Jack platform?

[zip]

Every year I jack my 5er up to check wheel bearings and brakes. I noticed how many 4x4 and 2x6 pieces of lumber it takes, not only for the jack, but for the jack stands too, and wonder if anyone knows of a good, sturdy stand on the market so I don't have to use so much lumber to reach the trailer frame with my 20 ton (bottle) jack? It takes a good bit of time just to tote and handle all the wood!

[zip]

Every year I jack my 5er up to check wheel bearings and brakes. I noticed how many 4x4 and 2x6 pieces of lumber it takes, not only for the jack, but for the jack stands too, and wonder if anyone knows of a good, sturdy stand on the market so I don't have to use so much lumber to reach the trailer frame with my 20 ton (bottle) jack? It takes a good bit of time just to tote and handle all the wood!

[RustyJC]

Unless your rig has the axles "flipped" (i.e., located below the springs), I jack mine up with the jack under the spring plates with a piece of wood between the bottle jack and spring plate as a load spreader. The spring plates carry the weight of the 5th wheel by design, so this isn't detrimental to the axles or springs and requires much less jacking than lifting the trailer by the frame.

Of course, our current 5th wheel has the Dexter NevRLube axles, so I don't do as much jacking as I used to.

Just a suggestion.....

Rusty

[powerboatr]

rusty
my book says to never jack up using the axle plates it puts the entire load on one set of springs and can lead to failure,
do you jack up up both axles on one side at the same time??? that would work and still evenly distribute weight on both set of axles???

[RustyJC]

Think about how the weight of the RV gets transmitted to a given tire, assuming the axle is located above the spring. The weight is carried by the spring - so, what keeps the spring from hitting the ground? The spring plate under the axle is holding the spring up by transmitting tensile loads through the U-bolts to the axle. All I'm doing when I jack under the spring plate is relieve the U-bolt loads - the spring plate itself is now under compressive loading between the spreader block I've placed between the jack head and the spring plate and the spring itself, and that's more evenly distributed than the tensile U-bolt loads that place a bending moment on the spring plates during normal operation.

Now, if I jack one spring plate up enough so that the wheel is 1" off the ground, why is that different insofar as spring loading is concerned than having that wheel sitting 1" higher than its companion on that side of the trailer? It's not, and that situation happens all the time if one wheel is in a pothole, on a small rock, etc. The wheel that is still on the ground is transmitting load - remember that there's an equalizer between the springs on the two axles, and the purpose of the equalizer is to balance loading between the axles in precisely this situation where one axle is higher or lower than the other.

As a mechanical engineer, if I saw anything wrong with my method, I wouldn't do it. I've used it for many years and never damaged anything yet. As I said, it's just a suggestion - it's your choice what you want to do with it.

For the sake of safety, I only jack one wheel off the ground at a time.

The admonitions I've seen only warn against jacking under the axle tube itself - which I agree with.

Rusty

[powerboatr]

Well now
that makes sense, 1" does force the equalizer to roll ,
i see clearly now, i was confused this morning,
i was thinking of it squeazing the tube between the u bolts .
but lifting the spring plate would negate any chance of damage to teh tube itself, i knew there was an easy explanation
thank you

[zip]

So let's see- my choice is either to follow the advice of the modern, young engineers who wrote the manual, or the advice of some old, broken down retired (Rusty are you retired?) guy who says I can lift under the spring plate...
[Just kiddin around there, Rusty-. Pls don't take that seriously.]
Thanks for the advice. I'll try the spring plate method next time..