Do we know for certain what causes torsion axle sag? - Fiberglass RV


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 11-12-2014, 11:09 PM   #1
Senior Member
 
Mike Magee's Avatar
 
Name: Michael
Trailer: Li'l Hauley
Oklahoma
Posts: 5,142
Do we know for certain what causes torsion axle sag?

In addition to my membership here, for several years I've been a member of a yahoo group forum for A-frame trailers (Chalet, Aliner, etc.). A trailer repair person on that forum recently said, "The only reason that torque flex axles wear out is overloading the weight."

That got me to wondering. I know I've read here many times the belief that the rubber in a torsion axle stiffens and distorts with age and with non-use, resulting in a sagging trailer and a harsh riding trailer. However, I've never seen documentation. Do we know of any statements by torsion axle manufacturers, one way or the other? Is it at all possible that sag could always (or even usually) be caused by overloading, rather than by age and/or relative lack of use?

If the cause really was overloading, then jacking the trailer up for storage would really be a waste of time and effort.

To test the hypothesis somewhat: I know there are plenty of sagging Scamps, for example. Currently, Scamp 13s come with 2200 lb axles and 16s come with 3500 lb axles. It seems difficult and unlikely to exceed these ratings, but perhaps Scamp was using lower capacity axles 20-30 years ago? Anybody know?

Anyone have any documentation or hard evidence that would prove or disprove the statement he made?
__________________

__________________
How much time do we have left? 2 Chr. 7:14
Mike Magee is offline   Reply With Quote
Old 11-12-2014, 11:18 PM   #2
Senior Member
 
Joe Z's Avatar
 
Trailer: Casita
New River AZ
Posts: 1,043
I have no hard proof but age and overloading would both be a contributing factor in my opinion.
For a comparison a rubber band sitting in a drawer will stay the same basically forever. put a 10 lb weight on it and let it sit like that for a week and it won't snap back to it's original position..... now overload it with a twenty lb weight and the results will be even worse. I may be way off base but it is my reasoning that memory of the rubber will come into effect.
That's why when i store for very long periods of time i jack the trailer up halfway to a neutral position like it would sit on a rack in the store when new.
I too would like to see some strong written proof of what's real
__________________

__________________
Joe Z is offline   Reply With Quote
Old 11-13-2014, 01:56 AM   #3
Senior Member
 
Name: Frank
Trailer: Casita
California
Posts: 251
Rather than wonder, I wonder(?), if the axle manufacture could give an answer to the question?
__________________
Frank F
frankcfx is offline   Reply With Quote
Old 11-13-2014, 04:54 AM   #4
Senior Member
 
Borrego Dave's Avatar
 
Name: Dave
Trailer: Casita SD17 2006
California
Posts: 2,918
Good question Frank but I doubt any company is going to give any hard line stats for life expectancy. I had the same thought as Joe after reading the first post question. A rubber band in a drawer, no sun light or uv and it falls apart when you stretch it a little bit. Tires on any trailer that sits most of the time outside are a good example of uv checking. Torsion axles don't get the uv or sun light either. The components used to make a rubber band or the rubber in a torsion axle I'm sure is different but they will all break down at some point. Even metal fatigues with age and becomes brittle and prone to easier breakage. I guess bottom line is it may depend on where you live and how you use your trailer makes a difference of how long the torsion axle holds up before needing to be replaced. A 25 to 30 year usefull life sounds pretty good to me even with over loading factored in.
__________________
Borrego Dave is offline   Reply With Quote
Old 11-13-2014, 05:09 AM   #5
Raz
Senior Member
 
Raz's Avatar
 
Name: Raz
Trailer: Trillium 2010
Vermont
Posts: 4,058
Better living through chemistry? Raz

https://en.m.wikipedia.org/wiki/Chem...on_of_Polymers
Attached Thumbnails
image-2831627113.jpg  
__________________
Raz is offline   Reply With Quote
Old 11-13-2014, 05:42 AM   #6
Senior Member
 
Donna D.'s Avatar
 
Name: Donna D
Trailer: Escape 5.0 TA, 2014
Oregon
Posts: 24,433
Perhaps this thread, with pictures of the interior of an axle will help: What a torsion axle should not look like
__________________
Donna D.
Ten Forward - 2014 Escape 5.0 TA
Double Yolk - 1988 16' Scamp Deluxe
Donna D. is offline   Reply With Quote
Old 11-13-2014, 06:35 AM   #7
Commercial Member
 
Ian G.'s Avatar
 
Name: Ian
Trailer: 1974 Boler 1300 - 2014 Escape 19'
Alberta
Posts: 1,304
Registry
Another very interesting article that basically says ALL rubber will deteriorate over time, just in different ways and at different rates.
Care of Objects Made from Rubber and Plastic - CCI Notes 15/1
Ian G. is offline   Reply With Quote
Old 11-13-2014, 08:04 AM   #8
Senior Member
 
Timber Wolf's Avatar
 
Name: Tim
Trailer: '88 Scamp 16, layout 4
North Florida
Posts: 1,440
I am not a Chemist, nor did I stay at a Hoiliday Inn Express last night but IMHO rubber ages. I believe this to be true based on my own life experiences. I am sure it did not help my Scamp's axle's time to failure that the factory used an under-rated axle back in the day. I am 54, and expect my new 3500 pound axle to about do me for the duration. If I happen to out live it I will gladly install another one. After all, since it is now bolted on instead of welded it should be alot easier next time!
__________________
Timber Wolf is offline   Reply With Quote
Old 11-13-2014, 08:15 AM   #9
Senior Member
 
Steve L.'s Avatar
 
Name: Steve
Trailer: 2003 Casita 16' SD
Michigan
Posts: 1,690
Registry
You were hoping for a simple, one source only answer? There isn’t one. The answer is more likely all of the above.

Rubber will degrade over time due to chemical changes, fatigue due to flexing, heat and ozone. So long as rubber is asked to operate in its “elastic” range the effects will be minimized but not eliminated. The elastic range being where it returns to its original shape after deformation.

Additionally, heat is an issue because rubber will take a “heat set” such as what is sometimes seen in tires. Generally most tire flat-spotting will work out but after reheating/running the tire but there is always some deformation that doesn’t work out. Usually it reduces to something less than what the vehicle is sensitive to. Same thing for any other rubber part.

Overloading can risk asking the rubber to exceed its elastic range to operate in its “plastic” deformation range. Plastic deformation implies something does not return to its original position after deformation. Think of plucking a steel ruler over the edge of a desk. Pluck too hard and ruler bends permanently. That would be plastic deformation. I use the term “risks” because I don’t know whether other axle parts might fail due to overloading long before the rubber gets to its plastic deformation point.

And the elastic/plastic transition point moves. The transition to plastic deformation generally lowers as the material is (over) heated. And as I’ve often related of tires, rubber doesn’t heal. Abuse an axle (or tire) once and that damage is carried for the rest of its service.

And I’d be surprised if there weren’t polyester or nylon cords longitudinally imbedded in the rubber components to add tensile strength to the bands and they’re not as flexible as the rubber is and may in fact be the part that is plastically deforming.

All of this is interesting (to a geek like me) but most of the torque is likely coming from that square metal bar running through the center of the axle. Steel being less flexible than rubber, it’s probably plastic deformation of the bar that’s causes the late life sagging. Its properties change too over time.
Attached Images
 
__________________
Steve L. is offline   Reply With Quote
Old 11-13-2014, 08:58 AM   #10
Senior Member
 
Name: Eddie
Trailer: 2014 Escape 21
Virginia
Posts: 1,556
FWIW until the mid 80's Scamp was installing 1.2K lb axles on the S-13's and 2.2K lb. axles on the S-16's. Also people assume a lot of S-13 axels are bad because they sit low but in reality they sit lower because the swing arm angles usually start at an up angle where the S-16&19's start with downward angle swing arms.
Eddie
__________________
Eddie Longest is offline   Reply With Quote
Old 11-13-2014, 09:42 AM   #11
Senior Member
 
David Tilston's Avatar
 
Name: Dave W
Trailer: Trillium 4500 - 1977, 1978 (2), 1300 - 1977, 1973, and a 1972
Alberta
Posts: 5,315
Registry
My 15' Trillium 4500 came with a 2000lb axle. Seemed kinda light, so I went with a 3500lb axle. I would go with a 2500lb axle next time, (on another trailer).
__________________
David Tilston is offline   Reply With Quote
Old 11-13-2014, 10:29 AM   #12
Raz
Senior Member
 
Raz's Avatar
 
Name: Raz
Trailer: Trillium 2010
Vermont
Posts: 4,058
Every picture tells a story.
Attached Images
 
__________________
Raz is offline   Reply With Quote
Old 11-13-2014, 11:45 AM   #13
Member
 
Name: will
Trailer: 16' Scamp
Wyoming
Posts: 63
Our '79 Scamp 16' had a 2200# axle. I replaced it with a 3500# Dexter torflex derated to 2400#. I wanted the heavier bearings and larger brakes.
__________________
Wyowill is offline   Reply With Quote
Old 11-13-2014, 01:19 PM   #14
Senior Member
 
Timber Wolf's Avatar
 
Name: Tim
Trailer: '88 Scamp 16, layout 4
North Florida
Posts: 1,440
Quote:
Originally Posted by P. Raz View Post
Every picture tells a story.
I have to wonder exactly how something like that fails. I would not think all four “rubbers” give up simultaneously or even at the same rate. So one gets a little weak and puts more stress on the next weakest one and so on. They might even swap the order around a bit, whichever one is the weak link at the time. I have an old backhoe, and it is a constant source of amusement and frustration. I fix one leak in a hydraulic circuit and pretty soon something else in that circuit is leaking. It finally dawned on me that a leak is acting as a pressure limiting device. Once fixed the pressure finds the next weakest area and causes it to start leaking and relieving pressure, and so on.
__________________

__________________
Timber Wolf is offline   Reply With Quote
Reply

Tags
axle


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
How much flex should a torsion axle flex, if a torsion axle could flex flex? JeepScamp Problem Solving | Owners Helping Owners 5 08-10-2014 06:03 PM
Torsion Axle vs. Leaf Spring axle camper1887 Towing, Hitching, Axles and Running Gear 9 10-01-2012 06:32 AM
What Causes Inside Tread Wear? KevinDR Towing, Hitching, Axles and Running Gear 10 05-24-2008 09:21 PM
A certain someone I know Legacy Posts General Chat 7 05-08-2003 08:19 PM

» Upcoming Events
No events scheduled in
the next 465 days.
» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 11:55 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.