color of spring

On Fri, 20 May 2016 12:12:06 -0700, Savageduck
wrote:

On 2016-05-20 18:44:44 +0000, nospam said:

In article 2016052011225163926-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

When you start talking about brakes on 18-wheelers then you are dealing
with vaccum and/or air-brake systems which will typically lockup if
there is a vaccum pump or compressor failure. The most common brake
failure on heavy trucks is overheating due to over use on serious
downhill grades. One typical grade of that type is on the Northbound
I-5 over the Tejon Pass, better known as 'The Grapevine'. There you
will find two runaway ramps below the summit. The second one is a
failsafe to be used if the first one is missed.

best of luck if the brakes fail after the second ramp.

The ramps are 9.5 and 9.8 miles below the summit, quite near the
bottom. Miss either one of those and you have to negotiate the final
wide curve to the left to where the I-5 in the Central Valley is
billiard table flat, so you can roll to a stop.

brakes don't pick a convenient place to fail.

The biggest problem these truckers have is overheating brakes, or a
missed shift which leaves them out of gear on the steep grade, and
dependant on brakes, which are doomed.

There is no way that a loaded 18 wheeler could safely descend such a
hill on friction brakes alone. The driver will have changed down
several gears and using an engine brake (if he has one) and a retarder
also (if he has one). God help him if he misses a shift and ends up
trapped in a neutral gear.

There is also a CHP brake check station on Northbound I-5 before they
reach the summit. The most use made of the runaway ramps is by large
bus type RVs which don't equate themselves with other heavy vehicles.

.... and are driven by less experienced drivers.
--

Regards,

Eric Stevens

On 2016-05-21 01:06:31 +0000, Eric Stevens said:

On Fri, 20 May 2016 12:12:06 -0700, Savageduck
wrote:

On 2016-05-20 18:44:44 +0000, nospam said:

In article 2016052011225163926-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

When you start talking about brakes on 18-wheelers then you are dealing
with vaccum and/or air-brake systems which will typically lockup if
there is a vaccum pump or compressor failure. The most common brake
failure on heavy trucks is overheating due to over use on serious
downhill grades. One typical grade of that type is on the Northbound
I-5 over the Tejon Pass, better known as 'The Grapevine'. There you
will find two runaway ramps below the summit. The second one is a
failsafe to be used if the first one is missed.

best of luck if the brakes fail after the second ramp.

The ramps are 9.5 and 9.8 miles below the summit, quite near the
bottom. Miss either one of those and you have to negotiate the final
wide curve to the left to where the I-5 in the Central Valley is
billiard table flat, so you can roll to a stop.

brakes don't pick a convenient place to fail.

The biggest problem these truckers have is overheating brakes, or a
missed shift which leaves them out of gear on the steep grade, and
dependant on brakes, which are doomed.

There is no way that a loaded 18 wheeler could safely descend such a
hill on friction brakes alone. The driver will have changed down
several gears and using an engine brake (if he has one) and a retarder
also (if he has one). God help him if he misses a shift and ends up
trapped in a neutral gear.

The posted speed limit for trucks on the decent is 35MPH. Most of those
18 wheelers are equipped with compression release engine brakes, better
known as a 'Jake Brake'. Before they start the decent there are
frequent signs advising of the grade, the speed limit for trucks, and
that a lower gear should be selected before starting down the grade.
The last thing those drivers want to do is depend on their friction
brake systems, they will fry their brakes before they are half way down.
http://www.crashforensics.com/tejonpass.cfm
https://en.wikipedia.org/wiki/Jacobs_Vehicle_Systems


There is also a CHP brake check station on Northbound I-5 before they
reach the summit. The most use made of the runaway ramps is by large
bus type RVs which don't equate themselves with other heavy vehicles.

... and are driven by less experienced drivers.

Sometimes.


--
Regards,

Savageduck

On Fri, 20 May 2016 18:46:55 -0700, Savageduck
wrote:

On 2016-05-21 01:06:31 +0000, Eric Stevens said:

On Fri, 20 May 2016 12:12:06 -0700, Savageduck
wrote:

On 2016-05-20 18:44:44 +0000, nospam said:

In article 2016052011225163926-savageduck1@REMOVESPAMmecom,
Savageduck wrote:

When you start talking about brakes on 18-wheelers then you are dealing
with vaccum and/or air-brake systems which will typically lockup if
there is a vaccum pump or compressor failure. The most common brake
failure on heavy trucks is overheating due to over use on serious
downhill grades. One typical grade of that type is on the Northbound
I-5 over the Tejon Pass, better known as 'The Grapevine'. There you
will find two runaway ramps below the summit. The second one is a
failsafe to be used if the first one is missed.

best of luck if the brakes fail after the second ramp.

The ramps are 9.5 and 9.8 miles below the summit, quite near the
bottom. Miss either one of those and you have to negotiate the final
wide curve to the left to where the I-5 in the Central Valley is
billiard table flat, so you can roll to a stop.

brakes don't pick a convenient place to fail.

The biggest problem these truckers have is overheating brakes, or a
missed shift which leaves them out of gear on the steep grade, and
dependant on brakes, which are doomed.

There is no way that a loaded 18 wheeler could safely descend such a
hill on friction brakes alone. The driver will have changed down
several gears and using an engine brake (if he has one) and a retarder
also (if he has one). God help him if he misses a shift and ends up
trapped in a neutral gear.

The posted speed limit for trucks on the decent is 35MPH. Most of those
18 wheelers are equipped with compression release engine brakes, better
known as a 'Jake Brake'. Before they start the decent there are
frequent signs advising of the grade, the speed limit for trucks, and
that a lower gear should be selected before starting down the grade.
The last thing those drivers want to do is depend on their friction
brake systems, they will fry their brakes before they are half way down.
http://www.crashforensics.com/tejonpass.cfm

One of the worst thing about that hill is that as drivers descend the
hill they will encounter an easier stretch at the 6 mile mark. This
will tempt those who don't know the road to change back up a gear or
two. Then they will hit the really steep part with hot brakes and in
too high a gear. It's at this point that a belated attempt to change
back down again may result in a missed gear change. If he is lucky the
driver may be able to get back into too-high a gear but that won't
help him much over the next several miles. No wonder they have run off
roads.

https://en.wikipedia.org/wiki/Jacobs_Vehicle_Systems

Yep, and variations thereof. Some Allison automatic transmissions have
hydraulic retarders built into them. Separate retarders are not
uncommon in Europe (and hilly New Zealand). These may be hydraulic or
electric.

https://en.wikipedia.org/wiki/Retard...engineering%29

For an electric retarder see
http://i00.i.aliimg.com/img/pb/980/5...web10_8277.jpg
or http://tinyurl.com/zpb7uzm


There is also a CHP brake check station on Northbound I-5 before they
reach the summit. The most use made of the runaway ramps is by large
bus type RVs which don't equate themselves with other heavy vehicles.

... and are driven by less experienced drivers.

Sometimes.
--

Regards,

Eric Stevens