15 years on related topics.
http://www.asmconsortium.net/deployment/guidelines/Pages/default.aspx

Might be something in there that help.
Specifically display standards and alarm rationalisation ("every alarm should have a unique action", if there is nothing the operator on shift can do about an alarm it should be journaled).

ZombieEngineer

Comment Possible practical implementation (Score 4, Interesting) 218 218

This could feasibly be used to make a practical air conditioner by having a segmented disk shape block that allows air to pass through.

Outside air would pass through one half of the disk that is currently energised (the electric field orders the polymer and thus releases heat).

The inside air would pass through the other half that is currently not energised (the relaxation of the electric field allows the material to absorb heat).

The disk rotates with segments shifting between the outside / inside halves, the electric field is applied by a simple electric comutation.

This is not a true "no moving parts" system but it has the potential to be an order of magnitude quieter than the current air conditioning units.

ZombieEngineer

"And do you think (fop that I am) that I could be the Scarlet Pumpernickel?" -- Looney Tunes, The Scarlet Pumpernickel (1950, Chuck Jones)

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