Scale system for dump trailers ?

[BKBoiss]

Gravel haulers around here use the load cells like us log haulers do. A set at the back of the dump box in place of the hinges and a set at the base of the lift cylinder. They just raise the box 5-6 inches when they are ready to load and presto. Our old jeep and pole set ups had all load cells and were usually within 50-100kg every load. The new hayrack rig ups we all run now have load cells under the fifth wheel and run off the air bags on the trailer. The front is always spot on but those air bags are VERY temperamental. While your plan sounds good in theory my opinion from what I've experienced is that you would end up with more hassle then it's worth. Load cells and all that goes with them are very pricey. I think you have a good start but instead of using bags and a pressure gauge why not just rig up a "gauge" of sorts on the axels that you can look at and shows you the distance that the suspension has squatted. Then of course either way you go what you have for weight on your hitch would still be the wild card. Sorry I got long winded. I'll be watching this to see what works, you have got me curious now.

 

[fried1765]

The local quarry by me sells by weight, their payloader has a scale built in that is apparently very accurate, I get 10k which is about max for my trailer and out of 2 loads on was dead on and the other was within 20 lbs of the target weight.

I still need to figure out the weight of the dump trailer by its self.

Hook your empty trailer to your truck, and go to the scales to get a total empty weight.
Take your empty trailer off, and weigh just the truck.
Subtract truck weight from total truck with trailer weight.
Now you have your trailer weight.

 

[TMGT]

Hook your empty trailer to your truck, and go to the scales to get a total empty weight.
Take your empty trailer off, and weigh just the truck.
Subtract truck weight from total truck with trailer weight.
Now you have your trailer weight.

I know how to scale it, I just need to get around to doing it, I have access to a scale at the refuse transfer site that I work on their equipment at times.

Last scale with the truck/trailer was about 11k empty, trailer should be around 3k empty.

 

[bcp]

Didn't some pickups have a height sensitive load sensor for balancing braking effort?

Bruce

 

[TMGT]

Toyota did I know, can't remember all the others, a handful of other other Japanese trucks did I believe.

 

[bcp]

A Google image search found these.

pickup load sensor brakes - Google Search

Looks like a mechanically operated hydraulic valve. They would have figured out a good mechanical method of actuating the valve. Maybe a similar mechanical method could be used to move a pointer.

Bruce

 

[TMGT]

The only problem I see with using height/squat is that it's very dependent on load distribution, you would need to do a 3pt measurement and, since the springs are progressive, some good data points to calculate the load, plus a solid flate surface to measure on.
Might give you a general idea once you get ebough data points but won't always be easy due to terrain and still won't be very accurate.
I guess it depends on what your trying to achieve but it sounds like it won't do what the OP was trying to accomplish.

 

[FredH]

On my semi , there a 4 air bags . With a empty trailer hooked up , pressure is a given amount . As load weight increases , the pressure gauge also shows a increase in pressure . Having actually scaled a load that ended up being right at the given limit for the drive axles , 34,000 ) , I made a pen mark on the gauge in the dash . Now when ever I hook to a loaded trailer , I can look at that gauge and if below mark , I won't even scale the load unless I feel there may be a problem with the trailer axles .

Thus My idea of using 2 smaller type airbags , similar to the airlifts I have on my pickup . Even if I made my own brackets and centered 1 bag on each axle under trailer , then only applied a minimum amount of air to bag , ( say 10 or 15 psi ) , As load increased , pressure in gauge would also increase , at least that is what my feeble brain is telling me ??????? .

Minimal air in bags would thus not actually be a overload type spring and should not really interfer with leaf spring operation . I know if I do not add any air to the pickup bags , ( their minimum pressure is 15 - 20 psi ) , Pickup acts like it always did under a load .

Fred H.

 

[vsteel]

I would bet that you could do it with a tape measure. I have found that for most of the range that the springs are used they can be considered linear. For example on my pickup when I load the trailer I have found that 300lbs is an inch of movement at the hitch ball.

So what you do is find out what movement you have at the hitch for a certain weight. Then you find out what an inch of movement weights at the trailer axle. You then add them when you load the trailer. It won't be exact but if you are just getting close it will work.