Weigh Trailer Using 2x4/Bathroom Scale???

[Francesca Knowles]

Hi, Y'all

It may be that I'm losing my marbles, but I distinctly seem to remember a recent reference by someone to a method of weighing the trailer using some kind of a bathroom scale-plus-2x4 setup.

I'm not talking about the tongue, mind, but the trailer itself.

Does this ring a bell with anyone? And if so, how would one go about doing this?

Thanks!

Francesca

P.S.

If as it turns out that I have indeed lost my marbles and imagined this whole thing, please feel free to say so!

F.

[cpaharley2008]

I think it was the tongue set up. Hard to measure 3000# via a 300# capacity scale. But you can measure up to 600# using the 2x4 set up with the bath scale.

[Francesca Knowles]

Yeah- sounds counterintuitive, doesn't it?

But it seems to me that whoever mentioned it also said something about "knowing the distance from point a to point b" or something- I think there's math involved.

Which of course makes it unlikely in the extreme that I'll be able to do it, even if it's possible!

Francesca

[cpaharley2008]

there is math in the t/w calculation set up, you do need specific length of 2x4.

[Francesca Knowles]

Originally Posted by cpaharley2008

there is math in the t/w calculation set up, you do need specific length of 2x4.

Really? I just set the tongue on a ballstand right on the scale....

But maybe you're right- I must have just misinterpreted a tongue-weighing conversation as related to the whole trailer weight.

Thanks!

Francesca

[rabbit]

The tongue on the beam method relies on proportionality of loads. Believe it or not, the simpliest method is two bathroom scales of 300# max wgt., one under each end of a beam and the tongue jack bearing on the beam at the precise center of the beam. If the t/w is less than 600#, adding the weights on both scales yields the tongue weight. Or, you can place a fulcrum at one end to replace the scale and multiply the scale reading by 2.

The more frequently seen proportional method involves placing a fulcrum (brick, wood block) under one end of the beam, scale at the other and the tongue jack at a third or quarter of the total length of the beam from the fulcrum. The scale "carries" a third or quarter of the weight, the fulcrum 2/3 or 3/4. It all depends how you hold your tongue. For a complete trailer, all you need is a good high jump to reach the call button on the CatScale.


jack

Incidentally, the scale should be an analog readout scale. For some reason, the digital readout scales don't work well for this purpose.

[Francesca Knowles]

Interesting...since my trailer tongue is only around 200 pounds, I've always just weighed it directly on the scale. But this has gotten me to thinking about the trailer itself.

I was idly speculating about going out to the shop and weighing one of our aluminum ramps, and then laying it down on the floor with one end on the scale. I'm interested in finding the weight at the scale...if it's 25% or so of the ramp's "gross weight", I think I might be within reach of weighing my 1900 pound trailer one side at a time by this method.

Further testing for exact position of the trailer wheel could be accomplished by placing/weighing the trailer spare and then correcting the math...hmmmm....

Important note:

My Engineer Husband isn't home at the moment to tell me how wrongedy-wrong-wrong this theory is, so please feel free to stand in for him!

Francesca

[rabbit]

Yeh, 850lbs the wheel. A quarter of that well inside the average max reading (300) of a cheap scale from Walmart or what you got out there on the wet coast. Sounds feasible in theory but safety first. I'll let your credentialed husband supply the critique but the wgt. of the ramp (acting as the load carrying beam) might not be negligible in the calculation. Also, as stated previously, the wheel or tire would bear on the beam at a point which is a measured distance from each end of beam based on a ratio or proportion such as 1:3 or 1:4. Might also be a complication in the pointy end of the ramp sitting on the ground (so you can drive on) and the ramp not being level. I think it's possible to use a beam of considerable depth (more than a 2X would provide even on edge) and place the weighing structure under a jacked up wheel. Might require some thought about the consequences of messing up, cracking the beam, dropping the trailer so Safety FIRST.

jack

[Francesca Knowles]

I DID mention that my "credentialed husband" is an engineer, right?

"Safety First" is more my motto than his, which might be best expressed as
"Ain't no problem that can't be made worse with a little re-engineering!"

I must mull this over before even discussing it with him...

Thanks!

Francesca

[Thomas G.]

Here is one technique:

How To Weigh Your Boat and Trailer Part 1

[Jared J]

It was me that mentioned it. No different than weighing a tongue with that method. For an example, take an 8' 4x4, put a foot of it on your bathroom scale, and a foot of the other end on a board(s) the same height as your scale. Now you have 6' of board between them. Put the tire on the end supported by a board(s). As an example, go 18" from the support (30" from the end of the board), and put the center of your tire there. The scale reading is 1/4 the weight on that tire. (Close enough, we can get into arguments over the way the board is supported shifting weight around, etc. if that missed 20lbs causes you to crash and burn, you shouldn't be pulling it anyway.)

Some people say to put a pipe on the scale, and between the boards on the other end. This will get it more accurate, I'm sure, but lets get real. We're weighing a trailer with boards and a bathroom scale, neither of which are scientific. The added sketchiness of sitting on pipes isn't worth it to me.

[Jared J]

Originally Posted by Thomas G.

Here is one technique:

How To Weigh Your Boat and Trailer Part 1

That's scary and overly complicated, IMHO.

[Francesca Knowles]

This is starting to look doable... instead of a board I'm thinking of one of our aluminum ramps. That would be stiffer and lighter, but still at least 6 feet long.

Question:

Would raising one side when weighing shift weight to the other side, thereby affecting the accuracy of the reading? Is it necessary to raise that side to a height equal to the scale side?


Francesca

[rabbit]

That's a great illustration of what we're spitballing, Tom. Never seen that one. However, I've never see the human back involved on the scale bearing end. Sort of like weighting a teacup Yorkie I guess. As for safety, I sure would want the tongue end anchored by the tow vehicle. It's more desirable to understand this technique than to be in a situation where you have to resort to it. A little light Platonic lifting never hurt anyone.

jack

[rabbit]

Yes keeping the weighed item level counts for something. For instance when determining t/w, the trailer should be level. So the same goes for weight athwartship. Practically, I don't think a few inches out of level in six to eight feet would mean much. A steep pitch would mean most of the weight on the downhill side.

jack

[Jared J]

Originally Posted by Francesca Knowles

This is starting to look doable... instead of a board I'm thinking of one of our aluminum ramps. That would be stiffer and lighter, but still at least 6 feet long.

Question:

Would raising one side when weighing shift weight to the other side, thereby affecting the accuracy of the reading? Is it necessary to raise that side to a height equal to the scale side?

Francesca

Kinda, sorta, not really. It will, but if you're trying to be that accurate, it's time to drive to a cat scale. It won't hurt to raise the other side if you want to. I'm curious to see the difference, my guess would be maybe 20 lbs.

[rabbit]

I've used short lengths of iron pipe between the beam (6/4 oak plank in my case) and the platform of the scale and also the brick or block playing the role of the scale height pier at the other end. Bit tiddly to get in place but I survived. Does give more of a precise placement. You do need to scribe a line across your beam at the three measured points at which you will place the two end piers (one incorporating the scale) and the foot of the tongue jack.

I agree with Jared on the CatScale. Don't think the side to side trailer weighing is worth the trouble over 10 bucks out of pocket one time. But it's your trailer, your toes, your ribs so you know what's of greater importance.

jack

[Jared J]

Originally Posted by rabbit

I've used short lengths of iron pipe between the beam (6/4 oak plank in my case) and the platform of the scale and also the brick or block playing the role of the scale height pier at the other end. Bit tiddly to get in place but I survived. Does give more of a precise placement. You do need to scribe a line across your beam at the three measured points at which you will place the two end piers (one incorporating the scale) and the foot of the tongue jack.

jack

While I agree it's more accurate, she's weighing the whole trailer. I know people have done it, but having a board resting on pipes, with a trailer tire on top, is a recipe for disaster, in my mind. If it was a tongue jack sitting on it, then it wouldn't be as bad, although I still skip the pipes (personal preference).

[rabbit]

As Jared says, the use of the pipe fulcrums should be restricted to the tongue weighing. If Jared's getting nervous, we ALL should be.

jack

[Jared J]

Part of me is tempted to go buy a scale and check mine now, even though its torn apart. 2000 just seems light to me.