To Shock or not to Shock

[Inland RV Center, In]

Originally Posted by richinny

one other factor with shocks is traction when braking. the tire will have a lot of 'air time' when riding over rough surfaces with bad or no shocks. shame on dexter.

AGREED.

Andy

[overlander63]

Airstream has certainly built late model trailers with no shocks. The aforementioned 22' trailer comes to mind. I'd snap a photo of one the next time it comes in, but I'm pretty sure everyone knows what a picture of something not there looks like.

[perryg114]

It would be nice if there was some real accelerometer data to back all these claims pro and con. My cell phone has an app that lets you display accelerometer data but you can't store it and compared to older runs. This sort of data with and without shocks would tell the tale.

I sorta feel like the rubber spring torsion axels are self damping to a large extent but since I have no data to back that up it is just a WAG. I have a small cargo trailer with a Dexter Axel with no shocks and it does not bounce even empty. It maybe that the rubber compound that Dexter uses have better damping chacteristics than the other manufactures. They may also add some plain old friction into the equation to help with damping.

Perry

[jlovelady]

Wow! Thanks for all the opinions, engineering and manufacturing information.
I will now move ahead and install shocks. I only have to determine which ones and, from what has been said, order them from Airstream.

[tarnished]

Shocks are used on cars trucks and motorhomes to keep the tires on the roadway to maintain traction. Please note these shocks are mounted vertically. How much forward motion is there on a torsion axel??? Not much, hardly any?? How do the shocks keep the tire on the road when mounted horizontally?? Or nearly so??
Paul

[overlander63]

Originally Posted by tarnished

Shocks are used on cars trucks and motorhomes to keep the tires on the roadway to maintain traction. Please note these shocks are mounted vertically. How much forward motion is there on a torsion axel??? Not much, hardly any?? How do the shocks keep the tire on the road when mounted horizontally?? Or nearly so??
Paul

The shocks used by Airstream are more like a steering damper than a real shock absorber. It resists motion horizontally, in both extension and compression.

[perryg114]

Well in this case they are damping the rotation of the torsion arm. It does not matter what angle the shocks are as long as they can damp the rotation of the arm. When the suspension compresses so does the shock.

Perry

[overlander63]

Originally Posted by perryg114

It would be nice if there was some real accelerometer data to back all these claims pro and con. My cell phone has an app that lets you display accelerometer data but you can't store it and compared to older runs. This sort of data with and without shocks would tell the tale.

I sorta feel like the rubber spring torsion axels are self damping to a large extent but since I have no data to back that up it is just a WAG. I have a small cargo trailer with a Dexter Axel with no shocks and it does not bounce even empty. It maybe that the rubber compound that Dexter uses have better damping chacteristics than the other manufactures. They may also add some plain old friction into the equation to help with damping.

Perry

If you have more patience than I do, you can search the forums for this info. There was somebody a few years ago that conducted these tests scientifically. He used accelerometer to measure the ride of his Airstream without shocks, then installed the shocks and retested. The difference was very small, but measurable. Almost no difference, though "almost no" is not the same as "none".

[jlovelady]

The original shocks were Monroe (1960-1967 Chevy Pickup) Napa PN94005
Is this correct for a 35 deg down angle??

[overlander63]

Originally Posted by jlovelady

The original shocks were Monroe (1960-1967 Chevy Pickup) Napa PN94005
Is this correct for a 35 deg down angle??

Are they going to be mounted more or less vertically? If so, they should work just fine. Have your brackets welded on the arms so the shocks are more or less in mid-travel when at rest.

[Inland RV Center, In]

Originally Posted by jlovelady

The original shocks were Monroe (1960-1967 Chevy Pickup) Napa PN94005
Is this correct for a 35 deg down angle??

The original shocks were made by Delco.

The starting angle has nothing to do with the shocks.

Andy

[Inland RV Center, In]

Originally Posted by jlovelady

The original shocks were Monroe (1960-1967 Chevy Pickup) Napa PN94005
Is this correct for a 35 deg down angle??

You also sent me a PM.

You have your PM set up that blocks all messages.

Therefore, I could not answer you via a PM.

Andy

[Tom Bray]

Just as a comment about whether shocks make a difference. Four years ago we replaced the shocks on our 23' safari. Prior to replacing them we would regularly find the vents from the air conditioner on the floor. Often tambour doors would open during the trip and add to the stuff scattered about. Once the shocks were replaced all that went away, even when we had to navigate some pretty ugly roads.

From an engineering perspective, springs usually need some form of damping, especially if there is any possible chance of resonance. Without shocks, a lot of assumptions go out the window as does the ability to deal with a wide range of loads. You may find that it works fine as long as there is adequate amounts of baggage on board and the holding tanks have at least some minimum amount of water in them. Of course fuel economy may suffer if you have to tote half a tank of water in the camper to keep it stabile.

Assuming the goal is to keep an old Airstream on the road as long as possible, the shocks are a relatively inexpensive part of the solution.

Tom

[Diesel1]

Originally Posted by Tom Bray

Just as a comment about whether shocks make a difference. Four years ago we replaced the shocks on our 23' safari. Prior to replacing them we would regularly find the vents from the air conditioner on the floor. Often tambour doors would open during the trip and add to the stuff scattered about. Once the shocks were replaced all that went away, even when we had to navigate some pretty ugly roads.

From an engineering perspective, springs usually need some form of damping, especially if there is any possible chance of resonance. Without shocks, a lot of assumptions go out the window as does the ability to deal with a wide range of loads. You may find that it works fine as long as there is adequate amounts of baggage on board and the holding tanks have at least some minimum amount of water in them. Of course fuel economy may suffer if you have to tote half a tank of water in the camper to keep it stabile.

Assuming the goal is to keep an old Airstream on the road as long as possible, the shocks are a relatively inexpensive part of the solution.

Tom

Thank you for your observations. I have followed this subject with interest for some time. I have a question, how old are your axles? The reason I ask , I wonder if older axles get less flexable and transmit more shock that the shocks then absorb?
Ever trying to learn.
John

[TG Twinkie]

Old axles will become ridged. The best way to prevent it is to use the trailer. Even new axles will become ridged if they are left sitting for long periods of time. So if you spend the money on axles, make sure you travel with the trailer.

[Inland RV Center, In]

Originally Posted by Diesel1

Thank you for your observations. I have followed this subject with interest for some time. I have a question, how old are your axles? The reason I ask , I wonder if older axles get less flexable and transmit more shock that the shocks then absorb?
Ever trying to learn.
John

Torsion axles can "bottom out" when the rubber rods have deteriorated.

As an example, if the torsion arm can move 3 inches when new, that dimension decreases when the rubber rods age out.

That dimension can approach zero.

Two basic things cause the rubber rods to fail.

1. Age. Torsion axles, if used properly, can last upwards of 30 years or so.

2. Lack of use. Rubber must be exercised to stay alive. Parking the trailer or the tag axle motorhome home for long periods, is the culprit.

Parking the trailer for long periods of time, can be successful, within reason, but only if you remove the weight from the axles.

Andy