Casita Why Carpet? and No shocks? Ruff ride and jiggles stuff lose? - Page 3 - Fiberglass RV


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Old 10-08-2018, 01:48 AM   #41
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Name: David
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Originally Posted by ntsqd View Post
FWIW they call it a "Torflex" axle, but it's not a torsion bar system. At least the unit that I bought to build a genset trailer (APU range extender for an EV) with was not.

Picture a square tube arranged with its sides horizontal and vertical. Now place a square bar inside of that only turned 45° so that a line from corner to corner is either horizontal or vertical. Then fill the air space between them with rubber that is vulcanized to all of the interior surfaces.

Suspension movement distorts the rubber, and being that it is rubber it doesn't exhibit the usual behavior of a metal spring. Thus making it somewhat self-damping.

I wouldn't accept the bounce. It is not the inherent nature of any trailer to do this. It is the nature of springs that are undamped to do this and the mfg not knowing better or not willing to add cost that causes this, and it doesn't have to be that way.
Three pages of posts to get to the best one. All materials have a property called hysteresis. It is the tendency of materials to absorb some of the energy that distorts them.

Clay has nearly 100% hysteresis. Spring steel has much less than 1% hysteresis unless you bend it to the point where it yields and takes a new shape. Rubber has something between these two.

Since rubber tends to absorb some of the energy that is used to distort it, when it is used in an axle, like Dexter does, it reduces repetitive bouncing in a manor similar to a damper. In fact if the right rubber compound was used it would damp out bouncing entirely.

Unfortunately that kind of rubber is also subject to a lot of creep, which is the tendency of a material to deform permanently when subjected to stress.

If Dexter used a really high hysteresis rubber compound in their axles you would have to replace the axles at least yearly. By using a more resilient rubber they can make their axles last much longer but it is at the expense of being more bouncy.

A trailer doesn't have to produce the smooth ride that a passenger vehicle must have so a bit of bounce and roughness in the ride is acceptable for many uses. In many cases the amount of damping in the rubber of a Dexter axle is enough and so that is all the trailer builder uses.

Trailers with steel leaf springs don't have much natural damping. What they do have is mostly caused by friction between the leaves of the springs. In a big rig trailer that can be enough. If you notice, most semis don't have shocks. In a travel trailer that isn't often enough. A large percentage of leaf spring travel trailers also have shocks.

Shocks can have very sophisticated valving inside that adjusts the damping for all kinds of conditions and so they do a much better job of keeping the trailer riding smoothly. This becomes more important the rougher the road becomes.

A small travel trailer that never leaves the pavement and gets occasional use will do just fine without shocks, if it has Dexter type axles. Let's face it. Most fiberglass RVs out there never see any full time use or even 1,000 mile trips. Most just go up to a local camp ground and spend a weekend, then go home. For those trailers, shocks aren't mandatory.

For those who really use their RV, a set of shocks can be a good addition both for the life of the trailer and for the equipment inside. It might cost a bit to put shocks on but they could easily pay for themselves if you make use of them.

If you have worn torsion axles, a set of coil-over shocks can compensate for extra load in the trailer and for sagging rubber. It will raise the spring rate of the suspension though so that has to be considered when making such a choice. Perhaps the best solution to sagging torsion axles, other than replacement, would be shocks and air bags or air shocks.

Lifting a trailer off its suspension when it is parked for extended periods can reduce the creep of the rubber and help the axle to last longer. Whether it is worth the extra effort is up to you to decide.

Many fiberglass RVs have nothing between you and the great outdoors other than the thickness of the shell. An eighth of an inch of fiberglass and resin doesn't provide much in the way of insulation or sound control.

Some manufacturers add a bit of insulation but generally it doesn't make a very attractive interior finish. Since the goal of most fiberglass RV makers is to provide a low cost, low weight, yet high value product, they have to come up with creative solutions to interior finishing.

Rat fur is something that has existed in the automotive industry for a long time. It is cheap, light and reasonably durable. It provides just enough insulation to give some control of condensation and helps the interior to stay a little warmer than it otherwise would. Nothing appeals to everyone and rat fur is one of the things that lots of people dislike. If it isn't applied correctly it can fall off with the least encouragement and over time even the good stuff fails. When that happens, replacing it can be a mess.

Carpet provides more thickness and mass so it does a better job of insulating heat and sound. It is also appealing to many people but of course not to everyone.

The thing about carpet is that it is intended for walking on so when it is applied to a wall it will last almost forever. The down side is that it lasts almost forever. If you don't like it or if you grow to dislike it, you may be stuck with it anyway because it is usually stuck on pretty solidly. Removing glued on carpet can be a tough job.

The good news about carpeted walls is that they can be cleaned with a carpet/upholstery cleaner just like the carpet and upholstery in your home. It is unlikely that you will get worse stains on your walls than you would get on your floor. Wall carpet can look and smell great for the life of the trailer. If you would rather not own a carpet machine then you can rent one or have someone clean it for you. There are lots of folks who will do your whole RV for less than $100. One cleaning at the end of a season aught to keep it in pretty nice shape. Of course 2-3 seasons of cleanings would buy you a nice home grade carpet/upholstery machine to keep.

If you want a fiberglass RV that looks and feels like a house then you will have to buy something other than the trailers typically featured here. If you like what we do then you have to embrace what they are. That includes the things that may not appeal to you at first.

I developed a bad case of wanderlust using only a small tent. When that became a large tent it was almost like cheating. Then we tried yurts. That hardly felt like camping. Then we rented a couple of houses and condos. That wasn't camping at all. Now we have an RV and it is the best of all worlds, considering our financial situation. There are lots of options out there and it is best to carefully consider what you really want before spending a lot of money.
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Old 10-08-2018, 06:19 AM   #42
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Thank you.

The problem for this type of axle in use over rough and wash-board roads is that the energy absorbed by the rubber in the damping process is turned into heat. When it is the occasional bump this heat has time to dissipate. On a rough surface, particularly when at a comfortable speed, this heat can't dissipate fast enough. This breaks down the vulcanizing and eventually the axle fails.


Adding dampers (shocks) to the suspension moves where most of that heat goes into a component that can dissipate the heat fast enough. The result is both a better ride quality and an axle that will last longer in that kind of service.
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Old 10-08-2018, 06:21 AM   #43
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Good post David!
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Old 10-08-2018, 04:21 PM   #44
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Originally Posted by ntsqd View Post
Thank you.

The problem for this type of axle in use over rough and wash-board roads is that the energy absorbed by the rubber in the damping process is turned into heat. When it is the occasional bump this heat has time to dissipate. On a rough surface, particularly when at a comfortable speed, this heat can't dissipate fast enough. This breaks down the vulcanizing and eventually the axle fails.


Adding dampers (shocks) to the suspension moves where most of that heat goes into a component that can dissipate the heat fast enough. The result is both a better ride quality and an axle that will last longer in that kind of service.
Absolutely true. In fact, bonded rubber torsion axles are not a good choice for those who regularly go into the wild, especially if they are in a hurry to get there.

Every option has a use or it wouldn't survive in the market. For rough use a metal spring and real dampers is better. For less strenuous use torsion axles are fine.

The truth is that Dexter axles are considered by many to be the finest option for a pavement bound trailer. They are an upgrade in many people's eyes. They have a welcome home under many RVs. It's all in what you expect and how you use your RV.

The further you flex anything, including rubber and steel, the fewer times it can be flexed before it fails. This property is called fatigue. If a torsion axle is flexed a lot by having the tires bounce off the ground or even just by having them rebound more than necessary without leaving the ground then the rubber inside will wear out quickly.

If you damp out some of the motion then the rubber will be stressed less and will fatigue less. Adding shocks to a torsion axle can add life to the rubber by protecting it from extra flexing.
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Old 10-08-2018, 04:40 PM   #45
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I've never seen shocks on a torsion axle. Does anyone actually offer them? They are considered self-damping. Airstream uses torsion axles, but I've never heard of anyone being told not to use an Airstream on rough roads for fear of damaging the rubber in the axles??
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Old 10-08-2018, 05:20 PM   #46
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I've never seen shocks on a torsion axle. Does anyone actually offer them? They are considered self-damping. Airstream uses torsion axles, but I've never heard of anyone being told not to use an Airstream on rough roads for fear of damaging the rubber in the axles??
YES ; My Casita has a torsion axle
YES ; My Casita has shock absorbers
The combination works extremely well

I also like the carpeted wall , it works for us !!
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Old 10-08-2018, 05:46 PM   #47
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There are lots of options out there and it is best to carefully consider what you really want before spending a lot of money.
David,

This was a really informative post.

I continue to try and find space in my brain-box to accommodate information like this. : )
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Old 10-08-2018, 06:10 PM   #48
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Name: David
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Originally Posted by Raspy View Post
I've never seen shocks on a torsion axle. Does anyone actually offer them? They are considered self-damping. Airstream uses torsion axles, but I've never heard of anyone being told not to use an Airstream on rough roads for fear of damaging the rubber in the axles??
When buying new from the factory it is often possible to specify shocks on a torsion axle. You won't find many on the sales lot though. It's a couple hundred bucks more money that most people won't even understand.

It isn't like not having shocks will doom a trailer. The majority of torsion axle trailers out there don't have them and do just fine. It is the boondocking full timers who want everything to last for 20 years who are most concerned. Shock on a torsion axle are a good thing but hardly essential.

It's like the new dress and shoes the wife always wants. There are benefits to buying them but you can live with out them too.

If your trailer didn't come with them and you want them, any compitent welding/fabrication shop can put them on for you. It isn't a big job.
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Old 10-08-2018, 07:14 PM   #49
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YES ; My Casita has a torsion axle
YES ; My Casita has shock absorbers
The combination works extremely well
I bet it does. Thanks Steve
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