Originally Posted by ntsqd
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.