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Old 09-01-2012, 07:21 PM   #57
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Very interesting indeed. How old is the oldest one you have found with 22.5 deg angle? I assume these are all down angles?

Within last 72 hours I have had occasion to look at my single axle utility hauler trailer and without putting my Starrett angle indicator on it it has to be 40 to 45 degree down angle. The place where I ordered mine said I could get the 5200s up to 45 down.

While you are looking could you also do a quick measure of the height of the bottom of the axle cross member to the ground loaded?

But back to the trailer, as it turns out my PTO on my tractor finally died as it has been loose since 93 when I bought the tractor and it is a mid 70s manufacture if I remember correctly. So it is off to the tractor surgeon.

In this same time frame I noticed one of the brake wires was broken about 1" from the backing plate so I gently went in and stripped the wire about 1/2" and same on other piece and twisted them together enough to solder it back together.

I pulled the tractor up on it and as stated above it has a 8000 lb torsion bar axle. The weight of the steel on the trailer frame is estimated at 800+ pounds starting off with 51 feet of 4X4X7/16 angle at 11.3 lbs per foot and various 2" channel cross members and 2" heavy angle rails. Per google the tractor is 3000 lbs so I estimate about 4000 pounds are on the axle so it is loaded at 50% of the axle working capacity.

I pulled it out and ran it about five miles to see how it would ride and whether I have to adjust the chain binders/ratchet strap holding it in place. We live on a tar & gravel road which is by no means as smooth as asphalt and I paid particular attention to the trailer frame movement on the uneven road. In the slight dips the trailer would depress perhaps an inch, recover and if there was a follow on bounce it was just visible in mirrors.

It was completely different watching the tractor as there is water in the rear wheels and only about 25 lbs of air and I could see the tractor going down and up as the rear wheels flexed.

The main thing is the trailer ride was stable on the 10 ply tires and no bouncy bouncy. The trailer does not have shocks.

Elfirebob, they told me I could get the angle anywhere from 45 degrees up to 45 degrees down and per the design engineer he suggested 10 degrees which he figures would put the spindle and axle center about neutral when the weight comes down on the axles leaving 12.5 degrees of travel before the next threshold of 11 degree movement is reached.

Since the rig is sitting on jack stands now when I get axles mounted I will take the Starrett gage and measure the angle of the axle frame and the down angle of the trail arm both with no load and load and give a report. The fresh water tank is still pretty much full and I have a fair amount of tools etc under the couch on front wall.

I think in the future when she goes back to "bed" I will jack it up and sit a jack stand or wood block under the vertical reinforcing plate which is .195" thick on my rig. Of note apparently some one has placed a jack stand ???? between the wheels before as there is a slight deflection of the plate to the inboard side. The bottom of the plate is still straight best I can tell. The more that I think about it I will probably block it with 6X6s and 1X6s when I put her to bed for the winter and take most of the weight off the torsion arms so they won't sit for so long compressed.

First winter with the 10 plys they sat on dry ground and then I read on another thread to pull them onto wood so last winter she had 2X12s to sit on.It rarely goes below 15 here in winters but I have seen it at 7F.

On another note the guy that did the measuring told me the light axles normally have 5 lugs. Next range goes to just below 6000 lb and these have 6 lugs. At 6000 pounds they are 8 lug hubs. Torsion bar axles go to 10,000 lbs GVW rating.
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Old 09-01-2012, 10:22 PM   #58
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Reinforcing the frame where the axle mounts is a sign that the frame isn't strong enough to start with. If reinforced properly, there will be no problems in that area. However, the problems will show up behind, or in front of those reinforcements. It is actually easier, to make the frame stronger, and attach right to the frame. I figure that AS was trying to save weight (and money) but it sure is costing them their reputation.
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.

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Old 09-01-2012, 10:28 PM   #59
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So Andy,
What size axle would you recommend for our 1970 Safari (23') single axle trailer?
No more than 5000 pounds with a 32 to 35 degree down angle.

Andy
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Old 09-01-2012, 10:35 PM   #60
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Hummer,
Online sites show the weight for the '70 Safari Special as 3500#s, about 400 lbs on the hitch. I believe the weight is dry, so add some for full tanks and gear.
You also mention the "start" angle for the unit during manufacture, 10 degrees. Is it possible to start with an increased down angle, say 20 degrees during manufacture?
Leaning toward thinking the lighter capacity with an increased down angle is a better ride, at least for the trailer and it's contents.
Seems like the trend is to just add axle capacity but many times, this leads to a stiffer ride, possibly more damage to already aged components in a 40+ year old Airstream...
Oh, galvinized, why not!
The starting angle on "ALL" Henschen axles from 1961 to at least into the 2000 model years is 22 1/2 degrees.

Since older Airstream's were towed with cars, which were low profile the small degree down angle worked fine.

But today, the vast majority of tow vehicles are trucks, which are high profile.

Accordingly, the starting angle then should also increase, so as to raise the original height of the trailer.

A good starting angle today is 32 to 35 degrees.

45 degrees down angle, according to Henschen, causes to much of a bounce, and shock to the trailer.

Andy
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Old 09-01-2012, 10:44 PM   #61
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axle torsion arm angles.

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
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Old 09-02-2012, 12:54 AM   #62
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Arrow Image from GKN (henschen) manual , tags added

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Old 09-02-2012, 01:27 AM   #63
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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.
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Old 09-02-2012, 01:41 AM   #64
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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.
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Old 09-02-2012, 01:50 AM   #65
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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.
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Old 09-02-2012, 05:33 AM   #66
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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
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Old 09-02-2012, 07:40 AM   #67
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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.
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Old 09-02-2012, 07:52 AM   #68
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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.
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Old 09-02-2012, 07:00 PM   #69
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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.
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Old 09-02-2012, 07:45 PM   #70
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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
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