Chucking?

[Blanco1]

As I research more & more I keep learning & the latest thing is chucking?
What the cheapest way to prevent it?

[Sabretooth007]

Reddog1 wrote:
Sabretooth007, have you driven on California highways? Some are plain horrible, especially state highways.

Wayne

Yes I have, but whereas California has rough roads they are not as bad as Louisiana, It matters not, but when you go over a Bayou you drop 4 inches and there are NO warnings, Plus the fact every expansion joint is like going over a speed bump, at least in California you have warnings and regular ongoing construction. There is also a huge difference in population and road users. Louisiana has a population of about 5 million whereas California has about 39 million.. You would think a larger population would have the worst roads but that is not true. I drive CA 101 to OR and WA quite regularly and the I 5 a lot. Plus various roads between Barstow and the Coast. I will take CA over LA but that's my opinion...
Can you open a thread for worst roads ??

Thank appreciated..

[justme]

Well I looks like everyone has a solution albeit some are rather faint. But I'll stick with my TrailerAire. That works well for me and I can set the Air pressure to correct for the variables.
I pull a 16500 GVW 40ft fifth Wheel with a F350 SRW. I have over 50,000 miles on the trailer and have not had any real chucking problems after I installed the TrailAir.

[rhagfo]

Bigg Al wrote:

Reddog1 wrote:
So, Bigg Al, you also think more pin weight reduces Chucking?

From my experience, it certainly seems to make a big difference having more Pin Weight.

X3!

[Reddog1]

Sabretooth007, have you driven on California highways? Some are plain horrible, especially state highways.

Wayne

[Sabretooth007]

richardcoxid wrote:
In my mind this is what happens- Chucking

Assume that you are going down the highway in a steady state condition. Level ground, constant speed, smooth pavement etc. this would take a constant amount of power (energy). Now you come to a concrete slab that is say 1 inch higher than than the previous slab.

When the front wheels of the TV contacts the higher slab the front of the TV has to raise which also compresses the front springs to absorb the 1 inch change. It takes energy to raise the TV and to compress the springs (i.e. the TV is going up hill). This energy is subtracted from the energy that is maintaining the constant speed which momentarily slows the TV. At the same time the RV momentum is pushing the RV ahead, Chucking! The same thing happens when the rear wheels of the TV contacts the higher slab, Chucking

When the RV tires contact the 1 inch higher slab the same thing but opposite happens, the RV momentarily slows while the TV is continuing to maintain the constant speed. Chucking!

When the TV comes down off the higher slab the TV momentarily gains speed (i.e. It is going down hill) while the RV is maintaining your constant speed, Chucking!

When the RV comes off the higher slab, same thing except the opposite- The RV momentarily speeds up while the TV is maintaining constant speed, Chucking.

Of course the more slop there is between the hitch pin/hitch jaws and in fact the whole hitch assembly the worse the Chucking. From some of the TDR comments it seems that some outfits are worse than others. RV springs, shocks and tires probably also enter into "Chucking" but the basic problem is the unevenness (chuck holes) of the pavement.

I am sure that some member that is more of a mathematician than I am could calculate the energy gain/loss for say a TV with a 3,000# front axle/ 5,000 rear axle weight and a RV with a 10,000 axle weight.

With all due respect I disagree, because the tow vehicle is pulling the trailer, therefore the trailer is reliant on the tow vehicle for forward and backward movement. Hence the trailer can only push a tow vehicle when brakes are applied or the prime mover is accelerating which causes a rear pull back. But up and down will vary with the road and conditions. This is plainly seen driving through Texas verses Louisiana. And I for one would vote Louisiana as the worst roads in the US, but I will yield that to other to vote on.

[Bigg_Al]

Reddog1 wrote:
So, Bigg Al, you also think more pin weight reduces Chucking?

From my experience, it certainly seems to make a big difference having more Pin Weight.

[Reddog1]

So, Bigg Al, you also think more pin weight reduces Chucking?

[Bigg_Al]

For me, I have experienced some Chucking when I forget to select the "Alternate Ride Height" on my Ram 3500 air suspension. It lowers the rear suspension a few inches and in that mode, I never feel any Chucking. By lowering the front ride height of the trailer, you're putting more pin weight on the hitch, which, in my case, makes a huge difference with my 36 foot Open Range Fifth Wheel.

[justme]

Here is a Trailer Life article that may help understand this problem.

http://www.trailerlife.com/tech/qa/trailer-surging/

[Reddog1]

I am probably going to step in it, but it seems to me that the greater the pin weight, the less chucking will be felt. Is this true?

[JIMNLIN]

In my mind this is what happens- Chucking

Good case scenario.
Your scenario is what we call freeway hop....just another of the many causes for chucking.
Freeway hop is hard to get a handle on why the combo does it and why other truck/trailer combos have no hop issues at all on the same concrete freeways with those type expansion joints.
My state tried angled joints on a couple of major US highways but slabs still tilted.
There a bitzch till the state chips the slabs flat to each other.

[neal10a]

richardcoxid.. You are correct about chucking. A software simulation using vector analysis is what an engineer would use to demonstrate it on a computer. It would take into account truck/trailer, speed, weight, harmonic/phase shift distribution, spring rate/dampening as well a leverage on the fifth wheel in three dimension which would be interesting to watch on a monitor. The vector sum would result in a back and forth movement of the truck. The pin box leverage on the truck is much different than a tow trailer which is the reason fifth wheel trailers call it chucking and tow trailers call it porpoiseing.
Chucking generally can not be compeltely limited unless the compenstion is very precise which is impracticle for all highways conditions and trailer/truck criticl dampening charactoristics. It can be minimized with some of the 5th wheel solutions like MorRide and TrailAir.

[richardcoxid]

In my mind this is what happens- Chucking

Assume that you are going down the highway in a steady state condition. Level ground, constant speed, smooth pavement etc. this would take a constant amount of power (energy). Now you come to a concrete slab that is say 1 inch higher than than the previous slab.

When the front wheels of the TV contacts the higher slab the front of the TV has to raise which also compresses the front springs to absorb the 1 inch change. It takes energy to raise the TV and to compress the springs (i.e. the TV is going up hill). This energy is subtracted from the energy that is maintaining the constant speed which momentarily slows the TV. At the same time the RV momentum is pushing the RV ahead, Chucking! The same thing happens when the rear wheels of the TV contacts the higher slab, Chucking!

When the RV tires contact the 1 inch higher slab the same thing but opposite happens, the RV momentarily slows while the TV is continuing to maintain the constant speed. Chucking!

When the TV comes down off the higher slab the TV momentarily gains speed (i.e. It is going down hill) while the RV is maintaining your constant speed, Chucking!

When the RV comes off the higher slab, same thing except the opposite- The RV momentarily speeds up while the TV is maintaining constant speed, Chucking.

Of course the more slop there is between the hitch pin/hitch jaws and in fact the whole hitch assembly the worse the Chucking. From some of the TDR comments it seems that some outfits are worse than others. RV springs, shocks and tires probably also enter into "Chucking" but the basic problem is the unevenness (chuck holes) of the pavement.

I am sure that some member that is more of a mathematician than I am could calculate the energy gain/loss for say a TV with a 3,000# front axle/ 5,000 rear axle weight and a RV with a 10,000 axle weight.

[ken_burke]

A potential problem would be with the hitch. You may have to bug the hitch manufacture to come out and check out the hitch.
Once you cucking problem is under control you may want to consider a TrailAir pin box. Get the right one and it sofens the trailer up and down motion, as well as the front and back motion. I have one and it really works.
ken

[IBcarguy]

Sabretooth007 wrote:
For what its worth in my opinion, the problem is created by poor manufacturing, the 5th Wheel axels are in the center of the trailer, which causes an easy up down movement. In retrospect a semi trailer, Horse trailer and the like have their axels at the rear which causes less up and down movement. Their is also the question of how the trailer is loaded and its weight plus levelness with the tow vehicle. A trailer which is high at the front (not level) affects the center of gravity and in turn having a poor center of gravity causes driving and stability problems. Also fresh water tanks don't have baffles so any movement of the trailer will cause the water to move in all directons (same with black and grey tanks)

One of the easiest ways to correct the problem is level the trailer to the truck, and slow down, 55 mph is a good speed as noted driving CA..
And if you don't want to slow down then don't complain..

I think "chucking" is a back and forth, jerking motion and not an up and down motion. That's why I don't think truck or trailer suspension has much to do with it. Shocks, springs, and air bags certainly has effect on up and down movement of the suspension/axles but won't have much effect on the back and forth movement of chucking.