On Tue, 30 Jul 2013 15:40:52 -0700, Walter Bright <newshound2@digitalmars.com> wrote:

> On 7/30/2013 12:06 PM, Adam Wilson wrote:
>> My dad has been an ASE Master Technician for my entire life and teaches
>> Emissions Certification classes for our state. What I am about to say is based
>> stuff I've picked up from him.
>>
>> I would go one step further and point out that in modern vehicles, those made
>> after the EPA catalytic converter and air quality mandates of the early 80's,
>> that any oil in the combustion chamber is a Very Bad Thing. Unburned
>> hydrocarbons are highly destructive to catalytic converters and oil never burns
>> completely during combustion. In fact we rebuilt the engine on my 1996 Honda
>> Accord in 2010 precisely because it was starting to burn oil. And indeed, a year
>> later the catalytic converter failed anyway due to the excessive strain placed
>> on it by the partially burned oil that was forced through it prior to the rebuild.
>>
>> My dad actually recommended engine braking (the correct term is "compression
>> braking" btw, Thanks Dad!) as a way to reduce wear on the brakes. The google
>> poster is correct in this statement that all you're doing is putting strain on
>> parts that aren't used that way much, unless you reverse a lot. We see cars
>> ranging from the early 80's on up, including carbureted, and we've NEVER once
>> seen a car with a transmission or engine that died because of compression
>> braking. Given our sample size of somewhere over 10,000 ... :-)
>
> How would you know if excessive wear was caused by engine braking or not? Excessive wear can be caused by all kinds of things, like not letting the engine warm up before driving it hard, or running long between oil changes, shifting prematurely or too late, etc.
>

Personally, I wouldn't. :-) But my Dad studied metallurgy as a minor at UW and let's just say that he enjoys Metal Failure Analysis WAY more than one could charitably consider normal for a human.

Aviation Sidebar: His favorite metallurgy class was taught by an active duty Boeing incident response team member and his favorite story was his teacher dragging the failed main gear bogey of a 727 into the room and asking the class to figure out what went wrong.

If my dad says he has never seen that type of problem, he probably hasn't. Based on watching do failure analysis' on cars, my guess is that there would be telltales that clue him into what was happening. As far as the combustion chamber goes, when we rebuilt my 96 Accord it had some minor pitting from the repeated explosions but nothing else of note at at 225k. We resurfaced the barrels and moved on. And I'm a commensurate compression braker. :-)

Indeed, the other things you listed are quite evil on the internals of the engine. Particularly going too long between oil changes. But compression braking isn't on the list from an engineering standpoint. The components of the transmission and engine and much beefier than they strictly need to be. No manufacturer wants THAT recall at 5k per repair. Essentially, it's not any different than driving forward, you are just reversing the stress on components that were engineered to handle it moving forward. And in the case of automatics, the Torque Converter acts as a buffer between the engine and transmission at cruising speeds (varying by model) until it hits the lock-up.

>
>> The automotive industry has spent obscene amounts of money getting the absolute
>> cleanest burn they can to meet CAFE standards, and the very first thing they did
>> was get the oil out of the combustion chamber. I'll also say that based on my
>> dad's experience's with the Emissions class that even competent techs are having
>> a VERY difficult time understanding this stuff, the chemistry involved is Ph.D
>> stuff, and now ignition system are getting they way too. My dad has often
>> lamented that working on cars is now more about understanding the computer
>> control systems than it is the mechanics of it. Your average dealer tech
>> probably has no clue what they are talking about since they have no reason to
>> invest in learning this stuff. They don't see the car again after the warranty
>> runs out and these systems rarely fail in five years. At least that's been my
>> dad's experience with them.
>
> I'll have to add that my knowledge of these things is pre-1990. So are the cars I work on :-)
>

Hehe, Emissions Control only really got complicated in the last 15 years or so. And most people drive cars newer than 15 years, unlike the Crazy Leader of D Who Shall Remain Nameless. ;-)

-- 
Adam Wilson
IRC: LightBender
Project Coordinator
The Horizon Project
http://www.thehorizonproject.org/

On Tue, 30 Jul 2013 15:43:36 -0700, Walter Bright <newshound2@digitalmars.com> wrote:

> On 7/30/2013 12:16 PM, Adam Wilson wrote:
>> Back driving ("compression braking" in the automotive world) is indeed a
>> recommend procedure in modern cars. My dad (ASE Master Tech) recommends it as a
>> way to save wear on the brakes and is as you've noted, quite an efficient use of
>> energy. Heck, it's one of the first things he taught me how to do when I was
>> learning how to drive.
>>
>> Toyota took it one step further and built a capability into the Prius where the
>> electric driveline reverses it's polarity and uses motors to slow down the car
>> while simultaneously recharging the battery as the car slows down instead of
>> using the brakes. It's called regenerative braking. Needless to say, we don't do
>> brakes very often on Prius'.
>
> If the engine *is designed for it*, that's a different story entirely. The engines I work on were not designed for it.
>

Well Toyota's Prius engine is just a simple powerplant with no connection to the road whatsoever, it's just a really cool technology. And electric motors are very different beasts from IC motors. :-)

-- 
Adam Wilson
IRC: LightBender
Project Coordinator
The Horizon Project
http://www.thehorizonproject.org/

On 07/27/2013 01:39 AM, Walter Bright wrote:
> Designers make mistakes even in redundant systems - sometimes they turn out to be coupled so a failure in one causes a failure in the backup. Sometimes certain failure modes are not anticipated.
> 
> But one thing they do NOT do is assume that component X cannot fail.
> 
>> The one that always springs to mind is
>> the De Havilland jets breaking apart mid-flight due to metal fatigue.
> 
> Boeing's fix for that not only involved fixing the particular fatigue problem, but designing the structure so WHEN IT DOES CRACK the crack will not bring the airplane down.
> 
> This design has been proven through a handful of incidents where an airliner has lost whole panels due to cracking and yet the structure remained sound.

I have to say, one of these days I'd really like to buy you a beer (or two, or
three...) and have a long, long conversation about these (and other) aspects of
aerospace engineering.  I imagine it would be fascinating. :-)

But I do think I'm correct in asserting that the particular disaster with the Comet didn't just result in learning about a new mode of failure and how to cope with it, but in an awful lot of new knowledge about designing safety procedures, analysing faults and crash data, and so on?

>> The number of flights and resulting near misses surely helps to battle test safely procedures and designs. That volume of learning opportunities can't readily be matched in many other industries.
> 
> The most important lesson learned from aviation accidents is that all components can and will fail, so you need layers of redundancy. The airplane is far too complicated to rely on crash investigations to identify problems.
> 
> I watched a show on the Concorde the other day, and was shocked to learn that there'd been an earlier incident where a tire burst on takeoff, the tire parts had penetrated the wing fuel tank, and the fuel drained away. The industry decided to ignore fixing it - and a few years later, it happened again, but this time the leak caught fire and killed everybody.

I want to stress that I never suggested relying on crash investigations!  I said "near misses" ... :-)

What I mean is that I would have thought that with the number of flights taking place, there would be a continuous stream of data available about individual component failures and other problems arising in the course of flights, and that tracking and analysing that data would play a major role in anticipating potential future issues, such as modes of failure that hadn't previously been anticipated.  The example you give with the concorde is exactly the sort of thing that one would expect _should_ have prevented the later fatal accident.

My point was that this volume of data isn't necessarily available in other engineering situations, so one might anticipate that in these areas it's more likely that minor failures will be overlooked rather than learned from, as they are rarer and possibly not numerous enough to build up enough data to make predictions.

Of course, even if sufficient data was available, it wouldn't save them if the design (or management) culture didn't take into account the basic principles you've described.

On 7/30/2013 4:22 PM, Adam Wilson wrote:
> Indeed, the other things you listed are quite evil on the internals of the
> engine. Particularly going too long between oil changes. But compression braking
> isn't on the list from an engineering standpoint. The components of the
> transmission and engine and much beefier than they strictly need to be.

Eh, I'm less convinced about that. I've had two transmissions shatter going steady speed at 30 mph. I doubled the horsepower in my dodge, the first thing that needed upgrading was the transmission (replaced the whole thing). I also upgraded the springs, driveshaft, bell housing (don't want my feet cut off), flywheel & clutch, brakes, and mounts. Not to mention everything inside the engine is upgraded, such as going from a cast to a forged crank (3x stronger).

I didn't upgrade the differential and rear axle. Those do tend to be beefier than necessary.

If I went to more than double the power, I'd have to do things like weld extra bracing into the frame, "tub" the rear chassis, go to fat tires, put in a roll cage, etc.


> No manufacturer wants THAT recall at 5k per repair. Essentially, it's not any
> different than driving forward, you are just reversing the stress on components
> that were engineered to handle it moving forward.

It also assumes that the profile of the gears and the hardening on them is symmetric. It probably is - but I don't know that for a fact.


> And most people drive cars newer than 15 years, unlike the Crazy Leader of D Who
> Shall Remain Nameless. ;-)

There's just something about a hotrodder doing it by reflashing the SD memory that leaves me cold :-)

I just don't care for new cars. The only ones that piqued my interest are the retro Mustang and the retro Challenger. Not even the new Ferraris look interesting. I'll rent cars on trips, and I can't even recall what brand they were. Zzzzzzz.

I'll just conclude with a video on why electric cars will always suck and why Detroit has never made anything worth buying since 1972:

http://www.youtube.com/watch?v=PsUnBQE8jhE

On 7/30/2013 5:16 PM, Joseph Rushton Wakeling wrote:
> I have to say, one of these days I'd really like to buy you a beer (or two, or
> three...) and have a long, long conversation about these (and other) aspects of
> aerospace engineering.  I imagine it would be fascinating. :-)

So there, Andrei!


> But I do think I'm correct in asserting that the particular disaster with the
> Comet didn't just result in learning about a new mode of failure and how to cope
> with it, but in an awful lot of new knowledge about designing safety procedures,
> analysing faults and crash data, and so on?

The disaster did usher in the modern era of crash investigation.


> What I mean is that I would have thought that with the number of flights taking
> place, there would be a continuous stream of data available about individual
> component failures and other problems arising in the course of flights, and that
> tracking and analysing that data would play a major role in anticipating
> potential future issues, such as modes of failure that hadn't previously been
> anticipated.  The example you give with the concorde is exactly the sort of
> thing that one would expect _should_ have prevented the later fatal accident.

You're right in that there's a flood of service data coming back, and there's an engineering team that is constantly improving the parts based on that service data. They track every single part, where it came from, what batch it was in, who inspected it, it's service history, what airplane it's on, etc.


> My point was that this volume of data isn't necessarily available in other
> engineering situations, so one might anticipate that in these areas it's more
> likely that minor failures will be overlooked rather than learned from, as they
> are rarer and possibly not numerous enough to build up enough data to make
> predictions.

I know that car companies will buy cars out of junkyards and take them apart looking for service issues, but yeah, tracking everything is too expensive for them.


> Of course, even if sufficient data was available, it wouldn't save them if the
> design (or management) culture didn't take into account the basic principles
> you've described.

Boeing (and every other airframe company) would be out of business if they didn't have that culture. What I find surprising is that other industries seem completely unaware of this methodology. They're stuck in the naive "the design requires that this part cannot fail" mindset.

On Tue, 30 Jul 2013 18:14:25 -0700, Walter Bright <newshound2@digitalmars.com> wrote:

> On 7/30/2013 4:22 PM, Adam Wilson wrote:
>> Indeed, the other things you listed are quite evil on the internals of the
>> engine. Particularly going too long between oil changes. But compression braking
>> isn't on the list from an engineering standpoint. The components of the
>> transmission and engine and much beefier than they strictly need to be.
>
> Eh, I'm less convinced about that. I've had two transmissions shatter going steady speed at 30 mph. I doubled the horsepower in my dodge, the first thing that needed upgrading was the transmission (replaced the whole thing). I also upgraded the springs, driveshaft, bell housing (don't want my feet cut off), flywheel & clutch, brakes, and mounts. Not to mention everything inside the engine is upgraded, such as going from a cast to a forged crank (3x stronger).
>

Huh, I can't recall a story of that ever happening to a Honda or Toyota. We've had people install towkits on Minivans without the required oil cooler and set their transmissions on fire. But never shattering... Now the Japanese tend to source higher quality metal than the American manufacturers do, so that might be it...

> I didn't upgrade the differential and rear axle. Those do tend to be beefier than necessary.
>
> If I went to more than double the power, I'd have to do things like weld extra bracing into the frame, "tub" the rear chassis, go to fat tires, put in a roll cage, etc.
>
>
>> No manufacturer wants THAT recall at 5k per repair. Essentially, it's not any
>> different than driving forward, you are just reversing the stress on components
>> that were engineered to handle it moving forward.
>
> It also assumes that the profile of the gears and the hardening on them is symmetric. It probably is - but I don't know that for a fact.
>
>
>> And most people drive cars newer than 15 years, unlike the Crazy Leader of D Who
>> Shall Remain Nameless. ;-)
>
> There's just something about a hotrodder doing it by reflashing the SD memory that leaves me cold :-)
>

It's kind of hard to be proud of 5 minutes of effort. :-D

> I just don't care for new cars. The only ones that piqued my interest are the retro Mustang and the retro Challenger. Not even the new Ferraris look interesting. I'll rent cars on trips, and I can't even recall what brand they were. Zzzzzzz.
>

I have to admit the tech in new cars is very appealing to me. But at this point now we're talking about taste, which I try not to debate people on. :-)

> I'll just conclude with a video on why electric cars will always suck and why Detroit has never made anything worth buying since 1972:
>
> http://www.youtube.com/watch?v=PsUnBQE8jhE
>

I'm with you on the electric cars. I'll proudly drive my oil burning pollution machines till I die. But if we want to make money in the automotive maintenance world, we gotta follow the crowd... *sigh*

-- 
Adam Wilson
IRC: LightBender
Project Coordinator
The Horizon Project
http://www.thehorizonproject.org/

On Tuesday, 30 July 2013 at 21:58:04 UTC, Andrei Alexandrescu wrote:
> On 7/30/13 1:01 PM, H. S. Teoh wrote:
>> My only regret was paying for the fuel plan (full tank of gas), because
>> I underestimated the car's efficiency, when I could've just let them
>> fill up half the tank at the end for a lower total price instead.
>
> Yah, never do that. Whoever came up with that idea was a marketing genius. Must have made a bunch of extra $ to the rental companies.
>
> Andrei

What exactly is the "fuel plan"? Every time I've ever rented a car, it was "here is a car with a full tank. You must return it with a full tank. (or pay for the missing fuel)".

On Wed, Jul 31, 2013 at 12:18:34PM +0200, monarch_dodra wrote:
> On Tuesday, 30 July 2013 at 21:58:04 UTC, Andrei Alexandrescu wrote:
> >On 7/30/13 1:01 PM, H. S. Teoh wrote:
> >>My only regret was paying for the fuel plan (full tank of gas), because I underestimated the car's efficiency, when I could've just let them fill up half the tank at the end for a lower total price instead.
> >
> >Yah, never do that. Whoever came up with that idea was a marketing genius. Must have made a bunch of extra $ to the rental companies.
> >
> >Andrei
> 
> What exactly is the "fuel plan"? Every time I've ever rented a car, it was "here is a car with a full tank. You must return it with a full tank. (or pay for the missing fuel)".

Like Andrei said, it's a marketing genius' idea. Basically they say, pay us a full tank of gas up front, and you can bring the car in without worrying about filling up at the end. Of course, nobody would fall for it if they don't also include a discounted gas price for the full tank. The temptation then becomes trying to run the tank as low as possible before returning it in order to "get your money's worth".


T

-- 
Just because you survived after you did it, doesn't mean it wasn't stupid!

On 07/30/2013 09:14 PM, Walter Bright wrote:
>
> There's just something about a hotrodder doing it by reflashing the SD
> memory that leaves me cold :-)
>
> I just don't care for new cars. The only ones that piqued my interest
> are the retro Mustang and the retro Challenger. Not even the new
> Ferraris look interesting. I'll rent cars on trips, and I can't even
> recall what brand they were. Zzzzzzz.
>
> I'll just conclude with a video on why electric cars will always suck
> and why Detroit has never made anything worth buying since 1972:
>
> http://www.youtube.com/watch?v=PsUnBQE8jhE
>

Grow up, Walter. You're not a teenager anymore. Driving a noisy, inefficient car doesn't make you cool. It makes you a pathetic man trying to recapture his youth while annoying the neighbors and making a fool of himself.

On 8/1/2013 3:52 AM, Jeff Nowakowski wrote:
> Grow up, Walter. You're not a teenager anymore. Driving a noisy, inefficient car
> doesn't make you cool. It makes you a pathetic man trying to recapture his youth
> while annoying the neighbors and making a fool of himself.

One advantage to growing older is ceasing to care what others think about the things I enjoy.

You might be amused to know that I've been driving muscle cars since I was a kid, and was the only one at college with one, the only one at any of the companies I've worked for, the only one in my neighborhood, etc. Motorheads are few and far between. The only time I run into others is at a meet or the drag strip. I'd drive my other car on dates because girls didn't like them. It's pretty rare to see one on the road. You could say those cars were never cool among my peers, who'd often just look at the car blankly, and pine for a BMW or Porsche.

BTW, you don't think the Prius is a status symbol? :-)