Free 7 Day Trial RV GPS App RV Trip Planner Campground Reviews RV Maintenance Free 7 Day Trial ×
 


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-28-2011, 07:59 AM   #1
Aluminum Falcon Mechanic
 
Darkspeed's Avatar
 
1972 31' Sovereign
Wesley chapel , Florida
Join Date: May 2011
Posts: 1,169
Images: 6
Bad frame design?

Having started doing the drawings for a new frame using the existing frame for a point of reference, and including the aluminum monocoque for strength.... Errrr it looks like the original frame was about 20% under engineered.

Is this correct?
Darkspeed is offline   Reply With Quote
Old 05-28-2011, 08:19 AM   #2
Rivet Master
 
r carl's Avatar
 
Vintage Kin Owner
Lin , Ne
Join Date: Dec 2009
Posts: 2,430
I would say by more than that.
r carl is offline   Reply With Quote
Old 05-28-2011, 08:37 AM   #3
Site Team

 
, Minnesota
Join Date: Aug 2003
Posts: 7,636
Images: 59
That sounds about right. Care to show your work?

What is the frame? Nothing more than a place to mount the floor and a convenient attachment point for the wheels.
markdoane is offline   Reply With Quote
Old 05-28-2011, 08:52 AM   #4
Aluminum Falcon Mechanic
 
Darkspeed's Avatar
 
1972 31' Sovereign
Wesley chapel , Florida
Join Date: May 2011
Posts: 1,169
Images: 6
If I went with a taller frame rail could I order axles with a lower -Deg to keep the wheels in the wheel well.

I'm thinking a talker major frame rail and possibly using boxed structural tube. Then new outriggers on that.
Darkspeed is offline   Reply With Quote
Old 05-28-2011, 09:15 AM   #5
Rivet Master
 
DanielB's Avatar
 
1974 31' Excella 500
Charleston , South Carolina
Join Date: Nov 2010
Posts: 1,073
Blog Entries: 8
When I did mine I took the path of least resistance.

I don't know about the boxed tube, but I went with the C5x6.7 (5 inch C channel 6.7 lbs per foot). It is standard stuff and any metal distributor will sell it.
Around here it comes in 20 and 40 foot lengths.

I used it for everything.. mail rails, cross members, and outriggers.
Total steel there was 2000 lbs if I remember correctly, and didn't include the tongue A frame thing which was reused from the old trailer.
Attached Thumbnails
Click image for larger version

Name:	Photo 38.jpg
Views:	134
Size:	80.0 KB
ID:	130884   Click image for larger version

Name:	Photo 41.jpg
Views:	132
Size:	90.0 KB
ID:	130885  

Click image for larger version

Name:	Photo 43.jpg
Views:	122
Size:	124.7 KB
ID:	130886   Click image for larger version

Name:	Photo 44.jpg
Views:	117
Size:	122.6 KB
ID:	130887  

__________________
As I grow older, I pay less attention to what men say. I just watch what they do.
- Andrew Carnegie
DanielB is offline   Reply With Quote
Old 05-28-2011, 09:51 AM   #6
Moderator
 
eubank's Avatar

 
Airstream - Other
2016 Interstate Grand Tour Ext
Bosque Farms , New Mexico
Join Date: Jan 2004
Posts: 6,784
I don't know if it's really fair to speak of a "bad" frame design for this rig. After all, we are talking about a frame that has survived nearly forty years of jostling; that alone speaks in favor of the original design. (I'm speaking here as an RV park owner who has witnessed a sufficient number of of relatively new white-sided rigs whose long-term survivability is already in doubt.)


Lynn
__________________
WBCCI 21043
eubank is offline   Reply With Quote
Old 05-28-2011, 10:02 AM   #7
Restorations done right
Commercial Member
 
Frank's Trailer Works's Avatar
 
1962 26' Overlander
1961 26' Overlander
Vintage Kin Owner
Currently Looking...
Baltimore , Maryland
Join Date: Aug 2007
Posts: 5,545
Images: 2
The only thing bad about the design is peoples continuing desire to change it. It was designed to work with all the elements, not the strong desire to over engineer things. Leave it alone, copy it, but do not "box it in" or "beef it up" as your manly instincts are telling you to.
Frank's Trailer Works is offline   Reply With Quote
Old 05-28-2011, 12:07 PM   #8
Rivet Master
 
overlander63's Avatar
 
1993 21' Sovereign
Colfax , North Carolina
Join Date: Jun 2003
Posts: 21,252
If you feel you really have to make it stronger/tougher/heavier, you can use 5" box channel, rather than the 5" C channel it was built with. That's what Airstream did in the mid 1980's. I'd leave everything else pretty much as it is.
__________________
Terry
overlander63 is offline   Reply With Quote
Old 05-28-2011, 05:32 PM   #9
Rivet Master
 
DanielB's Avatar
 
1974 31' Excella 500
Charleston , South Carolina
Join Date: Nov 2010
Posts: 1,073
Blog Entries: 8
Where could one find the wafer thin C channel that they made the chassis out of? The stuff that collapses like tissue paper when it gets rusty.

I think that it is pretty obvious that there were.. let's not say bad, but engineering design decisions that seem not so good.

Here are a couple that I have run across personally.
1) Side underbelly wrap overlapping shell. (water travels down, not up)
2) Plywood floor at doorway breaks between outriggers and there is no support under the break or under the edge (under the door). Really? Really.
__________________
As I grow older, I pay less attention to what men say. I just watch what they do.
- Andrew Carnegie
DanielB is offline   Reply With Quote
Old 05-29-2011, 06:54 AM   #10
Restorations done right
Commercial Member
 
Frank's Trailer Works's Avatar
 
1962 26' Overlander
1961 26' Overlander
Vintage Kin Owner
Currently Looking...
Baltimore , Maryland
Join Date: Aug 2007
Posts: 5,545
Images: 2
if you design a skyscraper using steel that is too rigid, the first good wind and it will snap right off. Engineers take these things into account. Just because it is thicker, does not make it stronger. The frame of an airstream is designed to flex and curve with the road. The typical male thought is the steel needs to be thicker and stronger. That is why many of us are not engineers, we follow instincts that are wrong.
DanielB, permission to speak freely? 1974 was a pretty dank year for just about everything built from houses to cars and everything in between. The issues you state are very common of your era. The ability of the steel to withstand oxidation has nothing to do with engineering, it has to do with a food company not wanting to spend for the good steel alloy. Hey, it was the 70's, that was when everything became disposable, even Airstreams.
Frank's Trailer Works is offline   Reply With Quote
Old 05-29-2011, 07:19 AM   #11
Rivet Master
 
overlander63's Avatar
 
1993 21' Sovereign
Colfax , North Carolina
Join Date: Jun 2003
Posts: 21,252
Quote:
Originally Posted by 62overlander View Post
1974 was a pretty dank year for just about everything built from houses to cars and everything in between. The issues you state are very common of your era. The ability of the steel to withstand oxidation has nothing to do with engineering,...
I remember having several of Ford's "biodegradable trucks" in that time. When I went to get in one every morning, I'd do a walk-around to make sure nothing vital had fallen off overnight from rust. Of course, the bright side of that is I learned how to apply Bondo...
__________________
Terry
overlander63 is offline   Reply With Quote
Old 05-29-2011, 07:59 AM   #12
Aluminum Falcon Mechanic
 
Darkspeed's Avatar
 
1972 31' Sovereign
Wesley chapel , Florida
Join Date: May 2011
Posts: 1,169
Images: 6
Quote:
Originally Posted by 62overlander
The typical male thought is the steel needs to be thicker and stronger. That is why many of us are not engineers, we follow instincts that are wrong.
I looked for the testosterone multiplier function when doing the finite element analysis, but was unable to find it.

I agree, build to safely suit the need within a given structure lifespan, but not allowing any safety margin for structural degradation from rust, stress, etc , and then rolling parts out of 70's chepo steel is not a blueprint for total success.

Modern A36 or A500 structural rectangular tube is flexible enough although it will have less ability to twist and fold on it's weak axis.

I was in no way putting airstream down with the title of this post. What was acceptable practice then is not always acceptable now, so when I put her back together she will have a better chance of outliving me
Darkspeed is offline   Reply With Quote
Old 05-29-2011, 09:20 AM   #13
Rivet Master
 
DanielB's Avatar
 
1974 31' Excella 500
Charleston , South Carolina
Join Date: Nov 2010
Posts: 1,073
Blog Entries: 8
Quote:
Originally Posted by 62overlander View Post
DanielB, permission to speak freely? 1974 was a pretty dank year for just about everything built from houses to cars and everything in between. The issues you state are very common of your era. The ability of the steel to withstand oxidation has nothing to do with engineering, it has to do with a food company not wanting to spend for the good steel alloy. Hey, it was the 70's, that was when everything became disposable, even Airstreams.
It all good. The point is that Airstream engineering is not perfect.
I chose C5x6.7 because it was the best choice that I could reasonably make. I posted many times trying to get information on what to use for the chassis and the only thing that was actually helpful was a guy that told me about C56.7 and C5x9 steel.

Instead of "don't do this and don't do that", how about "do this.."

Use this steel.. you can find it here.. this is good because..
That would be positive and helpful.
__________________
As I grow older, I pay less attention to what men say. I just watch what they do.
- Andrew Carnegie
DanielB is offline   Reply With Quote
Old 05-29-2011, 09:22 AM   #14
Aluminum Falcon Mechanic
 
Darkspeed's Avatar
 
1972 31' Sovereign
Wesley chapel , Florida
Join Date: May 2011
Posts: 1,169
Images: 6
You did good! C5 6.7lb is the default structural material for trailers in your weight range

BYW... anyone who is doing anything in tube frame this is a really good product

http://www.eastwood.com/internal-fra...ay-nozzle.html
Darkspeed is offline   Reply With Quote
Old 05-29-2011, 11:52 AM   #15
steel/aluminum fabricator
 
2004 22' International CCD
Penticton , British Columbia
Join Date: Oct 2010
Posts: 132
The only thing i would change in the frame design are the actual frame rails. I would use box tube . I hate c channel because its a wet noodle,it has very little structure. You weld to c channel and the web is already compromised. Box tube is alot easier to fabricate as all sides of tube are flat. Easy to weld to. Better, stonger, faster.Everything else i would use c channel. Thats just me though.
zedex is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Tube Frame Debate crzycpa Repairing/Replacing Floor &/or Frame 9 07-05-2011 09:34 PM
'69 Overlander frame repair colin57 Repairing/Replacing Floor &/or Frame 6 04-25-2011 10:45 AM
frame reinforcement - rear end separation silversafari Repairing/Replacing Floor &/or Frame 1 03-17-2011 10:16 AM
1965 Caravel Frame funhouse 1956 - 1965 Caravel 0 03-01-2011 09:12 AM
The frame is ok ~ Patching the floor. LawChick Repairing/Replacing Floor &/or Frame 12 01-30-2011 02:39 PM


Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by the Airstream, Inc. or any of its affiliates. Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.



All times are GMT -6. The time now is 07:03 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.