Fun With TV GVWR with T@B Attached Math

AirBoss

Question:
Weighed the TV and late model '19 T@B 400 Standard today. (Twin 6V AMG Batteries and Air 8 A/C under rear bunk)

1. With TV on scale and T@B hitched but off the scale, came in at 6100#.

2. Unhitched T@B with tongue on scale but its axles off. Moved TV of scale; Tongue Weight came in at 460# (NOTE: Box has twin full propane and 45# of stuff (tools, Home Depot bucket of gear, etc.), spare mounted under box. 

3. Pulled T@B completely onto scale and pulled truck off. T@B GVWR came in at 3575# (full H2O, empty tanks and fridge, all food and other gear onboard.  

I have removed the 45# of "stuff" from the box. IF the Tongue Weight was 460# with the box full, upon removing the 45# of "stuff", I presume the Tongue Weight was reduced but perhaps NOT by the entire 45#, correct?  Is there some formula to be used here? I didn't have time to remove the 45# of stuff while the T@B was being Tongue Weighed so I'm doing the math after the fact.

Can say I noticed a marked difference in the ride of the TV with the 45# of stuff now in the TV ahead of the rear axle, instead of in the box.

ChrisFix

You're correct that given the location of the 45lb bucket of stuff you removed, all of that should come off your tongue weight, or close enough to all of it for government work!
What was different about the ride quality with the lightened tongue weight?

rfuss928

The effect on "tongue weight" of adding or removing weight (W) from various locations is simply the weight times the distance forward of the axle (L1) divided by the distance of the hitch ball socket from the axle (L2). 
 W x L1/L2
On my DM CS the tongue box is about half the distance from the axle to the hitch, so the effect of weight added or removed is 50% on the tongue weight.
Have fun!
Bob

AirBoss

rfuss928 said:

The effect of adding or removing weight from various locations is simply the weight times the distance forward of the axle (L1) divided by the distance of the hitch ball socket from the axle (L2). 
 W x L1/L2
On my DM CS the tongue box is about half the distance from the axle to the hitch, so the effect of weight added or removed is 50% on the tongue weight.
Have fun!
Bob

Thanks Bob. When you say "...distance forward of the axle" and "..distance of the hitch ball..." is that expressed as a percentage? You state yours box is half way between axle and hitch (L2). Where's "L1" in this equation? Maybe I missed it.

Are you saying its "W x (L1/L2) instead of W x L1/L2? 

Gracias! 

AirBoss

ChrisFix said:

You're correct that given the location of the 45lb bucket of stuff you removed, all of that should come off your tongue weight, or close enough to all of it for government work!
What was different about the ride quality with the lightened tongue weight?

A noticable difference is the reduction of porpoising when travelling over undulating pavement (it wasn't too bad to begin with but it's noticably less now). Also felt smoother behind the TV...TV felt even more stuck to the ground. 

rfuss928

AirBoss
The distance is any units you prefer.  On my T@B the tongue box is 60 inches forward of the axle and the hitch is 120 inches.  =>  60/120=.50 or 50%

ChrisFix

The distance from the tongue box to the hitch coupler on a T@B 400 is a lot less than 50% of the axle to hitch coupler, but I don't have the measurements to say what the percentage is. 

AirBoss

MuttonChops said:

AirBoss said:

. . . IF the Tongue Weight was 460# with the box full, upon removing the 45# of "stuff", I presume the Tongue Weight was reduced but perhaps NOT by the entire 45#, correct? 

rfuss928 said:

. . . tongue box is 60 inches forward of the axle and the hitch is 120 inches.  =>  60/120=.50 or 50%

Using @rfuss928 dimensions and @AirBoss original TW . . . new @AirBoss TW is about 437 pounds.
Reference graphic:

You, sir...are a rock star! Thanks to each and every one of you! 

Sharon_is_SAM

@AirBoss and @MuttonChops - RFuss has a CS.  AirBoss has a 400.  Don’t you need to use the 400 dimensions?

ChrisFix

Like @Sharon_is_SAM asked and I mentioned above, the T@B 400 dimensions are very different than that diagram, although the same principle applies of course - but I believe you'll get much more than 50% weight reduction removing weight from the tongue box on the 400.

AirBoss

Yes, I have the 400 but the formula is the same, is it not. Only the factors differ. 

I'm heading out today for a week and will have all sorts of time to take those measurements on "Otto" as well as install the Air8 exhaust deflector and the 7-pin protector in the jack stand. Just based on my recollection, I'd expect something like 70% or better. But then, I'm no Copernicus. 

Would it make sense to move some of that 45# to the aft exterior storage under the bed, instead of into the TV? Basically, not just removing the weight from the tongue, but using it to further counterbalance the tongue weight ..addition by subtraction. Gain anything?

Many, many thanks all! 

MuttonChops

Sharon_is_SAM said:

@AirBoss and @MuttonChops - RFuss has a CS.  AirBoss has a 400.  Don’t you need to use the 400 dimensions?

Missed that . . . thought he had a 400, will delete my remarks, no need for more confusion.

AirBoss

@MuttonChops, no worries. The equation may change but the formula itself is static. W x (L1/L2). 

Thanks for the assist!

TNOutback

Interesting discussion.  First thing I did when we picked up our 2020 T@B 400 is head to the CAT scales.  Nothing in the camper but a full propane tank.  Trailer axle weight was 2600#, and the tongue weight was 400#.

AirBoss

A related question:

TV was 6100# while hitched. Can I assume something similar to actual weight of TV if it wasn't hitched? Some factor of the Tongue Weight (460#) deducted from scaled TV weight of 6100#. Seems reasonable.

GVWR for my Tahoe is 6800#. I'd think I could reduce the 6100# scaled weight by 300#'s or so? 

Dunno...Inquiring minds want to know! 

AirBoss

TNOutback said:

Interesting discussion.  First thing I did when we picked up our 2020 T@B 400 is head to the CAT scales.  Nothing in the camper but a full propane tank.  Trailer axle weight was 2600#, and the tongue weight was 400#.

Where are the batteries and A/C in you unit? 

MuttonChops

AirBoss said:

. . . TV was 6100# while hitched. Can I assume something similar to actual weight of TV if it wasn't hitched? Some factor of the Tongue Weight (460#) deducted from scaled TV weight of 6100#. Seems reasonable.

GVWR for my Tahoe is 6800#. I'd think I could reduce the 6100# scaled weight by 300#'s or so?

Full tongue weight is part of TV scaled GVW.
Adjusted TV GVW = 6100 - 460  ==>  5,640

Now were you in the TV or standing under the CAT Scale speaker.
If not 'on the scale pad' then GVW does not include you . . .
Adjusted TV GVW = 5,640 + you (if not no scale pad)

Note CAT Scales have different size pads.  One of my locals are small enough to place each axle on a pad. While another one I must weigh TV on one pad and T@B on another . . . I like the smaller pads with three axle data.

AirBoss

@MuttonChops...copy that. As weighed, actual GVWR for TV is 5640. I was not in TV. Good to know I have just over 1/2 ton to play with, give or take.

That of course does not count the 100lbs of wine...

TNOutback

@AirBoss my batts and the a/c are in the back under the bed.  The CAT scale I went to had three different pads where I could put the TV front and rear axles, and the T@B axle, on separate scales. Weighing with the trailer attached and axle on each pad, then disconnecting and weighing only the truck, you can do the maths and see the tongue weight contribution on the rear axle.  

AirBoss

@TNOutback, thats a nice scale set up. My bat's and A/C are stowed there as well. Helps with the tongue weight.

Havent used a CAT I scale. This was a public truck scale that was part of a very large garden and materials supply company. Sure its  close enough for gov't work!