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Old 01-03-2012, 11:31 PM   #71
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You should take this up with the people who use Airsafe hitches. Their experiences are quite different from what you describe.

doug k
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I don't know really what is meant by that. But to be clear on my part, I am simply hypothesizing as an exercise to understand the hitch. I am not speaking for other people, making definitive assertions, negating the experiences of others, or in anyway projecting anything beyond my own thought process about the physics of this hitch. In short, I am just thinking out loud.

As for "taking this up" with anyone else, I don't have the means or intention of such an endeavor, which lies well outside the bounds of me jabbering away with a few interested parties here in a forum thread to try to learn something through the exchange of ideas. I don't care to express any responsibility beyond that simple idea. I assumed anyone interested would join in if they like, right?

But all the same, I am sorry if I caused you any confusion about my intention here. Nothing ill was intended.
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Old 01-03-2012, 11:34 PM   #72
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I use an Equal-i-zer but am not in the camp that believes no stresses are transferred from tow vehicle to trailer. It seems to me if the truck is supporting a portion of the trailer weight, then surely the trailer feels some of the road shock the truck experiences.

Airsafe claims their hitch breaks the rigid connection of truck to trailer, relieving this stress. Many users of the Airsafe have supported this claim on this forum.

When I asked Andrew Thomson at CanAm about my Equal-i-zer hitch, he suggested I be careful at such gas entrance dips where the front of the truck is raised in relation to the trailer as it could bend the trailer's A-frame. He most probably has far more experience rigging hitches on Airstreams than anyone on this forum.

When I have driven on concrete roadways with pronounced seams, the truck and trailer are jolted together in a disturbing manner. Without the trailer, the jolts are much softer. Airsafe claims this is because of the rigid connection, and I think that is true, based on reports of Airsafe users.

It has been brought up here before that the Airstream feels only its own suspension, but I find that hard to believe when the truck carries some of its weight.

doug k
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Old 01-03-2012, 11:53 PM   #73
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Originally Posted by dkottum View Post
I use an Equal-i-zer but am not in the camp that believes no stresses are transferred from tow vehicle to trailer. It seems to me if the truck is supporting a portion of the trailer weight, then surely the trailer feels some of the road shock the truck experiences.

Airsafe claims their hitch breaks the rigid connection of truck to trailer, relieving this stress. Many users of the Airsafe have supported this claim on this forum.

When I asked Andrew Thomson at CanAm about my Equal-i-zer hitch, he suggested I be careful at such gas entrance dips where the front of the truck is raised in relation to the trailer as it could bend the trailer's A-frame. He most probably has far more experience rigging hitches on Airstreams than anyone on this forum.

When I have driven on concrete roadways with pronounced seams, the truck and trailer are jolted together in a disturbing manner. Without the trailer, the jolts are much softer. Airsafe claims this is because of the rigid connection, and I think that is true, based on reports of Airsafe users.

It has been brought up here before that the Airstream feels only its own suspension, but I find that hard to believe when the truck carries some of its weight.

doug k
I think I had a slightly different interpretation of the meaning of all this. My position here in this thread was that the stiffness of the bars didn't contribute (much) to the harshness. Meaning, any WD bar setup with a standard coupler + ball interface would produce about the same ride, plus or minus a molehill, as dznf pointed out. The ride is mostly a function of the suspensions in that situation.

It appeared that a lot of people wanted to use 600# bars instead of the 1000# bars in order to mitigate the perceived harshness caused by the 1000# bars. That's the only notion I was trying to dig into and investigate for my own edification. Whether such a change would substantially change the harshness of the ride. My motivation is simple - - I have an EQ with 1000# bars and I don't want my trailer damaged either. If I convinced myself that 600# bars would substantially reduce harshness of the trailer ride, I'd figure out where to get that change made.

Going to a totally different configuration of hitch, like an Airsafe, is a complete paradigm change. It adds a compliance between coupler and ball that doesn't exist in the Equalizer hitch. So, I would assume that all the dynamics are going to be analyzed under different terms, because of that compliance. In other words, it is an Apple to Oranges comparison against the WD system like the Equalizer.

Saying that an Airsafe is less harsh than an EQ is not the same as saying 600# bars on an EQ are less harsh than 1000# bars on an EQ. It's a different argument all together.
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Old 01-04-2012, 12:20 AM   #74
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Red', it's not an entirely different argument. I don't recommend Airsafe or any other, but use that as partial evidence that tow vehicle stresses are transferred to the trailer. I believe the w.d. bars can soften that transfer of stress if they are not as rigid. So 600# bars are less harsh than 1000# bars.

You and I have the same trailer and the same hitch. It works well for me but I am cautious with it. I avoid the rough roads or slow down a lot to lighten the jolt, and stay away from steep approaches at gas stations.

Of the friction type hitches on the market in this price range, I see little advantage of switching to another. I am interested in the Airsafe to be used with my Equal-i-zer, but am concerned about moving the hitch ball back away from the truck another 9''. This would seem to go against the wisdom that the pivot point of the hitch should be as close to the rear axle as possible for stability.

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Old 01-04-2012, 08:58 AM   #75
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Originally Posted by redwoodguy View Post
I think I had a slightly different interpretation of the meaning of all this. My position here in this thread was that the stiffness of the bars didn't contribute (much) to the harshness. Meaning, any WD bar setup with a standard coupler + ball interface would produce about the same ride, plus or minus a molehill, as dznf pointed out. The ride is mostly a function of the suspensions in that situation.

It appeared that a lot of people wanted to use 600# bars instead of the 1000# bars in order to mitigate the perceived harshness caused by the 1000# bars. That's the only notion I was trying to dig into and investigate for my own edification. Whether such a change would substantially change the harshness of the ride. My motivation is simple - - I have an EQ with 1000# bars and I don't want my trailer damaged either. If I convinced myself that 600# bars would substantially reduce harshness of the trailer ride, I'd figure out where to get that change made.

Going to a totally different configuration of hitch, like an Airsafe, is a complete paradigm change. It adds a compliance between coupler and ball that doesn't exist in the Equalizer hitch. So, I would assume that all the dynamics are going to be analyzed under different terms, because of that compliance. In other words, it is an Apple to Oranges comparison against the WD system like the Equalizer.

Saying that an Airsafe is less harsh than an EQ is not the same as saying 600# bars on an EQ are less harsh than 1000# bars on an EQ. It's a different argument all together.
I agree completely. The Airsafe takes out the harshness of the solid ball to coupler interface as it "isolates" the connection from the truck suspension. I still maintain that harshnes (choppy road and pothole inputs) is transferred through the ball connection and little through the spring bars. Steep drive entrances, etc. are a completely different story and spring bar choice is all important for that condition,
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Old 01-04-2012, 09:04 AM   #76
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Originally Posted by dkottum View Post
Red', it's not an entirely different argument. I don't recommend Airsafe or any other, but use that as partial evidence that tow vehicle stresses are transferred to the trailer. I believe the w.d. bars can soften that transfer of stress if they are not as rigid. So 600# bars are less harsh than 1000# bars.

You and I have the same trailer and the same hitch. It works well for me but I am cautious with it. I avoid the rough roads or slow down a lot to lighten the jolt, and stay away from steep approaches at gas stations.

Of the friction type hitches on the market in this price range, I see little advantage of switching to another. I am interested in the Airsafe to be used with my Equal-i-zer, but am concerned about moving the hitch ball back away from the truck another 9''. This would seem to go against the wisdom that the pivot point of the hitch should be as close to the rear axle as possible for stability.

doug k
Doug,
I think I get where you are coming from, but I don't think bars even come into play much until a road condition forces a relatively substantial bar deflection...say more than an additional inch of bend. Below that, I am relatively...no pretty sure that the A frames are not being unduely stressed. It's what happens after an ADDITIONAL inch of deflection that scares the crap out of me. Refer to Andy's chart. Shoot holes in his methodology or biases all yo want, I can't believe he'd misrepresent...and it is logical looking data. (except for the one curved line...that one is weird and didn't come out as I would expect).
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Old 01-04-2012, 10:13 AM   #77
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I imagine the expensive high-end hitches are better hitches, but they are 3X or 4X the price, and still require lifting greasy parts, which is my main gripe with ALL hitches.

Since there is a lot of talk about GREASE in this thread I thought I'd clear up this one minor point stated in the opening post.

I am one of those "high-end" hitch guys.

They do not require lifting any greasy parts. Just wanted to clear up that main gripe...


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Old 01-04-2012, 10:18 AM   #78
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If the bars affect ride harshness there has to be a physical mechanism. In this simple sketch it doesn't appear to be very obvious what that mechanism would be. The essential configuration in the hitch is that the ball and coupler are fixed with no compliance. It is impossible to move the body of the TV without moving the trailer. Effectively the trailer is part of the TV. A bump in the road which would deflect the TV body up is directly transferred through the coupler-ball to the trailer which will also move up. etc.

When you add bars to lift the rear of the TV you add resistance to the flex of the coupler-ball joint, but that is all. It doesn't change the transmission of jolts from TV to trailer at all. It might appear that the bars are a compliance between the TV and trailer - much like the coil spring tying the tire to the TV. But it isn't a compliance, it is only a resistance.

The Airsafe pitch is that they add a true compliance between TV and trailer and that occurs between the ball and coupler. It acts just like the coil spring between tire and car frame. At least in principle, that would make the ride in the trailer independent of the ride in the TV (potentially). And I only point out once more that that isn't the same as the difference between bars in an EQ hitch.
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Old 01-04-2012, 10:21 AM   #79
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Exactly, IMHO.
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Old 01-04-2012, 10:33 AM   #80
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Since there is a lot of talk about GREASE in this thread I thought I'd clear up this one minor point stated in the opening post.

I am one of those "high-end" hitch guys.

They do not require lifting any greasy parts. Just wanted to clear up that main gripe...


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Great! At the rate I am ruining pants, I may pay for a high end hitch without knowing it. Thanks Sean, sorry for the misstatement there.
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Old 01-04-2012, 11:08 AM   #81
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The Equalizer bars also have the least ability to bend when necessary such as going into driveways or gas stations.

That puts a huge and unnecessary load on the "A" frame, that sooner or later will cause damages.

The Hitch Torsion Bar Story

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Old 01-04-2012, 11:23 AM   #82
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Pretty nifty drawing red'.

My take on this is that the w.d. bars relieve the weight of hitch coupler on ball, and the weight is suspended on the w.d. bars. Then it is logical for me to assume the less rigid the bars, the softer the bar suspension, and therefore less road shock is transferred from truck to trailer because flexing of the bars absorbs that shock.

I believe that is the same reasoning others (Inland Andy has taken a lot of heat on this forum for this idea) have used to prescribe lighter w.d. bars in response to heavier truck suspensions.

doug k
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Old 01-04-2012, 11:26 AM   #83
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Pretty nifty drawing red'.

My take on this is that the w.d. bars relieve the weight of hitch coupler on ball, and the weight is suspended on the w.d. bars. Then it is logical for me to assume the less rigid the bars, the softer the bar suspension, and therefore less road shock is transferred from truck to trailer because flexing of the bars absorbs that shock.

I believe that is the same reasoning others (Inland Andy has taken a lot of heat on this forum for this idea) have used to prescribe lighter w.d. bars in response to heavier truck suspensions.

doug k
That's backwards, Doug. The spring bars INCREASE the clamping load between the ball and coupler.
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Old 01-04-2012, 11:46 AM   #84
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This use of the word "compliance" is new to me. It seems to mean according to Wikipedia "the inverse of stiffness". Post 78 makes more sense to me with this definition.

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