Axle condition: it ain't just the angle

[Inland RV Center, In]

Originally Posted by Ducatiman

These two pics from the factory are the best explanation I've seen showing how the "rubber meets the road" in a torsion axle. Not much of an angle seen on these particular fresh from the factory axles....

Those photo's were taken by me, at the Henschen plant that was in Jackson Center.

Note that the shock brackets are still not attached at least at that part of the production.

Andy

[overlander63]

Originally Posted by Greg@AirLA

You mean like this?

Was that axle from that 1969 Overlander we replaced the axles on? The one where the axles disassembled themselves spontaneously?

[Greg@AirLA]

A 1966 from Colorado, though that was the second one that happened on.
Greg

[Hummer]

This is a great thread now for some more questions:

It seems by looking at newer Airstreams I have pass me that they have more ground clearance which seems to jive since the height of pick up trucks went up X number of years ago. Or is this my imagination?

I had to buy a extra long hitch adaptor because the 76 Sovereign was low. The truck/Airstream are all nice and level. The mount is in the lowest position and I am constantly dragging the hitch.

Just went out and measured. With the truck on level ground, no load on it the bottom of the Reese hitch is only 8" above the ground and the top of the hitch ball is 17 3/4". Then when the trailer weight is added the truck goes down until the equalizers are hooked up.

Should I run over something in the road larger than a snake (or politician) the hitch is gonna get it for sure.

Secondly I just checked with a outfit and they can provide me with a 5200 lb axle assembly. What happens if I replace the factory 3200 lb axles with 5200 lb axles of the same external dimensions? It would seem the ride would have to be better.

With the weight off the factory axles they leveled out at zero best my Starrett machinest level can tell me and it took quite a bit of frame rise to get the tires to clear the shop floor. I am running 10 ply light truck tires on 16 " rims.Best move I have made yet on running gear. Now 18 wheelers have no effect on me when passing.

At first I tried to lift trailer with a 6 ton hydraulic bottle jack placed on the vertical piece to the rear of aft tire and there wasn't enough rise (about 4.5") to clear the tires so I took it to my buddies shop and we now have it with all four off the floor sitting on 10 ton jack stands.

I can purchase the 5200 lb axle with neutral or 22 1/2 deg down angle.

I did not think to look at axle angle prior to jacking it up as my attention was on replacing backing plates and drums but my recollection is the trail arms were slightly elevated which seems to fit since it took a lot of jacking before the tires cleared the floor.

Would there be any benefit to raising the ride of the trailer besides cutting down on rear drag coming out of some drive ways?

I also note it has Gabriel of Canada shocks 6156076 part number. Is this a good number.

Also the data plate says axle was made in 1970 at Henschen but trailer wasn't made till 5/76 so the rubber in my axles is 42 years old ! ! ! !

With two 3200 lb axles it seems the axles are at the max load when trailer is on the road and there is nothing "extra" left when bad dips are hit.

I had a F250 (7800 lb GVW) and I hit a very bad hole on Pennsylvania turnpike and it bottomed out on the blocks and I believe the 7800 GVW (ordered it that way) was what saved it from or worse condition as factory standard was down in 5600lb range GVW.As it was I sunk down under the steering wheel and if it had not been for seat belt probably wouldn't have stayed there. When I stopped I looked at the rubber blocks and they had been hit (all four).

Later I loaded gravel on it and we weighed in and weighed out of yard and I was 3415 lbs heavier coming out and truck still had about 2" to go to hitting the blocks.

[overlander63]

Originally Posted by Greg@AirLA

A 1966 from Colorado, though that was the second one that happened on.
Greg

I know of mine on our '74, the '69, and this one.
There may be enough to warrant a thread about how to tell if your axle is ready to fall apart.

[M2HB]

Originally Posted by Hummer

This is a great thread now for some more questions:

It seems by looking at newer Airstreams I have pass me that they have more ground clearance which seems to jive since the height of pick up trucks went up X number of years ago. Or is this my imagination?

I had to buy a extra long hitch adaptor because the 76 Sovereign was low. The truck/Airstream are all nice and level. The mount is in the lowest position and I am constantly dragging the hitch.

Just went out and measured. With the truck on level ground, no load on it the bottom of the Reese hitch is only 8" above the ground and the top of the hitch ball is 17 3/4". Then when the trailer weight is added the truck goes down until the equalizers are hooked up.

Should I run over something in the road larger than a snake (or politician) the hitch is gonna get it for sure.

Secondly I just checked with a outfit and they can provide me with a 5200 lb axle assembly. What happens if I replace the factory 3200 lb axles with 5200 lb axles of the same external dimensions? It would seem the ride would have to be better.

With the weight off the factory axles they leveled out at zero best my Starrett machinest level can tell me and it took quite a bit of frame rise to get the tires to clear the shop floor. I am running 10 ply light truck tires on 16 " rims.Best move I have made yet on running gear. Now 18 wheelers have no effect on me when passing.

At first I tried to lift trailer with a 6 ton hydraulic bottle jack placed on the vertical piece to the rear of aft tire and there wasn't enough rise (about 4.5") to clear the tires so I took it to my buddies shop and we now have it with all four off the floor sitting on 10 ton jack stands.

I can purchase the 5200 lb axle with neutral or 22 1/2 deg down angle.

I did not think to look at axle angle prior to jacking it up as my attention was on replacing backing plates and drums but my recollection is the trail arms were slightly elevated which seems to fit since it took a lot of jacking before the tires cleared the floor.

Would there be any benefit to raising the ride of the trailer besides cutting down on rear drag coming out of some drive ways?

I also note it has Gabriel of Canada shocks 6156076 part number. Is this a good number.

Also the data plate says axle was made in 1970 at Henschen but trailer wasn't made till 5/76 so the rubber in my axles is 42 years old ! ! ! !

With two 3200 lb axles it seems the axles are at the max load when trailer is on the road and there is nothing "extra" left when bad dips are hit.

I had a F250 (7800 lb GVW) and I hit a very bad hole on Pennsylvania turnpike and it bottomed out on the blocks and I believe the 7800 GVW (ordered it that way) was what saved it from or worse condition as factory standard was down in 5600lb range GVW.As it was I sunk down under the steering wheel and if it had not been for seat belt probably wouldn't have stayed there. When I stopped I looked at the rubber blocks and they had been hit (all four).

Later I loaded gravel on it and we weighed in and weighed out of yard and I was 3415 lbs heavier coming out and truck still had about 2" to go to hitting the blocks.

I don't think that the AS frame is strong enough to take a 5200# set of axles. They break with the factory axles. When you increase the weight rating that much, the trailer is going to have a harsher ride, and with the weak frame, I'll bet that some serious damage will occur faster than it would have with the proper axles.

There are some axle manufacturers that make axles that can be adjusted for the angle of the torsion arm.

[Hummer]

I agree with the weak frames but think of it this way. With the factory axles preloaded to perhaps 90+% of capacity when a big bump is experienced the axles only flex so far and then become solid when they reach maximum deflection and that solid stopping force has got to be much worse on a weak frame that an axle that never bottoms out.

This could be the reason of the multiple axle separations talked about above.

It would seem logical that over time the rubber has to have a physical change and either get softer or harder.

I have a heavy duty utility trailer and empty it tends to bounce around, (torsion bar with a down angle 8000 lb axle, 8 lug, 10 ply tires)but the more it is loaded the smoother it gets.

I have had a Jeep on it and a tractor which weighs about 4000 lbs and the ride is quite smooth.

Originally it had mobil home axles on it and Route 22 in PA ripped the shackles apart and it sat down on the frame. I went back with tool steel shackles and no more problems till one took out a set of bearings on our move here from Alabama. I had made 9 trips heavily loaded and on first eight trips I always felt the hubs when we stopped and no heat. On the 9th it was smoking when I noticed it.

It was getting harder to find wheels/tires so I decided to get a pair of 3500 lb axles for it that used Ford pickup rims and was at the place guying them and spotted the 8 lub axle. They had been ordered with a positive down angle and buyer wanted negative so they were stuck with them an they gave me a great price so I got it and mounted it to their instructions and it couldn't pull any truer. It handles like a utility trailer but I have never had a load on it that really impressed it.

Just spotted this doing research on google.

http://www.ehow.com/info_8768763_rub...axle-work.html

Check out the cons on the rubber torsion bar suspensions.

[Inland RV Center, In]

Originally Posted by Hummer

I agree with the weak frames but think of it this way. With the factory axles preloaded to perhaps 90+% of capacity when a big bump is experienced the axles only flex so far and then become solid when they reach maximum deflection and that solid stopping force has got to be much worse on a weak frame that an axle that never bottoms out.

This could be the reason of the multiple axle separations talked about above.

It would seem logical that over time the rubber has to have a physical change and either get softer or harder.

I have a heavy duty utility trailer and empty it tends to bounce around, (torsion bar with a down angle 8000 lb axle, 8 lug, 10 ply tires)but the more it is loaded the smoother it gets.

I have had a Jeep on it and a tractor which weighs about 4000 lbs and the ride is quite smooth.

Originally it had mobil home axles on it and Route 22 in PA ripped the shackles apart and it sat down on the frame. I went back with tool steel shackles and no more problems till one took out a set of bearings on our move here from Alabama. I had made 9 trips heavily loaded and on first eight trips I always felt the hubs when we stopped and no heat. On the 9th it was smoking when I noticed it.

It was getting harder to find wheels/tires so I decided to get a pair of 3500 lb axles for it that used Ford pickup rims and was at the place guying them and spotted the 8 lub axle. They had been ordered with a positive down angle and buyer wanted negative so they were stuck with them an they gave me a great price so I got it and mounted it to their instructions and it couldn't pull any truer. It handles like a utility trailer but I have never had a load on it that really impressed it.

Just spotted this doing research on google.

How Does a Rubber Torsion Axle Work? | eHow.com

Check out the cons on the rubber torsion bar suspensions.

Part of his comment is not true at least for Airstreams.

He says the one foot attachment of the axle, to the frame, makes it very tough on the frame.

But Airstream does not mount the axke to the frame, but they do mount it to an axle mounting plate, which in turn, is mounted to the frame.

That method of axle attachment further distributes the forces imposed on the frame, from one foot as he states to several feet.

That in turn, permits the useage of a somewhat "weaker frame', if you wish.

Andy

[M2HB]

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.

[Hummer]

Andy is quite right there is a vertical reinforcing plate perhaps five feet long and .195" thick the torsion axle is bolted to (on my 76 Sovereign). I can't see up above it but would assume it enclosed the C beam to box it which would be quite strong. The axles are quite easy to remove by the way. Once the rig is on jack stands two guys should be able to remove both axles in about ten minutes.

Did some more research today and talked with a torsion bar design engineer and he imparted some very interesting information in about a twenty minute conversation.

He told me when a load is imparted that is equal to the torsion bar axle specification the axle spindle rotates 22 1/2 deg and stops. In short if you have two 3200 lb axles and apply 6400 pounds of weight the trail arms will move that much and hold it.

I imparted to him my experience on the PA Turnpike and Rte 22 and then things really got interesting. Next comes the most interesting part, say you hit a big depression in the road and the dynamic load increases by 6400 pounds the axles will only move 11 degrees if they have already deflected 22.5 deg. If it is really bad the third rotation segment is only 5 degrees and things really get hard as movement is coming to something resembling a block.


In short the more it is rotated the stiffer it gets.

I told him the weight of the Airstream worst case loaded out and asked him what he would do and he said he would order 5200 lb axles with a 10 degree download. He went on to explain the axles would bring the load into the neutral range(which is spindle is even with axle as pictured above) and still have 12.5 degrees of movement in reserve before the next 11 degree area is entered. Thus giving lots of vertical travel reserve.

I bounced this off another ME buddy and he agreed with those figures and couldn't understand why mine only had 3200 lb axles for a trailer that heavy. He went on to say he would personally not load a axle over 66% of its capacity for normal operation as he would want a reserve.

Finally he said such axles should last for decades if not overstressed.

Of note is my utility trailer with 8 lug 8000lb axle upwards of a 4000 lb load. One might surmise that there would be a bounce condition. It has a 22.5 deg down angle and the trailer only tends to bounce with less than 500 lbs on it. When it has the above load on it the ride is quite nice in the towing vehicle be it my Durango or 2500HD. This trailer does not have shocks and the axle is bolted directly to the 4" heavy wall angle and tows very well. I run 10 ply Transport 110s on it with two piece rims as they were left over from my F250 days and the rubber is good so I am running them till they drop. Best I can recollect the tires are now 20 years old ! ! ! ! I had the truck from Nov 75 till about 28 months ago.

[elfirebob]

So Andy,
What size axle would you recommend for our 1970 Safari (23') single axle trailer?

[HiHoAgRV]

Let's not wander too far off from the original post...axle angles!

[elfirebob]

Hi Ho, this is about axle angles.
Terry's thread is spot on, angles don't tell the whole picture. When you replace a worn axle, you ask for advice from experts and as the thread adds, the capacity of the axles is critical along with the weight/use of the unit.
Many folks that purchase older used Airstreams share their new purchase with those on the forum, and get great advice on how to inspect worn components, great stuff.

[Hummer]

For info purposes would the original poster get us pics of newer Airstreams with no tire on them with axle in relaxed position? Even better if you have a angle indicator that would be neat information to have. I am interested to see just how much down angle they had/have as new.

I drove over to the axle distribution facility today and had them measure the Airstream Axle so they could dupe it exactly except heavier and less the shock mount. Must have been 400 axles outside and best I could tell they had about a 4000 ft warehouse that was full. Some of them were even galvanized.

If money had been no object I might have had them galvanize it ! ! ! ! !

As soon as he saw my axle in the truck he said it looked like it used to be a 10 degree down and it sure isn't now. As indicated by my Starrett Machinists angle indicator it is now neutral with absolutely nothing on it.

He got to looking at data plate about who made it and the weight and he commented he thought it was too light for a rig that heavy and I agreed. He said there was a massive Airstream bone yard nearby on I-95 and that the owner did custom rebuilds on them and got big bucks for them. He said there must be a hundred rigs on his yard and most of them are older.

I also asked him about the higher camper trailers and what came first, higher towing vehicles or higher campers and he didn't know what the rationale was for them.

Does anyone know? Inquiring minds want to know.

Elfirebob, for info purposes how much does your data plate say your rig weighs? Can you get to the data plate and read what it is rated for?

[elfirebob]

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!

[overlander63]

Starting angle before installation on the trailer is 22.5 degrees, except for the Sport models indicated above. I'm still looking to see if any other trailers have deviations from that angle when new, so far I haven't found any others. I do know the quickest way to find out if any are different is to make a blanket statement saying something like "They ALL are like that".

Higher starting angle will allow the trailing arm to have more of an angle when loaded, as well as give you the feeling you actually made an improvement when the trailer sits higher.

[Hummer]

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.

[Inland RV Center, In]

Originally Posted by M2HB

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.

Andy

[Inland RV Center, In]

Originally Posted by elfirebob

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

[Inland RV Center, In]

Originally Posted by elfirebob

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