Trailer Weight Calculations & Load Estimator Utility
Check it out.
I built this handy tool for the trailer towing community. It consists of the following two utilities:
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:
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.
Bookmarked the site.
Thanks for the spreadsheet, it's very useful.
Checked your weight calculations against mine and we agree. Displaying the results in percentages puts everything in perspective. My 130# over-weight rear axle doesn't seem so bad when displayed as 103%.:)
But I would add the trailer's GAWR to your sheet. Think a lot of trailer tire blowouts are due to overloaded axles and tires. Could even add a tire rating based on size and pressure I suppose, but the trailer's GAWR is a lot easier for people to obtain.
As for the Load Estimator, I find it less useful. The real problem is estimating the Loaded Trailer's tongue weight ratio, and there is no easy way of doing that. It's usually just "by guess and by golly". EDIT: But in your example above, using 15% is good, conservative practice. Make it the default? :)
This is exactly the kind of input I'm looking for, thanks for taking the time to comment! :thumbsup:
For some manufacturers, it's best to get the info off the stickers on the trailer rather than the catalogue. There you can find the trailer's GAWR as well as GVWR, tire size and rating (C,D,E), as well as Cargo Carrying Capacity (CCC).
The *catalog* dry weights or CCC for some manufacturers don't include standard or required options like a/c and so on. For example a Lance 1985 we looked at had a CCC of 1051# on the yellow trailer sticker, but CCC was 1955# in the catalogue. That's a huge difference.
Maybe with your program you can encourage prospective buyers to look more closely at those trailer stickers.
The calculator looks good however I do not agree with the WD% changing your payload requirement. A WDH will change your rear axle weight but not decrease the total load on the TV.
Also with most RVs (except Toy Haulers) if you take the dry tongue weight and divide it by the dry trailer weight you get a very close (I would say with in +/-1%) "projected" tongue weight percentage. How the trailer is load, particularly in reference to it size and # of axles can have any effect on tongue weight. But most RV trailers loaded by the average user will stay very close to the calculated %. Toy haulers are designed and offset for heavy weight in the rear and for that reason the dry tongue to dry weight ration is usually well over 15% closer to 20%. So if you ask for the dry tongue # and the dry Trailer # you can provide the calculated tongue weight %. Ask for the GVWR for the trailer and your calculator could provide the user estimated upper and lower payload limits that would be transferred to the TV by a given trailer.
Dry Tongue: 1000lbs
dry trailer: 9000lbs
% tongue weight: 11%
GVWR trailer: 10500lbs
minimum Tongue weight or payload transfered to TV: 1000lbs (dry trailer)
Maximum Tongue weight or payload transfered to TV: 1155lbs (when loaded evenly/correctly)
With a number like 1155lbs and the user knows he has a 1400lb payload, 2 kids, wife and dog. He can make a very informed decision on whether he can or cannot safely tow given trailer.
Hmmm, so my understanding is that WD actually removes tongue weight and redistributes to the trailer axles? Sounds like that's not the case however and instead a WD hitch uses leverage to force some percentage of the rear axle load to the front?
Looks like v3.0 is in order...
So yes, the amount moved to the trailer axles is not counted against the truck's payload.
In my case 140# is moved off the truck to the trailer. Without the WDH, the tongue weight is 1130#. So your 10% seems reasonable.
And I haven't had much success using dry % tongue weight to predict wet % tongue weight. My current trailer is supposed to be 12% dry TW, but when loaded with batteries, propane and all my stuff in the pass-thru, it's weighs in at a bit over 15%.
Which was a surprise. I'm now looking for a WDH with 1200# bars, and ditching the 1000# bars.
So from a calculation spreadsheet standpoint, I'm not sure how one could realistically estimate the amount of TW distributed using a WD hitch given these variables. Some tongue weight goes forward on the TV while some small percent goes back into the trailer axles.
Any suggestions on how to reflect the benefit of WD in a load estimate tool such as this?
Easier just to use your rough 10% approx. It's conservative, and people can change it to 20% or whatever, if they want.
No point in getting too precise, especially since the estimate of % tongue weight is going to be so dicey anyway. Over-precision can give people false confidence in the estimates ... ;)
EDIT: I see now that Ron Gratz over on RV.NET is suggesting that 20% is a good average estimate of the tongue weight transferred back to the axle. http://www.rv.net/forum/index.cfm/fu...2.cfm#27492302
He's been collecting data on WDH loadings over the years and knows what he's talking about.
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