Yair . . . Just curious as to how far you would haul with 200/300 ton class trucks and what would be the limitations, that is to say, would it be tyre life or other factors? Cheers.
Scrub, the key is TKPH on tyres. Here we haul up to about 10km one way, but I've seen hauls of up to 25km. You start with TKPH because it's a given (by the tyre manufacturers). That basically tells you what is your maximum permissible combination of speed and payload. The coming of SAE60 FD-1 oils for back ends means that there are generally no major bearing issues running long and hard, it's only if the tyres can stand it. Then you need: - 1. A scale study to determine the exact empty weight of the trucks with a full tank of fuel, covered in mud and with whatever carryback tends to stick inside the dump bodies. Subtract that from the Maximum Permitted GVW supplied by the OEM and you have your target payload. 2. Our trucks have an on-board programmable TKPH system that works on a rolling 4-hour average. We can set maximum permitted speeds for the truck both empty and loaded (45km/h & 40km/h in our case) and if even that proves to be insufficient if the TKPH approaches the trigger point the operator gets one or more warnings telling him to slow down. If he doesn't heed the warning the truck then becomes speed limited (we set ours at 30km/h) until the TKPH goes below a set limit at which point the full performance of the truck is restored. 3. Have all the above connected into the Dispatch system so that if the TKPH goes too high the Dispatcher has to manually assign the truck to a shorter haul with lower speeds for the next haul cycle(s) to make sure that the tyres are not over-stressed. This doesn't stop tyres failing altogether but it drastically reduces the number of failures.
Scrub, we don't get as fancy as Nige, but we have some fairly long hauls as well. Our soft roads pose a whole other set of issues, so we have monitors on each tire of the trucks. We generally limit speeds on the longer hauls to about 40km/h. Dispatch monitors tire temperatures, and rotates trucks off of a run if the tire temps are climbing too high. If we get a hot tire, we sequester the trucks to a hot tire laydown that is far removed from any other traffic. The driver is evacuated, and the temps are monitored remotely to ensure they cool down. I'm not sure the exact distances, as they change quite a bit as we progress. But an average would be about 12 to 14 km one way for the longest hauls we currently have. It's basically a tire life issue for us. Our tire life is short enough as it is on average, so we need to prolong whatever we can.
In-tyre sensors are pretty expensive - around $20,000 per truck. We have 3 trucks in the fleet running with in-tyre sensors and we use the data collected to validate what we see regarding the TKPH calculator for those 3 machines and by implication on the rest of the fleet.
Nige, I think they decided the TKPH calculators were not consistent enough for us due to extreme changes in ground conditions. I guess they figure 20 grand per truck is pretty cheap when you're looking at around 350 thousand per truck for rubber.
Yair . . . Thanks, fellers I appreciate your replies. Fascinating stuff. As you will realise in my situation it is just of academic interest but I remain interested in such issues . . . and possibly your knowledgeable replies may be of interest to others which is what this forum is all about . Cheers. **For others not familiar with the term TKPH used by Nige it is Ton Kilometre Per Hour.
That may be true in your location. We've seen extremely good correlation between the TKPH Calculator, internal tyre temperature, and the dynamic readings that the tyre suppliers get when they put their V-Box on the trucks. It's not the cost of installing temp sensors in every tyre that puts us off so much, it's whether the additional investment is worthwhile seeing as it simply confirms our other data and tells us nothing more than what we already know from those other sources. Based on what we've seen so far I don't think we'll be equipping every truck in the fleet with sensors but we will run a certain number of trucks with them simply as a check on the information produced from other sources.