Is there any practical use for a trolley break?

If you've ever totally lost your trailer brakes you will know how hard it is to stop a heavy loaded combination vehicle with only the tractor brakes. Doesn't matter how cool they are, you've put yourself and the public at risk with this selfish and erroneous behavior. There is a reason you're gonna want to have all your brakes working on all axles in concert- they were designed that way, don't try to outsmart the engineers or plant dangerous knowledge virii into the heads of new truck drivers reading this stuff. A lot of trucks are purchased in fleets sans trolley hand brake due to truck drivers having 'heard' old wives tales about their use and gotten thousands of innocent people killed and hurt in the process, hence why they are becoming rare in fleet trucks.

 

Maybe after some more experience the OP might find some uses for the trolly valve and understand they do come in handy. I like the fact that when I do my pretrip I can pull down on the bar and then I'll know right away where if any I have any air leaks. Then I like the reasons that were given before.

Here's a couple more. If you ever drive a truck and trailer, that's when you have cargo on the power unit and you pull a trailer but way of a pintle hook, you can use the bar to apply brakes to slide the trailer if you get into a very close area. What you do is lock your divider in go in reverse slowly and pull down on the bar and apply some power. The trailer will lock and you'll slide the trailer over to the side a couple of feet. Then you pull foward and leave. That's an old trick gas haulers use when they have to get an oversize truck into a gasoline station that was built many years ago. Second, if you're pulling more than one trailer and you're on ice plus going down a hill you can use the bar to keep the set straight. I pulled triples up in northern NV and used this method many many times. When you start down the hill very slowly, and I mean slowly, you apply just the right amount of air pressure to drag the brakes so they do not lock up even on ice. My tractor it took about 3 psi and that was it. I never once got out of shape and I passed many semis that were in the ditch.

The plain fact of the matter is companies got rid of the trolly valve because the new drivers had no idea had to use them. And the lease drivers would use them too much. Someone said they got rid of them because of the O/O's but that's just not true. How can you get rid of something in a private tractor? But it is a problem when O/O's just use them going down a hill. Why they would do that is simple but it's clearly a form of danger when you need all your stopping power and you don't have it. And to top it off there's been deaths resulting from a driver just pulling down the bar and then getting out without setting any other brakes and the bar would back off and kill someone.

 

Thats a clever idea on the dump truck portion there. Never thought of that. pulling transfer trailers, often times we'd use it if we had a split load. We'd empty our truck at one job and sometimes drive 5-25 miles with a loaded trailer. It helps with stopping in that situation.

GasHauler gave a few other good ones on truck & trailer setups.

 

I also forgot to mention a lot of our dump trucks - the RD688S Macks, specifically - didn't have a power divider switch. To kick in the power divider, you were required to pull down very lightly on the Johnson bar.

 

Well,you can always hang your washed skivvies on it until it's dried.

 

Someone mentioned a blue knob, I have never seen a truck with one yet, what was that one used for?

 

Red 8-sided knob = trailer air supply.
Yellow square or diamond shape, depending on how you look at it = parking brake (tractor only).
The blue knob was for the entire brake system. It was round, and sat just to the left of the parking brake (sorry, can't find any pics). Very convenient--one pull and all your brakes were set if you were hooked to a trailer or trailers, or just your parking brake if you were bobtail. One push and you were ready to roll. IIRC, by 1998 or maybe a year or two earlier, the blue knobs (and other parts) were eliminated, at least in Freightliners. Saved a few $, I guess, and simplified things: you now push/pull yellow for tractor brakes and red for trailer brakes. Or you push/pull both. Maybe some engineer decided that the blue knob was redundant. I don't recall the wording on the blue knob. Anyone else remember?

There may still be some applications that involve blue all-system knobs. If you'd gotten used to it, the dash looked kind of empty without that blue knob.

Also, IIRC, when you pulled the blue knob, the others popped out. Yeah, I think that's how it was.

If I can find a pic, I'll post it. Anybody have a pic?

 

The reason many companies no longer spec for a trolley valve............

$$$$$$$$$$$$$$$$$$$$ .

 

In our trucks, if you pull the tractor knob without a knuckle/thumb on the trailer knob, they both pop. So I can see the reason for elimination.