Torsion Axle Orientation - '93 Excella 34'

[binkers]

I've read several forum posts on torsion axles, as well as Inland-RV's article on dura-torque axles - very informative. It's mentioned in the article that "As the torsion arm goes rearward, it should have a negative angle (downward)." This is not the case on my '93, 34' excella, the angle is definately positive. I was told that the trailer did "sit" for a few years, but with tires removed and on jack-stands. The tires are all new, so can't see any history of unusual wear. I've just purchased the trailer, but have not moved it off the lot. The service manager at the place I bought the airstream says that the orientation of these axles is normal, and that some torsion axles (including these) are designed to have a positive orientation. Could I be reading them wrong? Any thoughts on this? Thanks very much in advance.

[87MH]

Originally Posted by binkers

...It's mentioned in the article that "As the torsion arm goes rearward, it should have a negative angle (downward)."... Any thoughts on this? Thanks very much in advance.

On an Airstream, flat is questionable, positive is probably bad. That being said, some trailers and vehicles ARE designed with a vast array of starting angles, but usually AS's have some downward angle when new.

One way to check if the axle has some resiliency left is to measure from the bottom of the wheel well to the center line of any one tire, then jack the trailer (or otherwise lift the tire with the measurement off of the ground), then remeasure the distance from the wheel well to the center of the wheel. There should be several inches of immediate movement.

Remember, it is this immediate vertical movement that gives a good "ride" to the trailer.

Any rubber will take a "set" over time - the more compressed it is, the more likely to take a set earlier on in the life of the rubber element. (I use the word "rubber" to describe any resilient natural or synthetic material designed to provide support or cushion.)

Unfortunately, unlike most trailers or trucks, RV's are left sitting for long periods of time with almost the max design weight on the axles, thus accelerating the actual demise of the resiliency necessary to provide a sufficiently smooth ride when on the road.

Also unfortunate is the fact that often the damage caused by too harsh a ride goes undiscovered until much damage has been done. Possible failures are rivets being sheared, sealing surfaces being worn and failing (including window, door, any of the seals on the top of the trailer, and the actual overlap seals between the sheets of aluminum), damage to interior furniture and storage areas, cracks developing in both the interior and exterior skins, and, most catastrophic, failure of the frame or suspension bolts.

The good thing is that axles on trailers are relatively easy to replace. ANY axle, regardless of age, is subject to compression failure.

The probability of axle replacement should always be used as a negotiating tool when purchasing a trailer with torsion suspension.

[Inland RV Center, In]

Originally Posted by binkers

I've read several forum posts on torsion axles, as well as Inland-RV's article on dura-torque axles - very informative. It's mentioned in the article that "As the torsion arm goes rearward, it should have a negative angle (downward)." This is not the case on my '93, 34' excella, the angle is definately positive. I was told that the trailer did "sit" for a few years, but with tires removed and on jack-stands. The tires are all new, so can't see any history of unusual wear. I've just purchased the trailer, but have not moved it off the lot. The service manager at the place I bought the airstream says that the orientation of these axles is normal, and that some torsion axles (including these) are designed to have a positive orientation. Could I be reading them wrong? Any thoughts on this? Thanks very much in advance.

The angle of the torsion arms that you describe, "is not normal."

All Airstream trailers built with torsion axles from the early 2000's on back to 1961 had starting angles of 20 or 22 1/2 degrees, downward, unloaded.

When loaded, that angle changed to 10 to 15 degrees downward, depending on the load.

The service manager, is "ill informed," and has mislead you.

Some commercial farm vehicles that use torsion axles, are indeed equipped with the torsion arms going upward. Total different story.

But, never, ever, under any circumstances, has any Airstream or Argosy trailer, been equipped with an upward angled torsion arm.

When the trailer is loaded for travel, the absolute maximum upward position of the torsion arm is parallel to the ground or chassis.

Your axles, by your description, are finished, and must be replaced if you intend to do any traveling with it.

Andy

[binkers]

Bummer. I was hoping you might say otherwise. This is what I feared...Thanks for the information though. A real shame because the thing is a beauty otherwise. Any suggestions? I must replace all three axles I assume? Can I move it or must I have the work done on site. App. 200 miles from it's location to my home now.

[Silverhobby]

The unit can be moved. It is not a good idea to travel extensively with the worn axles. Popped rivets, body damage, and front and rear end separation can begin to develop over time. The AS takes a "rough ride" with the worn out suspension. All of the components of the trailer do suffer when it is riding roughly.

[87MH]

Originally Posted by Silverhobby

The unit can be moved. It is not a good idea to travel extensively with the worn axles. Popped rivets, body damage, and front and rear end separation can begin to develop over time. The AS takes a "rough ride" with the worn out suspension. All of the components of the trailer do suffer when it is riding roughly.

I fully agree...I would not hesitate to latch onto it for a couple of hundred miles to get it to a place where it could be worked on. Be careful, go slow, and avoid rough roads.

All damage is cumulative, but, in the greater scope of things, 200 miles is not that far, especially if you GO SLOW!!!.

[norsim]

I am far from being a mechanical engineer,so may have misinterpeted data on Henschen web site, but the drawing for axle with 22.5 degree negative starting angle shows horizonal position for full load with 2.31 inch vertical spindle travel from no load position and 12.5 degree positive angle for full shock load with 3.6 inch total vertical spindle travel and only 1.3 inches vertical spindle travel from full load to shock load position. If this is correct interpertation ,there should never be much axle travel and 12.5 degrees would be maximum positive angle if 22.5 degrees negative angle is indeed starting angle. My Minuet has positive angle, so I road a few miles in trailer (I know-should not have done that but have done much worse things) over fairly rough road and things seemed to be traveling fairly smoothly.

[Inland RV Center, In]

Originally Posted by norsim

I am far from being a mechanical engineer,so may have misinterpeted data on Henschen web site, but the drawing for axle with 22.5 degree negative starting angle shows horizonal position for full load with 2.31 inch vertical spindle travel from no load position and 12.5 degree positive angle for full shock load with 3.6 inch total vertical spindle travel and only 1.3 inches vertical spindle travel from full load to shock load position. If this is correct interpertation ,there should never be much axle travel and 12.5 degrees would be maximum positive angle if 22.5 degrees negative angle is indeed starting angle. My Minuet has positive angle, so I road a few miles in trailer (I know-should not have done that but have done much worse things) over fairly rough road and things seemed to be traveling fairly smoothly.

The Henschen specs are for a "brand new" axle, in perfect condition.

Most any torsion axle that's 30 years old, is far from perfect.

An upward angle of the torsion arm, on an Airstream or Argosy trailer, when unloaded, let alone loaded, says the axle is done.

The total movement of the spindle is measured from no weight to the shock position. That measurement holds true, when the rubber rods are in excellent condition.

It does not hold true when the rubber rods have solidified.

Andy