What is Jack-Kniving?

The rig jackknifes when the drive axle brakes lock up.

Figure 1. If you lock the steering axle brakes, the rig will move straight ahead regardless of the wheel angle.

Figure 2. If you lock the drive axles, the rig will jackknife.

Figure 3. If you lock the trailer axles, you will get trailer swing.
 

Case 1. is the best situation although it's not really good, you can't steer.

Case 2. is very bad, you will jackknife sooner or later if you lock your drivers regardless of what your steering axle is doing- even if you have your steering wheels pointed straight ahead. Road crown or left/right imbalances will get you if you slide long enough.

Case 3. Like case 2., once you lock the brakes, you lose directional control at the axle, and sooner or later a sideways pull will develop that effects the directional stability of the vehicle.

The basic problem is that pneumatic tires only offer so much traction and if you use it all in braking, you haven't got any left to resist even slight lateral forces. If you can keep the axles from locking up, even 5% short of lock up, you can generally preserve directional stability and even some steering capability. But this can be hard to do without ABS, especially with unbalanced brakes or a poorly distributed load.

Bottom line: In an emergency situation-without ABS- you've got your choice of directional stability or maximum braking. If you dynamite the brakes you may lock some axles and get one of the problems listed above. Which axles, if any, lock depend on the condition of the brakes and the weight on each axle. Case 2. should be avoided at virtually all costs, if you jackknife you may rollover. Case 3 is a little better, it will take a little longer for trailer swing to get you into serious trouble, unless the trailer hits another vehicle when it swings out. Case 1. is the least dangerous, you can't steer much in a semi anyway. A hard steering manouevre will roll you.

So:
Don't back off or disconnect the steering axle brakes! You need them bad when your bobtailed and even when your deadheaded or fully loaded they are important. Steering axle brakes provide about 12% of the total braking of a loaded vehicle and you need all the braking you can get.

Whilst it maybe very tempting to relive the skateboarding days of your youth, it also can be very dangerous on a pallet truck.

Well after another exciting week of football, we have a new Team in first place North London Logistics. And from last night

LUKASZ FABIANSKI left fans rubbing their eyes as he put in a star turn between the sticks.

Fabianksi has built up a reputation as a clanger keeper in his blundering time at the Emirates.

But he was the best player on the park as the Gunners turned over Partizan 3-1.

At Stamford Bridge, John Terry (7) and Nicolas Anelka (7) found the net in Chelsea's 2-0 win over Marseille.

But it was Florent Malouda who took the top billing with an 8.

At the weekend, Jerome Thomas took his revenge on Arsenal for shipping him out of the club.

Thomas, a Gunners old-boy, led the charge in West Brom's amazing 3-2 win at The Emirates.

This week we have a new leader in our Mini-League "Dave's Destroyers", but the surprising thing about this is that the team has 5 players in it that have scored less than 10 points each and of which 2 of them have scored nothing. If the team manager had picked some better defenders then the team would be unstoppable.

Here is the table as it stands to date:

A couple of weeks ago I got involved with helping out on a job that was for charity. The local press turned up and wrote an article and took some pictures.

The job entailed picking up 1,500 cartons of food for the Pakistan Flood Relief which was donated and loaded by the volunteers of the Husseini Islamic Centre in Stanmore and shipping it their along with the help of one of our customers Middle East Cargo.

Both companies offered their services for free as it was such a good cause. Here is the article:

Well the weekend saw alot of happiness and misery for some teams and other teams were left without their players who were cheating on and off the pitch, mentioning no names. Rooney played last night in the Champions league which saw them draw against Rangers.

Anyway back to the PPL mini league and there were definitely a couple of DJ's spinning the wrong tunes at the weekend leaving them in 7th and 34th place. Plumbonline Punters are at the top of the league now and I wonder how long they will stop there for, maybe a little while as they are 17 points in the lead. But who knows what will happen at the weekend folks, so stay tuned to the hottest Mini-League on the planet. Manage your team right and you could be one of the most successful managers in the world, just like this guy

Ok well maybe not :-/

So here is our Mini-League as it stands to date:

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We have just launched our newest website www.pplonline.co.uk So for all of you out there without an account and need something shifting on a pallet anywhere in the UK you can now book online and we will come and collect from you and we will even bring a pallet if you need one. We have had lots of orders already ranging from ovens, car gear boxes and a 6ft bath. We can take all major credit cards online at www.pplonline.co.uk

This week was very exciting in our mini league and the places have changed quite dramatically. We have a new leader with quite an amazing score. Also this week we will see how good the England team will play against Bulgaria on Friday night 3rd September 2010. I'm sure Mr Capello is fully aware that there needs to be some drastic changes if we are going to stand a chance in the Euro 2012 competition, so I hope the boy comes good tomorrow night. But things are not going to change overnight and 1 victory is not going to impress the media or me.

Anyway here is the Mini League as it stands to date: