All small trucks I am familiar with (like the Mercedes 814 or the Mercedes 1317), have a button on the floor that is operated with the heel of the left foot for the exhaust brake.
But what about modern big trucks and tractors? These vehicles have about a dozen of different braking systems (retarders, intarders, compression brakes, electric brakes etc). Do all these things have separate controls or you simply use the brake pedal and the computer decides which systems to use?
One method is to have another control off the steering column with off and 3 “on” positions, each with increasing retardation. The retarder cuts in when the driver lifts off, and automatically drops out when the engine reaches idle revs.
AFAIK, if there is more than one retarder fitted, each has it’s own control system. I don’t know if retarders are now integrated with the anti-skid systems, as too much retardation can cause a jackknife.
Every truck I have driven has only had one type of engine brake and it was controlled by a switch on the dashboard. Touching the accelerator or clutch will turn off the engine brake even if the switch is on.
My “limited” experience with HEMTT tractors pulling PATRIOT missile launchers around is that they have a 3 position retarder switch and a separate lever to apply the trailer brakes apart from the tractor. The trailer brake was used in moderately slippery conditions (steep hill, sandy road surface) to provide a bit of drag to keep everything straight. In very slippery conditions that would be a disaster as the rears would lock up and the trailer would be passing you shortly.
I always left the retarder on max, loved the sound //residents of small towns at bottom of steep grades gather pitchforks and torches//
Hold on… if you locked up the TRAILER brakes, how would the trailer be passing you?
Because locked wheels have less grip than turning wheels. If you ride a bicycle and apply front and rear brakes and the rear wheel locks then the rear wheel will slide and try and overtake you. You’ll either fall off or come to a cool sideways stop.
Ah.
I was envisioning using rear brakes ONLY in that scenario, which was the source of my conclusion.
My bad.
We have Hydraulic retarders on our fire apparatus, and the problem with this is the rocker switch can be left in the On(retard on) position and the next driver may not notice until the throttle is let up on and the retarder engages causing a dangerous loss of control (ice on roads).
Not as much a problem with trucks that are driven by the same driver, as a fire truck that may be driven by many different people.