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07-03-2019, 06:37 PM
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#1
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Air Al
2010 25' FB International
Santa Fe
, New Mexico
Join Date: Aug 2012
Posts: 16
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3-Pass CAT scale Basics -- help!
I am planning to do a 3--pass CAT scale weigh-in with my 25’ International FB and 2012 Tundra. Reading a recent forum, I came to understand that my Tundra may be close to maxed out. Do I have the 3 -pass method clear?
a) I weigh ready-to-travel, with full propane tanks, water, etc. with my Equalizer WD hitch set up
b) I weigh everything again without the WD hitch engaged
c) I weigh the Tundra alone
First, subtracting the weight of the truck from the total gives me the weight of the trailer, which lets me know if I’m under towing capacity of the Tundra (9,000 lbs). Secondly, doing the weighing with and w/o the WD hitch gives me a reading of the GAWR on the rear axle with and w/o the tongue weight of the trailer, thus giving me the pounds of payload that are being used up by the tongue, which I then calculate in with weight of passengers, dogs, and paraphernalia.
Is that it in a nutshell? Trying to keep the process and simple as possible in my brain. I get it that it’s a whole other process to get the WD hitch just right, but my first goal is to know whether I can be comfortable towing with the TV that we have.
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07-04-2019, 07:37 AM
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#2
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"Cloudsplitter"
2003 25' Classic
Houstatlantavegas
, Malebolgia
Join Date: Jun 2007
Posts: 20,000
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I do C,B,A.
That gives me a 0 WD baseline to work from. 👍
If you guess right you're done.
Bob
🇺🇸
TV alone, loaded. No WD. WD set.
__________________
I’m done with ‘adulting’…Let’s go find Bigfoot.
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08-09-2021, 01:41 PM
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#3
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OGJerry
2017 27' International
2020 23' Globetrotter
Any Town - USA
, New Mexico
Join Date: Feb 2021
Posts: 12
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Quote:
Originally Posted by ROBERT CROSS
I do C,B,A.
That gives me a 0 WD baseline to work from. 👍
If you guess right you're done.
Bob
🇺🇸
TV alone, loaded. No WD. WD set.
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Robert: What WDH and TV did you use when you took these weights. Your weight distribution is fabulous and I'm not anywhere near your numbers!
__________________
DW says that I can accessorize a hammer!
2017 Int'l 27FBT
2020 GT23FBT
2022 RAM 2500 Limited CC 4X4 6.7L Turbo Cummins
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08-09-2021, 01:54 PM
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#4
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Rivet Master
Currently Looking...
Evergreen
, Colorado
Join Date: Aug 2020
Posts: 2,592
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I also do C, B, A.
It's an interesting and potentially eye-opening exercise. I like it because you can see how your WDH is actually distributing weight across the truck and trailer axles, and it also gives you some information on your real world tongue weight and how that's distributed to your vehicle.
One thing that I found particularly interesting is that my Sherline tongue weight scale tends to show a lower weight than the calculated tongue weight on the CAT scales. I think it's due to the way that the weight is distributed to the truck axles through the hitch vs. a linear load applied to the tongue weight scale, but it's interesting nonetheless.
It's always great to have data!
__________________
Dennis
Past:
Airstream International Serenity 23FB
Newmar Ventana 3715
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08-09-2021, 02:26 PM
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#5
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Rivet Master
1988 25' Excella
1987 32' Excella
Knoxville
, Tennessee
Join Date: Oct 2010
Posts: 5,103
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Pass A tells you and awful lot by itself. It certainly tells you whether you are withing your axle limits. You can certainly deduce if you are "maxed out". It is extremely easy to do. You can do it in 10 min without interrupting a trip. The other passes add some information but pass a actually tells the main story.
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08-09-2021, 02:51 PM
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#6
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Rivet Master
2019 25' Flying Cloud
Houston
, Texas
Join Date: Jan 2019
Posts: 997
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When I weigh the truck alone, I position the trailer to be on the back CAT scale platform. That way I also get the weight of the trailer in that weigh.
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08-09-2021, 04:16 PM
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#7
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"Cloudsplitter"
2003 25' Classic
Houstatlantavegas
, Malebolgia
Join Date: Jun 2007
Posts: 20,000
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Quote:
Originally Posted by OGJerry
Robert: What WDH and TV did you use when you took these weights. Your weight distribution is fabulous and I'm not anywhere near your numbers!
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A combination of factors helped get it done.
One of the main contributors is/was a new Class 5 Reese hitch.
You can see from the pictures that the mount arms are much longer than the stock OEM unit.
Longer arms provide better leverage and easier weight transfer.
We started with 1400lb bars and needed a lot of WD to move the needed weight, with the Reese we use 1000lb bars and still can move 720lb
860lb receiver wt with WD set
560 to the FA
160 to the AS
720 moved
Another important factor is a perfectly proper loaded and balanced,(as much as possible), level rig, both AS and tow vehicle, with WD set properly. POI...the 1400 bars also stiffened the lash-up considerably which can cause the dreaded front end separation.
Forgot...we use a Hensley Arrow PPP hitch. Notice the flex in the lighter 1000 bars, not so stiff equals a softer more compliant lash-up & helps control porpoising,
Good luck & don't give-up.
A more recent set of tickets.
Bob
🇺🇸
__________________
I’m done with ‘adulting’…Let’s go find Bigfoot.
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08-09-2021, 05:15 PM
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#8
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Rivet Master
2006 25' Safari FB SE
Spokane
, Washington
Join Date: Sep 2009
Posts: 1,848
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The ever-handy Ron Gratz [RV.net] chart might be of help in making it quick:
Weighing #1 -- TT attached and Weight Distribution Activated
Let Front Axle Load be "FA1"
Let Rear Axle Load be "RA1"
Let TT Axles Load be "TT1"
Then, while in same position on scales, take
Weighing #2 -- TT attached and Weight Distribution Not Activated
Let Front Axle Load be "FA2"
Let Rear Axle Load be "RA2"
Let TT Axles Load be "TT2"
Then, drive off scales and drop TT. Return to scales and take
Weighing #3 -- TV only -- TT Not Attached
Let Front Axle Load be "FA3"
Let Rear Axle Load be "RA3"
From the above values, you can calculate:
TV weight = FA3 + RA3
Gross Combined Weight = (FA1 + RA1 + TT1)
- should also be equal to (FA2 + RA2 + TT2) if scale weights are correct
TT Weight = Gross Combined Weight - TV Weight
Tongue Weight = (FA2 + RA2) - (FA3 + RA3)
Load Transferred to TT Axles
when WD System in Activated = TT1 - TT2
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08-09-2021, 06:42 PM
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#9
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"Cloudsplitter"
2003 25' Classic
Houstatlantavegas
, Malebolgia
Join Date: Jun 2007
Posts: 20,000
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^
FFT1 RA2 F21 Hike
SORRY Ron....Looking at three or four tickets is much easier for this simpleton.😂
Bob
🇺🇸
__________________
I’m done with ‘adulting’…Let’s go find Bigfoot.
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08-09-2021, 08:29 PM
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#10
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Rivet Master
2017 25' International
West Lake Hills
, Texas
Join Date: Dec 2020
Posts: 1,633
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Just use this: https://fifthwheelst.com/conventiona...alculator.html. It does all the calculations for you. The scale weights are in section B.
I add a fourth pass through the scale to get AS individual axle weights.
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