Trailer Weight Calculations & Load Estimator Utility

[xcntrk]

Hi all, I've lurked on here for a while and have just now got around to creating an account.

I tow a number of different trailers regularly and I'm in the process of shopping for a new TT. As a result I've been researching & measuring all the specific manufacture ratings and real word scale weights surrounding my TV in order to help me identify trailer loads I can realistically support without being overloaded. To help in that process I built the following utility and wanted to share it with the rest of the towing community.


Weight Calculation utility:
Input your CAT or other truck scale measurement data and the utility will perform a number of meaningful weight calculations. This information is useful in measuring the "real" weights of your tow vehicle and trailer against the maximum limits of both vehicles. The tool will identify if you are over the manufactured specifications in any area and bring this to your attention.

Load Estimator utility:
Allows you to input information about a given trailer and estimate the amount of load required from the tow vehicle to support the trailer weight. Loads are projected in Tow Rating and Payload figures. Useful for trailer shopping to quickly determine if a prospective trailer fits your tow vehicle capabilities.

The tool is based in Microsoft Excel, but no need for any software on your computer as you can access the utility online via Microsoft Skydrive. You can input your data online and even download a copy for offline use (assuming you have Excel installed locally).


Here are a few screen shots of the utility in action:










Access the Trailer Weight Calculations & Load Estimator Utility here:
https://skydrive.live.com/embed?cid=A7EE35AF86FE78FE&resid=A7EE35AF86FE78FE%21142&authkey=ALI_KLtWUH...

EDIT: updated to version 4.0 to include corrections from comments originating in this thread.
PS: please contact me with any uncovered bugs or issues.

[BenK]

Blind acceptance of any OEM design or specification....

I question anything and everything, but do accept MOST of them

Like the Andersen WD Hitch.

I think an innovative and elegant architecture, but very poor execution there of.

Am lambasted...often

So understand keeping an open mind on things and also know my limits and strengths

[BenK]

Campin LI,

Key is that YOU are willing to see the other side and MAYBE change or adjust your position

Take that thread whether to grease or not...goes to the thread where I decided to leave for a while

Same topic, but know most won't get that either

The torque wrench used to tighten that ball to OEM spec (in some cases...+400 ft/lbs) is in the three feet range....if the trailer coupler needs grease and the general advice
here is to NOT grease...has the potential of a +20 feet lever arm loosening the ball

Some even say to ignore the OEM torque spec and just tighten it REAL GOOD...or some such

Worse if folks listened to advice that they can lightly tighten and then glue the nut on

How long will it take a bit of grit between the ball and coupler to further loosen it ?

Or this discussion where some folks chimed in to say OEM has dialed in margin...even 2X or more...so okay to go over is the potential assumption that some might take...as there is extra margin....or to ignore the RATINGS because there is margin...or that they have for decades or thousands of miles with no issue

Again, congratulate you for an open mind

[Campin_LI]

BenK wrote:
Some very poor to dangerous advice on technology based questions or issues by
NON techie folks.

Most times the school of hard knocks did teach the advisors correctly or close
enough...but too often...way off base to argue against engineering principles
which are based on the world's "laws of physics" that we all live in

On designed in safety factor...there are many to anything as complex as automotive.
There are compounding that even some designers of 'that' part of the assembly
does NOT know of (from other components/assemblies within the whole)

Myopia and out of context is often too common here and other Internet freebie
forums

That is only part of 'why' you bounce back and forth between, as
it maybe or is between two different aspects that has their own dialed
in margins (safety factors and design spec)

I dropped out on my last straw thread...how tight should a tow ball
be tightened to. Simple and just a tow ball right?

Missed by the poor advice is that is a key component in the food chain
of towing

Advice from makes not matter...just use a pipe wrench...the designers
over design and that +400ft/lb torque spec is okay to ignor...gluing
on the nut...to just use a cotter pin to hold the nut without much
torque...

Pure danger to anyone who might listen and follow.

This thread is way above that 'torque on the tow ball' thread, as
that ball torque is just a component in the food chain of towing...but
it is a critical link of that food chain.

Again, technology to non technology savevy folks that argue the merits
of technically based advice

Ron has way more patience than I...as I've put this forum off for a
while and just cruise by occasionally...but had to comment on this one
He has put up with way more disingenuousness than I've been able to take

I read your post a few times as I believe it was directed to me or at least people you think are like me. I'm not sure I understand your point. If I understand you correctly, people should never question existing technology or science. If people did not question why things are the way they are, technology would never improve or move forward. There are people in professions that operate within known parameters to produce items or goods and there are people within those professions looking for new cutting edge technology to make improvements or find new products. In keeping with the spirit of engineering related to rv towing, look at the recent WDH adjustment for front end rise. People questioned the way is has been done for years, engineers looked at it and the rules were changed. People accept the new changes, but it was the people and/or engineers that questioned the existing method to make the change. As far as designs that could use improvement, look at the Reese dual cam system (sorry to those of you that love it). This in my opinion is one of the worst designs ever. They want to fix a lobe in a stationary position and they use all moving parts to accomplish that. In my opinion, Equal-i-zer did better job with the L-bracket, but what were they thinking with that pin to hold the bar on the bracket. Also, why don't they suck it up, say you need to drill a hole in your A-frame so that the L-bracket can be bolted so it doesn't move. Even though each of these hitches have their problems, we use them because it is what is available.
Sorry for the rant if your comment was related to something as simple as manufacturers recommended torque setting.

I'm not sure anyone was advocating doing something that is wrong or unsafe in this thread.

On Edit: OK. Sorry Ben. I have to put my foot in my mouth. There is an active thread 5 pages long about whether or not a hitch ball should be greased.

I'm going back to the trips, locations, destinations (or whatever they call it) forum. Good luck 🙂

[Campin_LI]

xcntrk wrote:
So to the root of these last 4 posts; this utility is very simply based on the math and nothing more. It's a tool where a member of the towing community can hit the CAT scale, plug in their raw data against the corresponding manufacture specifications, and walk away with an understanding of where they fall in comparison. There is no 20% safety margin or subject of towing best practices involved in this tool. That responsibility falls to the user based on their level of comfort. For example this tool will tell you if you're at 99% of your GVWR, but does that mean it's a good idea to be at the bleeding edge of your vehicle limits? That's a question only the user can answer based on their comfort level....

This was the point I was trying to make, this version is much better than mine.

[Campin_LI]

Hi Ron, please don't change the way you question remarks from other posts on my account. After seeing how you did it above, I can tell you that your way is better. Plus, when you first did it to me, I thought you were trying to show me how smart you are by ripping my post apart to show me how stupid I am. It did not take me long to realize you are very thorough and very exact and you make no assumptions or inferences and that you just wanted to be clear about what I wrote. I realize that's why you use only math in your responses to explain your point or position and therefore, you will never give wrong information. It is a great quality for research or analysis, I hope it comes easy to you, makes for a real good engineer. it would be difficult for me.

Of course my above paragraph was not written with the intent that it be scrutinized and it definitely bounces back and forth between different references. If you want, I can explain myself further but I think the point is moot and explanation really does not help the thread.

[Ron_Gratz]

Campin LI wrote:
Ron,

Please don't be astounded by anything I say. I'm just a guy who comes to the forum to get advice and I try to reciprocate from time to time by giving some. I meant no disrespect to you, sorry if you took it that way.
I am on the "other side" in construction. I do not have the technical background to analyze and design things but I am very interested in it and I believe I have the ability to follow along. Most of my knowledge is based on trial and error without the math analysis. That is probably why I bounce back and forth between variables within the same paragraph. I also don't have the desire to ponder over the perfect words so that they can't be twisted to mean something I did not intend to say. For instance above, all I meant was usually a factor of safety is used as in sometimes there is not one. I actually don't know what you twisted it into other than saying there is no such thing as usually when determining a factor of safety or something to that effect.

That being said, the only intent of my post was to make people aware that specific to RVing, the variables in the analysis can be under constant change, and nothing more.
My last paragraph was meant to be a joke. Sorry you didn't get it.

Regarding the underlined portion of your above post: You say all you meant was usually a factor of safety is used as in sometimes there is not one. What you actually said is found in the underlined portion of the post below.

In the underlined text, you also said there was a 33 1/3% factor of safety involved.
I took your statement to mean that when a FoS is assigned, that FoS is equal to 33 1/3%. And, my comment was directed at the assertion of a single, specific Fos.
In your above explanation of meaning, you do not include the specific FoS value.

I found your FoS value of 33 1/3% to be problematic because you later said (also underlined below) the same FoS should be used when analyzing weights. Does this mean that it is okay for a weight to be as high as 133 1/3% of a rating? I thought you were advocating keeping all weights well below 100% of their respective ratings.

As regards your final paragraph about the 1 ton dually -- I took that paragraph to mean you believed a TV with large excess towing capacity would be completely stable even if its trailer were swaying all over the place. It's good to know your point was only to make a joke.

Ron

Campin LI wrote:
Thank you for taking the time to put this utility together. As long as the person reading through it can understand the math, it is a great way to learn what the weights are and what the effect of the weight has on the setup.

The only thing I would add is that it should be used as a learning tool, not as a tool to analyse a setup once to see if you are within limits. If you are concerned about limits, generally it means you are close to them. The reality is, every camping trip, the trailer is loaded differently based on location, duration and number of people. It is also loaded differently on the way to your destination vs the way home. Over the years, you accumulate more things in the trailer and it becomes heavier. Depending on the length of the trip, more or less items will be in the truck, the list goes on. As an example, my V10 Excursion has a 44 gallon fuel tank located behind the rear axle. Dependent on how much gas is in the tank, the dynamics change during the trip.

Usually when engineers design things or analyze them to this degree, there is a 33 1/3% factor of safety involved. That factor of safety usually covers things like uneven load, shifting weights, etc. I never see the factor of safety included in these analysis and that is why some people end up not being happy with their setups. The factor of safety was probably (I don't know for sure) included when the limits analyzed with the utility were set by the manufacturers, so I believe there is some wiggle room either way with respect to weight limits, but the same factor of safety should be used when analyzing your weights. I'm not saying a 1 ton dually is needed to tow a popup, but rest assured, when the owner says he doesn't know it's back there, he's telling the truth (even if it's swaying all over the place)

[JIMNLIN]

Campin LI wrote:
Thank you for taking the time to put this utility together. As long as the person reading through it can understand the math, it is a great way to learn what the weights are and what the effect of the weight has on the setup.

The only thing I would add is that it should be used as a learning tool, not as a tool to analyse a setup once to see if you are within limits. If you are concerned about limits, generally it means you are close to them. The reality is, every camping trip, the trailer is loaded differently based on location, duration and number of people. It is also loaded differently on the way to your destination vs the way home. Over the years, you accumulate more things in the trailer and it becomes heavier. Depending on the length of the trip, more or less items will be in the truck, the list goes on. As an example, my V10 Excursion has a 44 gallon fuel tank located behind the rear axle. Dependent on how much gas is in the tank, the dynamics change during the trip.

Usually when engineers design things or analyze them to this degree, there is a 33 1/3% factor of safety involved. That factor of safety usually covers things like uneven load, shifting weights, etc. I never see the factor of safety included in these analysis and that is why some people end up not being happy with their setups. The factor of safety was probably (I don't know for sure) included when the limits analyzed with the utility were set by the manufacturers, so I believe there is some wiggle room either way with respect to weight limits, but the same factor of safety should be used when analyzing your weights. I'm not saying a 1 ton dually is needed to tow a popup, but rest assured, when the owner says he doesn't know it's back there, he's telling the truth (even if it's swaying all over the place):)

Excellent post.
Some industries use a 2:1 safety margin in mfg their products.

As far as using GVWR to determine a payload we have to be careful now that GVWR is almost to the sum of the GAWRs. In fact we've had some members report using GVWR to figure their trucks payload and have over loaded the trucks RAWR/tires while still under GVWR.

Personnaly I prefer using DOTs method for determining any trucks payload. That way I'm not only legal but also safe.

[BenK]

That the designers design to the worse case scenario their specification dictates
That worse day out there when Mr Murphy crosses your or the other guys path

Most advice are for the good days out there when Mr Murphy isn't around

That is where the bean counter management comes in...twice

They decide what the specification shall be....then they approve the final design
AFTER the engineering management/team approves

[BenK]

howmuchcanitow howmuchshoulditow

That your wheels won't instantly fall off if over loaded...just sooner
and that your PERFORMANCE will be reduced

[BenK]

xcntrk wrote:
So to the root of these last 4 posts; this utility is very simply based on the math and nothing more. It's a tool where a member of the towing community can hit the CAT scale, plug in their raw data against the corresponding manufacture specifications, and walk away with an understanding of where they fall in comparison. There is no 20% safety margin or subject of towing best practices involved in this tool. That responsibility falls to the user based on their level of comfort. For example this tool will tell you if you're at 99% of your GVWR, but does that mean it's a good idea to be at the bleeding edge of your vehicle limits? That's a question only the user can answer based on their comfort level....

Agree

Repeat that those trying to figure this out, first decide if they
believe in 'ratings' or not

If no, then do whatever, but know that they have taken the OEM(s) off
the liability hook (mostly...our court system is whacky)

If yes, then understand how any ratings system works. That the weakest
link dictates the over all rating of the 'system'

Here is a diagram of how the vehicle ratings systems looks like in
graphical form.

Note that the diagram shows how2 using the actual weights...then
compare the results to the 'ratings'

howmuchcanitow howmuchshoulditow

[xcntrk]

So to the root of these last 4 posts; this utility is very simply based on the math and nothing more. It's a tool where a member of the towing community can hit the CAT scale, plug in their raw data against the corresponding manufacture specifications, and walk away with an understanding of where they fall in comparison. There is no 20% safety margin or subject of towing best practices involved in this tool. That responsibility falls to the user based on their level of comfort. For example this tool will tell you if you're at 99% of your GVWR, but does that mean it's a good idea to be at the bleeding edge of your vehicle limits? That's a question only the user can answer based on their comfort level....

[BenK]

Campin LI wrote:
Ron,

Please don't be astounded by anything I say. I'm just a guy who comes to the forum to get advice and I try to reciprocate from time to time by giving some. I meant no disrespect to you, sorry if you took it that way.
I am on the "other side" in construction. I do not have the technical background to analyze and design things but I am very interested in it and I believe I have the ability to follow along. Most of my knowledge is based on trial and error without the math analysis. That is probably why I bounce back and forth between variables within the same paragraph. I also don't have the desire to ponder over the perfect words so that they can't be twisted to mean something I did not intend to say. For instance above, all I meant was usually a factor of safety is used as in sometimes there is not one. I actually don't know what you twisted it into other than saying there is no such thing as usually when determining a factor of safety or something to that effect.
That being said, the only intent of my post was to make people aware that specific to RVing, the variables in the analysis can be under constant change, and nothing more.
My last paragraph was meant to be a joke. Sorry you didn't get it.

Gotta chime in...

This thread is in part why I've taken a break from here and occasionally come
by to check PMs (folks still ask for advice)

Some very poor to dangerous advice on technology based questions or issues by
NON techie folks.

Most times the school of hard knocks did teach the advisors correctly or close
enough...but too often...way off base to argue against engineering principles
which are based on the world's "laws of physics" that we all live in

On designed in safety factor...there are many to anything as complex as automotive.
There are compounding that even some designers of 'that' part of the assembly
does NOT know of (from other components/assemblies within the whole)

Myopia and out of context is often too common here and other Internet freebie
forums

That is only part of 'why' you bounce back and forth between, as
it maybe or is between two different aspects that has their own dialed
in margins (safety factors and design spec)

I dropped out on my last straw thread...how tight should a tow ball
be tightened to. Simple and just a tow ball right?

Missed by the poor advice is that is a key component in the food chain
of towing

Advice from makes not matter...just use a pipe wrench...the designers
over design and that +400ft/lb torque spec is okay to ignor...gluing
on the nut...to just use a cotter pin to hold the nut without much
torque...

Pure danger to anyone who might listen and follow.

This thread is way above that 'torque on the tow ball' thread, as
that ball torque is just a component in the food chain of towing...but
it is a critical link of that food chain.

Again, technology to non technology savevy folks that argue the merits
of technically based advice

Ron has way more patience than I...as I've put this forum off for a
while and just cruise by occasionally...but had to comment on this one
He has put up with way more disingenuousness than I've been able to take

PS...Ron...thanks for the tidbit on your background...me too in an
ancillary way associated with offshore drilling !

Back in the late 70's partner in a small startup that was contracted
to automate the largest automated factory with the largest mobile
robots in the world for US Steel in Alabama...seamless pipe for off
shore drilling.

Learned seamed pipe bursts at those depths.

US Steel became USX during our installation and what mess that created
and found that their strategists missed by a few decades on off shore
drilling...

[Campin_LI]

Ron,

Please don't be astounded by anything I say. I'm just a guy who comes to the forum to get advice and I try to reciprocate from time to time by giving some. I meant no disrespect to you, sorry if you took it that way.
I am on the "other side" in construction. I do not have the technical background to analyze and design things but I am very interested in it and I believe I have the ability to follow along. Most of my knowledge is based on trial and error without the math analysis. That is probably why I bounce back and forth between variables within the same paragraph. I also don't have the desire to ponder over the perfect words so that they can't be twisted to mean something I did not intend to say. For instance above, all I meant was usually a factor of safety is used as in sometimes there is not one. I actually don't know what you twisted it into other than saying there is no such thing as usually when determining a factor of safety or something to that effect.
That being said, the only intent of my post was to make people aware that specific to RVing, the variables in the analysis can be under constant change, and nothing more.
My last paragraph was meant to be a joke. Sorry you didn't get it.

[Ron_Gratz]

Campin LI wrote:
Usually when engineers design things or analyze them to this degree, there is a 33 1/3% factor of safety involved.---

As a civil engineer whose working career was mainly devoted to research and development on the structural design and analysis of offshore drilling and production structures, I am astounded by this statement. When it comes to factors of safety, there is no such thing as "usually". I suggest you read this, which is highly generalized, but should give you some idea of how much variability there is in factors of safety.

---I never see the factor of safety included in these analysis and that is why some people end up not being happy with their setups.---

If a factor of safety were known, how would it prevent people from not being happy with their setups? If someone knew that a 1000#-rated WD bar would fail at a static load of 3000#, how would that keep them from being unhappy?

---The factor of safety was probably (I don't know for sure) included when the limits analyzed with the utility were set by the manufacturers, so I believe there is some wiggle room either way with respect to weight limits, but the same factor of safety should be used when analyzing your weights.---

If a manufacturer's factor of safety were known, how would one use that FoS when analyzing weights? Can you give a specific example?

---I'm not saying a 1 ton dually is needed to tow a popup, but rest assured, when the owner says he doesn't know it's back there, he's telling the truth (even if it's swaying all over the place):)

If a 1 ton dually is not needed to tow a popup -- then what is your point?

Ron

[Campin_LI]

Thank you for taking the time to put this utility together. As long as the person reading through it can understand the math, it is a great way to learn what the weights are and what the effect of the weight has on the setup.

The only thing I would add is that it should be used as a learning tool, not as a tool to analyse a setup once to see if you are within limits. If you are concerned about limits, generally it means you are close to them. The reality is, every camping trip, the trailer is loaded differently based on location, duration and number of people. It is also loaded differently on the way to your destination vs the way home. Over the years, you accumulate more things in the trailer and it becomes heavier. Depending on the length of the trip, more or less items will be in the truck, the list goes on. As an example, my V10 Excursion has a 44 gallon fuel tank located behind the rear axle. Dependent on how much gas is in the tank, the dynamics change during the trip.

Usually when engineers design things or analyze them to this degree, there is a 33 1/3% factor of safety involved. That factor of safety usually covers things like uneven load, shifting weights, etc. I never see the factor of safety included in these analysis and that is why some people end up not being happy with their setups. The factor of safety was probably (I don't know for sure) included when the limits analyzed with the utility were set by the manufacturers, so I believe there is some wiggle room either way with respect to weight limits, but the same factor of safety should be used when analyzing your weights. I'm not saying a 1 ton dually is needed to tow a popup, but rest assured, when the owner says he doesn't know it's back there, he's telling the truth (even if it's swaying all over the place):)