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Old 03-19-2011, 01:44 PM   #31
Wavery
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Originally Posted by mjlaupp View Post
Please use the correct terms in the correct context as defined by the SME - Society of Mechanical Engineers. The following is from the ToolingU, Mechanical Systems Training web page: http://www.toolingu.com/definition-5...hock-load.html

Static Load - "A type of load that maintains the same direction and degree of force during operation." = Tow vehicle and/or TrailManor at rest.

Dynamic Load - "A type of load that changes in the direction or degree of force during operation." = Tow vehicle and TrailManor in motion, springs and WDH load bars working within their normal limits.

Shock Load - "A type of load characterized by extreme speed and a tremendous amount of force." = Tow vehicle and TrailManor in motion, Springs, shocks and/or WDH load bars hitting a limit such as the TV rubber bump stop on the axle, a coil spring fully compressed or extended, or a shock fully compressed or extended.
When I refer to "Shock-loading" in conjunction with the WDH, I am referring to when one goes over bumps and dips (I have commented on this regularly) the weight of the tongue of the trailer is lifted off of the trailer hitch by the upward thrust, then falls back down by the force of gravity, resulting in "Shock-loading" on the trailer frame and axle as well as the TV frame and axle when they "Bottom out". Like when one drops a bowling ball and it hits the ground.

The spring bars are designed to bend at a certain rate during the "Dynamic Load" and usually this load is not an issue unless the dynamic load is enough to cause the vehicle to bottom out due to over-loading. This over-loading and chance of bottoming out will be more severe with 1200# spring bars than with 600# spring bars.

When one uses spring bars that are far beyond the necessary rating needed, far more of the loading (of all types) is transferred to the trailer axle (via the trailer frame) then is necessary to accomplish the intent of the WDH. When this occurs, it is a negative as it may overload the trailer tires more than necessary and may cause tire damage.

On most pop-up trailers and some tow vehicles a WDH (of any kind) is not recommended because it can cause damage to the vehicle's structure. Common sense should tell one that if an owner were to use a 400# rated WDH hitch on one of these vehicles, they would stand 1/3 as much chance to cause damage than if they were to use a 1200# rated WDH for the same reasons that I have mentioned.

I never tried to discourage or even suggest that others not use a WDH. On the contrary. I go out f my way to encourage the use of them. They are definitely a safety tool. I just encourage people to explore the balance in using this device due the amount of tire failure that we seem to be having.

Can I prove that an over-rated WDH causes tire failure?...... NO!!!!!...... Common sense tells me that it could contribute. If my addressing the issue "Scares" some...... that is not my intent. Maybe those that get "Scared" by the topic need to do a little more research.
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Old 03-19-2011, 02:27 PM   #32
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Originally Posted by harveyrv View Post
.....the weight of the tongue of the trailer is lifted off of the trailer hitch by the upward thrust, then falls back down by the force of gravity......
Please explain the details of the source and mechanics of the upward thrust that lifts the tongue off of the hitch. The only source of lift (upward thrust) on the trailer tongue that is capable of lifting the tongue off of the hitch that I know of is from the tongue jack on the ground.

Quote:
.....This over-loading and chance of bottoming out will be more severe with 1200# spring bars than with 600# spring bars......
You have this backwards. You need a stronger spring to prevent bottoming out. This applies to tow vehicle axles, trailer axles and weight distributing hitches. However, you can overload the hitch and/or tongue with excessive rated spring bars.
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Old 03-19-2011, 04:46 PM   #33
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Originally Posted by mjlaupp View Post
Please explain the details of the source and mechanics of the upward thrust that lifts the tongue off of the hitch. The only source of lift (upward thrust) on the trailer tongue that is capable of lifting the tongue off of the hitch that I know of is from the tongue jack on the ground.
It's called "Inertia". I said nothing about "lifting the tongue off of the hitch". I said, "the weight of the tongue of the trailer is lifted off of the trailer hitch by the upward thrust"........Inertia.
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Originally Posted by mjlaupp View Post
You have this backwards. You need a stronger spring to prevent bottoming out. This applies to tow vehicle axles, trailer axles and weight distributing hitches. However, you can overload the hitch and/or tongue with excessive rated spring bars.
I wasn't talking about "Preventing" bottoming out (where did you get that?). I was talking about "Causing" bottoming out by the transfer of excess energy through the use of over-rated WDH spring bars. I'm not sure if you 2 are just being silly or you really don't get it. Heavier trailer springs would indeed help prevent bottoming out but they would have no effect on the amount of energy transferred to the tires but that has nothing to do with the discussion.

The energy transferred from a 1200# spring bar will be double the energy transferred from a 600" spring bar. That is why they have differently rated spring bars.

Help me understand your side of this theory. So far, all you have done is bash me and twist my words. From my point of view, you seem to be purposely distorting what I'm saying. Then again, maybe I'm just doing a poor job of explaining.

Are you saying that a 1200# spring bar transfers the same amount of energy to the trailer frame (and frt TV suspension) as a 600# spring bar while traveling down the same stretch of rough road? Are you saying that is doesn't transfer any energy? Are you saying that any amount of energy transferred to the trailer frame has no effect on the amount of energy transferred to the tires? What exactly is your point?
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Old 03-19-2011, 08:31 PM   #34
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Sample: "The spring bars are designed to bend at a certain rate during the "Dynamic Load" and usually this load is not an issue unless the dynamic load is enough to cause the vehicle to bottom out due to over-loading. This over-loading and chance of bottoming out will be more severe with 1200# spring bars than with 600# spring bars."


No one has reported these hypothetical issues with a WDH in the real world.

Inertia is not an upward thrust or any other kind of thrust. It's actually the resistance of a mass to be set in motion.

None of this is making sense.
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Old 03-19-2011, 09:33 PM   #35
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Originally Posted by harveyrv View Post
It's called "Inertia". I said nothing about "lifting the tongue off of the hitch". I said, "the weight of the tongue of the trailer is lifted off of the trailer hitch by the upward thrust"........Inertia.

I wasn't talking about "Preventing" bottoming out (where did you get that?). I was talking about "Causing" bottoming out by the transfer of excess energy through the use of over-rated WDH spring bars. I'm not sure if you 2 are just being silly or you really don't get it. Heavier trailer springs would indeed help prevent bottoming out but they would have no effect on the amount of energy transferred to the tires but that has nothing to do with the discussion.

The energy transferred from a 1200# spring bar will be double the energy transferred from a 600" spring bar. That is why they have differently rated spring bars.

Help me understand your side of this theory. So far, all you have done is bash me and twist my words. From my point of view, you seem to be purposely distorting what I'm saying. Then again, maybe I'm just doing a poor job of explaining.

Are you saying that a 1200# spring bar transfers the same amount of energy to the trailer frame (and frt TV suspension) as a 600# spring bar while traveling down the same stretch of rough road? Are you saying that is doesn't transfer any energy? Are you saying that any amount of energy transferred to the trailer frame has no effect on the amount of energy transferred to the tires? What exactly is your point?
A Weight Distributing Hitch is for distributing weight, not energy. Energy and Weight are different things (you may have both Weight and Energy confused with Force in your narrative as well).

There is no theory under discussion that I am aware of here. The hypothesis mentioned earlier that added weight from a WDH on already heavily loaded 14" tires might be unwelcome and possibly related to 2720 14" tire failures is of interest, but this part isn't yours to claim because it's been proposed a dozen times already by other posters on other threads.

The idea that heavier bars could make the problem worse on a bumpy road is both yours and possible, particularly if you cranked the bars to their maximum setting. But, as anybody using a WDH knows, you set the hitch where it works for you, not on it's maximum setting (unless, of course somebody took your advice and bought a hitch that lacked the bar capacity to do the job). I've been curious myself for awhile about the possible differences between 600# bars at max versus 1200# bars at 50%. But with a possible exception for going across steep upward slope transitions, I'm not seeing this as a big deal (if there is anything to this, there should be data, right?).

But the real problem is not hitch bars, but rather the potentially overloaded state of 14" trailer tires and their allegedly high failure rates. So, the fix is really about keeping the trailer lighter or making the tires heavier, and not so much about hitch bars.

Your models for the actions and reactions of the WDH make no sense. Give up on this and work on something else.
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Old 03-19-2011, 10:49 PM   #36
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It's called "Inertia". I said nothing about "lifting the tongue off of the hitch". I said, "the weight of the tongue of the trailer is lifted off of the trailer hitch by the upward thrust"........Inertia.
Ok, I misquoted you here. But the intent of my statement remains the same as yours. The weight of the tongue becomes negative with respect to the hitch. Your reason "upward thrust......Inertia". Once again, a one word explanation. At this point I have to reason that this inertia is imparted by the upward movement of the TV hitch as the TV rear axle encounters a bump and/or the rebound of the WDH bars. Is this correct?

Quote:
I wasn't talking about "Preventing" bottoming out (where did you get that?). I was talking about "Causing" bottoming out by the transfer of excess energy through the use of over-rated WDH spring bars.
Causing bottoming out of what? Again you leave it hanging. The use of higher rated WDH bars can prevent bottoming out of the TV rear axle due to dynamic loading.

Quote:
I'm not sure if you 2 are just being silly or you really don't get it.
@

Quote:
Heavier trailer springs would indeed help prevent bottoming out but they would have no effect on the amount of energy transferred to the tires but that has nothing to do with the discussion.
At what point did the trailer springs enter into this discussion? And FYI the rating of any and all of the springs and shocks in the system; TV front axle, TV rear axle, WDH bars and TM axle will have an effect on the loading transferred to any and all of the tires.

Quote:
The energy transferred from a 1200# spring bar will be double the energy transferred from a 600" spring bar.
I'll agree if this statement is changed to: At their respective maximum deflections, the dynamic load and/or static load transferred from a 1200# spring bar will be double the amount transferred from a 600" spring bar.

Quote:
That is why they have differently rated spring bars.
Spring bars are rated for static load (weight) of the tongue, hitch components and the addition of TV load behind the rear axle. By extension, you can include the dynamic loading on the system if you can quantify it.

Quote:
Help me understand your side of this theory. So far, all you have done is bash me and twist my words. From my point of view, you seem to be purposely distorting what I'm saying. Then again, maybe I'm just doing a poor job of explaining.
I have no interest in "bashing" and "twisting".

Quote:
Are you saying that a 1200# spring bar transfers the same amount of energy to the trailer frame (and frt TV suspension) as a 600# spring bar while traveling down the same stretch of rough road?
No, the dynamic load transfer can be greater using the 1200# but only if the deflection of the bars is enough (over 600#) to transfer this additional dynamic load.

Quote:
Are you saying that is doesn't transfer any energy?
No, There is transfer of load (or as you put it, energy). It's just not as dramatic as you are saying.

Quote:
Are you saying that any amount of energy transferred to the trailer frame has no effect on the amount of energy transferred to the tires?
No, dynamic load on the trailer frame will be transferred to dynamic load on the tires.

Quote:
What exactly is your point?
Your comments about "shock-loading" far overstate the consequences of using heavy rated WDH bars.

A Newbee reading these discussions would be hard pressed to make the right decision while worrying about tire blowouts and suspension damage caused by using the wrong WDH bars. While this decision requires some study, it should not be a make or break situation such as you suggest.

The dynamic loading and shock loading on the trailer tires from direct contact with the road far exceeds the dynamic loading transferred to the tires by the use of a WDH. Your shock-load / energy transfer theory does not stand up to close examination. There is no way that a shock load can be transferred from the WDH to the trailer tires. In fact, I can not figure out how the WDH would encounter shock loading unless it contacts the road surface.

However, I will agree that the use of a WDH causes additional loading on the trailer tires and that this can be a problem with a heavily loaded TrailManor on load range C 14 inch tires.

WDH bars should be selected based on the (tongue weight of the trailer + the weight of the WDH and receiver + the load added to the TV behind the axle) X 1.25. If you google the web you can find this approximation on most of the WDH and RV how to sites. Too much WDH and you could damage the TV or TM in extreme conditions. Too little WDH spring bar rating and you could overload and stress the WDH spring bars. Ride and possible stability of the TV/TM system suffers at both ends of this spectrum.
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Old 03-20-2011, 10:08 AM   #37
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You two are peeing into the fan here! My thought is to purchase what you think you need! READ THE INSTRUCTIONS, ADJUST ACCORDINGLY, Have a Nice Day! ROFLMAO!
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Old 03-22-2011, 08:48 AM   #38
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You two are peeing into the fan here! My thought is to purchase what you think you need! READ THE INSTRUCTIONS, ADJUST ACCORDINGLY, Have a Nice Day! ROFLMAO!
I second that emotion!

Phew! Talk about overthinking something!
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Old 03-22-2011, 03:12 PM   #39
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Among the reasons why I avoid threads like this. If a someone wants to know something from on this subject I have them PM me.

In cowboy action this is like whether you should be shooting 38s or 45s...
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Old 03-23-2011, 07:32 PM   #40
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THAT's an easy one -a 45!

On the WDH debate - I enjoyed the lively discussion and most of the comments provide me with additional perspective and concepts to consider.

I have no idea what # bars I use with my WDH for my front wheel drive Honda Odyssey and 2720, but I do know my dealer got it right and it tows like a dream.
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