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Old 10-18-2006, 08:23 PM   #127
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Quote:
Originally Posted by scottanlily
There are torsion axles with the airbags ,is that right Barry? Then does the
airbags move air between them ,say back and forth as the road changes?
could the porpousing be from the loading and unloading of the bags ?Seems
unusual to have really 2 suspensions going here at once ,bags and torsion arms ,you either have one or the other .I can see lots of shifting of the weight and the unloading of the hitch with this setup ,and the 40 psi is
having an effect on it ,has to as they are pressurized .It would make sense
if your trailer frame is constantly changing its attitude with rgards to the leveling with the bags .Two suspensions here ,can they really work
together ?? do the bags raise the trailer for ride height or for soft ride ,and
doesn't the torsion axles ride smooth already .somthing to really consider
with this setup ,many may say yes its ok ,but that trailer should never
porpouse along the road . this whole setup is a tricky one as well as being
a super long trailer .Im thinking more thought on the suspension .

Scott
Yes, It's Dexter Axle's AirFlex system. It uses the TorqueFlex as suspension and air bags for ride height. dexteraxle.com

Each axle has it's own ride height valve. Air is added or exhausted to maintain a level attitude. The axles are piped in pairs. Each axle has its own dump valve. Each axle has a digital sender for air pressure. The suspension reacts slowly to changes as the air supply is ony 40 lbs. after the regulator.

The equalized pressure air bag set up does nothing but add a cushioned ride. I can tune the tongue weight to a specific weight because I can change the attitude of the trailer with the simple spin of a turnbuckle. Different attitudes change the work load on the axles. These are 8,000 lb axles. The trailer has 24,000 pounds of bearing, brake, lift and suspension capabilities.

There's a safety issue, too. Originally, the engineer at Dexter had drawn me a diagram that would have equalized air pressure for each side. I pointed out that the failure of one element in that piping scheme would lead to severe dynamic change when one side of the trailer instantly drops 6".

They agreed that it was much safe to pipe the axles individually. The failure of any pair would result in the changes I posted above, I think there was a maximum difference of 300 lbs. That's not enough to change the dynamics even if I lost 2 sets of bags.

You keep talking about porpoising. The trailer was bobbing up and down because I loaded the Porsche too close to the rear. That was the dynamic. The ride home was flawless at 60 mph. No porpoising. All I did was tie the load down 4 feet further forward. That eliminated the problem. Flawless ride home. No problems.
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Old 10-19-2006, 02:26 PM   #128
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Sorry to take so long getting back to you on this...

Quote:
Originally Posted by 59toaster
Quote:
Originally Posted by 59toaster

Read that. Understand that Andy literally wrote the book for Airstream when he was their investigator. He has done a lot of testing on the subject and he outlines it in that post.

The bars are to transfer weigh to the front axle of the tow vehicle to level it. So basic logic does say bigger is better in relation to the bars BUT The truck already has stiff suspension for carrying weight. So it sags less then a car. So knowing that we can agree it takes less tension on the bar to level the tow vehicle. We all agree on that part correct?
Not so fast. I read the thread and post you have linked and, while Andy makes good points, his points are about the Reese Straight Line Hitch. I have the Equal-i-zer brand of trailer hitch like the one that Barry has ordered, and probably received by now. That is what my post has been about. Perhaps I was unclear about the specisificity of my comments. Andy's "book" doesn't pertain to the Equal-i-zer brand hitch. They use different methodologies to arrive at the same conclusion.

I'm not sure you understand the way the Equal-i-zer system works. I have never used weight distribution hitches before this summer nor have I dealt with sway control so forgive me if I use incorrect terminology or if I use the wrong term to describe a hitch part. For weight distribution, the spring bars on my hitch are 2X2 solid steel bars held in place in the trunion hitch head by steel pins that are locked into place by cotter pins...they can't fall out like Barry's did no matter how much the rear of the truck comes up and the nose dives...no matter how little tension is on the bars. The rear of the bars are secured to the A-frame by resting on L-brackets with L-shaped retainers that are held in place by cotter pins. The spring bars are free to slide in these brackets during turns. The weight of the tongue on the ball, like on the Reese System is counter acted by the tension on the spring bars. It is like the front axle is the front tire of a wheel barrow, the rear axle is like the legs of the wheel barrow, and the spring bars are the handles. They lift up on the hitch head. This pivots on the rear axle (legs) as you have said and pushes down on the front axle of the tow vehicle as weight is shifted to the front axle. The stiffer the front suspension, the more force is required on the wheel barrow handles to lift up on the hitch head to shift weight to the front axle. In the process of lifting the hitch and tongue of the trailer, some of the weight of the tongue is shifted back onto the axles of the trailer as the trailer pivots on its axles. The key is to balance all of these forces (weights) equally on all four axles. When the weight distribution hitch is set up, if done properly, the correct number of washers will be placed in the trunion, the correct number of holes will be used in the L-bracket (chain links in the Reese system) and this balance will be achieved no matter what the rating is or how stiff the spring bars are. The adjustments to the brackets and washers will compensate for this.

The 3/4 ton truck does indeed have a stiffer suspension and my 3/4 ton diesel truck has an even stiffer front suspension than the average gas job. Therefore, it will take more force from the spring bars to compress the front suspension than, say, a mid-70's Ford Country Squire Station Wagon. Yes, Andy may have written the book on hitches and, I for one will not cast doubt on his vast knowledge of Airstream trailers, but the fact is he was an investigator for Airstream during the '60's-'70's. Books tend to become obsolete with time.

Now for sway control. The sway control for the Equal-i-zer is achieved by the angle of the trunion in relation to the spring bars. This angle when loaded creates a tremendous bind on the pivot bolts that hold the sockets in the trunion head of the hitch. The bind of the sockets against the pivot bolts resist the lateral forces that would allow sway. Porposing or rising of the tongue of the trailer in relation to the front of the tow vehicle would lower the binding force slightly, but only for a micro-second and then it would return immediately. You mention cresting hills allot, but I don't drive on any hills that have the kind of crest that you allude to. None have that a crest that is that acute. They would be called pyramids not hills if they did. The ones that I drive on have extremely gradual curvatures that don't allow for a decrease in the tension on the spring bars. The only time I come close to what you describe is when I am exiting driveways or at exits from fuel stations and I try to keep my speed under 35 MPH - 40 MPH max when exiting truck stops and fuel stations so I don't have to worry about sway! Excuse my sarcasm, I couldn't help myself. Anyway, even if I experienced the kind of "unloading" you are talking about, it would be for a micro-second and the conditions would return to normal without the spring bars dropping out like Barry's did. Ultimately, whatever caused it to occur, the spring bar falling out is what caused his hitch to fail.

I read Andy's article in Airstream Life and am aware of his preference for the Straight Line Reese Hitching System. It is one of the best towing systems on the market. In fact I had determined to buy a Reese hitch for my trailer until I discussed hitches with not one, but three Airstream dealers and they all recommended the Equal-i-zer brand hitch. I also discussed hitches with my local utility trailer manufacturer and he recommended the Equal-i-zer brand of hitch. But the clincher was when I discussed hitches with an Airstream Factory Representative and she said that Airstream had switched their recommendation to the Equal-i-zer brand of hitch and had for the past couple of years. Then I changed my mind about which brand to get. My Airstream dealer is an Equal-i-zer dealer, but he does not stock them because of their cost. He had to order one in the size I requested. When I picked up my Airstream the service manager told me that the Equal-i-zer was the best on the market short of spending $3K for a hitch.

Quote:
Originally Posted by 59toaster
Now here is where the problems start. Since it took less tension to level the truck that means the if the hitch comes up from brake dive (nose of the truck comes down the rear at the hitch goes up because not only does the rear axle act as a fulcrum the suspension unloads), cresting a hill, wave in the road the angle that the hitch has to come is up less before all tension is lost. Think that out for a minute.
The more tension there is on the spring bar, the less likely this will happen because the spring bars are trying to press down on the front axle so the front springs will already be countering the tendency to "dive" or compress before the nose dive tries to occur: the soft portion of the compression curve will have already been surpassed leaving only the stiff portion of the compression curve before the nose dive begins.

Quote:
Originally Posted by 59toaster

If it isn't clear then go hook up your trailer. Hook up the bars where you normally do and see how many inches the end of the bar comes up. Now run the jack up with it all attached to the tow vehicle to simulate a crest or brake dive or porpoising and see how easy it is to get that bar unlatched.
Since we live about 30 minutes apart, I would be more than happy for you to come over one Saturday and let me demonstrate my hitch and its set up procedure to you. To lift the spring bar up onto the bracket with out using the snap-up bar, I usually have to lift the rear bumper with the tongue jack a good four or five inches in my level drive way. Same to get it off the brackets when I unhitch. In fact I recently camped in a site that had a steep slope to the camp site where the trailer was level with the tongue three or four inches off of the ground and the truck at a steep uphill slope. In order to get the spring bars off the brackets without pulling the entire rig out of the camp site I had to raise the tongue jack to its highest point which happened to raise the rear of my truck tires about three inches off of the ground...yes there was a minimum of three inches of clearance under the roadside tire!
Quote:
Originally Posted by 59toaster

What the lighter bar does is allow the bar to flex more so that it cant unload totally when the attitude of the tow vehicle changes in relation to the trailer. If the system is one that fights sway if it unloads you lose sway control. Brake dive on the tow vehicle is going to cause the rear of the tow vehicle to raise so if the bars unload you loose the sway control at the worst possible time....
As you point out with the stiff suspension of a 3/4 ton tow vehicle, the front suspension is going to be stiff enough to prevent this. Also, if properly distributed, the extra weight of the trailer tongue will keep the tow vehicle level and more stable.

Quote:
Originally Posted by 59toaster

When did Barry start to really get in trouble?.......the delay it took for his trailer brakes to react. The tow vehicle nose dived, The hitch unloaded the bars and the bar failed for what ever reason. The ONLY reason it wasn't worse is the amount of braking his trailer had. The trailler stopped the truck.

Think of the rating as more of guideline.
What, are we doing the "Pirates of the Caribbean, Curse of the Black Pearl" thing now? "Not exactly rules, but actually more like guidelines."

Quote:
Originally Posted by 59toaster
Those bars were originally rated when people towed with cars and station wagons The soft suspension needed a LOT of help to get the vehicle level. So they were labeled pretty close to Tongue weight as a guide when 4 bags of fertilizer in the trunk was pointing the headlights at the moon.
Quote:
Originally Posted by 59toaster

You are towing with a truck that can handle the weight of a Honda Civic in the bed. You don't need half as much tension on those bars as a car would on the same bars. So once you start talking truck what that bar is rated needs to go out the window. You are matching the bar to the suspension capacity of the tow vehicle not to the tongue weight.
Now that you mention the towing capacity of a 3/4 ton vehicle, your expert Andy chastised me for purchasing a 3/4 ton truck to tow my 6,215 lb dry weight (8,400 lb GVWR) 30' Airstream and even said I wasn't going to "tow the Queen Mary!" suggesting that I should have purchased a 1/2 ton truck instead. I can assure you that if I had purchased a 1/2 ton crew cab as a tow truck instead of a 3/4 ton I would have been cursing the person that gave me that piece of advice every time I came near a hill or wanted to merge into traffic.
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Old 10-20-2006, 05:07 PM   #129
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10-20-2006 Update on the Porsche

Stripping all the paint uncovered a lot of bad previous bodywork, but no rust except for the bottoms of both doors. Actually there were no perforations but the doors had swelled slightly at the bottom and couldn't be aligned flush with the door sills.



I know it looks ugly now but it will be a prize when it's done.

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Old 10-21-2006, 06:44 PM   #130
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10-20-2006 Found some hidden damage after removing the upper door to fit the new latch mechanism. One of the hinge plates had ripped away from the wood frame. Since the holes were stripped I drilled them out and bolted the plates through the frame with nylock fasteners.



The latch mechanism was designed to mount through a sheel metal facade like a cabinet or locker door. The unit was about 1/4" too tall to fit within the space so I altered it slightly to fit.





The old mounting location for the steel license plate bracket was badly corroded from dissimilar metal being in contact. It turned out to be an ideal place for the locking latch.

After careful measuring (I hate cutting holes in this thing) I played connect the dots again and roughed out the proper size hole. When I was done I polished the area and flipped the door over again











The central mechanism pull two rods toward the handle drawing back the latches.





One of the door panels was damage so I duplicated it from a salvaged section of side panel.



The door is ready for reinstallation. I'm trying to decide whether to cover the access ports with white material, semi-polished aluminum or polished tread plate.

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Old 10-21-2006, 07:47 PM   #131
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Foam!

Barry, I really like your foam idea.... I'd been thinking that if I ever did take my inside skins off, I'd do something simular. How did the installer get the foam flush to the ribs? Was this expensive to do?
Marc
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Old 10-21-2006, 08:01 PM   #132
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My trailer was entirely gutted. They sprayed fast setting foam so that it wouldn't push the sides out. It was eerie. You could watch it grow rapidly and the immediately stop within seconds.

They kept laying wide shallow patterns and built it up in 3-5 passes. I did the trimming to make the overfill flush with the wall studs.

Had I to do over again I would have removed the tar that was sprayed on the inside of the aluminum. The foam does not stick to it so I didn't get all the rigidity I had hoped for. The first time I opened the bay door and let some cold air in the trailer sounded like it was sizzling. It was the sound of the skin separating from the foam because of their difference in expansion rates and lack of adhesion.

Had I taken the shell to their shop it would have been $600.00. The mobil price was $1,200 and it was worth every penny. The roof is simple 3/4" plywood rafters holding up a layer of aluminum. The foam made the roof so strong it doesn't move under my near 300 lbs.
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Old 10-31-2006, 05:47 PM   #133
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10-30-2006

The Porsche is nearing final paint. The body work, from what I can tell in primer, is flawless. The color they mixed is very near what was on there and it's a standard formula based on Porsche color charts.

They said they would shoot the door jambs and inside of the doors, hood and engine cover separately today. Tomorrow the edges and overspray will be sanded and the final coats of urethane paint and clearcoat will be applied.





The Phoenix is nearer to completion. I reinstalled the upper hatch after completing and testing the latch. The wiring to the tail and license plate lighting was rehooked in the hinge access hatches and the system tested.

During the original build some had commented on how cheesy the white plastic moulding looked interfacing with the aluminum body. I found some aluminum edging made for do-it-yourself teardrop top edging. It's made of a very soft alloy so it can be bent. A little polishing and it should blend right in.

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Old 11-03-2006, 07:07 PM   #134
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11-3-2006 Porsche update

WOW!

It's going to be beautiful. Almost too perfect. No Porsche ever came out of the factory looking this straight.

Most Porsche headlight trims don't fit perfectly as there is a slight variation in all of them. My headlight trims served as a guide to shape the metal of the fender to fit the trim rather than use body filler to create a proper gap.

I asked the painter today what the paint job entailed. Earlier photos showed a green primer. That is an epoxy primer shot over bare metal. It seals off all oxygen and bonds to the rough metal and provides a base for the body filler to bond to.

Body fillers are a necessary evil but the object is to use as little as possible. The body filler is only to be used to take out hammer marks, not straighten body curves. A thin layer of body filler is applied to the whole car. It is block-sanded until it reveals high or low spots in the sheet metal. The metal in the flawed area is reworked to need the least amout of filler. This process often exposes raw metal so the finished work is shot in green primer again.

I believe he said they then spray gray primer and block the car again. The green underlayment serves as a visual guide to proper filler thickness. I'm told that a small magnet should stick anywhere on this car. Multiple sprays of gray primer sanded in-between builds the base for the color coat.

The car was shot in urethane, or two-stage color. Any imperfections can be removed at this stage. Numerous coats of clear coat are sprayed to further build up the base.

The surfaces are then sanded with 800, 1,000 and 1,200 grit before buffing. The smoother the surface the less heat will be generated significantly lowering the risk of burning the paint. The only part that hadn't been buffed yet was the hood. they are going to remount the hood, engine cover and doors and ship it back to the guy that took it apart for painting.

He's restoring the steering wheel while the car's being repaired. He'll do the reassembly of the windshield, wipers and all the trim. Then it will come back to Autometrics for detailing and spraying the fenderwells black again. Then we can bring it home.





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Old 11-03-2006, 11:17 PM   #135
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Quote:
Originally Posted by Barry2952
10-14-2006






Just a reminder of what I started with after the accident.





/


Great thread


Sweet pics , sorry to read about the mishap. One thing I did see in one of the pics of the porsche, and I hate to make a negative comment. You wrote some place that a "professional" tied the car in place. From what i can see that the straps are not tied in a criss/cross fashion. Each of the straps are tied from front and back, yea the car will not roll but nothing will will hold it form sie to side . I seen this happen all the time. You are on the road trip to a show a bad bumps the straps loosen up and the next few bumps the car taps the side of the trailer and dents. Maybe your case is a bit differnt but making the straps criss/cross will stop any side to side movement. I hate to see any more misfortune. Sweet ride and pics Jim
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Old 11-04-2006, 12:01 AM   #136
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I might add that a strap arraingment that straps over each tire and then sinches down to the floor tracks ,the straps form over the tire on top and sides to control any movement or josseling around that can happen ,it does
not look like the tires are held down in the photo .Further with that ,chocks that engage the floor tracks that go in front of the tires and in the rear of
the tires ,kind of locking in place possibly . It does appear that the car is just strapped to the floor tracks by the frame ,and the suspension can load and unload with the trailer movement and the car can move all around. Any way
cars looking great Barry ,and we want the best to happen for you in your
next towing experience.

Scott
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Old 11-07-2006, 06:39 PM   #137
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11-7-2006

I took the PHOENIX out today. I towed it 15 miles to the shop that foamed the damaged areas. The trip made me very nervous. I drove it empty and without the weight equalizing hitch, just to see how it handled and it did just fine. I drove it just to see if there was a natural wag, and there isn't. It tracks straight and true but it is a big trailer and I have to get used to it.

The wall cavities were filled and I headed home.



The countertop had just been installed a couple of hours when we took off on the maiden voyage. The accident shifted the trailer so badly that the top moved and the glue cured with the top in the wrong position. Using lots of shims I was able to free and reset the top where it belongs.



These appliances were installed just before we left. I'm not sure if I posted the pictures. The top cabinet contains a microwave and a 6-bottle wine cooler. I've had it running for days and it holds steady at 40į.



Installed the latches in the front access doors. Simple devices that look pretty natural in this environment.



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Old 11-07-2006, 07:37 PM   #138
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Sigh.....

Just beautiful work again.... wanna do my Argosy?
Sometimes it's hard to get on the horse after the fall, but you've already fallen once, it's all behind you.

You'll have good karma from now on...
Drive ON!
Thanks for the updates!
Marc
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Old 11-12-2006, 05:25 PM   #139
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Thanks Marc. I've got a '68 Lincoln limousine waiting in the wings as the next project.

11-12-2006

The Mark II left today for the Naples Concours on the 17th of November. His trailer is much bigger than mine.



The inside of the Phoenix is back to where it was before the accident.







Things that remain to be done:

Flooring for garage area.

Box-in ramp springs.

Install braces and FRP to complete belly pan.

Install lighting in garage.

Add 4 batteries to bank. (8 Optima marine batteries total)

Finish cabnetry in cabin and garage.

Replace bent 15,000 lb hitch on trailer tongue.

Install new Equal-I-Zer weight distributing hitch.
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Old 11-12-2006, 07:29 PM   #140
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Quote:
Originally Posted by Minnie's Mate

I'm not sure you understand the way the Equal-i-zer system works.


The rear of the bars are secured to the A-frame by resting on L-brackets with L-shaped retainers that are held in place by cotter pins. The spring bars are free to slide in these brackets during turns.


The weight of the tongue on the ball, like on the Reese System is counter acted by the tension on the spring bars.

Thats exactly how I thought it worked when I looked at them years ago. No tension no sway control.

The stiffer the front suspension, the more force is required on the wheel barrow handles to lift up on the hitch head to shift weight to the front axle.
But you are not considering that the rear suspension is already stiffer so it didn't squat nearly as much so the front didn't come up as much.


In the process of lifting the hitch and tongue of the trailer, some of the weight of the tongue is shifted back onto the axles of the trailer as the trailer pivots on its axles. The key is to balance all of these forces (weights) equally on all four axles. When the weight distribution hitch is set up, if done properly, the correct number of washers will be placed in the trunnion, the correct number of holes will be used in the L-bracket (chain links in the Reese system) and this balance will be achieved no matter what the rating is or how stiff the spring bars are. The adjustments to the brackets and washers will compensate for this.

EXACTLY MY POINT it works this way on any WD hitch even with chains. The chains lessen the effect but it still has it. Under tension the bars want to swing out to the side...they counter each other. Even the DC will have gains from the trunnion being tilted.

The 3/4 ton truck does indeed have a stiffer suspension and my 3/4 ton diesel truck has an even stiffer front suspension than the average gas job. The weight counters it. Therefore, it will take more force from the spring bars to compress the front suspension than, say, a mid-70's Ford Country Squire Station Wagon. Yes, Andy may have written the book on hitches and, I for one will not cast doubt on his vast knowledge of Airstream trailers, but the fact is he was an investigator for Airstream during the '60's-'70's. Books tend to become obsolete with time.

no....think about it. The rear has to come up less. The rear axle is the fulcrum point to shifting the weight forward. So it actually takes less tension on the bar to move the weight forward because you don't have to lift the rear of the vehicle as much......think about it...it didn't sag at the rear axle as much so it takes less upward pull on the bars to lift the rear and shift the weight forward.
Actually lets get technical about this. I see where we are failing to see eye to eye on this so let me see if I can clear the air on this.

It takes exactly the same tension if you keep the tow vehicle and trailer the same and change from a 1000lb bar to a 550bar.

Actually lets not even put a weight rating on them because that's part of the confusion. We use two bars of different stiffness.


We will use a 350 cid 88 3/4 ton suburban as an example...My truck. It rides like a brick empty. It rides better with a trailer on a WD hitch.

If you measured the pressure where the bar exerts its force on the trailer it will be the same with both the stiff bar and the more flexible bar. You are dealing with the same weights you need to transfer....what is different is the bar flexes more to achieve the same weight transfer on that SAME truck. That makes sense right?

Now take a 1988 1/2 ton suburban with a 350 so the weights are nearly identical but the 1/2 ton has much softer suspension. It can't carry nearly the load on its own suspension without bottoming out but it rides like a caddy empty compared to my 3/4 ton.

So to overcome that softer suspension you need a bar that resists bending more. This is because you have to lift the rear more to transfer the weight forward and push the front back down. What you will find is the amount of defection of the less flexible bar on the 1/2 ton will be nearly the same as the more flexible bar on the 3/4 ton suburban.

Its about how much that bar bends not what they say its rated.

If the bar is not bending it is no longer providing sway control. I know we agree on that point and thats my whole argument.

The physics of the first WD hitch is still the EXACT same as one you buy today. Andy's observations still stand as fact. They were based on sound analysis of the physical dynamics of the loads and still completely applicable and will continue to be proven fact till cars fly and it eliminates the ability of the trailer to change axis in any relationship to the tow vehicle and they effectively become a solid unit with no articulation possible at their union.

Andy's argument is also for the fact that the softer suspension of the tow vehicle is going to follow the irregularity of the road better and transfer less abrupt motion to the body of the tow vehicle and on to the the trailer. Its a prooven fact that if something is engineer too stiff that it is more prone to fail when subjected to constant rhythmic applications of force.

Think about a hard sprung 3/4 ton truck going down the road empty compared to that cushy ride of the 1/2 ton. The airstream trailer's suspension is tailored to its weight when the tow vehicle becomes too stiffly sprung it transfers those force to the trailer and beats it into submission since its lightness and stiffness comes from its monocoque. design. Going to the less ridged bar on the higher spring rate tow vehicle helps reduce that to some extent as well.

Quote:

Now for sway control. The sway control for the Equal-i-zer is achieved by the angle of the trunnion in relation to the spring bars. This angle when loaded creates a tremendous bind on the pivot bolts that hold the sockets in the trunnion head of the hitch. The bind of the sockets against the pivot bolts resist the lateral forces that would allow sway. Porposing or rising of the tongue of the trailer in relation to the front of the tow vehicle would lower the binding force slightly, but only for a micro-second ( 1 second at 60mph is 88 ft of forward travel....Any loss of sway control is dangerous ESPECIALLY in an evasive maneuver where you are dealing with body roll of the tow vehicle in relation to brake drive or Porpoising as you try to make a corrective manuver...A blink of any eye...The durations of Berry's accident was about 4-8 seconds and he traveled and in that time between one or two foot ball Fields before he had it all back under control and stopped) and then it would return immediately. You mention cresting hills allot, but I don't drive on any hills that have the kind of crest that you allude to. None have that a crest that is that acute.
You fail to take into consideration the dynamics of the suspension. It doesn't take much at all. 6 inches of elevation change over 14ft (the rough wheel base of a full size truck) doesn't sound like much at all does it? Now think about 4ft from the back axle to the ball. That is common distance on a long bed truck or a suburban. Then add 20 or so inches for the length of the bars, Now also add in that it just pitched the rear up and the suspension compresses and then extends....that 6 inches at the axle is more like 8-10 or on a really bad road 12 inches could easily be seen at the tips of those bars. If the spacing of that 6 inch rise fell in line with the spacing of the axles at the tips of the bars where they attach to the trailer it it would be in line with the harmonics of the vehicle and it could disrupt it enough to cause a problem. The amount the bars flex is a huge part of the harmonics of the unit.

They would be called pyramids not hills if they did. The ones that I drive on have extremely gradual curvatures that don't allow for a decrease in the tension on the spring bars. The only time I come close to what you describe is when I am exiting driveways or at exits from fuel stations and I try to keep my speed under 35 MPH - 40 MPH max when exiting truck stops and fuel stations so I don't have to worry about sway! Excuse my sarcasm, I couldn't help myself. Anyway, even if I experienced the kind of "unloading" you are talking about, it would be for a micro-second Again thats not true...the duration's would be much longer...suspesnion/shocks work by resisting the movement of the axle and the conditions would return to normal without the spring bars dropping out like Barry's did. Ultimately, whatever caused it to occur, the spring bar falling out is what caused his hitch to fail.

Yes it is possible that it was an unforeseen failure


The more tension there is on the spring bar, the less likely this will happen because the spring bars are trying to press down on the front axle so the front springs will already be countering the tendency to "dive" or compress before the nose dive tries to occur: the soft portion of the compression curve will have already been surpassed leaving only the stiff portion of the compression curve before the nose dive begins.

Again...think about it and what I posted above. The tension is the same in realtion to the force at the conection to the ttailer...its about how much flex the bar had to get the vehcile level again.

The less flex to get it level the less flex it will take to loose all tension.



Since we live about 30 minutes apart, I would be more than happy for you to come over one Saturday and let me demonstrate my hitch and its set up procedure to you. To lift the spring bar up onto the bracket with out using the snap-up bar, I usually have to lift the rear bumper with the tongue jack a good four or five inches in my level drive way. Same to get it off the brackets when I unhitch. In fact I recently camped in a site that had a steep slope to the camp site where the trailer was level with the tongue three or four inches off of the ground and the truck at a steep uphill slope. In order to get the spring bars off the brackets without pulling the entire rig out of the camp site I had to raise the tongue jack to its highest point which happened to raise the rear of my truck tires about three inches off of the ground...yes there was a minimum of three inches of clearance under the roadside tire!

I can totally believe that, now go the other way with it...you said you only have to lift the bumper 5 inches to unhitch.....Think about it...your bars are not flexing enough. That 5 inches at the bumper was about 2-3 inches directly above the rear axle.

As you point out with the stiff suspension of a 3/4 ton tow vehicle, the front suspension is going to be stiff enough to prevent this. Also, if properly distributed, the extra weight of the trailer tongue will keep the tow vehicle level and more stable.

What, are we doing the "Pirates of the Caribbean, Curse of the Black Pearl" thing now? "Not exactly rules, but actually more like guidelines."

[color=black]

Now that you mention the towing capacity of a 3/4 ton vehicle, your expert Andy chastised me for purchasing a 3/4 ton truck to tow my 6,215 lb dry weight (8,400 lb GVWR) 30' Airstream and even said I wasn't going to "tow the Queen Mary!" suggesting that I should have purchased a 1/2 ton truck instead. I can assure you that if I had purchased a 1/2 ton crew cab as a tow truck instead of a 3/4 ton I would have been cursing the person that gave me that piece of advice every time I came near a hill or wanted to merge into traffic.
'
Yes he did and think about why...his complaint was about how stiff the suspension was more so then the over kill on the motor....I pull with a 454 burb its overkill for my 59 Caravanner both suspension and motor but you can never have too much motor. I wanted the stronger differential, transmission, drive shafts... You can however have to much suspension. I have seroiusly thought about putting 1/2 ton springs under mine to soften the ride up and then suplement the softer leafs with air bags when I really do need that stiff suspension for a load IN the truck. Till it gets 400-500lb in it shes a mean girl on your kidney's on a bumpy road.


The trailer carries all but its tongue weight so you don't need a truck capable of caring the weight ON it just needs to be able pull that weight.
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