Calculating Tongue Weight at the CAT scales?

[ROBERT CROSS]

KISS...just replace the front axle loading.

FALR....what's the point, what am I missing?

Oh wait....the rules have changed, now we are told that we can just replace a percentage of the weight and everything will be fine. A little for you, more for me and none for him.
No thanks' I prefer to make that determination by actually driving my rig, plus I'm rotten at werking my calculater while driving.

Bob

[SteveSueMac]

Ridgerunner3 - looks like your method would produce 1080 and that makes more sense to me than something in the 800s. The 1080/6840 would suggest a 15.7% TW...that seems ok to me.

Ron - thanks so much. It's so gracious of you to share your knowledge like this!

I'm seriously thinking about those 1400# bars. In an earlier attempt, I got to 100% FALR at 6" and now apparently I'm at 56% which makes no sense to me...much more noodling and testing to do. We'll get this right eventually. I will get you the measures you suggested in your PM.

Bob - thanks too for your encouragement and the practical advice. Unless WD on the PP works like decibels - one inch is going to get me 60-80 lbs so at 7, I'd be closer but still not where I want to be. I'm very confident I'm going to get this dialed in - really appreciate everyone's help. The ride still seems fine to me but this is my first rig. How would I know any better? :-)

I'm trying to KISS and feel like having a boatload of data is helping me understand more and more about it so I can get to something simpler that I know I can manage more intuitively having the background of the math behind it all. Math was definitely not a strong point for me! :-)

[Ron Gratz]

Tongue weight usually is defined as the upward force against the ball coupler required to keep the trailer in a level attitude when it is sitting on a level surface.
When a trailer has independently suspended axles, the "level attitude" is especially important to get an accurate measure of tongue weight.

When a TT is attached to the TV with no WD applied, the "sag" at the rear of the TV usually will cause the TT to be in a "nose-down" attitude.
Is so, an independent suspension on the TT will cause net load to be added to the TT's axles (decrease on rear but larger increase on front) and the upward force against the ball coupler will be reduced.
This means the load which is added to the TV will be somewhat less than the actual tongue weight. And that means if you subtract the "TV ONLY" weight from the "TT HITCHED WITH NO WD APPLIED" weight, the result will be somewhat less than the actual tongue weight.

For Steve's data, the usual direct method of estimating tongue weight gives (4120+4860)-(4620+3280) = 1080#.
A second "direct" method using data for the TV on the scale, the TT off the scale, and no WD applied, gave an estimated tongue weight of 840#.
This probably was due to having the TT's tires partially or fully on the up slope to the scales -- likely causing a fairly large "nose down" attitude relative to the plane on which the tires were sitting.

An indirect method of estimating, using data for "WD APPLIED" along with TV and TT dimensions should get us closer to the actual tongue weight because, with WD applied, the TT should be closer to "level".
For Steve's 5" data this method gave an estimated tongue weight of 1169# with 149# transferred to the TT's axles.
For Steve's 6" data this method gave an estimated tongue weight of 1126# with 166# transferred to the TT's axles.

However, without knowing the attitude of the TT at 5" or 6", we cannot say if either the 5" or 6" data would give a more realistic estimate of TW.

Perhaps a more accurate method for estimating TW (if permitted by the scale operator) would be to position the TT with its axles on Pad 3 and its tongue jack over Pad 2. Then lower the jack and disconnect with the TT level. Next move the TV so both of its axles are on Pad 1.

The above method will give the load on the jack, which is not equal to the TW -- but a correction can be applied.
Measure the distance from the center of the jack to the midpoint between the TT's axles. Call this distance "d1".
Then measure the distance from the center of the jack to the middle of the ball coupler. Call this "d2".
The TW then is equal to jack load times d1 divided by d1+d2.
For example, with jack load = 1000#, d1=240", and d2=10", we would have TW = 1000*240/(240+10) = 960# (plus or minus the accuracy of the scales).

And, of course, with a PP or HA hitch, the drawbar should remain in the receiver for all weighings.

I'm sure this does not simplify matters for the OP, but it does point out factors which should be considered if one wants to get a really good estimate of tongue weight.

Ron

[bonginator]

Originally Posted by SteveSueMac

I don't have a Sherline scale and don't want to spend $150 on one, and I don't like the bathroom scale method (seems way too prone to variation). So I'm wondering if this would work:

1) pull TV on to cat scale with TT connected BUT trailer axle NOT on the platform.
2) track weight - let's say it's 6000 lbs
3) drive off the scale and disconnect the TT
4) weigh the TV on the cat scales alone - let's say it weighs 5000 lbs
5) tongue weight = step 2 (6000) - step 4 (5000) (or 1000 in this example)

Is this an accurate way to calculate tongue weight? Are there other ways to calculate it without a dedicated scale or bathroom scale/boards/pipes?

Thanks!

Edit - this is based on a recommendation I found on a web search - not an original idea on my part...

Would this approach for determining how much the tongue adds to the payload of the truck (taking measurement #1 with weight distribution bars removed) or would it be better to do measurement #1 with weight distribution bars?

I am trying to figure out how much my full TT adds to my truck's payload.

I weighed the truck today empty at the CAT scales and now want to figure out what the tongue adds to the payload...

[Ron Gratz]

Originally Posted by bonginator

I am trying to figure out how much my full TT adds to my truck's payload.

I weighed the truck today empty at the CAT scales and now want to figure out what the tongue adds to the payload...

Have the TV loaded the same as when you weighed it empty.

Hook up your full TT to the TV.
Hook up the weight distribution hitch for the amount of load distribution you want.

Weigh the TV with TT attached and weight distribution applied,
with steer axle on pad1, drive axle on pad2, and TT axles on pad3.

Your towing TV weight is the sum of the steer and drive axle loads.
Subtract the empty TV weight from the towing TV weight to get the amount added to the payload.

Ron

[bonginator]

Thanks, Ron.

Anyone have a good printed guide that instructs step by step how to do proper CAT scale weighings and record values and call results for a dual axle TT and TV? I had one before but can't seem to put my hands on it now...

[SteveSueMac]

Originally Posted by bonginator

Thanks, Ron.

Anyone have a good printed guide that instructs step by step how to do proper CAT scale weighings and record values and call results for a dual axle TT and TV? I had one before but can't seem to put my hands on it now...

Hi. Try here: http://catscale.com/how-to-weigh


Now as it happens this was apparently my 499th post which means my next one makes me a Rivet Master - which can not mean what it sounds like as I'm not a master in this game by a long shot!

So - any recommendations or traditions I should know about for post 500??

[richinny]

i think you buy the forum a round of drinks!

[slowmover]

Originally Posted by bonginator

Thanks, Ron.

Anyone have a good printed guide that instructs step by step how to do proper CAT scale weighings and record values and call results for a dual axle TT and TV? I had one before but can't seem to put my hands on it now...

These two are complementary:

Rig basics:

Scale Chart

Tire loads:

Chapter Four of this RMA Service Guide tells the final story.

Where the rubber meets the road is, in the end, what all of this is about.

.

[bonginator]

Thanks!

[egraham]

Does this sound reasonable ?
2009 Chevy Silverado 1500
AS Interational Serenity 28 RQ
Propride hitch

GAWR Frt. 3950
GAWR Rear. 3950
GVWR. 7000
GCWR. 15000


Weight #1 WD Activated
FA1 3020
RA1 3840
TT1 6420

Drove off scales and back on:
Weight #2 WD bars unloaded
FA2. 2760
RA2. 4040
TT2. 6380

Drove off scales dropped AS and back on:
FA3. 3260
RA3. 2660

TV Weight = FA3+RA3. 5920
Gross Combined Weight= Fa1+RA1+TT1. 13280

TT Weight= GCW-TV Weight 6860

Tongue Weight= (FA2+RA2)-(FA3+RA3) = 860


Airstream says the Tongue Weight on my trailer dry is 950 ???
Did I do something wrong?
Also, if I add tongue weight to TV weight (5920 + 860) I get 6780 so Looks like I am under
My GVWR by 220 . I assume that means I am in good shape as to payload?

Thanks

[Rocket53]

Goôd information, getting my trailer in December and I will need this.

Thanks

[Al and Missy]

Originally Posted by egraham

Does this sound reasonable ?
2009 Chevy Silverado 1500
AS Interational Serenity 28 RQ
Propride hitch

GAWR Frt. 3950
GAWR Rear. 3950
GVWR. 7000
GCWR. 15000


Weight #1 WD Activated
FA1 3020
RA1 3840
TT1 6420

Drove off scales and back on:
Weight #2 WD bars unloaded
FA2. 2760
RA2. 4040
TT2. 6380

Drove off scales dropped AS and back on:
FA3. 3260
RA3. 2660

TV Weight = FA3+RA3. 5920
Gross Combined Weight= Fa1+RA1+TT1. 13280

TT Weight= GCW-TV Weight 6860

Tongue Weight= (FA2+RA2)-(FA3+RA3) = 860


Airstream says the Tongue Weight on my trailer dry is 950 ???
Did I do something wrong?
Also, if I add tongue weight to TV weight (5920 + 860) I get 6780 so Looks like I am under
My GVWR by 220 . I assume that means I am in good shape as to payload?

Thanks

My Opinion -
1. Tongue weight is the force exerted on the ball of your hitch by the trailer which is not the same as the force exerted on your TV. "Tongue weight" is a concern for two reasons - the rating of your hitch, and the balance of your rig. I don't know what the tongue weight rating is, so I can't comment on that, but as for balance it is recommended that the tongue weight be between 10% and 15% of the TT GVW. Now, there is a difference of opinion as to whether it really means tongue weight, or the apparent tongue weight as measured at the TV axles. Assuming your TT weight of 6860 is correct, that is 686#-1029#, so you are within the recommended range either way.

2. Was your trailer dry when you weighed it? Depending on the location of the tanks, tongue weight might decrease with tank fills.

3. What would seem to be important is the condition of the combination when towing. Measurement #2 allows calculation of the actual tongue weight, but I'd calculate the TV GVW by adding FA1 and RA1 which is 6860, still within your GVWR.

4. Similarly, I'd calculate GCW by adding all the #1 weights for a total of 13,280.

5. To calculate the TT weight, you need to weigh the TV (in case 1) with the hitch on the TV, not as Propride users typically unhitch by pulling the stinger. Otherwise, assuming the TV is carrying the hitch, to calculate the TT weight you need to know the weight of the hitch. I don't see that you described how you unhitched, so I can't say how I'd calculate the TT weight.

6. Finally, did the conditions during the weighs include everything you plan to carry when traveling, e.g. passengers, full fuel tank, dogs, clothes food, etc. If not you'll need to account for anything that wasn't included, or load up and re-weigh.

There is a wealth of information on here about how to weigh. Search for CAT Scale weights and you should turn up a lot of posts.

Al

[Ron Gratz]

Originally Posted by egraham

TV Weight = FA3+RA3. 5920
Gross Combined Weight= Fa1+RA1+TT1. 13280

TT Weight= GCW-TV Weight 6860

Tongue Weight= (FA2+RA2)-(FA3+RA3) = 860


Airstream says the Tongue Weight on my trailer dry is 950 ???
Did I do something wrong?
Also, if I add tongue weight to TV weight (5920 + 860) I get 6780 so Looks like I am under
My GVWR by 220 . I assume that means I am in good shape as to payload?

Your scales numbers show inconsistencies.

Weights #1 & #2 give two estimates of GCW -- 13280# & 13180#. These should be equal (within scale accuracy).

When WD is applied, the addition of 260# to the front axle is not consistent with removal of 200# from rear axle. Load removed from the rear should be equal to about 150% of load added to front.

The indicated TW of 880# is about 200# less than I would expect -- especially with the PP hitch installed.
Also, when the TT is hitched with no WD applied, the rear of the TV will "sag". This can cause the TT to have a "nose down" attitude.
With independent axle suspension, a nose down attitude will cause the apparent "tongue weight" to be less than when measured with the TT level.
In short, using scales data directly can result in erroneous TW estimates when weighing an AS.

For meaningful estimates of tongue weight and load transfer, the loading (driver, passengers, and cargo) of TV and TT must be the same for all three weighings. Do you recall what the loading conditions were? The driver or passengers sometimes move off the scale or to a different scale pad between weighings.
Was the PP's adjustable drawbar in the TV's receiver when the unhitched weights were measured?

Also, what is the wheelbase of your 2009 Silverado 1500?

Assuming the weights from Weight #1 are correct, we can say you were:
930# under front GAWR
110# under rear GAWR
140# under TV GVWR
1720# under GCWR

Ron

[egraham]

The trailer was loaded for camping with propane and fresh water full. Black and gray empty

PP stringer was in TV. How does this affect tongue weight????

Difference in weights 1 & 2 was co pilot was not in truck in 2


Thanks for your help

[egraham]

Forgot, hitch is rated for 1000 lbs
Wheel base 143.5

[Ron Gratz]

Originally Posted by egraham

PP stringer was in TV. How does this affect tongue weight????

Difference in weights 1 & 2 was co pilot was not in truck in 2

If weight of PP stinger is not included in TV weight, the tongue weight calculated from axle loads will be too large by an amount equal to weight of stinger.

If weight of missing copilot is added back to the #2 weights (with 60# allocated to front alxe and 40# to rear), the "adjusted" data indicate a TW of approximately 1000# if using #2 weights, and a TW of approximately 1060# if using #3 weights.

Using the GCW of 13280# and the unhitched TV weight of 5920# gives a TT GVW of 7360#.
The indicated tongue weights of 1000-1060# give a TW% of 13.6-14.4%.
Note: The portion of the PP hitch which remains attached to the TT's tongue (all PP weight except the stinger) will be included in the calculated TW.

Ron

[Rpatrick16]

This is an older post of using a CAT scale to determine Tongue load. After reading all the data my head is about to explode so if I may let me pose this question. I should state that I tow a 2016 Bambi 22FB. I am trying hard to keep this weight issue as simple as possible.

The three sections of the CAT SCALE will tell me the various weights of my Front Axle,Rear Axle, and TT. If I position my vehicle and trailer properly on each section of the three part scale.

And with my TV and TT loaded as it would be for travel and "level" with the WD bars at the suggested tension.

Taking into considering the values posted upon my vehicle door sticker I know my "maximum" weights for each axle of the TV and the Gross combined towing weight capacity of the tow vehicle. The maximum "tow capacity" is stated in the manual.

With the vehicle on the CAT SCALE and each axle placed on a section of the scale if the "readings" of the SCALE report indicate that I am "at or under" the stated weight of each of each axle and the combination of my set up is "at or under" the Gross Vehicle Weight Capacity as stated in my vehicle manual...

..."is it really important that I be concerned with what my tongue weight is"?

[Adventure.AS]

Originally Posted by Rpatrick16

..."is it really important that I be concerned with what my tongue weight is"?

Tongue weight, combined with the WD system put a lot of twisting force on the hitch receiver. Exceeding the posted tongue weight could be putting a lot of stress on an under engineered part of your system. However, if your rig is otherwise within spec, as you have stated in your post, it is fairly easy to have the receiver strengthened to withstand your tongue weight and the twisting moment by a good hitch shop.

[slowmover]

TW is a static measurement of dynamic force. The "at rest" number.

What matters is the distribution of TW. Returning the TV Steer Axle to the same value as when solo, is basic. The starting point.

I linked to a post on RVnet in 2010 or so by Ron Gratz. The Three Pass Method.

Use that.

Take a helper and use a day off at a Cat Scale to run three passes. Adjust hitch as well as possible.

And set TV tire pressure to specs. TT tires all the way up. Leave alone until WD is best.

Both vehicles need same load as when camping. Full fresh water and propane. Etc.

A set of scale tickets is basic to future checks and potential trouble shooting.