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Old 08-04-2021, 04:20 PM   #1
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Tongue weight.

How do you weigh your tongue? (on the Airstream)
I understand the 4 x 4 plank/bath scale concept, but it's kind of clunky and I'd need a bathroom scale anyway.
I almost bought the Sherline weigh scale, but I balked at spending $150 for something I'll use once a year.
How do you do it? Or do you guess? Use the Airstream spec?
Cat scale and unhook?
I think I'm right at the 1000# area, when a step up in WD might make sense.
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Old 08-04-2021, 06:47 PM   #2
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My opinion is to buy the Shereline and use it till you satisfy that itch to know your true tongue weight under certain loads. Then once you’re comfortable you can sell it in the classifieds or Craigslist. I was just about to sell the one I bought for my Jayco and then we bought our Globetrotter. I’ve yet to use it but after I do a few times I’ll probably get rid of it.

If you poke around on the interweb and YouTube you can find some Rube Goldberg methods for weighing it, but I did not really want to mess around just to save a few bucks
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Old 08-04-2021, 07:23 PM   #3
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I do not know my tongue weight. I do know that from my 2 pass CAT scale weightings the trailer adds 800 lbs to the truck when hitched and the WD engaged. If you want the tongue weight too you can do it with a third pass across the Cat scales. Or just do a 2 pass at the CAT scales with the truck only and then with the trailer hitched but no WD bars.
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Old 08-04-2021, 09:09 PM   #4
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I used the bathroom scale method shortly after we bought the our Airstream. It reminded me of freshman engineering statics from a very long time ago, so that was fun. It was 833 lb empty and nearly factory stock. I need to do it again because of lithium batteries, solar, transfer switch, Goal Zero Yeti, not to mention equipped to travel. Maybe it will get done when it’s not 114 outside.
Good luck,
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Old 08-04-2021, 09:29 PM   #5
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I copied this years ago from a post by Ron Gratz. I have used it twice and the numbers come out very close. My calculated TW is 880.




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 08-04-2021, 09:34 PM   #6
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MollysDad,


I might add, I live in Washington and our weigh stations are open to the public, when not in use. On most state highways when you see a "weigh station closed" you can drive in and use their scales. They leave them on, and make the readout readable from one of the windows. It takes a bit of driving, walking to the window to record, more repositioning, more walking, etc. I have never had anyone around and can take my time. A pretty slick perk for us tax payers.
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Old 08-04-2021, 10:05 PM   #7
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Curt BetterWeigh: https://www.amazon.com/CURT-51701-Be.../dp/B081FTQCYN
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Old 08-05-2021, 06:03 AM   #8
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Surprisingly accurate. Once you know your true wrights by scale measurement itís a quick way to check before trips.

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Old 08-05-2021, 06:40 AM   #9
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I picked up one of these used on eBay for $250. New they are pricey but I have used it for many applications and it is great for measuring load at each tire on TV and trailer (with other tires up on equal height shims for best precision).
https://www.intercompcompany.com/whe...portable/pt300
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Old 08-05-2021, 07:37 AM   #10
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Originally Posted by jondrew55 View Post
My opinion is to buy the Shereline and use it till you satisfy that itch to know your true tongue weight under certain loads. Then once youíre comfortable you can sell it in the classifieds or Craigslist. I was just about to sell the one I bought for my Jayco and then we bought our Globetrotter. Iíve yet to use it but after I do a few times Iíll probably get rid of it.

If you poke around on the interweb and YouTube you can find some Rube Goldberg methods for weighing it, but I did not really want to mess around just to save a few bucks
Exactly....But I kept ours.
It is a scale, and is not limited to tongues.👍

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Old 08-05-2021, 06:31 PM   #11
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Originally Posted by Bill M. View Post
I do not know my tongue weight. I do know that from my 2 pass CAT scale weightings the trailer adds 800 lbs to the truck when hitched and the WD engaged. If you want the tongue weight too you can do it with a third pass across the Cat scales. Or just do a 2 pass at the CAT scales with the truck only and then with the trailer hitched but no WD bars.
Yep. A third pass on the CAT scale can determine tongue weight.
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Old 08-06-2021, 08:13 AM   #12
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Yep. A third pass on the CAT scale can determine tongue weight.
A more accurate number can be gotten on a scale, at the ball, with a level trailer.

The main concern with the CAT, the lighter the weight the less accurate the results.

Bob
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Old 08-06-2021, 08:22 AM   #13
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Thanks for the advice.
In the end, I bought the Sherline on E-bay.
I'm surprised e-bay charges sales tax on shipping, but they claim it's our state law.
Regardless, I'll have it and experiment with the water tank full or empty, etc.
Then maybe someone else will need one and I'll help.
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Old 08-06-2021, 08:48 AM   #14
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Yea, still need to play with mine a bit before I let it go. If you lived a bit closer Iíd loan you the one I have

Quote:
Originally Posted by Mollysdad View Post
Thanks for the advice.
In the end, I bought the Sherline on E-bay.
I'm surprised e-bay charges sales tax on shipping, but they claim it's our state law.
Regardless, I'll have it and experiment with the water tank full or empty, etc.
Then maybe someone else will need one and I'll help.
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Old 08-13-2021, 08:49 PM   #15
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Bobís right to mention that CAT Scales are less accurate at low platform loads. I called CAT Scaleís corporate office a couple of years ago and asked this question. The rep said that at very low platform loads like our trailer hitches, accuracy can vary +/_ 10%. But for commercial truck axle weights CAT Scales are certified accurate. I bought a Sherline scale after that conversation and itís been an eye-opener. My 25FB hitch weight has weighed as much as 1,240lbs!
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Old 08-14-2021, 01:12 PM   #16
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Bobís right to mention that CAT Scales are less accurate at low platform loads. I called CAT Scaleís corporate office a couple of years ago and asked this question. The rep said that at very low platform loads like our trailer hitches, accuracy can vary +/_ 10%. But for commercial truck axle weights CAT Scales are certified accurate. I bought a Sherline scale after that conversation and itís been an eye-opener. My 25FB hitch weight has weighed as much as 1,240lbs!
I don't weigh the tongue at the CAT scale.

A. Weigh the truck with the trailer hitched and WD disengaged.
B. Weigh the truck alone (no trailer, and stinger removed if ProPride or Hensley).

A - B = Tongue weight

My case: 7280 - 6140 = 1140

I'm hoping that when weighing between 6100# and 7300# the scale is relatively accurate/inaccurate. Meaning, if it is inaccurate it is inaccurate by similar percentages at those two weights.

One study showed the CAT scales at 40# inaccurate at these weight ranges, ~.5%). But for arguments sake, let's assume that the scale is ten times as inaccurate at these weights or 5%.

7280*1.05 - 6140*1.05 = 1.05 * (7280 - 6140) = 1197 (also 1.05*1140)

1197 - 1140 = 57 (also 5% of 1140)

I guess 57# could make a difference if you're cutting it close and if the scale is 5% inaccurate around 6500#.

If the inaccuracy is 10% in the range of 6100# to 7300#, then I do have a problem. But that would be 20 times the inaccuracy from the study and nearing the weight of some commercial axles.

10% error at 6100# to 7300#: 1.1*1140 (114# difference)
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Old 08-14-2021, 01:23 PM   #17
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^
?
A-B not actually. A-B equals receiver weight.

Tongue weight is much more accurate when weighed separately at the ball.

Bob
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Old 08-14-2021, 02:40 PM   #18
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^
?
A-B not actually. A-B equals receiver weight.

Tongue weight is much more accurate when weighed separately at the ball.

Bob
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OK. I'm trying to understand this. Bear with me.

Should I not be concerned with the downward force on the hitch receiver itself?

The receiver rated for a particular weight. If the weight at the ball is, say, right at the receiver rating, but the weight at the receiver is over the rating, is the rig within the limits of the receiver?

Which weight should I be more concerned about when determining the safety of the rig, particularly with the potential for the receiver separating from the truck: receiver or ball?

How much difference (ballpark) is there between the weight at the ball and the weight at the receiver?
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Old 08-14-2021, 02:55 PM   #19
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OK. I'm trying to understand this. Bear with me.

Should I not be concerned with the downward force on the hitch receiver itself?

The receiver rated for a particular weight. If the weight at the ball is, say, right at the receiver rating, but the weight at the receiver is over the rating, is the rig within the limits of the receiver?

Which weight should I be more concerned about when determining the safety of the rig, particularly with the potential for the receiver separating from the truck: receiver or ball?

How much difference (ballpark) is there between the weight at the ball and the weight at the receiver?
Though many people don't realize it, tongue weight and receiver weight are two different values. Both words are frequently used interchangeably. They are not the same thing. Tongue weight is what the trailer manufacturer feels is safe to load the coupler onto the ball. Weight distribution of items in the trailer manipulates this number while NEVER going below a minimum of 10% of the total trailer weight. (A bit over 10% is better). Receiver weight is the effective weight the tongue places on the receiver combined with the effective weight that the hitch system places on the receiver. They are not simply additive though. If you just add them together you will have a false high weight calculation. How much depends upon the trailer and hitch dimensions. In my personal case, if I add together my tongue weight and the weight of the propride, I would be at 1083.5# receiver weight. Actual receiver weight is 981#. Now, mind you, thats with a PPP hitch that moves the trailer almost 20" from the receiver mouth, whereas a conventional hitch's ball is usually around 9" from the receiver mouth.

BTW, the definition of receiver weight is the total weight that the TV manufacturer determines the TV receiver (and maybe TV components) is capable of handling.
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Old 08-14-2021, 03:00 PM   #20
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Got it.

So, it seems that I should be concerned with both...

To make sure my receiver doesn't fall off the truck, I should be concerned about receiver weight.

To make sure the trailer tracks behind the ball, I should be concerned with tongue weight.
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