Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror
×

Comment Re:Mercedes, BMW engineers are dimwits. (Score 2) 360

They saw diesel electric locomotives replace steam engines in just one decade in 1950s.

The reason was different. Diesels cost about 3x as much as steam locomotives pre-WWII. But by the 1950s, diesel engine manufacturing was a production line process and the price had come down.

The real advantage of diesel over steam was that steam locomotives are incredible maintenance-intensive. Here's daily maintenance. That's what had to be done every day, by a whole crew. That's just daily. Here's 120,000 mile maintenance, done about once a year for a road locomotive. This isn't an oil change; this is a full teardown, boiler replacement, and rebuild.

Electric cars don't have that big an edge over IC engines at this point.

Comment Should we say hello? (Score 1) 239

We could send radio signals that far, with the big dish at Arecibo. If they have intelligence, and radio, we can communicate with a 1000-year round trip time. Maybe we should transmit some of the proposed canned messages to other civilizations every month or so.

If there is other intelligent life out there, it looks like they're a very long way away. Too far to talk to round trip, even at light speed. None of the known extra-solar planets within a few light years look promising.

Comment Re:Festo has been doing this for years. (Score 1) 36

Right. Traditional pneumatics is rather dumb - most of the time it's on/off, with air cylinders pushed up against hard limit stops. Positional control of pneumatic cylinders works fine, but it takes proportional valves, feedback sensors, and a fast control system. Until recently, industrial systems tended not to get that fancy.

I was interested in using pneumatics for running robots back in the 1990s, but the available proportional valves back then were big and expensive. One useful model of muscles is two opposed springs, and a double-ended pneumatic cylinder can do just that. You can change both position and stiffness, separately. You can simulate a spring, and recover energy. Someone did that at CWRU a decade ago, but the mechanics were clunky. Festo does that elegantly with their new kangaroo. Very nice mechanical engineering.

Shadow Robotics has a nice pneumatic robot hand. Shadow has been doing pneumatic flexible actuators for many years, but now they have good controllability.

Comment Festo has been doing this for years. (Score 5, Interesting) 36

Every year, Festo, the German robotics company, builds an exotic new kind of robot as a demo. Many of their robots have been "soft".

Here's their whole list of experimental projects. They've been doing "soft robots" since 2007. Others were doing "soft robots" before that, but the control usually wasn't that good. Festo builds soft robots with smooth, precise control. Festo's specialty is precise control of pneumatic systems, so they know how to do this.

Comment E = (T2-T1) / T1 (Score 3, Informative) 174

E = (T2-T1) / T1

Everyone with an engineering degree knows this. Trying to extract much energy from low-grade heat at the output end of an engine is inefficient. This was figured out a long time ago. Here it is in The Manual of the Steam Engine. It's possible to increase steam engine efficiency by compounding, where the exhaust from each cylinder feeds a larger, lower pressure cylinder. This is cost-effective up to about 3 cylinders ("triple expansion"). Engines up to quintuple-expansion have been built, but the additional power from the last two cylinders in the chain isn't worth the trouble.

Comment Re:When will they gentrify the Tenderloin? (Score 1) 359

In 2005, this appeared in SF Weekly, about the gentrification of the Polk St. area of the Tenderloin:

Gay Shame calls the Lower Polk Neighbors Association a "brutal gentrification squad" of wealthy business owners, slumlords and bureaucrats.

"They are trying to transform Polk Street from the city's last remaining gathering place for marginalized queers and street culture into a hip destination for wealthy suburbanites," Mary said. "We want a safe place for marginalized people, and Polk Street has historically been that space.

"The neighborhood may soon be known more for green-apple mojitos and stretch Hummers than trannies and tweakers (methamphetamine users)."

That was back in 2005. Gentrification won.

Comment Re:When will they gentrify the Tenderloin? (Score 3, Interesting) 359

It's happening. First, take a look at a map of the Tenderloin, from "Areas to Avoid, San Francisco." Twitter HQ is in that area, between 9th and 10th on Market, and the long-standing "mid-Market area" around there is rapidly being rebuilt. In fact, just about everything south of McAlliister has been gentrified, except for parts of 6th St and a small section around 7th and the north side of Market. Rebuilding is underway along the Van Ness corridor too, and has more or less chopped a block off the Tenderloin on the west side. That's the old "Polk Gulch" area, once a gay rent-boy hangout.

So the SF Tenderloin is about half the size it was a few years ago. Progress continues.

Comment It's a training program, not production (Score 1) 80

This is a training program, not a production process. They have a few people doing forging by hand, but not to make production parts. See the original article in the Japan Times. Toyota's process of continuous improvement of production requires that people working on assembly lines understand the process well enough to suggest improvements. They recognize that they've dumbed down the workforce too much.

Ford Motor funded the building of the Detroit TechShop for similar reasons. They need more people who have a good sense of how stuff is made. Who in the US gets a degree in production engineering any more?

Comment Re:Not getting funded. (Score 1) 157

Why does a small jet engine have to cost too much? A quick search of jet turbines for model aircraft shows that the 52lbs max thrust P200-SX from JetCat costs $5,495. Sure you would need 6 or 7 of these to get an average sized adult off the ground vertically with some minimal airframe, but we aren't talking about millions of dollars we are talking about something under $100k to put together some sort of ultralight VTOL.

The JetCat isn't man-rated. It's for model aircraft.

A JetCat needs an overhaul every 50 hours of operation. Mean time to failure is maybe a few hundred hours. A commercial jetliner turbine needs an overhaul every 3500 to 5000 hours of operation. Mean time to failure is around 100,000 hours.

A Williams FJ44 is suitable for light aircraft, and could be used for a VTOL, but a pair of them costs over $1M.

Comment Not getting funded. (Score 1) 157

Current status: "€140 raised of €2,250,000 goal".

The thing is, it's quite possible to build a flying car. The prototypes of the 1950s make that clear. The world needs some good small VTOL craft. But none of the people doing it seem to be able to bring it off.

Small jet engines cost too much but can make VTOL work. Wankel engines (the Moller embarassment) or electric motors and batteries (this thing) don'tt have the power/weight ratio needed to do it well. It's probably quite possible to build a battery powered VTOL today, but the flight time will be a few minutes, like quadcopters.

Comment Re:Does the "fix" include scrubbing? (Score 1) 149

Ignoring the performance hit with this (that many application won't take)

Clearing recently used memory is cheap, because it's in the cache. Clearing memory in general is cheap on modern CPUs, because the superscalar features do it really well. MOV is 35% of instructions, so CPUs are designed to do it efficiently.

It's security code. You have to scrub memory.

Comment Anyone can buy Google Glasses right now, cheap. (Score 2) 167

Anyone can buy Google Glasses right now on eBay. The going rate is about $1100. Google Glass "invitations" have been for sale on eBay for months. The going rate is about $50.

As an "exclusive launch", this is a flop. There have been XBox and Sony PSn launches where pre-order prices exceeded list price. Google Glasses are already selling at a discount before the launch. This thing is overpriced. It needs to launch at $995, and that will only hold until Samsung starts shipping.

Slashdot Top Deals

"Protozoa are small, and bacteria are small, but viruses are smaller than the both put together."

Working...