## Need a way to approx. weight of a tractor trailer being loaded

Hi All,
I have a question, which is how do I figure out what the weight is of a 45' tractor trailer that is being filled with a semi-solid product and the tractor is not attached to the trailer.
I'm thinking of using the pressure of the air bags by inflating them to raise the trailer up and get a pressure which I could match to the scaled weight to come up with a chart which would tell me went I hit this pressure, approx weight would be this amount.

Another problem I have is the trailer. When I inflate the air bags, the trailer will rise up about 8" and the weight moves to the front with the potential of breaking the front jacks. If this happens, the trailer front hits the ground and I would have a real mess.
I am thinking 2 trailer stands under the front would stop this along with wheel chocks so the trailer would not move.
The problem arose because some trailers end up underloaded or overloaded. In both cases it cost money!

Regards,
Scooter
 PhysOrg.com science news on PhysOrg.com >> Intel's Haswell to extend battery life, set for Taipei launch>> Galaxies fed by funnels of fuel>> The better to see you with: Scientists build record-setting metamaterial flat lens

Recognitions:
Gold Member
 Quote by scooter1900 Hi All, I have a question, which is how do I figure out what the weight is of a 45' tractor trailer that is being filled with a semi-solid product and the tractor is not attached to the trailer. I'm thinking of using the pressure of the air bags by inflating them to raise the trailer up and get a pressure which I could match to the scaled weight to come up with a chart which would tell me went I hit this pressure, approx weight would be this amount. Another problem I have is the trailer. When I inflate the air bags, the trailer will rise up about 8" and the weight moves to the front with the potential of breaking the front jacks. If this happens, the trailer front hits the ground and I would have a real mess. I am thinking 2 trailer stands under the front would stop this along with wheel chocks so the trailer would not move. The problem arose because some trailers end up underloaded or overloaded. In both cases it cost money! Anyone have a suggestion or first hand experience how to go about this? Regards, Scooter
So basically you want to know how much of the product is being loaded into the trailer right?

Just calculated the volume of the trailer (the portion that is full of the product) and multiply it by the specific weight of the product.

CS
 That's where the problem comes in, The product has a variation in the weight of it depending on how much water is removed from it. Regards, Scooter

## Need a way to approx. weight of a tractor trailer being loaded

Instead of your airbags, making a resilient system, use the springs/tires. Each rig gets a table of sag height versus weight and a distance scale.

 Quote by scooter1900 That's where the problem comes in, The product has a variation in the weight of it depending on how much water is removed from it. Regards, Scooter
Calculate for intervals of how much it weighs with so much % of water content.

Calculate for 10% water content, 20%, 30% and so on. Once you know the approx. weight of each water content percentage, you can guesstimate how much the actual product will weigh once you know its actual water content.

 Quote by scooter1900 Hi All, I have a question, which is how do I figure out what the weight is of a 45' tractor trailer that is being filled with a semi-solid product ... The problem arose because some trailers end up underloaded or overloaded. [ ... ] The product has a variation in the weight of it depending on how much water is removed from it.
Now it sounds like you're trying to acquire two bits of information.

Recognitions:
Gold Member
 Quote by scooter1900 That's where the problem comes in, The product has a variation in the weight of it depending on how much water is removed from it. Regards, Scooter
I suppose using scales are out of the question then?

CS

 Quote by Doug Huffman Instead of your airbags, making a resilient system, use the springs/tires. Each rig gets a table of sag height versus weight and a distance scale.
How do you account for changes in temperature?

The most practical solution is just to use a scale. You don't necessarily need to weigh the hole trailer, but just the objects that are being placed into the trailer. Are things being loaded with a fork truck or trolly?
 Use a truck scale, like one of those in freeways. Just a suggestion. If its not easy than try to make the trailer float, by making it waterproof, and creating a small pool of water.
 Recognitions: Gold Member Science Advisor Tyre pressures and contact areas?
 I suggest using a strain gage mounted on a nearby bridge, or constructing a simply supported platform and bonding the strain gage to that. A strain gage gives a resistance value in ohms based on the amount of strain(stretch) in the member its boned too. Once you have that, you can apply known weights to the bridge or simply supported member to get strain values. Then take the strain values collected and develop an equation using a regression method in excel, usually linear. Now armed with your equation, you can reasonably approximate the weight of the truck given a resistance value. Information about strain can be found here and here.
 The trailer cannot be weighted by scale because it is loaded and picked up when the mill calls and says it is full. There is no tractor attached to the trailer. We are going to try blocking the front of the trailer with jacks up by the pin. Then measure from the bottom of the trailer to the floor when empty, then Full. The tractor driver will then weight the trailer on a scale and we will record that info to construct a chart based on data gathered. Don't know if temp will effect it much, Trailer is inside building when loading and warm. Goes directly to scale house to be weighted. Material is dropped by auger into the truck. The goal is to make it so the people at the mill can look at a measurement and know the truck is not overloaded or underloaded. What could prevent this from not working? (I know acts of God, etc.) :-) Sorry for taking so long to reply. Scooter
 Recognitions: Homework Help Science Advisor If the trailer is unhitched what about putting a load cell under the front legs. Assuming the trailer is loaded fairly evenly with bulk material it's easy to get a weight from this. If you were loading a single heavy piece you would also need the distance from the wheels. You can get portable scale pads for on site checking of trucks before they hit the highway.
 Hi There, I will check out load cells. Are Load cells another name for portable scales? Any sites with good info on load scales for a novice? I checked out putting portable scales under the trailer but they cannot be left under a trailer for long periods of time. It tends to ruin them. The State Police use them to check trucks but they drive you on and drive you off very quickly. ( I know because, been there, done that) What are your thoughts on our idea of measuring from the trailer to a fixed object( floor )?? I am also learning about strain gauges, not sure how to hook up but still reading. Regards, Scooter
 Recognitions: Homework Help Science Advisor Load cells are basically weight measuring cylinders, they are generally a load cell inside - but that doesn't matter. They look like a small hydraulic bottle jack with a cable coming out to a digital readout. You can also get them to attach to a crane hook, which is another approach, like a giant fishing scale!

 Quote by scooter1900 Hi All, I have a question, which is how do I figure out what the weight is of a 45' tractor trailer that is being filled with a semi-solid product and the tractor is not attached to the trailer. Anyone have a suggestion or first hand experience how to go about this? Regards, Scooter

Scooter, I would like to ask you a question. Could you please post here if you are still watching this thread, or send me a private message if see this message?

Cindy