Torsion Axle Lifespan - Fiberglass RV


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Old 01-23-2007, 04:29 PM   #1
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Here is a link to an axle diagram if you aren't familiar with how they are constructed:
Axle Pictures
Here is also a link for start angles and travel limits: Axle Start Specs
According to the new Trillium trailer manufacturer, the start angle on my axle when new was 0 degrees. Now 28 years later it starts at 15 degrees up. At first I assumed that the 0 degree was wrong. After researching, it appears that the axle was a zero degree but the rubber has broken down and it has sagged. I called an axle manufacturer and asked how much sag was ok. They said up to 10 degrees is about the limit of droop. Any further than that indicates the rubber has broken down and the axle won't have the shock and damping qualities necesary.
Has anyone examined their droop lately?
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Old 01-23-2007, 06:17 PM   #2
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YUP- --sortly after I discovered this site a couple years ago.. Had NONE!!!! Then inspected frame-only found five (5) broken places. Axle after investigation was frozen in 20 degree up on one side and about 17 degree on the other side (maybe this is why Scamp set a little lopsided?) So, a new Dexter axle was ordered and the welding began. Now Scamp sits level and sprong is in axle. (also sits higher) Things don't fall off the shelves as bad as before either. Larry
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Old 01-24-2007, 06:57 PM   #3
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According to the literature, Dexter wants to see about three inches of 'bump clearance' between the top of the tire and the inside of the fender well (which roughly translates to getting a clenched fist between the two) -- Anything less is not enuf.

Clearly, it may be possible to have a torsion axle that originally had more than that amound of clearance, but there's still some life left in it if it passes the above test.

The earlier axles on eggs were spec'd and 'rubbered' for a lot less than they are today -- I believe one person's 82S13's axle was about 1,200#, my 91S13's was 1,600#, an 00S13 was about 2,000# and current Scamp 13's are 2,200# (the max rubbering for a Dexter #9 Axle).

BTW, according to Dexter, an axle can be ordered in 100# increments from the smallest to the largest capacity within an axle model range, but most trailer manfs seem to prefer standard rubbering for obvious reasons.
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Old 01-24-2007, 07:52 PM   #4
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Pete,
Bump clearance is necessary so the tire doesn't contact the wheel well. Beyond that, the ride and ability of the axle also will degrade with age. The 10 degree sag limit indication, stated by a Dexter Axle engineer, is a way to judge the health of the rubber. You could actually have an axle that still has 3" bump clearance with the rubber completely degraded and no shock absorption left. In the end both clearance and shock absorption is required.
Dave
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Old 01-25-2007, 07:03 AM   #5
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To answer the topic question...of all the reading I've done over the years here on FiberglassRV...the lifespan is 15-20 years....no matter how many miles towed or how stored (weight off frame, etc.). I replaced the axle on my Scamp when it was 14 years old...the difference was amazing.
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Old 01-25-2007, 11:14 AM   #6
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I don't know that I can justify spending that kind of money on an axle for a trailer that cost me only $1,100. I know it should be done since it's 22 years old, but it needs a bunch of other stuff just to make it camp-worthy right off the bat.... like $1,200 worth. I still have plenty of wheelwell clearance and she tows just fine for now.

But I am somewhat concerned about the hubs and the bearings, just because I can't take it apart to see what's in there. I was thinking of just replacing the hub itself to hold me over until I can change out the axle in another two years. According to folks over at the U-Haul site, GM hub #513018 is a perfect fit and costs $76 each. It looks like this...



Unless someone has an absolute "must" reason why the entire axle needs to be changed out immediately, I'm thinking it should be okay for now.
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Old 01-25-2007, 11:29 AM   #7
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Quote:
I don't know that I can justify spending that kind of money on an axle for a trailer that cost me only $1,100. I know it should be done since it's 22 years old, but it needs a bunch of other stuff just to make it camp-worthy right off the bat.... like $1,200 worth. I still have plenty of wheelwell clearance and she tows just fine for now.

But I am somewhat concerned about the hubs and the bearings, just because I can't take it apart to see what's in there. I was thinking of just replacing the hub itself to hold me over until I can change out the axle in another two years. According to folks over at the U-Haul site, GM hub #513018 is a perfect fit and costs $76 each. It looks like this...



Unless someone has an absolute "must" reason why the entire axle needs to be changed out immediately, I'm thinking it should be okay for now.
BUCK- ---Hmmmm I think the main thing you need to check is, does the axle have any travel left in it? In other words, is the axle flexing when you move it up and down? Have someone else look under and see. If it does not, axle needs replacing. Remember my post from the other day referring to five (5) cracks in the frame? I didn't say anything about the stress crack in the fiberglass above the door from the door being bounced up and down. It grew from two inches to about 4 inches the same summer excursion that precipitated the frame cracks. (in fact that trip is a STORY all in itself ) (also learned how to do fiberglass repair too)
Soo, if the axle has lost its flex, one cannot afford to put it off. Larry
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Old 01-25-2007, 11:50 AM   #8
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Soo, if the axle has lost its flex, one cannot afford to put it off. Larry
Great... another expense I can't afford.

Anybody want to buy a trailer?
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Old 01-25-2007, 12:12 PM   #9
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And just to add to the problems, U-Haul campers seem to be more complicated when it comes to replacing axles, as evidenced by this thread...

http://www.fiberglassrv.com/board/index.ph...3&hl=dexter

Translation: Very costly and a pain in the butt to replace.

Has anyone here had this done to their U-Haul?

How much did it cost?
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Old 01-25-2007, 01:59 PM   #10
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Quote:
And just to add to the problems, U-Haul campers seem to be more complicated when it comes to replacing axles, as evidenced by this thread...

http://www.fiberglassrv.com/board/index.ph...3&hl=dexter

Translation: Very costly and a pain in the butt to replace...
Although my post in that thread probably contributed to the level of concern, I really don't think the tongue-to-axle-crosstube connection is a big deal. As long as the brackets are the right size for the frame (the U-Haul isn't a weld-it-on-anywhere situation), a bolt-on version of that bracket in the middle of the axle cross tube should be easy. To me, it would likely be trivial cost and an afternoon of fabrication (cutting, bending, bolting...), but even with someone else doing the work I would not expect it to be hours of labour charges, and a welded solution would be really quick. It's mostly a matter of realizing that there is a unique requirement, and working with it.

Since that discussion, I have realized that the U-Haul Parts Manual and U-Haul Repair Manual are in the FiberglassRV Document Center, and they show the situation very well.
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Old 01-25-2007, 03:22 PM   #11
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I've already made printed copies of both manuals, thanx.

I guess what I really need to know is what the specs for a new axle would be for an old U-Haul like mine. Is it something that has to be custom made? Or are there standard widths and such to choose from?
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Old 01-25-2007, 04:00 PM   #12
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Pete,
Bump clearance is necessary so the tire doesn't contact the wheel well. Beyond that, the ride and ability of the axle also will degrade with age. The 10 degree sag limit indication, stated by a Dexter Axle engineer, is a way to judge the health of the rubber. You could actually have an axle that still has 3" bump clearance with the rubber completely degraded and no shock absorption left. In the end both clearance and shock absorption is required.
Dave[/quote]Agreed, however, with most of our eggs, if the axle is indeed degraded, there won't be three inches of bump clearance -- Also, not all axles started with the same angle (up or down) -- Scamp, BTW, uses 22.5* down on all their axles (Dexter and Al-Ko).

Hot Flash -- Occasionally I like to recheck myself and I just found this definition of Bump Clearance in a Dexter Application Manual PDF:

Bump Clearance - Bump is the upward
displacement of a wheel center relative to the
trailer frame (sprung mass). Clearance is the
amount of trailer frame to axle clearance
necessary to allow the axle to clear or NOT
contact the trailer frame.

This definition seems to better fit a leaf-spring axle were the main beam moves vertically (and bump clearance would decrease as springs got weak) -- On my Scamp, the main axle beam is welded to the brackets and the brackets are welded to the frame, so the beam effectively doesn't move unless the frame flexes in/out, regardless of the rubber condition, and the Torflex design/engineering spec says "3 in. of bump clearance", so I am going to stop using the term.

That said, however, if one cannot get a fist between the tire and fender well, or if there are tire marks on the inside of the well, likely the axle needs replacement.

There is a table of values from a Dexter PDF for the #9 Axle (typically used for 13' eggs; #10 for 16/17/19), showing measurements of the various dimensions under the various load conditions; significant variation from these dimensions would indicate replacement. The numbers are hard to read; the original for this table and the one for the #10 can be found on the DexterAxle web site.
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Old 01-25-2007, 04:28 PM   #13
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1. Start with matching the OEM brand of your axle. It will make the attachment bracket style line up and attachment simpler.
2. Choose a weight capacity of the axle and spindles. If you can actually weigh the trailer, great, or use past history of what others have done. Note: Some mfgs spec smaller size brakes for lighter axles.
3. Measure the outside dimension of your axle's brackets where it attachs to the frame.
4. Choose wheels and tires. If you want to make a change, this is the time to do it. Its nice to have wheels that are a common size (5x4.5") and back spacing.
5. Spec your hubs to match the wheels.
6. Hub face to hub face won't change if your wheels don't change. If your back spacing on the wheels is changing you need to alter this dimension so the tires are in position in the wheel wells.
7. The last is start angle on the arms. You can go with OEM spec if not changing your tire diameter. You can also spec a larger start angle to increase ground clearance. There are more variables here. If you cannot find the OEM spec, you could work it out with tape measure and axle web sites.
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Old 01-25-2007, 05:23 PM   #14
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Quote:
1. Start with matching the OEM brand of your axle. It will make the attachment bracket style line up and attachment simpler.
2. Choose a weight capacity of the axle and spindles. If you can actually weigh the trailer, great, or use past history of what others have done. Note: Some mfgs spec smaller size brakes for lighter axles.
3. Measure the outside dimension of your axle's brackets where it attachs to the frame.
4. Choose wheels and tires. If you want to make a change, this is the time to do it. Its nice to have wheels that are a common size (5x4.5") and back spacing.
5. Spec your hubs to match the wheels.
6. Hub face to hub face won't change if your wheels don't change. If your back spacing on the wheels is changing you need to alter this dimension so the tires are in position in the wheel wells.
7. The last is start angle on the arms. You can go with OEM spec if not changing your tire diameter. You can also spec a larger start angle to increase ground clearance. There are more variables here. If you cannot find the OEM spec, you could work it out with tape measure and axle web sites.
Wow- --I always heard that U-Haul trailers were built sturdier. After looking at the manuals I can see why. I really like the tongue tied to the axle and then to the rear bumper. Definately stronger than the Scamp frame..... (Maybe that's why I had to reinforce my frame... ) As for ordering an axle, I just called a Dexter dealer, talked to a knowledgable service man, told him what I was doing and gave him the measurements for my axle. (mounting width, lug bolt pattern, w/ or w/o brakes, etc) Since every Dexter is built to customer specs, it took about 3 weeks (was supposed to be 2, delayed our vacation) and in the door via UPS it came. (around $250, I think) Then it was just weld it in place. But since yours is a bolt-on, you'll save on the welding. And, since every one is built to specs, there should be no reason why those extra brackets could not be put on at the Dexter factory. Hope this is of help. Larry
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