Big Surprise - Broken Frame

[Eagle & Bear]

This is a follow up to a previous post. Our Airstream is a 1976 Ambassador 29’. It was in remarkably good condition when I bought it in 2006. From what I can deduce from the PO, it had less than 30,000 miles on it. I have done a lot of preventative maintenance and do routine checks on this rig. The frame is 5” channel.

We’ve put 40,000 miles on our Airstream in the past several years. After returning from WashingtonDC (approximately 6000 miles) I noticed that the plates that the axles are bolted to have started to warp a bit. I inspected the plates just before we left DC and they were straight.


I have been working on bending the axle mounting plate back so that I can bolt it into place. After pulling the belly pan back I found a crack in the lower horizontal part of the frame. It goes through the 1 1/2 inch lower part if the frame rail and extends about 1/2 inch up the face of the frame.

Can I weld metal reinforcing plates onto the frame and expect a good outcome?

What kind of material should I use and how should it be welded on?

Do I need to put a frame stiffening kit on?

[helmsman]

Hi Eagle & Bear:
While on a WBCCI Western Canada Caravan back in about '87 we pulled into the camping ground in Calvary, Canada (pouring rain) to discover the floor inside was like climbing a steep mountain. The frame had broken. Only one place in Calvary could weld it. I had to remove the aluminum skins, then back it onto two narrow rails over a pit. The welders Vee'd out the break and welded that. Then welded a steel plate over the break (reinforcing). We finished the caravan and have since been to Alaska twice + it's still on the road -- A great little trailer!

[Eagle & Bear]

I am adding two photos of the broken frame. One shows the broken lower rail. The other shows the lower rail and the back of the frame. There are two lines on the back of the frame. The longer line is spatter from the weld below. The shorter line is the crack that extends up the back of the main part of the frame body.

Hmmmm.....I have to figure out how to post a photo on this forum.

[Bettye]

When you learn how to post the photo, let me know! I don't know how to post it so it shows up with my message.

[azflycaster]

Originally Posted by Bettye

When you learn how to post the photo, let me know! I don't know how to post it so it shows up with my message.

Post #7 in this thread should help...
http://www.airforums.com/forums/f138...ics-44928.html

[Eagle & Bear]

Photos of frame.

[Eagle & Bear]

Originally Posted by Bettye

When you learn how to post the photo, let me know! I don't know how to post it so it shows up with my message.

Bettye, see AZflycaster's note above. Posting photos is fairly simple if you follow the directions on the link below.


http://www.airforums.com/forums/f138...ics-44928.html

[Bauxter]

Any rust perforation on the frame? What is the condition of your axles? That break in the short leg of the channel looks like their was a lot of movement.

[Eagle & Bear]

The axles are two years old and are rated at 4000 pounds each. The lower shock hanger is on the other side of the crack.

The axle mounting plate was warped outward about 1/2 inch. I was straightening the mounting plate and getting ready to bolt it to the frame when I discovered the crack.

The tires are new (October 2011 w/about 6000 miles on them). Two of them have over 12 ounces of lead and are still out of balance. The plates were not warped in October but the ends of the crack are rusted enough to lead me to believe that the crack formed some time before.

[Eric H]

Could you post a few more pictures? Some a bit wider?
And for sure a couple of pictures of the warped plate.

From what it looks like to me it may not be a crack due to weight, the odd bend near the crack would suggest some sort of trauma that caused the crack. It looks like some sort of torsion pulled the metal down and broke it. This is what I think due to the fact that the plate that the C channel is attached to is much thicker than the C channel and is supporting it so it would be an unlikely place to see a crack, but I'm certainly not 100% sure.
That would be a good thing, since the worries about the frame being structurally unsound wouldn't apply. But since you mentioned that the plate was warped I'm not sure on this...
The only way I could see this being a break due to something other than trauma is if the trailer was wrenched from side to side and bent sideways causing that metal to crimp in on itself and then break...possible... are there issues on the other side that would match this?

This can certainly be fixed.
I just did a big frame reconstruction and I assume the C channel is the around 1/8th in on yours as well.
It would need to be bent back to butt up against each other and (if it is just a trauma break) I would just butt welded it and call it good (just what I would feel comfortable with IF that was the case).
You could certainly add additional steel if you thought it needed it.

The big question in my mind would be; why is the axle plate warped? Rust can get between the plate and the channel and bulge it out, is that what is happening? If so you'll want to decide how involved you want to get with this issue...I had the same bulging rust issue and opted to cut out the parts of the plate and replace them with new plate.

Here are some pictures of the frame work I just finished.

http://www.airforums.com/forums/f421...e-85368-2.html

[Inland RV Center, In]

Originally Posted by Eagle & Bear

The axles are two years old and are rated at 4000 pounds each. The lower shock hanger is on the other side of the crack.

The axle mounting plate was warped outward about 1/2 inch. I was straightening the mounting plate and getting ready to bolt it to the frame when I discovered the crack.

The tires are new (October 2011 w/about 6000 miles on them). Two of them have over 12 ounces of lead and are still out of balance. The plates were not warped in October but the ends of the crack are rusted enough to lead me to believe that the crack formed some time before.

The biggest problem your Airstream has is that the axles should not be rated at more than 3500 pounds each, for normal RVing.

However, you can load the trailer up with some sand bags to add at least several hundred pounds.

The next problem, is that the running gear "MUST" be properly balanced. If not, then the cracks in the frame and axle mounting plates will continue.

During my time, I have seen hundreds of Airstream and Argosy trailers with the same cracks, and all from the same reasons.

Andy

[Eagle & Bear]

Thanks Andy. When the axles were installed there was a 1/8th inch gap between the piece that the frame is supposed to rest on (foot/shoe/perch/? that is welded to the axle) and the frame. In other words, the axle mount (?) was not in contact with the frame and there were no shims between the axle mount and the frame. What that means is that the entire weight of the coach has been supported by the two thin, vertical pieces of steel (axle mounting plates) that are welded to the face of the frame.

It was obvious to me that the shop that sold me a new set of tires in October did not balance them correctly and may have sold me tires that required almost a pound of weights. Unfortunately they are in Maine and I am now in AZ.

The crack is between the two axles. I do not want to take my rig back on the road in this condition. I can get a welder but need to know how to weld the frame back together so that the repair will hold for many more years.

[Eric H]

Originally Posted by Inland RV Center, In

The biggest problem your Airstream has is that the axles should not be rated at more than 3500 pounds each, for normal RVing.

However, you can load the trailer up with some sand bags to add at least several hundred pounds.

The next problem, is that the running gear "MUST" be properly balanced. If not, then the cracks in the frame and axle mounting plates will continue.

During my time, I have seen hundreds of Airstream and Argosy trailers with the same cracks, and all from the same reasons.

Andy

So just out of curiosity, is this kind of crack due mainly to a weight issue (over for the trailer or under for the axle rating) that stresses the metal enough to crack it with the unbalanced gear, or is it more about the unbalanced gear and it could happen to a properly weighted trailer?

[Lumatic]

I will bet you $1 that a major factor leading to cracking your frame was bad axles.

[Eagle & Bear]

Hi Lumatic, The axles (Henschen/sp?) and shocks are relativly new. We had them installed 2 1/2 years ago. The axles seem to be holding up well - no drop in height. They are rated at 4000 lbs each. The one thing I thought might contribute to the break is that the frame is not sitting directly on the perch that is welded to the axle. All of the weight is on the two bolts that attach the axles to the axle mounting plate. The coach weighs in at 7300 lbs at the axles and around 600 lbs at the hitch.

I drive slowly especially when the roads are rough. Some of the roads have been under construction. Haven't taken the AS to Chaco but we have traveled around 100 - 150 miles over washboard in the past 3 years. We have also towed it through rolling terrain in areas like Quartzite. In the process of taking everything apart this week I found that the tires we bought in October were not balanced correctly.

I am just glad that the crack does not extend any further than what you see in the photos. We are full timing and are spending the winter in Tucson. I found a guy who builds trailers here. He is willing to bring a portable welder over and put things back together. But before he starts to cut and weld I want to know what experience others have had in repairing a crack like this. I am also wondering if I need to put one of the frame reinforcing kits on.

[Inland RV Center, In]

Originally Posted by Eric H

So just out of curiosity, is this kind of crack due mainly to a weight issue (over for the trailer or under for the axle rating) that stresses the metal enough to crack it with the unbalanced gear, or is it more about the unbalanced gear and it could happen to a properly weighted trailer?

Cracks like that are very common to unbalanced running gear, and lastly to bad rubber rods in the axles.

Lightly loaded heavy rated axles could also contribute to frame cracking, but it would take a long time to show up.

Andy

[Jim Foster]

I would wonder how the cracked portion of the frame became bent.
I can understand the crack, but not the bending on each side, especially with the two sides being bent at different angles. I would think that something had to push or pull that metal into that shape. I think what ever caused that bending happened after the crack otherwise, it seems to me, it would be the same on both sides of the crack.

Any ideas?

[Inland RV Center, In]

Originally Posted by Jim Foster

I would wonder how the cracked portion of the frame became bent.
I can understand the crack, but not the bending on each side, especially with the two sides being bent at different angles. I would think that something had to push or pull that metal into that shape. I think what ever caused that bending happened after the crack otherwise, it seems to me, it would be the same on both sides of the crack.

Any ideas?

Jim.

Airstream shells and chassis flex when traveling.

The reason the axle mounting plate flexes is because the frame flexes.

If you look at the backside of the axle mounting plate, you will clearly see that the bending of the axle mounting plate, is between welds, that are way too far apart.

Had the welds been made closer together, that outward bending would never happen.

The cure, for those that have not as yet experienced the problem, is to have the welding added to considerably shorten the distance betwwen the existing welds, in the area of the axle mounting plates, where they attach to the chassis, only.

Andy

[Aage]

Originally Posted by Eagle & Bear

The coach weighs in at 7300 lbs at the axles and around 600 lbs at the hitch.

The dry weight of your trailer is between 4,795 and 4,855 lbs, so at 7,300 lbs you are loading it up pretty heavily.

I wonder if this could have contributed to your cracks. Is the Gross Vehicle weight of your Ambassador stated in any of your documents?

[Eagle & Bear]

Originally Posted by Aage

The dry weight of your trailer is between 4,795 and 4,855 lbs, so at 7,300 lbs you are loading it up pretty heavily.

I wonder if this could have contributed to your cracks. Is the Gross Vehicle weight of your Ambassador stated in any of your documents?

Each axle is rated at 4000 pounds. Hitch weight is around 600 pounds. I cannot imagine what broke the lower rail and how the ends bent the way you see in the photos. Though I do not understand the mechanics behind it, Andy's explanation is consistent with the findings. I will be able to look at the other side of the frame tomorrow. Will keep you posted.