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Old 07-03-2019, 06:37 PM   #1
Air Al
 
2010 25' FB International
Santa Fe , New Mexico
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Red face 3-Pass CAT scale Basics -- help!

I am planning to do a 3--pass CAT scale weigh-in with my 25í 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 Iím 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 itís 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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Old 07-04-2019, 07:37 AM   #2
CLOUDSPLITTER "Tahawus"
 
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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.
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Old 08-09-2021, 01:41 PM   #3
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Quote:
Originally Posted by ROBERT CROSS View Post
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.
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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Old 08-09-2021, 01:54 PM   #4
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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!
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Old 08-09-2021, 02:26 PM   #5
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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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Old 08-09-2021, 02:51 PM   #6
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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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Old 08-09-2021, 04:16 PM   #7
CLOUDSPLITTER "Tahawus"
 
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Quote:
Originally Posted by OGJerry View Post
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!
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
🇺🇸
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Old 08-09-2021, 05:15 PM   #8
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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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Old 08-09-2021, 06:42 PM   #9
CLOUDSPLITTER "Tahawus"
 
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^
FFT1 RA2 F21 Hike
SORRY Ron....Looking at three or four tickets is much easier for this simpleton.😂

Bob
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Old 08-09-2021, 08:29 PM   #10
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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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