Tongue weight: physics help and options?

[Larryjb]

The 30 lb tank is the weight of the tank only. The propane in the thank is extra. If your weight dropped by 140 lb, 60 of that come from the tanks. That means that 80 lbs came from the propane itself. Think about how heavy that tank was, I bet it felt a lot heavier than 30 lbs.

[J_Norris]

Good job for checking your vehicle and trailer numbers for real rather than assuming things are OK!

Since you mention the possible removal of a bike, I'm guessing the weights were done at different times? I didn't see the confirmed re-weighing of the highlander alone, and it looks like a difference of 10 gallons of gas in the highlander's gas tank could change its weight by over 60 lbs, changing part of your equation.

Another alternative: I don't know how your hitch works, but on ours we have an approximate amount of tightening of the WDH so although it's close to the same every time, it's never identical.

[lisasTM]

we carefully checked the propane tanks again with bathroom scale.
most they weight is 35 lbs each.

[lisasTM]

we only weighted the highlander once, but i don't think we put gas in after that. but good thought and worth checking.
especially cause there is no other answer.

so you think the WDH could affect the measurement ?
we were using same WDH settings both times.
the tough tow WDH may be a bit overkill for our case, i think the nice man at Street Scene in watsonville said it was the smallest version he had, and apparently it's designed for 800lb tongue weight.
but could a WDH somehow amplify the propane tanks on the tongue...hmmm..beyond my pay grade !

we've decided to put our bikes on top of highlander with friends borrowed racks(and hope we don't forget)
and probably well put the propane tanks inside the TM.
we both kind of think highlander rides a bit better with them off the tongue.

now if we could just get out the door for our very 1st trailer trip in midst of pandemic, horrific election and dodging smokey air in Sierra's after having been recently evacuated due to wildfire here on the coast, and did i mention the cooling weather trend....whew.

[Larryjb]

Ah ha! I should have clued in, but I didn't realize that your WDH was hooked up for this. A WDH will have a multiplying effect on the tongue weight. So, if you removed 60 lbs, the tongue has 60 lbs less on it. Then the WDH transfers more weight off the tongue meaning that more than 60 lbs is removed from the tongue.

I don't see the multiplying effect to be as much as 120 lbs, but you did say that you removed the bikes as well, so that may make up the difference.

[J_Norris]

Actually the I think the expected direction of change would not be filling the gasoline tank, but instead if you drove and used up some of the gasoline in the Highlander between the first and second readings, lowering the Highlander's weight by however many gallons times ~6 lbs per gallon.

So as an example, if you drove around and used 10 gallons of gasoline, your equation would change from what you originally wrote:

"new tongue weight is 5360 - 4940 = 420 lbs."

to an adjusted highlander weight of 4940-60 lbs. Like this:

new tongue weight is 5360 - 4880 = 480 lbs.


It sounds like with possible WDH interactions you got things figured out one way or another! It's always reassuring to not be defying the laws of physics

[Larryjb]

I hadn't thought of the gas tank either. A WDH connects the masses of the tow vehicle to the trailer. As the WDH tries to lift the center to transfer weight to the front and trailer axles, less weight from the fuel tank will, in effect, reduce the tongue weight.