ProPride for smaller Airstreams

[dznf0g]

Originally Posted by pteck

What you don't understand is that only the sway component is projected 52" forward of the ball. It does that and does it well.

Vertical forces, or tongue weight, is projected ~12" further aft. Let that sink in. Said another way, the tongue weight of the trailer is carried in cantilever 12" further aft. An analogy is like holding a watermelon close to the chest. Now try to hold that same weight with your arms out. Apply WD they say.. it's going to take that more tension to compensate for worse geometry there, nevermind the forces that it puts on the TV and trailer structures. That cantilevered weight is why PPP type hitches suffer more from harmonics and porpoising.

A PPP type hitch is not the win-win that marketing wants you to believe.

You are absolutely correct for a non-WD (towing on the ball) hitch setup. What you aren't recognizing is that when WD is applied, the hitch head and its drawbar are no longer cantilevered. Visual evidence of this is observing the position of the drawbar at the receiver opening. If the drawbar is resting on the bottom of the receiver opening, it is cantilevered. If it is forced up against the top of the opening, it is not. The first thing that happens when wd is applied is the spring bar force applies torque to the head and forces(opposing gravity and overcoming the weight of the head) the ball up into the coupler. Meanwhile the rear end of the spring bar begins forcing the coupler down onto the ball (and begins trailer axle spring compression (additive to the force for gravity). Dimensions determine how much.

Bottom line: the drawbar and hitch head are no longer "part of the truck", but are part of a trussed span of the trailer, with that span being from the receiver pin to the trailer axle.

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[switz]

After the PPP setup, if the vehicle side of the adjustable stinger is pointing down, I take it to a machine shop and have is cut flat to the bottom plates of the trailer side part. It is not expensive to get another vehicle side part in the future if needed.

For the Land Cruiser, we drilled another pin hole 2" closer to the hitch head which allows the stinger to be less than ½" from the receiver opening. That also required cutting about 2" off the length of that piece of steel to be able to seat and not touch the auxiliary gasoline tank. We also cut the protruding vehicle side 2" steel bar above the frame of the trailer side. Probably took 8 to 10 pounds of weight off. Makes it easier for an old fart like me to handle the assembly.

[pteck]

Originally Posted by dznf0g

You are absolutely correct for a non-WD (towing on the ball) hitch setup. What you aren't recognizing is that when WD is applied, the hitch head and its drawbar are no longer cantilevered. Visual evidence of this is observing the position of the drawbar at the receiver opening. If the drawbar is resting on the bottom of the receiver opening, it is cantilevered. If it is forced up against the top of the opening, it is not. The first thing that happens when wd is applied is the spring bar force applies torque to the head and forces(opposing gravity and overcoming the weight of the head) the ball up into the coupler. Meanwhile the rear end of the spring bar begins forcing the coupler down onto the ball (and begins trailer axle spring compression (additive to the force for gravity). Dimensions determine how much.

Bottom line: the drawbar and hitch head are no longer "part of the truck", but are part of a trussed span of the trailer, with that span being from the receiver pin to the trailer axle.

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If it were only so easily mitigated. WD tension only compensates, and surely does not hide what is worse geometry than a standard WD hitch for vertical forces, i.e. the load.

Everything we have learned is that a 5th wheel ball location over the rear axle is ideal. No further WD bars or sway control necessary.

Sway was never the primary consideration. That again is being able to carry a load with a bumper pull in cantilever.

That a PPP hitch moves the very load we're carrying further in cantilever? And markets a red herring that it's all about sway?

A properly setup bumper pull will manage and mitigate sway more than adequately as proven by the masses that use such setups. And do a much better job of actually carrying the load as it doesn't try to carry that load 12" further aft.

[dznf0g]

First off, we aren't discussing fifth wheels. Completely different animal.
You will have to clarify for me specifically what "bad geometry" is, by your declaration. I am very unclear what you mean. Please use mathematical examples.

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[pteck]

Let's start with a picture.

On a tow vehicle, where would you ideally locate, say a 1000lb tongue load. Where do you think the PPP locates it?

[dznf0g]

Originally Posted by pteck

Let's start with a picture.



On a tow vehicle, where would you ideally locate, say a 1000lb tongue load. Where do you think the PPP locates it?



Attachment 416419

Again you are correct if you were towing with no wd....on the ball only
..or removed the spring bars on a ppp. When I can get to my laptop I'll show the formulas with wd hooked up and not hooked up.

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[pteck]

Originally Posted by dznf0g

Again you are correct if you were towing with no wd....on the ball only
..or removed the spring bars on a ppp. When I can get to my laptop I'll show the formulas with wd hooked up and not hooked up.

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WD bars are only limited compensation for a cantilevered load. Notably, they are less effective and require more compensation with loads further in cantilever, e.g. PPPs. Where dynamic load forces are even harder to control, and why people report more excessive porpoising. Increasing WD tension is not a magic elixir as it puts huge stresses on the structures, especially when going over dips and transitions.

The best solution for a bumper pull has always been to keep the ball as close and tight to the bumper as possible. While paying attention to other contributing factors for stability. This maximizes vehicle stability, in both sway and load forces, by keep the wheelbase to rear overhang ratio as high as possible. That in itself will pay huge dividends to maximizing the stable performance envelop, while minimizing the possibility for sway.

A PPP trades better sway control for poorer load control. If that's the trade that's necessary for a setup, then that's a win. But PPPs are certainly not a win-win that many assume it is and to use it for every setup which may not need one is missing out on what could be a better setup. Especially when considering the other trades like extra length when hitched or unhitched, weight, cost, difficulty hitching, hensley bump, etc.

[dznf0g]

Originally Posted by pteck

WD bars are only limited compensation for a cantilevered load. Notably, they are less effective and require more compensation with loads further in cantilever, e.g. PPPs. Where dynamic load forces are even harder to control, and why people report more excessive porpoising. Increasing WD tension is not a magic elixir as it puts huge stresses on the structures, especially when going over dips and transitions.

The best solution for a bumper pull has always been to keep the ball as close and tight to the bumper as possible. While paying attention to other contributing factors for stability. This maximizes vehicle stability, in both sway and load forces, by keep the wheelbase to rear overhang ratio as high as possible. That in itself will pay huge dividends to maximizing the stable performance envelop, while minimizing the possibility for sway.

A PPP trades better sway control for poorer load control. If that's the trade that's necessary for a setup, then that's a win. But PPPs are certainly not a win-win that many assume it is and to use it for every setup which may not need one is missing out on what could be a better setup. Especially when considering the other trades like extra length when hitched or unhitched, weight, cost, difficulty hitching, hensley bump, etc.

Again???

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[pteck]

Originally Posted by dznf0g

Again???

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Right, you were going to show us your math.

[dznf0g]

Originally Posted by pteck

Right, you were going to show us your math.

I'm still away. Need my laptop. May be a few days.

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[JJTX]

Originally Posted by hikingcamera

There have certainly been some very strong opinions, but I did ask for opinions and I agree I'm not sure anyone has said I "have to" do anything. This has been a not surprisingly contentious thread, and it's been useful to hear the varied opinions. Nothing I didn't ask for.

At this point we're going to use the BlueOx that we have now to start and see how it feels. Our last TV/TT combo (Toyota Highlander and 3300-lb, 19-foot TAXA Mantis) felt very solid with the BlueOx in terms of sway. Of course the Highlander is such a light tow vehicle, so you could definitely feel the trailer. Well see how the F-150 / FC23CBB feels.

I have a fastway E2 8000 LB rated version. One of these would work for you just fine, as well. I have about a 4500LB max trailer gross so a little lighter than yours. I don't think you would need the 10K version of my E2 hitch.

I've been very happy with the E2 system.

I think if you dont over-pack, and ensure a level ride, You'll be fine with the OX system too. Most people have trouble because they are over-loaded and are driving too fast.

[dznf0g]

First, a definition of cantilever, "a long projecting beam or girder fixed at only one end, used in bridge construction". So your thinking is correct when a hitch head (stinger and rocktamers) are hanging from the receiver. Not only that, but if you are going to tow on the ball, or lower your jack, without any WD applied, you add a load (trailer coupler weight) to the cantilevered end of the head at the ball. With a PPP you add the head and the TW, and in both cases the load placed on the rear axle is higher than the calculated weights of the tongue and hitch components. I think everyone understands that and I don't need to go through that exercise. I think what formulas you were expecting have to do with what happens when WD is applied....correct?

So, I am going to use my setup (propride), My TV and my trailer for all loads and dimensions, as that is what I have worked up. All conventional WDs work in the same fashion, but with different weights and dimensions. (Anderson uses same principles, but in a very different application of those principles and I am not interested in going there).

All calculations start with a CAT scale set of results, some Sherline readings, and a physical weighing of the hitch components on a doctor's scale. You also need to know the CoG of the hitch components as best you can. Since I don't have engineering line drawings of my PP, I had to balance the components on the edge of a 1/2" piece of plywood. Pretty easy for all the PP components, except the head...heavy and very unevenly shaped on the bottom.

Also, in order to know the forces applied by the spring bars, you have to back into the rear end bar force from the CAT scale tickets. There is a WHOLE BUNCH of calculations that go into that result.

When I weigh, I do 5 passes. truck alone (NO STINGER IN THE RECEIVER), combo with no WD, combo with 3, 4 and 5" of jack showing. The 3 positions verify the linear progression of WD application by the spring bars.

I know I am going to forget to cover some background points, but I'll move on, More to follow...

[dznf0g]

So, when WD is applied, the tension you put into the system (either by jacks, chains and snap-ups, or whatever) results in force being applied in two locations. a downward force on the A-frame at the jack and a torque on the front end of the spring bars, which is counter-clockwise (looking at the hitch from the driver side). That torque results in a vertical up force at the ball. The torque also is exerted all the way through the drawbar, the receiver, and through the TV frame all the way to the front axle. The resultant forces of that torque varies with the dimensions..WB, rear overhang to the receiver pin, receiver pin to ball, and ball to TA.

WB = wheelbase
RA to Pin = rear TV axle to receiver pin distance
pin to ball = receiver pin to hitch ball or coupler distance
ball to jack = ball or coupler to jack distance
ball to TA = ball or coupler to trailer axle center distance
SBF = spring bar force
Jacks to pin = WD jack to receiver pin distance


Remember...NO WEIGHT IS MOVED! We are applying an additional force (spring bar) which assists or opposes the force of gravity at 3 locations, FA, RA and TA.

The miracle of physics is that the true effect of the forces on these points DOES equal the results of the phrase, "we are removing x pounds from the RA and moving it to the FA and TA.

So the rear of the spring bar does two things:

1) applies a downforce at the trailer coupler

SBF*((TA to ball - jack to ball)/TA to ball)+TW

2) applies a down force at the TA

SBF*(jack to ball/TA to Ball)

Meanwhile the front of the spring bar is exerting an upward force (countering gravity) through the application of torque.

Relative to the above discussion, this is where the hitch head/drawbar (stinger and PP head) cease to become a cantilevered mass hanging from the TV receiver:

SBF*((jacks to pin/ball to pin))

The result of this formula, at the receiver, forces the head upward with great force (you will find that the clamp load at the coupler/ball interface is in the thousands of pounds)
Ultimately this same force, through torque lifts the rear TV axle and allows gravity to be opposed less and settle back to your desired TV manufacturer ride height or weight return on the front axle. (of course, that determines the amount of spring bar force to apply).
If you plug various scenarios into these formulas, you can see the effect of different dimensions on the outcome....but it should become clear that the "no WD' scenario of a cantilevered weight on the ball is replaced by a rigid beam running from the TA to the receiver pin (in the system's static state anyway). Of course the system has to have dynamic flexibility about the ball, thus the "springy" truss.

Again, simplistically, if the visible lower horizontal edge of the drawbar is resting on the bottom of the receiver opening, there is a cantilevering situation. If the upper horizontal edge of the drawbar is forced to the top of the receiver opening ...no cantilever and a trussed trailer/hitch system is acting on the TV.

There are a LOT more calculations involved with the hardware between the receiver and trailer axle. This just addresses the "is the hitch part of the truck or part of the trailer?"

Like...what's the effect on receiver weight (hitch weight) with the trailer coupler 20" away from the receiver pin instead of 10"?

What is the effective weight of the hitch head and drawbar at the receiver pin?

How much of the spring bar weight, jacks/snap up bracket, yoke is carried by the head vs the coupler?
How much of those weight splits are carried by the coupler and how much carried by the TA?

[pteck]

Originally Posted by dznf0g

So, when WD is applied, the tension you put into the system (either by jacks, chains and snap-ups, or whatever) results in force being applied in two locations. a downward force on the A-frame at the jack and a torque on the front end of the spring bars, which is counter-clockwise (looking at the hitch from the driver side). That torque results in a vertical up force at the ball. The torque also is exerted all the way through the drawbar, the receiver, and through the TV frame all the way to the front axle. The resultant forces of that torque varies with the dimensions..WB, rear overhang to the receiver pin, receiver pin to ball, and ball to TA.

WB = wheelbase
RA to Pin = rear TV axle to receiver pin distance
pin to ball = receiver pin to hitch ball or coupler distance
ball to jack = ball or coupler to jack distance
ball to TA = ball or coupler to trailer axle center distance
SBF = spring bar force
Jacks to pin = WD jack to receiver pin distance


Remember...NO WEIGHT IS MOVED! We are applying an additional force (spring bar) which assists or opposes the force of gravity at 3 locations, FA, RA and TA.

The miracle of physics is that the true effect of the forces on these points DOES equal the results of the phrase, "we are removing x pounds from the RA and moving it to the FA and TA.

So the rear of the spring bar does two things:

1) applies a downforce at the trailer coupler

SBF*((TA to ball - jack to ball)/TA to ball)+TW

2) applies a down force at the TA

SBF*(jack to ball/TA to Ball)

Meanwhile the front of the spring bar is exerting an upward force (countering gravity) through the application of torque.

Relative to the above discussion, this is where the hitch head/drawbar (stinger and PP head) cease to become a cantilevered mass hanging from the TV receiver:

SBF*((jacks to pin/ball to pin))

The result of this formula, at the receiver, forces the head upward with great force (you will find that the clamp load at the coupler/ball interface is in the thousands of pounds)
Ultimately this same force, through torque lifts the rear TV axle and allows gravity to be opposed less and settle back to your desired TV manufacturer ride height or weight return on the front axle. (of course, that determines the amount of spring bar force to apply).
If you plug various scenarios into these formulas, you can see the effect of different dimensions on the outcome....but it should become clear that the "no WD' scenario of a cantilevered weight on the ball is replaced by a rigid beam running from the TA to the receiver pin (in the system's static state anyway). Of course the system has to have dynamic flexibility about the ball, thus the "springy" truss.

Again, simplistically, if the visible lower horizontal edge of the drawbar is resting on the bottom of the receiver opening, there is a cantilevering situation. If the upper horizontal edge of the drawbar is forced to the top of the receiver opening ...no cantilever and a trussed trailer/hitch system is acting on the TV.

There are a LOT more calculations involved with the hardware between the receiver and trailer axle. This just addresses the "is the hitch part of the truck or part of the trailer?"

Like...what's the effect on receiver weight (hitch weight) with the trailer coupler 20" away from the receiver pin instead of 10"?

What is the effective weight of the hitch head and drawbar at the receiver pin?

How much of the spring bar weight, jacks/snap up bracket, yoke is carried by the head vs the coupler?
How much of those weight splits are carried by the coupler and how much carried by the TA?

I appreciate the effort and detail put forth here.

I think it would also be useful to step back and consider that this is not a static system. The reality is when underway, the forces in the system change, sometimes dramatically. The more cantilever, the more leverage the load has on the system. WD hitch tension has to be enough to compensate nominally for the cantilever, but it cannot fully truss and isolate forces to the point that things can and will break. Hitches need to articulate after all.

And that's where a standard WD hitch has a strong advantage - less cantilever. Less WD tension to compensate for the same load. And load forces don't have as much leverage to play seesaw with the TV.

[ROBERT CROSS]

Engineer...getting paid for being rong.

Explain the less tension for the same load.
I went from 1400 bars to 1000.
I "tension" the 1k more, move more than I could with the 1400, with the added benefit of a much more compliant, less stressful lash-up.

Bob
🇺🇦🇺🇸🇺🇦

[dznf0g]

Originally Posted by pteck

I appreciate the effort and detail put forth here.

I think it would also be useful to step back and consider that this is not a static system. The reality is when underway, the forces in the system change, sometimes dramatically. The more cantilever, the more leverage the load has on the system. WD hitch tension has to be enough to compensate nominally for the cantilever, but it cannot fully truss and isolate forces to the point that things can and will break. Hitches need to articulate after all.

And that's where a standard WD hitch has a strong advantage - less cantilever. Less WD tension to compensate for the same load. And load forces don't have as much leverage to play seesaw with the TV.

Oh yes, when dynamics start, everything changes constantly and dramatically. Everything we do to set up and all instructions given as to weight distribution in the truck and trailer, and hitch setup, and scale readings are all at the static state. It is hard to load, adjust and read weights while running along side of the combo at 60 mph. All we can do is comply with the setup advice (as lacking as it is at times) and trust that the folks who designed all the parts of the system accounted for dynamics.

Again, there is no cantilever in the hitch system when WD is applied...but I think what you are saying is there is more mass with a PPP undulating up and down during trave than there is with a conventional WD hitch system. That is true, but I think you are placing more impact of that fact than is practically valid. I have noticed no more propensity for porpoising with either hensley or propride PPPs over the Eq, and Reese dual cam which I ran in the past.
Your concern could equally be stated for 125# of bikes and rack placed on the tongue....or full 40# capacity propane tanks over empty 20# tanks....or loading a generator on the tongue, or loading heavy items near the front wall inside. All of these things, including a heavier hitch system have an effect, in proportion to their physical location, but not as much detrimental effect as you seem to be communicating.

With a 50% return to FA (by weight and by height) I am applying just a bit over 700# of spring bar end force with 1k bars when loaded for my heaviest trip of each season.

[dznf0g]

Originally Posted by ROBERT CROSS

Engineer...getting paid for being rong.

Explain the less tension for the same load.
I went from 1400 bars to 1000.
I "tension" the 1k more, move more than I could with the 1400, with the added benefit of a much more compliant, less stressful lash-up.

Bob
������������

When you say tension the 1k more, I assume you mean that you are raising the jacks more????

It takes the same spring bar end force to "move" the same weight with both ratings. The 1400s just flex less to arrive at that end force. I don't understand the "move more" statement. Movement to the front axle is strictly dependent upon spring bar end force and physical dimensions.

[ROBERT CROSS]

Originally Posted by dznf0g

When you say tension the 1k more, I assume you mean that you are raising the jacks more????

It takes the same spring bar end force to "move" the same weight with both ratings. The 1400s just flex less to arrive at that end force. I don't understand the "move more" statement. Movement to the front axle is strictly dependent upon spring bar end force and physical dimensions.

Exactly...I appreciate the flex, stiff is good for other things but I'd rather have a compilable connection.
Move more?...I neglected to remember that I also swapped out the OEM receiver for a V Reese..that improvement in the receiver moment arm also helped.👍

Bob
🇺🇦🇺🇸🇺🇦

[dznf0g]

Originally Posted by ROBERT CROSS

Exactly...I appreciate the flex, stiff is good for other things but I'd rather have a compilable connection.
Move more?...I neglected to remember that I also swapped out the OEM receiver for a V Reese..that improvement in the receiver moment arm also helped.👍

Bob
🇺🇦🇺🇸🇺🇦

Absolutely, flex is good. That is the major reason I very quickly realized that I did not like the Eq (1k bars) that came with my AS. That and noise and greasy.
My dual cam (800# bars) is very compliant moves all the weight I need, but 800# is a bit of a narrow margin dynamically.

The PPP (both of them) is the "just right porridge" for my setup. Quiet, incrementally better in the anti-sway, no greasy pant legs, etc.

[pteck]

Originally Posted by ROBERT CROSS

Engineer...getting paid for being rong.

Explain the less tension for the same load.
I went from 1400 bars to 1000.
I "tension" the 1k more, move more than I could with the 1400, with the added benefit of a much more compliant, less stressful lash-up.

Bob
🇺🇦🇺🇸🇺🇦

I suspect you're not here for the discussion and your mind is made up. If it's working for you, that's all that matters.

As this is a discussion board, the rest of us are here to learn and exchange ideas.

To that point, this may be a simpler way to understand how supporting a weight further in cantilever is not great as it gives the tongue load more lever arm. The rear axle can be modeled as a fulcrum. For an equivalent weight, held further off the rear axle, it will: 1) Transfer more load off the front axle 2) Increasing rear axle load.

WD tension therefore needs to be increased to restore front axle weight. It's also is at a geometric disadvantage with a longer lever arm, again needing more tension.

Invite dynamic forces, and again, because of the increased cantilever and lever arm, it will disturb (porpoise) the system more. These PPP systems have excellent adjustable WD jacks. Using more tension is easy, and may not be as easily perceived by the user. But the structures are certainly feeling it and would not be a great combination for those wandering off the pavement.