Hey, I can out-run bicycles even on my Harley. So there. Most of them, anyway...

I see a lot more cars driving stupidly around trucks than trucks driving stupidly around cars.

Agree,

Before I settled into my profession, I did some time behind the wheel of a
tractor/trailer...some people just like to take chances...

When I am in my DD I give Semis wide berth...

So you're saying that braking systems are being radically improved...but that the existing brakes are fine so this is a non issue?

Indeed this is a stupid thread.

+1

Is this thread for real?

LOL. It really is worth a larf from an engineering perspective. What WOULD be required to bring an 80,000lbs Peterbilt to a stop in the same distance as a Toyota Camary, in the wet?

I'm thinking systems like 'rocket thrusters' and 'Gods will when he's having a good day' would be involved.

those aircraft carrier cables every 5 feet would work. every truck would need to retrofitted with a hook.

256,000-pound at 100 knots (115 mph) http://spaceflight.nasa.gov/shuttle/reference/shutref/orbiter/lgear/brakes.html

Obviously (I would hope) more tire(s) on the ground would allow softer (stickier) compound. ..and shorter stopping distance.

About the topic.

I always give trucks a wide berth. Not every vehicle has the same capabilities, nor every driver. You cannot expect it to be so. Give the truck driver some space and some respect.

On a related topic:

I recall taking a college logistics course years and years ago. One of the studies we reviewed concluded that 100% of damage to highway surfaces was caused by Semis. Cars, Pick-ups etc, just don't have the weight to cause that much damage.

Yet, Semis do not in anyway proportionately pay for the damage caused via tolls, etc.

This and other studies made a strong case for:

1. Adding more axles to rigs to reduce road pressure.
2. Levying higher tolls/fees on trucks to compensate for road damage.
3. Using railroads to ship freight instead.

Will any of those things come to pass? Probably not as long as the Teamsters have a say.

Carry on.

So roads would last forever if we keep trucks off of them?:confused:

Kind of tangential, but if you are interested in traffic and vehicle safety issues, here is a site where you can view all sorts of studies done by NHTSA (Nat'l Highway Transp Safety Agency)

http://www-nrd.nhtsa.dot.gov/cats/listpublications.aspx?Id=C&ShowBy=DocType

I have no view on the OP's question. Surely semi truck stopping distances can be significantly improved (NHTSA proposed a regulation for improved semi braking, but it went nowhere) but the question is at what cost vs for what benefit. I started looking into the data but lost interest . . .

Some other links:
http://www.iihs.org/research/qanda/trucks.html
http://www.truckaccidentinfo.com/

Not needed. Example:
I don't know what the (relative) landing speed was, but still impressive to stop something that big, that quickly, on a pitching deck. ...and in 1963.

I don't think anyone thinks that the Peter should be able to stop in the -same- distance as a camry, just in a shorter distance than most trucks currently do.

From a deisel tech's view (admittedly i never worked that field, i went into cars instead, but i was schooled in the field), it's perfectly reasonable to me that they should be able. And lo and behold, trucking manufacturers are working toward that as we speak.

I've always wondered why European semi trailers have 3 axles but ours only have 2.

I always thought one of the reasons trucks use drum brakes is the need to for them to fail-safe in case of a loss of air pressure. From what I understand the brakes are locked by spring tension until enough air pressure builds to release them. This keeps trucks from losing brakes from something like a bad o-ring.

I do think we could do a better job designing trucks for safety. I see a lot of rollover accidents in my area and to me it has always seemed stupid to load 80,000 pounds onto a loading deck that is 5 feet in the air balanced on top of may-pop retreads. It seems that if trucks sat lower they would be safer and more efficient.

Short of that I always thought it would be cool to have a gigantic series of bank teller tubes running underground for shipping purposes. The capsules could be loaded up and blasted to their destination without any drivers.

I'm pretty sure that any decent engineer could design lock on loss of pressure disc brakes too.

It seems your right. From what I can tell it seems that some of this technology is patented which may be slowing the market penetration.

These are what Peterbilt is using, http://www.roadranger.com/Roadranger/productssolutions/brakes/airdiscbrakes/index.htm

Wonder if they would fit on my 930...
http://www.roadranger.com/ecm/groups...rakesimage.jpg

Good point. Trains use the same philosophy - air pressure releases the brakes, it does not engage them. This is an important safety issue.


Now you sound like my (pointy haired) boss. ;)

It's always amazing "what any decent engineer" can do in the eyes of anyone who isn't one. I have a big red "easy" button on my desk just for such occasions.

Cool stuff. I wonder how economically viable it would be to retrofit the several million over-the-road trucks in use in the United States today. Time for that "easy" button...

Yes, technology marches on. Improvements are made. Will big trucks ever stop in significantly less distance than they do today? Probably, but the technology isn't here yet. These disc brakes are not that technology yet, either.

It seems folks today believe disc brakes to be some sort of voodo magic; vastly more powerful than drums. They could not be more wrong. Drums actually have more ultimate stopping power - through greater swept area - than discs. Where discs shine is in repeated, rapid back-to-back use; they dissipate heat better. That's whe we use them on race cars, and now passenger cars. But for the one time, this one's gotta work kind of stop, drums work better. That, and the limiting factor in stopping a semi is still traction. Coefficient of friction between rubber and road, and how much rubber is on the road. Drums will lock them all up just fine, so they are already too powerful. Anti-lock on drums is probably the best one-time panic use system on trucks today.

In light of that, I would imagine Peterbuilt's goal with these discs is to improve things like mountain pass braking performance. Long, steep downhill grades where drums are overheating and failing. They can do that without giving up the one-time emergency stopping power of their drums.

We need more government regulation to fix the failures of capitalism.

But they already invented them. ;)

Seriously, getting a spring lock mechanism if air pressure fails should be no harder for disc brakes than for drum. Peterbilt has exactly such mechanisms already in production on their disc brakes.

Jeff i think you are discounting how quickly big truck brakes can overheat in regular stop and go. If your brakes are already quite hot, that one panic stop can be less efficient than it should be. I'm pretty sure we can get better performance from disc brakes.

And i agree....trucks need better, wider tires.