I’ve just begun a job hauling cement powder for a company as new to pneumatic bulk trailers as I am. Today I hauled a freuhof 3 hopper pneumatic trailer of around 40 or so feet to pick up cement powder using a freight liner day cab. I was told to load to 78,500 gross. Hauling through Colorado got pulled into a scale with 37,000 lb on drive tandems, 31,000 on trailer tandems. Trailer was loaded through rear top manhole, and although I did drive through mountain grades, I had no unusual braking events. Cement powder shifted from back to front to be overweight (no baffles above hoppers). We have overweight permit to 36,000 on drive tandems, but still 1,040 over. I believe shifting the 5th wheel so that kingpin is further from the cab may solve this, but company and management is clueless. Do I load for a lower weight? Is the trailer not intended for cement powder? Are the absence of baffles abnormal? Experienced advice much appreciated! Thank you!
Pneumatic trailer weight shift/cement powder
Discussion in 'Tanker, Bulk and Dump Trucking Forum' started by Truckerbase, Nov 24, 2022.
Page 1 of 3
Trucking Jobs in 30 seconds
Every month 400 people find a job with the help of TruckersReport.
Apparently, this is happening “all the time” according to the other driver here, due to zero company wide experience in the cement powder bulk pneumatic trailer market. They are learning by “ trial and error”, apparently….
Your logic won’t work. Sliding the 5th away from the cab, backward, puts even more on the drives. You’re already way over on the drives. Follow along closely, here.
You loaded to 78,500lbs. That only gives you 1,500lbs of leeway total, across all three axle positions. Because you’re light on the trailer by 3,000lbs, you’re going to be heavy by 1,500lbs, on the tractor. Yes. You have a permit to cover that. But, with your current 5th wheel setting, you’re not properly distributed on the tractor.
You need your 5th wheel slid way forward. You need it positioned so you know when you’re sitting at 36,000lbs on the drives, you’re at 12,000lbs on the steers. This would allow you, in the worst case, to be as light as 32,000lbs on the tandems. But, your tractor distribution would be perfect.
How this works is: at 80,000lbs, if you’re 32,000lbs on the tandems, you’re 2,000lbs light back there, which means this 2,000lbs would have to be in the nose. Now, you’re 2,000lbs heavy on the drives, which you’re permitted for. Since, you’re only permitted for overage on the drives, AGAIN, you need your 5th wheel set to hit 36,000lbs on the drives at the same time you hit 12,000lbs on the steers, to cover that 2,000lb shift in weight. No matter what, you’d always be perfect on your tractor. Currently, you’re way off.
Someone with more experience could have looked at your weights, slid your 5th wheel, and got you legal. You were 1,500lbs under max gross, as a starting point. You were 3,000lbs light on the trailer, that meant you needed to cover that 3,000lbs, at the front of the trailer. You scaled at 3,000lbs over on your drives. You had 2,000lbs of permit on your drives. Now, you’re left to cover the remaining 1,000lbs. That needed to be on your steers, which would’ve left you 500lb to play with and NOT be over weight on any axle position.
So once more, you loaded 1,500lbs under gross (your cushion), you’re over at the front of the trailer by 3,000lbs, you have a 2,000lb drive permit, leaving you to put that 1,000lbs on the steers, and you still have 500lb left of the 1,500lb cushion you left yourself. Get your 5th wheel correctly positioned to hit 12,000lbs when the drives hit 36,000lbs and that’ll leave your 2,000lb permit to cover ever being light as much as 2,000lb on your trailer.
Lastly, for anyone who thinks to set up this operation to be 12K/34K/34K on the axle positions. You can’t. As soon as he’s over on his drives, he’s over on his steers. He has to ensure his weight distribution uses his 2K drive permit as his cushion and the distribution is at 12K/36K, on his tractor.
I hope that all made sense.
Ok, so basically you are balancing the overweight condition between steers and drive axles by moving the fifth wheel forward towards the cab rather than shifting the weight toward the trailer tandems, the way you would on a 53 foot reefer trailer by sliding rear trailer tandems toward the weight? The axle weights I recall were 10,000 something on steers (unusual to see), the ticketed drive axles at 37040, and the trailer tandems at 31,400. About how much weight shift occurs in the balancing act between drives and steers per fifth wheel hole when you take weight off drives and move to steers (2019 freightliner daycab)? On 53 foot reefer trailer tandem slide this is about 300lbs per hole.
Also, is load shift not an issue on these tankers? We loaded the rear most top manhole to try and avoid a recurring problem, believing the issue was that the cement started legal and shifted forward (in the absence of baffles) piling up forward without equalizing the way a liquid would after braking and mountain grades.
And lastly, in your experience, how much leeway should we give ourselves on loading? Here we asked for total gross to be 78,500. They loaded just under that. I think that’s 24 something tons. Normally, what do these trailers haul when driven by experience? Thanks so much for your help and patience!!!
In other words, in this situation could we have pulled 80,000? Would we have had the room to balance that. If I understand everything correctly, we could have loaded 79500 and still been ok, but would it have been advisable?
wis bang Road Train Member
- Jan 12, 2011
3 hopper bulker may be under 40' long and there are no baffles.
When I worked at a Chem Leaman cement terminal that plant dropped the entire load in to the center hatch in one shot.
I think that balanced the product in a pile that filled the center and flowed front and rear.
The product dropped straight into the center hopper.
Your rear hatch may [should] be over the rear slope of the 3rd hopper and that could shoot it forward.
Try dropping into the center.
LTLTRUCKDRIVER Light Load Member
Been years since I pulled a pneumatic tanker, if its only got 1 manhole to load into pull off the scale until just the trailer tandems or on the scale get you weight, pull up about 100 feet put in in reverse come back and pull your trailer hand brake down and slide the product to the back get it as close to 34000 as you can. If it's a two 2 manhole trailer (Center& Rear) load until your 65000 gross in the center and finish in the rear manhole until your 78500. It's kinda trial and error with the equipment you're loading.RockinChair Thanks this.
ducnut Thanks this.
bad-luck Road Train Member
- Nov 16, 2013
When you slide your 5th wheel, count the number of notches you moved it and how much weight moved forward. Then, take the weight amount and divide it by the number of notches. That’ll give you the amount each notch is worth in weight transfer. Then, write that number somewhere permanent, like on top of your sun visor. If you ever get in a bind again, you’ll know exactly how many notches to move the 5th wheel. It’s a right PITA to do, as they don’t normally like to slide very easily. Once you get it set, you’ll be good, though. In my experience, each notch is usually worth 450lbs-500lbs of weight transfer.
That last paragraph is for drivers who’ve been taught to set up their combo with 12K steers/ 34K drives/34K trailer. If they start counting on the permit to cover their overage on the drives, it’ll also put more weight on the steers, making them overweight up there, provided they can only scale 12K up front. Therefore, I’d set up my combo to hit 12K on the steers at the same time I hit 36K on drives. That way, I’d know I was never heavy on my steers, unless I was overweight on my drives. It’s kind of an insurance thing. I’d know, no matter what, the tractor is always set up right and I’d never have to touch the 5th wheel, after that.
My previous employer had bolt-on 5th wheels. We always loaded out over 79,000lbs. However, my tractor would be over on the drives, yet I still had 1,000lbs left at the steers. I had the shop move the 5th wheel forward two holes and my tractor weights were always perfect, from then on.
Page 1 of 3