Reply
 
Thread Tools Search this Thread Display Modes
 
Old 11-21-2005, 08:08 PM   #1
Rivet Master
 
JimGolden's Avatar
 
Vintage Kin Owner
1977 31' Excella 500
Berkeley Springs , West Virginia
Join Date: Sep 2005
Posts: 1,619
Images: 7
Frame Rail Sectional Dimensions

Hi Everyone.

Does anybody happen to know the actual measurements of the frame dimensions of the 70's Airstreams? By this, I mean, what are the dimensions of the channel section of the main frame?

My '77 Excella has the 4" deep frame. But, what is the flange width and what is the thickness of the section?

For you engineer types, I want to calculate the moment of inertia of the frame. So I need the web thickness, the flange thickness, and the flange width. I know the height of the rail is 4". I just need the other dimensions.

I do know that the axle mounting plate is 0.190" thick on my trailer. I figure that was 3/16" plate (should be 0.1875) and the variance is due to tolerances. I mic'd it with a digital caliper. But, I've not removed the belly pan yet and so can't get at the main channel to mic it.

I am working on the design of a doubler to beef the frame up. I'm wanting to know by what degree I will enhance the stiffness of the main frame, and so would like the dimension of the basic channel.

Can you help me?

Thanks!

Jim
__________________

__________________
JimGolden is offline   Reply With Quote
Old 11-21-2005, 08:12 PM   #2
Rivet Master
 
1977 31' Sovereign
1963 26' Overlander
1989 34' Excella
Johnsburg , Illinois
Join Date: Jul 2005
Posts: 2,941
Airstream sells a doubler plate. You could likely get you to give you the thickness that they used if you called them or one of the servicing dealers.
__________________

__________________
dwightdi is offline   Reply With Quote
Old 11-22-2005, 08:58 PM   #3
3 Rivet Member
 
1960 24' Tradewind
Riverside , California
Join Date: Mar 2005
Posts: 189
"doubler"

Jim:

I'll mic a plate tomorrow and post the thickness. Airstream refers to it as an axle re-enforcing plate.

Greg
__________________
ZoomZoom is offline   Reply With Quote
Old 11-22-2005, 09:15 PM   #4
Site Team
 
, Minnesota
Join Date: Aug 2003
Posts: 6,940
Images: 59
Jim,

I don't have a 70's, and the frame on my 1959 is rectangular tubing. But, I would assume the frame is standard C4×5.4 (4" channel, 5.4 lbs/ft), and you can look up the I's on this chart: http://www.engineersedge.com/standar...properties.htm
__________________
markdoane is offline   Reply With Quote
Old 11-22-2005, 09:32 PM   #5
Rivet Monster
 
wahoonc's Avatar

 
1975 31' Sovereign
1980 31' Excella II
Sprung Leak , North Carolina
Join Date: Jun 2003
Posts: 7,174
Images: 40
Quote:
Originally Posted by ZoomZoom
Jim:

I'll mic a plate tomorrow and post the thickness. Airstream refers to it as an axle re-enforcing plate.

Greg
Greg,
I will be interested to see what you mic at...I am guessing somewhere in the 14-16 gauge range (.0747-.0598) I have the plates on mine, but have not really paid attention to them yet

Aaron
__________________
....so many Airstreams....so little time...
WBCCI #XXXX AIR #2495
Why are we in this basket...and where are we going
wahoonc is offline   Reply With Quote
Old 11-22-2005, 09:47 PM   #6
Site Team
 
, Minnesota
Join Date: Aug 2003
Posts: 6,940
Images: 59
Quote:
Originally Posted by JimGolden
. . .I do know that the axle mounting plate is 0.190" thick on my trailer. I figure that was 3/16" plate (should be 0.1875) and the variance is due to tolerances.
Jim
Jim,

This is likely 6 gauge, steel is not manufactured in fractional inch.

6 ga. is 0.1943" +/- .0090".
__________________
markdoane is offline   Reply With Quote
Old 11-25-2005, 01:06 PM   #7
Rivet Master
 
JimGolden's Avatar
 
Vintage Kin Owner
1977 31' Excella 500
Berkeley Springs , West Virginia
Join Date: Sep 2005
Posts: 1,619
Images: 7
Thanks guys.

I checked out that engineers edge link. Good stuff on there, makes it easier than calculating it by hand. I wrote a little spreadsheet to do it. Been awhile since I did by hand like that. Did the sum of the I + ay^2 thing. My numbers were pretty close to what they had on there so I think I did it right.

One thing of interest; if you look at the 5" section at 7.2lbs per foot so that it works out to about the same web and flange thicknesses as the 4" section, the moment of inertia is nearly double what it is for the 4" frame. I think that would pretty much cure any saggy issues.

I was thinking of welding on some .19" thick plate fore and aft of the axle mounting plates, maybe 8 feet on either side. This would then give me a smooth surface down the side of the frame. I'd then weld a .25" thick doubler onto this and maybe stop it a foot short of the end of the .19" plates. Something along these lines anyway... This would get the flexural stiffness up there where it should be.

The other option is build a new frame entirely, but man is that a lot of work. If I were to go that route, I'd pull out all the stops and probably use a 10" deep I-beam section, .19" thick, with 4" flanges. That'd give me an I value of around 33, as opposed to 3.8 like it is now. I'd never have to worry about it bending, the sag and separation problems would be gone, and I could mount my KLR-650 (340lbs) on the back bumper and not worry about it.

I'm hoping the stock frame is good enough to just beef up though. I figure it will be. I see minimal signs of sag from the outside. I put a laser along it and the one side seemed to have more droop than the other, but neither was bad. Curbside showed none at all, street side just a little. When I rip the belly pan off, I'll find out for sure.

Greg, did you get a chance to mic your factory reinforcing plates? I'm curious to know what Airstream did to fix it.

Thanks guys!

Jim
__________________
JimGolden is offline   Reply With Quote
Old 11-28-2005, 01:16 PM   #8
3 Rivet Member
 
1960 24' Tradewind
Riverside , California
Join Date: Mar 2005
Posts: 189
axle plate

Yes, it mics at .175" Pretty thick huh? Here's a picture of it.

Greg
Attached Thumbnails
Click image for larger version

Name:	MVC-014F.JPG
Views:	164
Size:	46.5 KB
ID:	16717  
__________________
ZoomZoom is offline   Reply With Quote
Old 11-28-2005, 06:43 PM   #9
Rivet Master
 
JimGolden's Avatar
 
Vintage Kin Owner
1977 31' Excella 500
Berkeley Springs , West Virginia
Join Date: Sep 2005
Posts: 1,619
Images: 7
Greg, Thanks. I appreciate it.

How exactly does this mount? Does it go on the inside or the outside of the frame? Do you bolt it on or weld it?

Thanks again for your help.

Jim
__________________
JimGolden is offline   Reply With Quote
Old 11-28-2005, 06:49 PM   #10
Rivet Monster
 
wahoonc's Avatar

 
1975 31' Sovereign
1980 31' Excella II
Sprung Leak , North Carolina
Join Date: Jun 2003
Posts: 7,174
Images: 40
Jim,
I can answer that question.....it goes on the outside behind the wheels, mine is bolted on. Apparently done by a dealer some 25+ years ago.

Aaron
__________________
....so many Airstreams....so little time...
WBCCI #XXXX AIR #2495
Why are we in this basket...and where are we going
wahoonc is offline   Reply With Quote
Old 11-28-2005, 07:14 PM   #11
Got gandkids?
 
Jim & Susan's Avatar

 
1973 27' Overlander
'Possum Holler , Georgia
Join Date: Oct 2004
Posts: 5,406
Images: 39
Aaron & Jim, I'm not and engineer and didn't play one on T.V., but I think this is the answer to a question that I have been asking incorrectly in a couple of different threads.

Is this item intended to stiffen the frame BEHIND the axles? There is a lot of sway and wiggle to the frame AND shell of the trailer behind the axles. I currently have the trailer stripped down to the frame (floor is out). And I'm trying to find a way to stop or reduce the frame wobble/wiggle/sway aft of the wheels/axles before I put the floor back in.

I've read a lot about "elephant ears", gusset additions and so on, back in the back part of the trailer, but none of the things I'm looking at seem to fix the movement back there OR prevent "sagging". I only want to do this once, so I'm looking for the correct answer.

Thanks, guys, for the info.

Jim
__________________
www.nesa.org

Air No. 6427
Jim & Susan is offline   Reply With Quote
Old 11-28-2005, 08:10 PM   #12
Rivet Monster
 
wahoonc's Avatar

 
1975 31' Sovereign
1980 31' Excella II
Sprung Leak , North Carolina
Join Date: Jun 2003
Posts: 7,174
Images: 40
Okay Jim,
I have done massive amounts of research...well a whole bunch anyway The 70's vintage long Airstreams (28'-31') rear bath had a couple of issues, one was frames that would crack near or behind the rear axle mount, that is what the plates Greg has pictured below are for. The elephant ears were a separate repair to stiffen the rear end where the shell was separating from the frame and floor at the extreme rear. Apparently due to the weight distribution and tankage this separation was more common in rear bath models. Also running gear condition and balance plays a large part in this too. Andy has posted good insight into the repair and stiffening of the rear frame area. The frames on an Airstream are only a part of the total support equation, the floor and the actual shell also play important and probably equal roles. You can't take just one piece of the equation...I have not had my 31 footer down to a bare frame, so I can't tell if what you are experiencing is normal or not, but I would expect the frame to be a bit on the flexible side, as long as all the metal, out riggers and welds are solid, it is the way Airstream designed it. Add the plywood and reattach the body the way Andy described and you should be good for another 25+ years.

Aaron
__________________
....so many Airstreams....so little time...
WBCCI #XXXX AIR #2495
Why are we in this basket...and where are we going
wahoonc is offline   Reply With Quote
Old 11-28-2005, 08:40 PM   #13
Rivet Monster
 
wahoonc's Avatar

 
1975 31' Sovereign
1980 31' Excella II
Sprung Leak , North Carolina
Join Date: Jun 2003
Posts: 7,174
Images: 40
Jim,
Just to help you out here are a couple of pictures of what the frame cracks look like, these are behind the wheels, typically near the rear axle. In extreme cases you can see a bulge in the body of the trailer right behind the wheel arches, and some cases the frame will be completely broken.

Aaron
Attached Thumbnails
Click image for larger version

Name:	broken small.jpg
Views:	142
Size:	20.8 KB
ID:	16720   Click image for larger version

Name:	broke close small.jpg
Views:	131
Size:	31.4 KB
ID:	16721  

__________________
....so many Airstreams....so little time...
WBCCI #XXXX AIR #2495
Why are we in this basket...and where are we going
wahoonc is offline   Reply With Quote
Old 11-28-2005, 09:49 PM   #14
Rivet Monster
 
wahoonc's Avatar

 
1975 31' Sovereign
1980 31' Excella II
Sprung Leak , North Carolina
Join Date: Jun 2003
Posts: 7,174
Images: 40
Quote:
Originally Posted by Jim & Susan
Aaron & Jim, I'm not and engineer and didn't play one on T.V., but I think this is the answer to a question that I have been asking incorrectly in a couple of different threads.

Is this item intended to stiffen the frame BEHIND the axles? There is a lot of sway and wiggle to the frame AND shell of the trailer behind the axles. I currently have the trailer stripped down to the frame (floor is out). And I'm trying to find a way to stop or reduce the frame wobble/wiggle/sway aft of the wheels/axles before I put the floor back in.

I've read a lot about "elephant ears", gusset additions and so on, back in the back part of the trailer, but none of the things I'm looking at seem to fix the movement back there OR prevent "sagging". I only want to do this once, so I'm looking for the correct answer.

Thanks, guys, for the info.

Jim

Jim,
I am not an engineer either...but I did stay at HI Express the other night Before you yanked the floor out, did you put jacks under the frame to stabilize it? And how much of the floor do you have out? And how much of the interior panels?

Aaron
__________________

__________________
....so many Airstreams....so little time...
WBCCI #XXXX AIR #2495
Why are we in this basket...and where are we going
wahoonc 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
Oval Window Frame Replacement MikeMikeMI Windows & Screens 8 12-30-2007 11:49 AM
year frame size reduced yukonsilver Airstream History 1 04-19-2004 01:53 PM
Cushion Dimensions, Front Sofa Alan and Julie General Interior Topics 2 08-05-2002 03:14 PM
Window Frame Removal 64GT Windows & Screens 4 04-09-2002 01:40 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 04:54 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.