Hydraulic Pressure gauge on loader.

The post below got me to thinking if I had a pressure gauge on the bucket lift circuit of my tractor how could I use it as a hydraulic scale to tell the weight in the bucket. Anybody have an ideal how to work out the pressure to weight calculations. If you put items in the bucket of known weight and recorded pressure would that work?? Thinks DH

Yes, I think you could make up a conversion chart, by putting known weight, (sacks of cement, for example) in the bucket and recording the change. I think it would change with the height of the bucket because of the loader geometry.

Yes, that"s the usual procedure. 50/100 lb feed/salt/etc. are easy to use. Then record the needle reading at various weights. Oil-filled gauges are recommended.

You are correct Russ about the bucket height. I hadn't thought of that.

Go to your local Caterpillar Dealer or Komatsy or JD industrial. They can set you right up with a scale as many wheel loaders have them on board. of course it would likely be way more than you would want to pay.

It also changes based on where it is in the bucket. Way to the back will be lower pressure. Hanging from a chain will be vastly different if it is hanging over the front of the bucket versus hanging from the frame behind the bucket.

You would need to know the position for an accurate weight. The angle on the cylinders changes as it is lifted.

Watch the guys at the quarry with the factory scales on the big loaders. They roll the bucket all the way back then raise to a predetermined or weigh place and get an instant reading of the weight of what is in the bucket. Our dump trailer 18 wheelers can scale 28 ton and they can get within 500 lb. almost ever time. Takes about 4 buckets to load the trailers. I think you could get close with a farm tractor and hydraulic gauge but again you will have to have the material all the way back in the bucket and the lift at a constant height.

Yes, it will work, you have the basic idea figured out. The other posters mentioned the details that will cause inaccuracy (although nobody mentioned friction). Maybe for your use it wont matter, maybe it will but now that you know the problems, you can get around them with the understanding of the issues. Maybe its as simple as attaching a chain to a single spot and lifting to a certain lift height. That would eliminate most of the problems but would be inconvenient. But it would work.

It should be noted that the idea you have is exactly how they test air and hydraulic gauges. Well, without the things that cause inaccuracies. http://www.grainger.com/product/5WG...8&ef_id=261Ph4Thc38AAE-d:20150101031348:s Here is one for testing up to 1000psi. Add weights to the test machine to equal the PSI you want to test on your gauge. Pump the test machine till the oil lifts the weights, spin the weights to eliminate as much friction as you can. Then the gauge SHOULD be at the designated PSI.

As for the math, look at the test machine I posted the link to. Thats simple math where the area of the cylinder will be the same pressure applied to the gauge. When the weights lift, you know you are applying the proper known pressure on the gauge. Example: if the area of the cylinder is 1 square inch, putting 10 pounds of weight on the test machine will show 10 PSI on the gauge... or it SHOULD show 10PSI if its a good gauge. Thats the math, simple. For your loader you have geometry that comes into play, it would be easier to just do known test weights and record your readings and make a chart of that info. What you would have then is a custom load chart like they put in forklifts and old cranes but your chart would be actual weight, not safe lifting loads at certain extensions. But it WILL work, the math works and people have made machines as proof that it works.

The math also works in reverse too. If you know how many PSI your hydraulic pump puts out, you know the size of your cylinders and can figure out the leverage of your loader, you can calculate what the tractor will lift. Sorry for the long answer but yes, it will work.