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Frames and axels

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offgrid View Drop Down
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Topic: Frames and axels
    Posted: 21 Nov 2022 at 3:16am
There is DOT oversight in the trailer load rating system, just not formal engineering standards for what safety factors need to be assumed when designing the trailer axle and structure  

As I understand it the DOT requires the manufacturer to post a max trailer weight (dry plus cargo) not to exceed the axle weight rating plus tongue weight (or lowest tongue weight if there is a range). The DOT  doesn't mandate what constitutes a reasonable axle or frame weight rating as far as I can tell. 

When I looked into the safety factors (expressed as g forces) engineers use when designing vehicle structures and suspensions I found numbers in the range of 2.5-3 g's for heavy trucks and more like 3-3.5 gs for lighter passenger vehicles, which get thrown around more. I could find general ranges only, the actual numbers used by each vehicle manufacturer are proprietary. 

When I analysed the axle and frame of my 179 I came up with yield points (loads there you'd expect the steel structural members to begin to fail in bending) at around 2gs or a bit less on a fully loaded trailer.

 2gs isnt normal but also isn't all that uncommon when hitting a pothole or curb, for example. You'd  notice it when it happened, but you might also think it wasn't that serious an event.  If you want you can download  an app on your smartphone and use it to record g forces as youre diving around. 

So it isn't very surprising to me that some folks end up with bent franes and axles, while most folks can go through their whole trailer ownership and not have any problems. You likely have to be pretty heavily loaded and then also hit a pothole or curb fairly hard, but perhaps not so hard that you'd expect to have bent something.

In contrast, 2.5 gs on a heavy truck or 3  on a passenger vehicle would be really quite an extreme event. As the driver you would probably expect to have broken something under those conditions. 

 I think what's going on is since there isn't a formal  standard the RV industry, in the interest of light weight and low price the RV engineers are selecting structural members that provide that 2g ish safely factor, just high enough to prevent a flood of complaints. That's good engineering actually, no engineer anywhere, not even at NASA, will design something to survive all possible conditions, he or she would be quickly looking for alternative employment. 

Engineers without external regulatory requirements design stuff with the safety factors the company has established internally. They also all sign NDAs as a condition of employment so they can't talk about it. They do know what they're doing for sure  the engineering involved isn't rocket science by any means. 

So because of the limited DOT oversight, to be able to call out the manufacturers on this issue you would need to show that a reasonable engineer would not select structural members with such low factors of safety. That would be quite difficult because the designs arent wildly out of expectations.

 So what to do as an owner? I think there are 5 choices, listed below in rough order of effectiveness at preventing damage. YMMV.

Buy a motorized RV built on a truck chassis by a global vehicle manufacturer. You're more likely to get something designed to the 2.5 plus g range that way  

Buy a trailer from a high end long established coachbuilder with a reputation to protect.

Buy a cheap trailer and reinforce it yourself. Drive carefully. 

Buy a cheap trailer, keep it lightly loaded, and be very diligent about curbs and potholes.

Buy a cheap trailer, load it up and go banging down bad Forest Service roads at 50 mph. At the end of each season  rather than winterize, drop it off at the landfill and buy another one in the spring.







1994 Chinook Concourse
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David and Danette View Drop Down
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Post Options Post Options   Quote David and Danette Quote  Post ReplyReply Direct Link To This Post Posted: 21 Nov 2022 at 9:58am
  Thank you offgrid for your explanation, I think you could have been an engineering professor! I think I will be cautious in driving to avoid big bumps driving fast and be very careful not to overload our camper. I did take it to a scale once when loaded to get an idea where our camper weight was loaded.
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Post Options Post Options   Quote Scuba Steve Quote  Post ReplyReply Direct Link To This Post Posted: 23 Nov 2022 at 9:19pm
Thank you for the response. 

The knowledge you have to offer is appreciated. The Axel lifts was installed by the dealer I purchased the trailer from. I hope someone covers the damage. The trailers being 2 years old. 

I will keep you informed as to how FR chooses to handle this.
Steve
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2022 at 4:20am
Since the dealer is responsible for the lift kit he will be  your ally, he wont want FR to blame the lift. He probably got the lift kit from FR or Lippert anyhow. FR needs happy dealers so I don't think you need to worry about the lift part of it. Good luck!
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Post Options Post Options   Quote lostagain Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2022 at 7:11am
The axle problem seems to be very curious.  Presumably, Lippert sells chassis and axles to trailer manufacturers based on the performance and dimension specifications provided by the trailer manufacturer.  To our more knowledgable board members:  Is this a correct assumption, or does Lippert (and other chassis manufactures) build them as a more fungible product that the trailer builder just picks from a list of chassis and axles that are manufactured generically and sold based on weight capacity, length, and width?

If the axle they provide does not meet the dimensional and performance specifications either specified by the trailer builder or as listed in the Lippert specifications, then ultimately they bear responsibility for the failure.  If the chassis and axle are built to the trailer builder's specifications and it fails when the trailer is used in a manner that is reasonably foreseeable for a vacation trailer, then it is the trailer manufacturer's responsibility if a failure occurs within the warranty period.  If the use of the trailer is unreasonable or constitutes an abuse, then the warranty is void.

The real question are what constitutes reasonable and foreseeable use, and what is a "subtantial" defect.  [The pre-June, 30,2021, warranty language is pretty much irrelevant as the warranty period has already expired, except to the extent the Lippert axle warranty may apply.  The Lippert frame warranty, according to their web site, is 1 year.]  Under the current "warranty," Forrest River is not responsible for much.  https://www.forestriverinc.com/downloads/TowableWarranty2021.pdf  If the defect is not "substantial," then it's not covered. "Substantial Defects are those defects which prevent the RV from performing its intended use for short term recreational camping." [Emphasis added.] Dealer representations about what is covered or not covered by the warranty are specifically disowned by FR.  The warranty only applies to the first retail sale of the trailer by an authorized dealer.  It is not transferable.  If you purchase a trailer that is not the current "model year" then the warranty is 90 days, not 1 year.  Also, little stuff, such as door or window adjustments, are only covered for 90 days.  Specifically excluded from the warranty:  "The chassis including without limitation, any mechanical parts or systems of the chassis, frame, axles, tires, tubes, batteries, gauges, or optional generators."  [Emphasis added.]  Also excluded are road hazard damage and damage from "off road" use.  So if you hit a pothole on I-20 in Louisiana, which I am told there are some huge ones, tough luck.  The warranty limitations can vary from state to state, but in most states where there is little in the way of consumer protection law, you're screwed unless FR or the dealer feels like being nice to you.

The warranty overrides the Uniform Commercial Code protections in most states, so the implied warranty of fitness for the intended use doesn't help you.  A failure of the product which damages the product leaves you with essentially no remedy, except as specifically stated in the warranty.  If there is a design defect in the trailer, such an axle or chassis failure, that leads to an accident, then different rules apply and the manufacturer is responsible for compensation for the injury, but not consequential damages to the trailer.

If you have a warranty claim, the best you can hope for is that FR wants you to buy another trailer from them someday and might be nice to you.  If they deny your warranty claim, even if you are right and they are giving you the proverbial middle finger, there is really not much you can do.  Of course, you can sue them, but the attorneys fees would very quickly exceed the value of the trailer.  Also, you have to go to Indiana to sue.  They chose the forum in their warranty and you can count on Indiana law not being very favorable to consumers with travel trailer warranty disputes.

Speaking for myself, I would never, ever, buy a new FR travel trailer product again.  The warranty is illusory and it isn't worth the extra money you'd spend on a new trailer.  If I were to be in the travel trailer market again, I would buy a used one that has been used enough to reveal any structural or other defects.  If you can't fully inspect the used trailer for defects yourself, then it's worth hiring an independent trailer mechanic to do a thorough pre-purchase inspection.  Also, buying a trailer that is out of warranty and your not being in "privity" [having a contractual relationship] with FR means that the limitations for legal remedies, such as having to sue in Indiana, would not apply in the event someone got hurt using the trailer.  As for fixing or replacing the trailer itself, you are on your own.

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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2022 at 10:01am
LA, great write up. I'd only add that Lippert would very likely go beyond the 4 corners of it's written warranty if FR asked, they have to be one of Lipperts largest sales accounts. IOW, if there was a gray area if responsibility between the two companies, FR would very likely win that battle without having to fire much of a shot. That doesn't help the end customer  we have zero leverage with either company.

As to your other question, without doubt Lippert and FR's engineering staff collaborate closely during the trailer design process, and if FR needs a new design from Lippert, they will get it. For example, I was told by Lippert that the part number on my 179s axle indicated that it was specifically built for that trailer, not generic at all. 

 
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Post Options Post Options   Quote David and Danette Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2022 at 4:18pm
   I am in the process of replacing the leaf springs on our Vista 19BFD the factory put 2,000 Lb springs on the axle with a 4,000 lb axle. If you check their website and look at the specifications of a 19BFD the 4,000 Lb leaf springs will not be strong enough and that's why I am replacing them. Broken leaf springs on their Vista and Vintage cruiser trailers were mentioned on Facebook owners forum and upgrading their leaf springs. I am replacing them with 2,500 lb leaf springs the factory 2,000 lb leaf springs were nearly flat from not being able to support the weight within the factory specifications. My experience with owning two FR campers and one Gulf Stream camper they are built with minimum quality and my own opinion they are built for looks not reliability. I agree with offgrid buy a used camper and do not buy new and hopefully the previous owner will have made most of the necessary repairs and upgrades.
2018 Vista Cruiser 19BFD (2018-              
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Post Options Post Options   Quote lostagain Quote  Post ReplyReply Direct Link To This Post Posted: 24 Nov 2022 at 4:32pm
As sure as the sun rises in the east, we can count on RV manufacturers building nearly everything they offer to absolute minimal standards.  It's all glitter and ting ting to catch the eye of the buyer, but the underlying structure is just barely.  We've had good luck with our leaf springs, but we tend to travel relatively light.  Since laundromats and food shops are mostly available all over the country, we have little need to pack the trailer to the gills.  I'd like to put some shock absorbers on the suspension, but it'd probably void what's left of the Lippert limited axle warranty.
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Post Options Post Options   Quote offgrid Quote  Post ReplyReply Direct Link To This Post Posted: 25 Nov 2022 at 2:25am
Well, look at it this way. Upgrading leaf springs is cheap and simple and they're easy on the trailer frame. Often you can just add a leaf to an existing spring, not sure if that's possible on Lippert springs. If  that's all that's needed to get an inexpensive trailer to survive reasonable usage then I'd go for it. But unfortunately you still have the cabin integrity issues (water leaks and joints coming apart)...
 

So I do think the two piece fiberglass RVs (either trailers or motorized) are going to result in a better long termownership experience. That's where I'm heading, in my case motorized this time. I'm looking at old 1980s Toyota mini motorhomes with fiberglas cabins. But I'd have to find a rust free unit, rust was a big problem in vehicles of that vintage. The other options are Chinooks and Xplorers on Ford, Chevy, or Dodge chassis, and Casita or Scamp on the towable RV side. And one other option I'm looking at on the motorized side. 1990s Japanese domestic imported micro motorhomes on 4wd diesel light truck chassis. Right hand drive, manual transmissions with 2 speed transfer cases, what could be more fun than that? 
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Post Options Post Options   Quote lostagain Quote  Post ReplyReply Direct Link To This Post Posted: 25 Nov 2022 at 6:00am
Just as happened with the automotive industry, when foreign competitors entered the market with better quality vehicles at lower prices, if we ever get foreign competition coming into our market place, we may see some significant improvement in quality.  Some of the Canadian trailer companies are putting out some very nice products, but they are still on the upper end of the price scale.  When I was in Spain a few  years ago I looked at the offerings there and the build quality was noticeably better and the prices were competitive for under 25' travel trailers.  
Never leave footprints behind.
Fred & Maria Kearney
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Our Pod 172
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