Weigh Your Own Tongue

[kodabear]

Most of us don't have a scale that goes up high enough to register a 350-700 lbs force.  Here's an easy way to do it with only some scrap lumber and a bathroom scale.
1. Level your trailer (front-to-back) with the tongue jack, then drop your front stabilizers to just take the weight
2. Retract your jack until you have about 5" clear under the dolly wheel or foot.
3. Measure a length of 2x8 (2x6 works, but better safe.)  Length is not important, but you want a piece 18-24" long. Mark the middle. For ex: If your plank is 20" long, you want a mark at 10"
4. Place a short piece of narrow material (long bolt, electrical conduit, 1X1 pine, etc) on your bathroom scale toward the middle. We'll call this piece the "bearing."
5. Place a similar piece on a brick set on edge. It really does not matter too much what you use, so long as it's reasonably strong, and of similar thickness to your bathroom scale. We'll call this the "fulcrum."
6. Place the scale and brick equidistant from your jack's contact point, with the bearing and fulcrum about 1" less apart than the length of your 2X8. Now carefully place your plank on the bearing and fulcrum. The center line you marked should be right under the jack's contact point.
7. Lower the jack until it has taken all the weight. Multiply the scale's reading by two. Voila.

Time for a picture or three: 

1. Jack on the scales

[img style="max-width:100%;" style="" src="http://www.portfoliofotos.com/photos/i-nxKw7D9/0/L/i-nxKw7D9-L.jpg"]
2. The 2:1 rig. Half the weight is on either end.

[img style="max-width:100%;" style="" src="http://www.portfoliofotos.com/photos/i-kcLCMsk/0/L/i-kcLCMsk-L.jpg"]

3. The "fulcrum."



[img style="max-width:100%;" style="" src="http://www.portfoliofotos.com/photos/i-VnZdt2C/0/L/i-VnZdt2C-L.jpg"]

6. 314 lbs.

[img style="max-width:100%;" style="" src="http://www.portfoliofotos.com/photos/i-7prBVvq/0/L/i-7prBVvq-L.jpg"]

For extra credit, you could rig  a 3:1 (if you have a really heavy trailer) by using a longer bridge and putting your jack 1/3 of the distance between the bearing and fulcrum. You might want to use a 4x4 as a bridge if you're weighing something with a tongue weight of a thousand pounds or so, but with a long enough bridge there's no theoretical limit to the tongue weight you can measure with a 300 lb bathroom scale (mine only goes to 275 lbs anyway.)

[fasteddieb]

Parallel paths!

My 21BHS "Weighty Matters" thread covers a similar solution.

Thanks for the options!

[kodabear]

Holy Cow, FastEddie, that's krazy!

Now for the full disclosure. I just went back through my photos and realized I'd fooled myself. The actual reading when I weighed using the jack  was 322 lbs, not 314. So yes, there was a slight difference of 8 lbs, about .003 of the trailer weight. Close enough for me, and I think safer to weigh on the jack. 

Scale reading when weighed on the jack: