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Tongue Weight redux

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fwunder View Drop Down
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Post Options Post Options   Quote fwunder Quote  Post ReplyReply Direct Link To This Post Topic: Tongue Weight redux
    Posted: 13 May 2015 at 1:10pm
OK, got my scale today and did some interesting driveway testing. It's a 400# digital scale. Calibrated to our known weights (me and wife) and Henry, the cat. BTW, Henry weighs 10.2#

First, I rigged a simple lever scale just cuz I didn't know what to expect. I quickly discovered I could measure the tongue weight directly with a 400# scale. I took several measurements. They were always +-5#

The pod is always pretty much ready to go except for food and clothes and that's the way I weighed it. The dome, electric cords, chairs, hoses and some other weighty stuff is all in the aft locker. I may change that based on these results.

The propane tank is 3/4 empty.

My results.

Tongue weight with *full* water tank, including HW tank. Black and gray tanks empty. Level Bubble: 220#
Tongue weight with *empty* water tank, HW tank full. Black and gray tanks empty. Level Bubble: 300#

Tongue weight with *empty* water tank, HW tank full. Black and gray tanks empty. 1/8 bubble down (about an inch): 310#

Weight of stuff normally carried behind TV rear axle:

WDH hitch: 30#
Two bikes @ 40# and 35#:  75#
Bike Rack: 30#
Yamaha 2400 w/gas and cover: 83#
Misc: 50#
Stuff Total: 268#

Total load behind axle ==> 268 + 300 = 568#

My spring bars are rated for *up to* 800# and recommended by Reese for between 400-800#

I have not weighed the trailer yet, but do not believe we have more than 300# (hi estimate) in it which would put us right about 3,000#.

One surprising take away is how much that full tank of water affected tongue  weight. In my case, it was an 80# difference or more than 20% difference in tongue weight.

So, that's my report. I'd really be interested in similar tests/results and any comments!

Thanks!

fred

















2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6
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Luv2Q View Drop Down
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Post Options Post Options   Quote Luv2Q Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2015 at 2:04pm
Not only interesting but useful.  I don't, however, understand the significance of the bubble level being 1/8 down.  If it had been level, would that suggest less weight on the tongue?

I need to do that with our 171 plus take it to a scale .. just to know.

Thanks, Fred.
John & Teri
Tundra 5.7L V8 / RP 180
E2 WDH / Integrated controller (POS) replaced by Tekonsha P3
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fwunder View Drop Down
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Post Options Post Options   Quote fwunder Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2015 at 2:15pm
Hi John,

The bubble level is my reference for tilting the trailer down in front a little (about an inch). This transferred about 10# more tongue weight. It should be exponential I believe. In other words, lowering the tongue 2 inches would transfer more than 20# weight to the hitch. Does that make sense?

fred
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Post Options Post Options   Quote furpod Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2015 at 3:07pm
The 268lb of stuff won't effect the tongue weight by 268lbs. The only way for it to do that would be if you stacked all 268lbs DIRECTLY on top the coupler.

Also if it's behind the axle as you said, it's going to effect it NEGATIVELY not positively. It has to be in front of the fulcrum (axle) to add to the tongue weight. But because the lever is shorter behind the fulcrum, weight place there has less effect than weight set equidistant from the opposite end of the lever.

This is why 240lbs of water only changed the tongue weight by 80lbs.

ARGGHH.. just reread that.. this 268lb is stuff in the TRUCK.. it also doesn't effect the tongue weight by 268lb from there, because it's weight is carried across the two axles of the truck. It does however count against your max GVWR. For tongue weight calculations, you strictly use the measured tongue weight of the trailer.
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Post Options Post Options   Quote fwunder Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2015 at 3:49pm
Gotcha furpod. Yeah, I measured everything behind the truck axle and before coupler just cuz reading that you really need to know that to correctly size wdh hitch (and spring bars):


Based on that, I got the right size spring bars. If I went strictly by tongue weight, the bars I got would be way overkill for 300# tongue weight. Does that sound right?

This may be wrong, but I just read this too:


To determine the proper weight rating for a weight-distribution system, you must first determine your trailer's tongue weight. Then add to that the weight of the cargo behind the rear axle of your tow vehicle. These two measurements make up the tongue weight rating for a weight-distribution system.

You got much more experience than me. Just tweaking here...

Thanks.

fred
2014 RPod 178 => MyMods and Buying Habits
2008 4Runner Limited 4.0-liter V6
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fwunder View Drop Down
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Post Options Post Options   Quote fwunder Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 2015 at 7:37pm
With all the engineers here I'm surprised no one called me out on this! 

Don't need no scale to measure tongue weight differences with water load. All you need is a freshman engineer nephew with an iPhone app or a tape measure!

Fe = Fl dl / de

Tongue Weight Force = (Gallons of water)x(8.3454 lbs./gal)x(4 feet distance fresh water tank behind axle)/12.5 feet distance tongue to axle

TWD = (Gallons)33.3816/12.5

Full tank (30 gal), TWF = 80.11584 lbs.

Funny how that is exactly what I measured. Ain't math grand!

Half tank (15 gal), TWF = 32.3048 lbs.

Fun!

fred



2014 RPod 178 => MyMods and Buying Habits
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