Axle condition: it ain't just the angle

[Inland RV Center, In]

Hummer.

Most all Airstreams, ever built, that were equipped with torsion axles, had a starting angle of 22 1/2 degrees.

That today, has changed for the replacements.

Starting angles should be increase to 32 to 35 degrees, to help raise the trailer a little more than original because of higher profile tow vehicles.

Your Airstream, came with 3200 pound axles.

Increasing them to 3500 pounds is fine.

Rarely can they be increased to 4000 pounds. for a 31 foot Airstream, except the Excella models.

Going beyond that, will destroy the trailer, due to a very harsh ride.

Andy

[Distantdrummer]

[Distantdrummer]

The 22.5 degree tag is just for discussion purposes as I understand that these "new" GKNs now have greater degree angles. Also I read that the GKNs do not have shock mounts.. In fact do not "need" shocks. What's that all about? I hope Andy will comment on whether when you order new axles for 70's era Airstreams, do you have to jerry rig shock mounts or will GKN add them.

[M2HB]

Originally Posted by Inland RV Center, In

The frame does not need to be strong since the method of construction of an Airstream is semi-monocoque, where-in the strength is in the shell.

The shell, in fact, supports the frame.

Andy

That is correct. The shell is part of the structure. When the shell starts to seperate from the frame, major problems occur. Or when the frame isn't strong enough, it damages the shell. Either way, bad things can happen.

[M2HB]

Some of the adjustable torsion arm axles say that you can go down as far as 45 degrees. The reason for the "harsh" ride is that at 45 degrees down, the torsion arm doesn't have the same leverage. It actually has less leverage, therefore making the ride more "harsh". 22-1/2 to 0 degrees is the best, with 22-1/2 degrees being the best zero weight angle for the torsion arm. With 22-1/2 degees down, when the weight is added the angle will be closer to level and the travel will allow the torsion arm to cross the "level" zero degree angle which has the most leverage at that point. Remember, the leverage is from weight being vertical, not perpendicular to the torsion arm. If the torsion arm is level, or horizontal, then the vertical weight is perpendicular to the torsion arm.

[Inland RV Center, In]

Originally Posted by Distantdrummer

The 22.5 degree tag is just for discussion purposes as I understand that these "new" GKNs now have greater degree angles. Also I read that the GKNs do not have shock mounts.. In fact do not "need" shocks. What's that all about? I hope Andy will comment on whether when you order new axles for 70's era Airstreams, do you have to jerry rig shock mounts or will GKN add them.

Sad to say, but GKN owned Henschen.

Henschen is now a part of history, as GKN closed the plant in Jackson Center.

Dexter refuses to install shock mounts, as they feel shocks are not necessary.

However, they are putting shock mounts on axles shipped to Airstream for current production.

Airstream feels that shocks, INDEED, are required since they dampen the trailer bouncing when hitting bumps.

Take the shocks off your tow vehicle, and then drive, over a few bumps. You will quickly learn the necessity for shocks on the trailer.

When an Airstream trailer bounces, the shell flexes, which in turn, can cause many failures to the shell, chassis and many other components. The useage of shocks, minimizes the bouncing, or vertical movement, which then eliminates those damages.

But, Dexter will not install shocks on after market replacement axles.

Accordingly, we have them made and supply them with every axle order, at no charge.

Test riding in an Airstream or Argosy trailer equipped with torsion axles, will easily confirm the need for shocks.

Test ride in it over a bumpy road without and then with shocks, and you will be amazed at the difference in the ride.

I don't feel that Airstream installs shock, "just because", since they have been doing it since 61 years.

There is in fact, a difference in trailer towing performance.

Andy

[Hummer]

Andy, thanks much for that info. I figured sooner or later someone would have the straight poop from AS.

I was thinking AS must have increased the angle as you point out AS and all other campers newly made ride high due to increased vehicle height. I had already bought a extra low mounting arm to level the trailer with the truck.

Based on all axles starting at 22.5 that means my axles have already sagged 22.5 with no load as it is neutral now with no load on it and now has almost nothing left but very harsh ride which explains why my bunk overhead was torn from the bulkhead on one end.

I guess the good news is I cannot detect any sag in back end.

Thusly with the load on it and axles at neutral when it was loaded it was really sinking giving a ride that was extremely harsh.

Based on the statement to me that after 22.5 rotation the next level of 11 deg travel is where me and most likely many others are at now.

I now have had three MEs tell me they can't understand why with rigs that heavy they only speced 3200 axles.

[overlander63]

Originally Posted by Hummer

I now have had three MEs tell me they can't understand why with rigs that heavy they only speced 3200 axles.

The reason is old-school Detroit. A car would be engineered with under-size suspension components to give a softer ride. Ralph Nader took the auto makers to task for this, and eventually the practice stopped. Now we have higher-capacity tires, variable rate springs, and double action shocks to smooth the ride, rather than overloading the suspension.

[Hummer]

That makes perfect sense and there was probably cents involved as well and thus belt and suspenders engineering was not considered. Nader definitely did some good things though lots of the industry cursed him.

Had a long conversation today with a owner of a large tractor repair shop and he does lots of work on horse trailers as well and he says he sees the same thing in high dollar horse trailers all the time with axles that are at their high end before a load is ever placed on them.

Also have a friend who runs a RV dealership and repair and he does not touch AS. We were talking at his shop and when he told me he did not do AS work I asked why not and he said simple and pointing out the window he said, "Do you see all those new trailers out there on the lot?" I indicated I did and he said something amazing. "There won't be a one of them still on the road in 10 years." Bottom line is you sell more trailers if they drop dead and they make more money.

I also know a guy who was a diesel engine design engineer for one of the major makers and he told me to never buy anything with a engine they made as they were ordered to design stuff as cheap as possible.

He also told me if he was buying a vehicle it would have a Cummins or Detroit Diesel in it and nothing else.

I worked with another ME who told me he interviewed with a major car manufacturer when he got out of school and one of the interviewers told him they wanted the product to last just beyond the warranty. He turned down their offer. Another manufacturer told him they wanted him to design quick and dirty fixes for problems that arose once the vehicle was sold. He turned it down as well.

Also interesting in that shocks were not felt to be needed and that was going to happen if it rode bad. I was going to keep the axles and grind off the shock plates and store them away if needed.

As soon as I get it going I plan on riding about 30 miles on back roads (tar and gravel) around me and then take a quick overnight or weekend trip down to Charleston and back and see how it did on the road.

The tractor guy also gave me another good hint which is to get a IR Laser thermometer and every time you stop check tire and hub temps. He uses it all the time diagnosing engine problems in his tractor work. He said just today they were coming in and his tires were running about 118F and a guy with him had a tire running like 146F and he told him something was wrong and guy paid no attention to his warning. He said the tire completely failed within a hundred miles. He found out the guy was running them 20 lbs under recommended temp for softer ride. So one of them is now on my list. I know the power company energy saving guys use them to evaluate houses for heat loss areas in winter so there are plenty of uses.

[Inland RV Center, In]

Originally Posted by Hummer

Andy, thanks much for that info. I figured sooner or later someone would have the straight poop from AS.

I was thinking AS must have increased the angle as you point out AS and all other campers newly made ride high due to increased vehicle height. I had already bought a extra low mounting arm to level the trailer with the truck.

Based on all axles starting at 22.5 that means my axles have already sagged 22.5 with no load as it is neutral now with no load on it and now has almost nothing left but very harsh ride which explains why my bunk overhead was torn from the bulkhead on one end.

I guess the good news is I cannot detect any sag in back end.

Thusly with the load on it and axles at neutral when it was loaded it was really sinking giving a ride that was extremely harsh.

Based on the statement to me that after 22.5 rotation the next level of 11 deg travel is where me and most likely many others are at now.

I now have had three MEs tell me they can't understand why with rigs that heavy they only speced 3200 axles.

I have no idea how the axle ratings were dictated, except by Airstream engineers.

I have the axle rating specs starting with the foirst year that Airstream used them, which was 1961.

It's interesting to note, how the ratings were increased for the same exact models, over time, due to the improvement in the ride.

A overloaded torsion axle, simple bottoms out, again, not good.

According to these specs, Airstream has never installed a torsion axle on any tandem axle trailers, except single axles models, having a rating of more than 5000 pounds.

We automatically increase replacement axle ratings, within limits, as approved by Henschen, many years ago.

As an example the common 3200 pound ratings are increased to 3500 pounds, but can go to 4000 pounds as Airstream did with the Excella models, in the 70's.

However, unless the trailer will always be heavily loaded, we do not recommend going to the 4000 pound rating for the older 27, 29 and 31 foot models.

High rated torsion axles, lightly loaded, will cause a rough ride for the trailer, resulting in damages caused by a rough ride. Not good.

Increasing the starting angle, makes hookup much easier, as well as easier access to slanted driveways as well as most fuel stations.

Andy

[elfirebob]

Originally Posted by Inland RV Center, In

No more than 5000 pounds with a 32 to 35 degree down angle.

Andy

Thanks,
So a new 4,000 lb axle with 32 degree start down angle should provide a safe ride and keep our 40+ year old trailer from getting beat up...makes sense.
Great axle thread, ya'll.

[Inland RV Center, In]

Originally Posted by elfirebob

Thanks,
So a new 4,000 lb axle with 32 degree start down angle should provide a safe ride and keep our 40+ year old trailer from getting beat up...makes sense.
Great axle thread, ya'll.

The single axle 23 foot model started out with a 4000 pound axle rating, then changed to 4500 pounds and finally to 5000 pounds, depending on the year.

I will post those years once I get back to my office.

Andy

[Shacksman]

I did some repairs on a 2002 CCD Airstream and it came from the factory with Dexter axles and no shocks. Were the engineers asleep for that model?

[Inland RV Center, In]

Originally Posted by Shacksman

I did some repairs on a 2002 CCD Airstream and it came from the factory with Dexter axles and no shocks. Were the engineers asleep for that model?

Dexter engineers pushed for the "no" shock deal.

Finally, Airstream won the battle.

But, Dexter still refuses to put shock brackets on replacement axles.

That's why we have them made to the original specs.

There is some work in the mill, within Dexter, that we are aware of, to get that changed, even though at the moment it's in a very slow pace.

Andy

[M2HB]

Andy, do you have pictures of the brackets that you have made to convert the Dexter axles to use shocks?

[Inland RV Center, In]

Originally Posted by M2HB

Andy, do you have pictures of the brackets that you have made to convert the Dexter axles to use shocks?

I will post a picture later today, after I get to my office.

Andy

[Inland RV Center, In]

Originally Posted by M2HB

Andy, do you have pictures of the brackets that you have made to convert the Dexter axles to use shocks?

Photo's of shock brackets that we have made, for the Dexter axles.

They are the same as used by Henschen.

The steel plate is 1/4 inch thick.

The edge to be welded to the torsion arm, is 4 inches long.

The studs are from the Airstream supplier.

Andy 13.4

[M2HB]

Andy, thanks for the picture. It appears that when welded on it is perpendicular to the torsion arm so that it rotates toward to front (when the torsion arm moves upward) so that it can use a horizontal shock.

For those axles that don't have a shock mount, it seems that one could be fabricated to attach to the four backing plate bolts, so that no weld would be required on the torsion arm. Having it attached to the torsion arm would be better, but I would be concerned about any warping caused from the weld. It is such a massive piece of steel that I don't think it would be much, but I wouldn't want a warranty voided, or any issues with such an important piece.

[Inland RV Center, In]

Originally Posted by M2HB

Andy, thanks for the picture. It appears that when welded on it is perpendicular to the torsion arm so that it rotates toward to front (when the torsion arm moves upward) so that it can use a horizontal shock.

For those axles that don't have a shock mount, it seems that one could be fabricated to attach to the four backing plate bolts, so that no weld would be required on the torsion arm. Having it attached to the torsion arm would be better, but I would be concerned about any warping caused from the weld. It is such a massive piece of steel that I don't think it would be much, but I wouldn't want a warranty voided, or any issues with such an important piece.

Reasonable welding will not hurt the rubber rods.

Henschen installed the shock brackets after the axles were assebled for years.

Never caused an issue.

Andy

[Hummer]

As Andy points out the axles got heavier with experience which is he logical progression and follows the way many things are done in several fields. I was in small arms engineering and the weapons testing and evaluation field and the M16 has had over 500 "improvements" added to it 45 years and testing is underway at this time for a dozen more.

I suspect as someone pointed out they were pulled with passenger cars and weight was the enemy. Now with most folks using light trucks/SUVs with more capacity they were changed to make the interface.

The single axles at 5000 lbs is very interesting indeed.