On-Board Weighing/Scales for Haul Trucks?

Hi, guys, a new guy here.
I got into a good sized Cement/mining/trucking company just this year. Before that, I was just working at an IT desk job.
Well, my manager for some reason has tasked me to find On-Board scales for our big old Haul trucks. We have a mix of trucks, from Caterpillar and Komatsu.
We'll be looking into installing them in our dump trucks too later on, so it seems. Apparently they've been mostly eye-balling it so far.
BTW, I'm not in the US right now, I just moved to Asia for the job, so regulations here aren't as strict as in the US.

Well any suggestions for reputable companies related to On-board scales would be greatly greatly appreciated. And cheap. my boss kept yelling it needs to be cheap. And very accurate. But also cheap. Ugghh, sigh.

Thank you very much in advanced

What model Cat trucks do you have..?
Can’t comment regarding the Dark Side....

One thing I’m fairly sure applies to the haul trucks from both manufacturers is that to get anything like reasonable accuracy (+/-3% is considered world class) the suspension charging has to be kept absolutely spot-on. No ifs ands or buts.

I can think of at least three ways to do it. Like Nige suggests one is to measure the pressure in the struts. I don't know exactly how the factory systems work, but the fact that precharge is so critical to accuracy leads me to believe they are only measuring the pressure on one side and assume the other. If you measured both sides of the piston and calculated the differential load this wouldn't be a concern, but the system would be much more complex.

I previously worked for a major industrial forklift OEM and we measured one side of the cylinder. The main accuracy issue we ran into was seal stiction. Lowering then stopping, raising then stopping, and dynamic all gave different numbers. In order to be repeatable you had to always do it the same way. I'm going to guess that stiction won't be as big of a deal with the struts because of the higher pressures and seal style, but something to watch out for. You also have to be careful that a blown sensor could rapidly lower a strut. Adding a small orifice in series wouldn't prevent the problem but it would happen much slower and give the driver a chance to react. Plus it will act as a snubber to help protect the sensor from major pressure spikes.

The second way to do it is load pins. This is very accurate but not cheap. The have to be manufactured for each specific joint design.

And third, it may be possible to mimic the load pins by using strategically placed weld-on strain gages on the structure to make a bridge on each corner. Then use a summing scale display. The accuracy and sensitivity would greatly depend on the structural design and where the gages are placed. This is the hardest to do.

And with any homebrew system you have to factor in the engineering time and it will tough to get the reliability of an OEM or good aftermarket system.

ISZ

There is nothing cheap about any on board scale system. That someone would say "find something cheap" tells me they aren't serious about the project. It sounds like an edict send down from an office above and people on the shop floor are just shrugging their shoulders. A cheap system is not accurate. A not accurate scale system is just wasted money.

John C. said:

There is nothing cheap about any on board scale system. That someone would say "find something cheap" tells me they aren't serious about the project. It sounds like an edict send down from an office above and people on the shop floor are just shrugging their shoulders. A cheap system is not accurate. A not accurate scale system is just wasted money.

Click to expand...

A big Thanks to you and Nige for replying and trying to help.

A real big Thanks to icestationzebra for the detailed answer but I don't think we're going the homebrew route btw.

And yeah.... the edict DID come from the office way above my pay grade, a relatively new guy who was "scouted" from a non-mining/non-trucking company, who's now trying to make a name for himself to show he's not useless to the Big Boss president. He's the type of guy who just finds a hot buzz word and just keeps throwing them out hoping one of em will stick. I was researching and out flying/testing new drones with the survey team for over a month because of him.

Now, apparently he's found that Komatsu offers on-board scale systems and he's working some sorta deal with em. But so far the initial testings has been really frustrating, a lot of incompatibilities with our current displays/readers/tech systems etc., Komatsu technicians have been no help at all, plus the BIGGEST kicker is it only works on our Komatsu trucks and not our CAT trucks. I have no idea what we're gonna do with em, but when the higher up says test and use this damn Komatsu system, whatcha gonna do.
And yes, the people at the actual people at the sites are apathetic at best and pretty annoyed at worst.

Sorry this suddenly turned to a rant post guys

The typical way that on-board weghing systems function on off-highway trucks is by measuring the increase in gas pressure in the four suspension units. It's not neceesary to measure both sides of the piston because the gas pressure is only on one side. The problem is that netiher of the major manufacturer's systems will work on the opposition's machinery AFAIK.

With Cat it would be a simple plug & play of the module + software. The kicker regarding the display (or indeed of wireless data transmission of the payload to "base") would be what models you have, which is why I asked earlier.

Back to my earlier comment regarding suspension servicing. The critical factor in getting accurate readings was in fact not the gas charge, it was actually the oil charge, which determines the strut damping. I have practical experience of this from the time I first came across on-board weighing systems about 25 years ago. As a result of that we actually developed a new charging system that took away seal friction entirely and required the strut to be fully extended by jacking up the truck and then charge the gas into a fixed volume above the piston.

What did you guys do about carry back. We had scales in our loaders for loading trains and any gummy sticky material that stayed in the buckets fouled up measurements pretty bad. I can imagine anything in the truck bed might do the same.

John, the Cat system recalculates the empty weight of the truck every cycle. So if you calibrate the payload system after every PM as carryback increases cycle after cycle the payload system updates the “empty truck” strut pressures for each new cycle. Also the definitive payload for each cycle is not stored until the truck hits 2nd gear, in other words after it’s well away from the loading face. There are enough algorithms in the calculation it would make your head spin.

Side note: Log trucks have been using scales since the 1950's. Started with Williams Air Scales and has morphed into high tech electronic units. Try poking around the US Pacific Northwest area to find out more.