TRUCKERS!!! Quick Question

[sms001]

MY wife has an ongoing problem. She gets a trailer in three or four times a week and all too often the driver "can't slide the tandems."

I've got no idea what this means except by context - I assume it's some way of sliding the floor of the trailer back a little bit? In any case, it seems to create a bit of hassle in the unloading process.

My question is actually twofold.

Is this really so common?

Are there any alternatives?

Most of her drivers are pretty good guys, so the thrust of my first question isn't really "Are these guys just being lazy?" but more a maintenance thing - does the mechanism freeze or rust or just not work well over all or what?

As for alternatives, have any of you found a good way to "unstick" them that I could pass along, or a way to keep them from sticking in the first place, or a way to (what I assume is the desired result) get trailers right up to the edge of loading docks?

Thanks in advance, folks.

[mjr]

I think I can answer the first part. You know the double sets of wheels on the trailer? That's the tandem (short for "tandem axle", I believe). And that little rail with the holes in it, well, you can slide the tandem back and forth along that.

I think it's supposed to be all the way to the back for a "full" trailer, and all the way forward for an "empty" one. I think. Don't hold me to that. Could be the opposite.

I think there's some sort of bar or pin that goes in the holes to keep the tandem in place. Perhaps they're getting stuck somehow? Not sure how one would go about getting them un-stuck, though.

[wolfie]

As MJR posted, the tandems are the trailer axles (2 axles, refered to as a tandem pair). There are 3 reasons to slide the tandems:

1) For weight distribution. Moving the tandems forward puts more weight on them and less on the drive axles, with the reverse for sliding them back. You aren't allowed over 34,000 pounds on either set.
2) For manouverability. The further forward they are, the tighter you can turn. My last outbound delivery was at a place NOT designed for 53 foot trailers. Even with the tandems all the way forward, going around the building I was climbing the left curb with my steer tire at the same time I was climbing the right curb with my trailer tires.
3) To reduce "tail dive". When the tandems are all the way back, it reduces the amount the tail of the trailer will dive when the forklift drives in, since there's less lever arm to amplify the motion of the suspension. Note that a trailer set up this way is not street legal - the tandems must be slid forward again before going on the road.

Generally, the tandems must be set so the trailer wheelbase (kingpin to midpoint of trailer axle group) is no less than 37 feet, and no more than 41 feet, to be street legal. California is different - the maximum allowable wheelbase (and they measure from the kingpin to the rearmost trailer axle) is 40 feet.

There are a number of reasons it can be difficult to slide the tandems, some generic and some specific to the slider release on that particular trailer. Here are some that I have run into, along with workarounds (some don't have "in the field" workarounds):

Generic:
- There is a locking bar installed to limit how far the tandems can slide, and its latch is rusted solid. Fix: latch needs to be cut in order to take out the bar.
- One of the locking pins (there are 2 on each side) has too long of a shaft, so when the release is in the "locked" position it's bent like a spring, and when it's in the "released" position it's straightened out but the pin isn't pulled. Fix: Replace the pin with one that has the proper length shaft.
- A cotter pin has been lost, and the shaft of one of the pins has popped off the crank arm that pulls it. Fix: Slip it back over the crank arm, and rig a temporary way to keep it from popping off.
- Tandems haven't been slid in a long time, and the bogie has rusted onto the slider rails. Fix: The garage needs to break it loose, knock off the surface rust, and lubricate the sliders.
- Low friction at the wheels (e.g. ice). Fix: Instead of attempting a static slide (trailer bogie not moving when sliding the tandems), get moving and then "spike" the trailer (won't work with air slide). This is sometimes enough to slide them. Alternately, chock the trailer wheels before trying to slide the tandems. You need to see which axle group is affected by the low friction before choosing between these - if the drives spin on a static slide, try the "move and spike". If the (braked) trailer wheels slide, try the chocks.
- Driver is a lazy bastard (yep, I know some of my co-workers will use the "can't slide the tandems" excuse to get out of some work). Fix: Print out this list (with this item deleted), show it to the driver, ask them which problem they're having (and show you if it's something that needs shop work - it will be obvious if the problem is real), and for solutions that need a "helper", offer to help.

Air slide:
These have the pins pulled by an air cylinder, activated by a pull valve at the bogie. They use air stored in the trailer's air tank, and the pull valve is "piloted" so that when the trailer parking brakes are released, the valve jumps to the "locked" position and the lock pins re-engage.
- No air pressure in trailer (tank has leaked down while parked). Fix: Release trailer brakes, wait until tractor "A" and "B" reservoirs have both reached at least 100 PSI (i.e. trailer reservoir is pressurized, so no longer draining air from tractor), set the trailer brakes, and activate the slider valve.

Lift lever:
These have a lever that's lifted through an arc of (depending on model) between 45 and 90 degrees to pull the pins. This is a "direct acting" release - the pins move while the lever is being moved.
- Pins leaning against front or back edge of holes, so friction is more than the driver can overcome. Fix: "Helper" pulls the lever up while the driver rocks the tractor forward and back with the trailer brakes applied. The rocking moves the holes in the rails away from the pins (can overcompensate and lean against the opposite edge), so the friction is removed and the pins can be pulled.

Kwik-Release:
This is a brand name for a "pull the handle straight out" type of release. Pulling the handle "winds up" a spring (there's a notch in the handle to hold it in the "pulled" position), and the spring then tries to pull the pins. If the pins are leaning against the edge of the holes (see "Lift lever"), the driver can rock the tractor while the spring pulls the pins, eliminating the need for a helper.
- Notch in wrong place (either too close to handle, so the "pulled" position doesn't fully pull the pins, or too far from handle, so it can't be pulled far enough to engage the notch). Fix: Have a "helper" pull the handle while the driver operates the tractor.
- Mechanism is frozen/rusted solid, so it turns into a "direct acting" release. This has the same results as "Lift lever" type mechanisms. Fix: Have a "helper" pull the handle while the driver operates the tractor.

My workarounds: I carry a 24 inch bar clamp/spreader (woodworking tool) - the fixed jaw can attach to either end of the bar (changes its mode), and when one wears out (they last me around a year each) I take the fixed jaw from the "dead" one and put it on the new one so I can use either mode without moving the fixed jaw. This is also useful for holding down the brake pedal during pre-trip inspections. I also carry a tarp bungee (pretty much any length between 12 and 18 inches will do). This is pretty close to what I have (mine is a discontinued store-brand model). If you look closely, you'll see a black circle on the fixed jaw at bar-level - this is the screw you remove to switch modes, and the hole at the right end of the bar is where this screw goes through in spreader mode.

Lift lever: Either hook the fixed jaw (clamp mode) over the flange on one of the trailer floor ribs and the moving jaw under the lever, or the fixed jaw against the ground (spreader mode) and the moving jaw under the lever. Squeeze the ratchet handle to apply a fair bit of force, then rock the tractor with the trailer brakes applied. Apply a bit more pressure (lever will have moved somewhat) and repeat. Usually takes 2-3 cycles to get the pins pulled.

Kwik-Release: For notch in wrong place, put the fixed jaw (spreader mode) against the bogie frame immediately above where the handle comes through, and the movable jaw inside the handle. Ratchet it out as far as it will go (spreader, not notch, holds the handle out). For "frozen solid", put the fixed jaw (spreader mode) against the bogie frame immediately above where the handle comes through, hook both ends of the tarp bungee around the handle, and loop the middle of the tarp bungee around the movable jaw. Ratchet it out to put as much stretch into the bungee as you can (typically 3-4 inches, but might be more), rock the tractor (with trailer brakes set), then ratchet it out some more (bungee takes the place of the spring - it pulled the pins partway while the driver rocked the tractor). Might take 2-3 cycles to get the pins pulled, at which point you remove the clamp and bungee and engage the "pulled" notch. If the notch is in the wrong place, install the clamp without the bungee to hold the handle out, as above.

ETA: Are the "can't slide tandems" trailers all from the same company, or is it different companies each time? If it's always the same company, keep a record of the trailer numbers for a while, then contact the trucking company. Sliding tandems to avoid "tail dive" is a fairly common REQUIREMENT for shippers and consignees. Sound a bit ticked off that they are unable to meet this requirement (list the trailer numbers involved), and imply that if they can't meet it, perhaps another trucking company could. After all, if they're not maintaining THIS aspect of their trailers, what else are they skimping on? If it results in a wreck, YOU don't want to have any involvement (plaintiff's attorney theory: go after EVERYBODY connected to the truck, including the company that made the merchandise, the warehouse that loaded it, and the place it's supposed to be unloaded). That ought to "light a fire" under the maintenance department to get it fixed, and if it turns out that the sliders actually DO work, the maintenance department is not going to take the heat - and dispatch can check who took that trailer to the site. Regardless of what happens (improve maintenance, drivers get told to do their job, or another company gets the business), you'll get trailers where the tandems CAN be slid.

[Kaylyn]

I will say that, as a female driver who doesn't have the upper body strength of most of the guys out there, I rarely have a problem with tandem sliding, even with traditional release tandems. I may have run into trailers I absolutely could not budge the pin on maybe...less than ten times in my whole trucking career. (This means trailers I haven't been able to move the tandems with even with the use of a helper trying to pull the pin while I am in the truck "rocking" the rig back and forth to dislodge it, or that a hammer hasn't been useful in knocking the pin loose...I've never tried any of the other suggestions that wolfie had for more stubborn cases.) I suspect if your wife is getting complaints THAT often, it's most likely the drivers being lazy. Because trust me, many truckers ARE lazy and generally will complain about ANY extra work they have to do. I see it all the time at work; every time I have to correct another driver on something they're doing incorrectly, when there's a SIGN right in front of them that says "use doors X through Y, slide tandems back, and use safety strap to open doors first to check load before opening doors all the way" they throw a hissy fit and say it's all ridiculous. Sorry, but I've SEEN forklifts go into (dropped) trailers where tandems were slid all the way forward and it has caused them to lift up to about a 30 degree angle where the landing gear has left the pavement by several feet, and those safety straps have saved my life on one occasion so don't act like they're pointless extra work. 99% of the time it may seem pointless, but when you have the trailer door yanked from your grip because a bale of cardboard had been leaning against the door and that strap is the only thing standing between you and being crushed by said bale, you'll be thankful that you did that two minutes of extra work and you'll NEVER complain about it again. And that forklift driver has likely at least seen videos of what happens to trailers that don't have tandems slid all the way back, and there is a reason they insist on it. So the drivers most likely need to suck it up and grab some chocks to stick under the tires to help if the tandems truly are stubborn and won't slide (the most likely situation if they're not just lying to her).

(This isn't to say that drivers don't have genuine problems with tandems. They do. I've had them on occasion. But to be getting told that THAT often is likely a sign of laziness or just wanting to rush on to the next load.)

[sms001]

Wow! TIL.

Thank you all very much. I'm going to print this out and arm my wife. I think the three of you covered just about everything she'll need to know. And thanks for the safety tips: she's the forklift driver and I had no idea things could be so chaotic.

You folks are the best, thanks for your time.

[Ironclad Alibi]

Since to OP's question has been answered, I will toss in a horror story from when I worked for the government agency that does vehicle safety recalls.

Back around 1981, on an Interstate (I-95 I think) the locking pins on a tandem axle failed, allowing the tandem axle to separate from the trailer. As the tandem axle left the trailer, the air hoses disconnected and, since the air pressure keeps the brakes off, the brakes immediately applied, and the tandem axle stopped dead in the road. This was a deadly event for the car following the truck as they ran into the tandem axle at highway speeds.

I changed jobs just after this happened, so I do not know the outcome of the investigation. I suspect there were much stronger requirements put in place for stop blocks on the trailers to keep it from happening again.