Sliding 5th wheel weight transfer

No you didn’t. You observed something but you did not observe a slid 5th wheel add or remove weight from trailer tandems.

 

@AModelCat is correct.

If the slider went all the way to the steer axle it would still not change the trailer ground pressure.

 

Unless the kingpin itself moved, there is absolutely no way a tractor on level ground with brakes released will affect the weight on the trailer.
If you did see weights change, it was because he didn't release the brakes and caused pressure to shift. That's all it was though is pressure, not weights.

 

No

 

I think I figured out how the 780 driver changed the weight on the trailer tandems by sliding the fifth wheel.

He had a 40 foot rigid I-beam affixed to the tractor rail on a hinge, immediately behind the cab. This beam layed across the top of the nose of the trailer. A hoist and cable set was affixed to the rear of the trailer. Then the cable was stretched tight and affixed to the other end of the i-beam [which is now high above the front of the trailer at about a 10-15 degree angle]. Then as the nose of the trailer moves forward in relation to the hinge point of the i-beam, this raises (moves forward) the opposite end of the beam, thus lifting weight off of the trailer rear, and shifting it to the tractor. Note. This apparatus will not work well in a flatbed application

So. I guess it is possible.

 

Actually made me wonder.... I need to pull out pencil and paper to figure it out, or as I'm don't care enough to do it, ask.

Would 5th wheel heights matter at all? Even in the slightest by 10-50 lbs? Liike if one is running on 24.5's vs 22.5's on the trailer? I still don't see it as the king pin is still in the same spot and the trailer will be the same slight angle no matter what.

 

Aaaah. Bugger. Now you’ve got me thinking.

Yes it would - say if you jacked the tractor WAY up, so the bed of the trailer is on a 30 degree angle, with some monster truck tires jacking it up to do so.

Wouldn’t matter in this situation - unless you’re suggesting he runs with dumped / over inflated airbags to comply with the mythical agreed figure of axle weight maximum.

 

I have to assume the tractor frame rail is “level”. Sliding along that path isn’t going to change the pitch of the trailer floor any. Yes. Assuming an equally distributed load on a level plane, if you somehow lift one end, the opposite end will get heavier but you’re not/can’t make any such pitch changes of the trailer load with a changing of the 5th wheel position along the frame rail.

And I’m not sure of the numbers or percentages of weight shift when manipulating a load on an incline but they are probably enough that if the trailer dumps it’s bags when brake supply air is removed, there could be noticeable changes in the weight distribution of at least several hundred pounds but who pulls the trailer knob on a scale?

 

When I slid my 5th on my tank I got my steers higher drive lower and trailer higher lol. But it worked out how i wanted. Steeper angle meant more liquid pooled at the back

 

That would be the only selling point for a Volvo.......