First the dumb question. Ya know the outrigger type things on the sides, that they use to hold the truck up when the tractor is pulled away. How do they raise and lower them? Let me rephrase that (the question isn’t meant to be that dumb) I know they use a crank on one or both sides, but how does that crank work, internally. I always assumed it was rack and pinion style, but that wouldn’t work since the crank is so close to the top. Does that make sense, what I mean is with the leg all the way extended, for the rack to be up next to the pinion, it would go through the floor of the trailer when it’s raised. I hope that makes sense. Along those same lines, what keeps it extended when all that weight is on it?
Second question…Why no reverse lights on the rear of the trailer (only on the tractor) especially with the amount of backing up they do. I know I’ve almost been hit a few times (my fault though…must follow my fathers instructions…never get the forklift behind the truck until the driver get’s out cuz they might not be done backing up…and don’t put your finger in front of the sandblaster :smack: )
The truck stands are made of a telescoping unit (either tube or square tube). I believe that most landing gears follow the practice of extending the inner (lower) part of the leg is by a screw. Here is the manual for some landing gears by Jost. (1.2m .pdf) with the gear unit displayed in cutaway.
Years ago the landing gear were locked with a pin placed through predrilled holes matched between the inner and outer sleeves. I think that this has generally been discontinued since it does not allow for infinitely variable height, but there may be still some units that use them.
ahhhhh, never even thought of that. Makes so much sense now, and even if I had known that I NEVER woulda guessed that it had it’s only little mini transmission in it. So does the driver actually have to lift the trailer off the tractor, that brocure seems to suggest that.
I just told my dad about this wonderful new insight I had about how it’s not rack and pinion style but actually a screw, and he went on to tell me about the gear shifting and lifting the trailer, so that answered that. Now, what about the reverse lights.
I don’t know much about the internal workings of the landing gear but I do know a lot about operating them. All the landing gear I have used is the crank type with a high and low range (speed), like the one in the link tomndebb provided. Even in the high speed setting it requires quite bit of cranking to move them the foot or so through their range. In the low speed setting it requires lots of cranking to move them any distance at all but this is seldom necessary. Most modern tractors have air suspension and a switch to lower it about 6", you just crank the landing gear until it is about an inch off the ground then lower the tractors suspention to lower the trailers weight onto the legs. To hook up to the trailer the 5th wheel (the plate that holds the pin and the trailer sits on) is angled so it can silde under the trailer and lift it. If the trailer is to low for the fith wheel to slide under you can lower the tractors suspension to get under the trailer, then reinflate the suspension to lift it.
Trailers don’t have back up lights because the have never had them. The electrical connetors are standardized and there are no free wires for reverse lights.
That was exactly my guess. Still though, they do do a lot of backing up and often times it’s hard to tell if they’re stopped or still trying to position themselves somewhere.
European trailers have reversing lights fitted, but in general are pretty much the same, although we generally have more axles and carry more weight. (44 tonnes gross = just short of 100,000Lbs).
We have hardly any tractor units (prime movers) with old fashioned cart springs left. Air suspension makes life so much easier. Coupling and uncoupling trailers is probably the most dangerous part of a driver’s job.