How long does it take a truck to stop & is it criminal if he doesn't?

[Ed Pawlowski]

Not all, but many have the engine brake.

[Tony Hwang]

Hmm, To me PT cruiser seems to be a pisscutter!

[Pico Rico]

I think downshifting fits the question too.

[clare]

To some extent - not terribly effective with an automatic trans and/or no Jake.

[clare]

Actually I found my PT cruiser to be quite capable. Not fast, or quick, but capable. And vdry versatile. But I did replace it with an old pickup truck

[richard]

No it is not required for big trucks. While some similar hills have areas set aside for truckers, it is only required to stop when posted. Having been a US trucker, nationwide, there are only a handfull of hills in the country where I will stop and check the brakes before going down. Otherwise, if I can, I'll just stop at the top and sit for a minute or two.

[richard]

This formula does not apply to big trucks.

Stopping distance in a truck also depends on how and where the load is placed.

[richard]

Here's a simple experiment to confirm your stance on this. Take a standard pickup truck, empty, to a race track. Obtain a speed of 60mph and hit the brakes. Measure the stopping distance. Now load the bed with sand and repeat. I"m sure you will find that it takes longer to stop.

[J Burns]

I looked it up, and I'm a little confused. I believe an engine brake simply lets the compression out the exhaust valve, while an exhaust brake saves it in a container. I understand the exhaust brake isn't good for heavy-duty engines. I believe the jake is the former, the one that simply lets it out the exhaust valve, and it's pretty quiet with a proper muffler. Some truckers cheat and make a racket.

[clare]

Engine braking, on any engine, is using the compression of the engine to slow down the vehicle. On gasoline engines it works pretty easily by just closing the throttle and allowing the engine to try to suck air through a closed door. Diesels do not have (generally speaking) a throttle, so there is no "inherent" engine braking. An "exhaust brake" plugs the exhaust, causing the engine to run as an air compressor, which absorbs power and slows down the vehicle. A "jake" brake works by controlling the exhaust valves, The exhaust valves are opened just before TDC under no fuel conditions, evacuating the compressed air into the exhaust. If the valve was not opened, the compressed air would push the piston back down, recovering the energy required to compress the air by returning that enegry to the drive train.

[Steve W.]

Smoke from brakes means the brakes are failing, the brake material starts to heat up which causes gases from the binder materials to come to the surface, Those build up between the shoes and drums and act like lubricant. The friction starts to drop BUT the friction is still enough to cause heat that can ignite the grease and rubber components in the brake system.

Just like holding the brakes in a car. Both cause brake fade.

The problem then becomes, can you let off the brakes and let them cool, as well as did the shoes get hot enough that it glazed the shoes and drums. If that happens you lose a LOT of braking ability.

[Steve W.]

Wrong. The driver said he had too much speed and weight to stop in the available distance. That doesn't mean he was speeding.

What it means is that for the amount of room he did have the truck couldn't have been stopped.

[clare]

It means he was driving too fast for conditions. 40MPH on a 6% grade is just being totally stupid, even if the speed limit is 60. Control speed with a jake on an average rig is closer to 25MPH

[Steve W.]

None of which matters because the brakes worked. "witnesses saw smoke coming from the brakes"

[Steve W.]

The actual limiting factor was gravity.

The smoking brakes means that he had been using the brakes coming down the grade, they started to heat up (which is what they do, convert the kinetic energy of rotary motion into heat energy through friction) Want to demonstrate this, take DRY hands and rub them together rapidly, what happens? They heat up.

Now in this case the brakes were already heated from the earlier usage, When he "jammed" on the brakes the heated shoe surfaces started to outgas. This is common and actually normal to an extent. Basically the binder material that glues the friction material together gets heated and small amounts of gas/smoke are released. After the first few NORMAL stops heat the brakes up the process slows because the heat levels never rise much more.

In a panic stop the brakes create far above normal friction, the heat rises VERY rapidly and the shoes try to absorb the heat and try to release the heat into the air. The drums also get VERY hot and they try to dump the heat into the air as well.

While this is happening the gases from the brake shoes actually act like lubricant, that destroys the friction coefficient. The remaining friction keeps heating things up in a vicious cycle.

What the CHP will do is go over the drivers records. Then the trucks records, including ALL the paperwork. They will look at the weight ratings of the components as well.

Those ratings will be a key item. Every vehicle on the road has brakes engineered to stop a given weight. Basically they take the GVWR and calculate the amount of braking force that will be able to stop that weight in a given distance at a given speed while still maintaining control of the vehicle. Then they add in a safety margin to cover some misuse/abuse and unforeseen circumstances.

Most big trucks have brakes far larger than they actually need, BUT it is also possible that they don't.

[dsi1]

My brother-in-law took one of those courses for a trucker's license. He dropped out when he realized the class was a scam and that the graduates were unfit to drive those big rigs. He said that the situation was quite scary and that it's not safe on the highways with these drivers out there.

[Steve W.]

That was the number we used as a baseline for training in ideal conditions in a modern rig. The thing is how many times do you try to leave yourself open braking room only to have 10- 4 wheelers drop into the hole? I know I could never open a hole in most places with traffic, So you do the next best thing, look for ways to slow down and try to leave yourself a way out.

[Steve W.]

Even worse when it looks like the grade drifts to the inside of the curve. The tractor moving right just cracked the whip on the trailers.

Yep, descending grades are just one place you don't try to keep up with the flow of traffic.

BTDT pulling doubles with a flat nose K-worth.

[clare]

I would strongly agree that the training required to get a truck licence is inadequate and there are WAY too many guys out there driving vehicles WAY beyond their competence level. Get them into an out-of-the-ordinary situation and they don't have a clue what to do, or how.

[clare]

You can depend onsomeone cutting you off and taking away your buffer zone - so you NEED to adjust your speed accordingly - approach the downhill at reduced speed - preferably close to "control speed" so the brakes are not required to maintain the speed. A good Jake can be worth it's weight in gold.