Homade Jack Scale

[Horizon170]

I see folks wanting to weigh different stuff, like tongue weight, 4 corners, etc so here is an idea first posted by Proffesor95 from, I think open roads forum.

here is what He and I did to different size jacks.
Marvin

My homemade jack scale.
You will need to locate a hydraulic bottle jack that has a service port. This will be a screw out plug on the bottom of the jack. Unfortunately, jacks at Wal-Mart and Pep Boys (made in China) no longer seem to have the service port. So, you may need to search out yard sales or an older friends garage to find a bottle jack with the port. Remove the plug from this port and install a pressure gauge - I selected a liquid filled gauge that will measure up to 3,000#. To convert this to weight, measure the diameter of the jack cylinder (mine was 1.125 inches) and apply a little math to get the area of the cylinder (3.14 x radius squared). In my case 1.125 diameter /2=0.5625 radius x 0.5625 radius = 0.3164 x 3.14159 (pie) = 0.994 (my jack factor). Multiply the area by the pressure and you get weight.

The above information was originally found on an RV Camper forum and written by “Professor95”.
I changed the numbers to match my jack dimensions.
If you use a jack with a 1-1/8” cylinder you can use the direct read from the gauge and be accurate within 6 pounds per thousand. Gauge reading =1000# = 994# actual.


Gauge at Northern Tool was 12 bucks and the adapter fitting was about $6.59.
If you have a rubber plug and spring behind the service port metal screw remove the rubber and leave the spring. If the spring is so small in diameter that it slides into the new fitting you should cut a small hole in the rubber disk and use it as a spring stop. I think the spring holds pressure on a metal ball valve.





The front of my Baja weighs 706#


Dia Factor
1.125" 0.994018711
1.5" 1.767144375
2" 3.14159
2.5" 4.908734375

Good Luck, Marvin

[Dusty_R]

http://www.albroswift.com/jack.htm
You can go here and it will show you where and how to drill and tap for installing a pressure gauge on a hydraulic jack.

Dusty

[MEXICOWANDERER]

Excellent tip! When I was towing I did an axle by axle then gross summation weigh at a commercial scales. The difference of rear axle weight with an without the tow told me a lot. 3 axis calculation.

[Horizon170]

I don't think a bathroom scale and 2x4's would work measuring the weight of the left rear dually corner of my MH. Your idea will work with BR scales but the weight must be distributed across the entire platform of the scale, otherwise a 4x4 in the center of most scales and added weight will damage the scale platform.
Marvin

[ghorn]

Simpler method: Use any bathroom scale and place a 2x4 block on it (cut it about 4" square). Take a 4-foot long 2x4 and place one end on that block of wood. Place the other end on a couple of 2x4 blocks on the ground. Place your tongue jack onto the long 2x4 at the mid-point. REad the bathroom scale. Multiply that reading by 2.
Example: 150 lbs read on the scale would indicate your tongue jack is supporting 300 lbs.

If you wish a more delicate/accurate measurement, make the block on the bathroom scale and the one at the opposite end shaped like a pyramid for more accurate placement.

[Calicajun]

Nice idea and DIY project.

[CJW8]

This should work great if you can find a ported jack. I use an hydraulic scale from Sherline which works on the same principle except it goes between a floor jack and the tongue or axel. I have used mine to weigh many heavy things. No math needed.

[TomG2]

It would be good to know if any low cost jacks are available new with the necessary port.

[Dusty_R]

A few years ago I found on the internet how to drill a hydraulic jack to add a pressure gauge. I went one step farther and added a remote hand operated pump. Now I don't have to lay under our mh while I'm jacking it up, especially a rear wheel.

Dusty

[CloudDriver]

Great idea! Going to check my jack for a service port in the morning.

Thanks for posting!