Oliver Factory Tour

[Art Davis]

Just about any structural material will work if appropriately sized and configured; you could build a steel-reinforced concrete trailer frame if you could stand the weight.

Building in aluminum with the same outside dimensions would require very thick box section walls, partially (or entirely, depending on alloy) offsetting the weight advantage of the less dense aluminum. Proper aluminum stock selection - size, shape, alloy, and heat treatment - can allow comparable strength at less weight... but higher cost for both material and fabrication. For examples, see almost any aircraft - they do the same things in aluminum that are normally done in steel on road vehicles (beams, structural skins, brackets, etc), because aircraft are more sensitive to weight and less sensitive to cost than cars or trucks.

Brian,

Sure, I understand that aluminum can be used virtually anywhere. For instance, a torsion box construction would be very strong---but still not as strong as steel in any given application if the amount of material in each is the same. So---not knowing anything about trailer design, what I am asking is whether an aluminum design here is more practical and safer than steel?

Car frames and bodies at one time were steel, now they are aluminum and plastic. Whether they were safer than current vehicles, with the airbags, ABS, etc, I don't really know. I'll have to leave that to the automotive engineers.

BTW, if anyone is interested, there is a lot of discussion on the Casita Club Forum about the Oliver. Unfortunately, it seems to have degenerated into a dog and cat fight as so many of their threads do, but even that is kinda' funny.

Art

[Steve R.]

The leaf spring suspension mounts at two points per side; the rubber torsion axles mount with one bracket per side. If the bracket is long enough, the stress concentration with the rubber torsion axle brackets would be lower... and since they can't be welded on anyway, the obvious design would be to bolt the axle's brackets to long (load-distributing) flanges on the frame rails.

I'm not saying that there's anything wrong with the Oliver design, only that the aluminum frame does not - to me - lead to a leaf spring suspension. They seem to have chosen it for other reasons.

The Oliver uses a separate bracket (one continuous piece from front to back spring mounts) to receive the spring mounts and shock absorbers. The brackets on the Casita Torflex axle are about 10" long. The brackets on the Oliver look to be at least 3 times in length. The load at the frame is therefore definitely distributed over a much larger area on the Oliver. Take a look at the manufacturer's website for photos on the setup.

[Brian B-P]

...For instance, a torsion box construction would be very strong---but still not as strong as steel in any given application if the amount of material in each is the same. So---not knowing anything about trailer design, what I am asking is whether an aluminum design here is more practical and safer than steel?...

The amount of material will be greater with aluminum - if anyone tries to render a design intended for steel in the same volume and arrangment (e.g. box of particular dimensions) of aluminum, it will be inadequate, so more material (by volume) should be a given.

I don't think any material can be relied upon to lead to the most practical and safest result, so there is no simple answer to Art's question. There are a couple of relevant facts proven by existing mass production trailer (and motor vehicles) structures:

• aluminum is both practical and safe when properly used
• steel is cheaper and easier to build to the same strength

[Brian B-P]

The Oliver uses a separate bracket (one continuous piece from front to back spring mounts) to receive the spring mounts and shock absorbers. The brackets on the Casita Torflex axle are about 10" long. The brackets on the Oliver look to be at least 3 times in length. The load at the frame is therefore definitely distributed over a much larger area on the Oliver. Take a look at the manufacturer's website for photos on the setup.

Here's one of those photos:




The aluminum bracket which incorporates the spring mounts is clearly visible, with the rounded fasteners (presumably the heads of carriage bolts) through it; it could be an angle but I think from other photos that it is a channel (opening upwards). The upper shock mounts are also part of the same bracket.

It appears to be about 2" longer than the spring eye-to-eye length, which is probably about 26" (standard Dexter spring lengths for their D35 3500 lb axles are 21", 24" and 26"), so that's likely 28" overall. The corresponding #10 Torflex brackets are 8" between mounting holes, and thus agree they're about 10" overall - the Legacy bracket is about three times the Torflex length.

Exactly the same approach could be used with a Torflex: the same length of bracket (say, 28") could be fabricated with mounting holes to match the Torflex bracket, and carry load to the same area of the frame through the same bolts; it would extend both forward and backward beyond the Torflex bracket.

Again, I think the Oliver construction is fine... I just don't see any real structural benefit to the leaf springs.

[Anders Laurits]

The bolts, nuts, washers and larger square washers are thru bolted alright. I asked about the heavy plating on them, it gave them a slightly different color, I think he said they were cadium plated. When we were in the area where they cut the structural members for the frame, I noted that they must get their aluminum tubing by the container load, because of the way it was bundled and stacked.
They had the largest band saws that I have ever seen ! Most home owner band saws aren't very true cutting, but the frame jig and welds told me that theirs must be very true. I saw the alloy numbers on the bundles of tubing, but they had no particular meaning for me.
I guess that the welding on the frame components was the thing that caught my eye because it seemed to be nearly flawless.
As to the floor, the inner bottom shell had the floor recessed to contain one foot square ceramic tile squares, there was a choice of designs in the order sheet I saw. When walking on the floor, even on a partially assembled Oliver, there was no give. It added to the feeling of sturdiness one gets when inside.

[Steve R.]

... One of the modifications that I asked about was a way to put a reciever hitch at the rear. The rear bumper folds down and cannot be used for a reciever mounting location. Strength and weight bearing capability was the main part of that particular conversation. Their answers to my questions and my own personal observations, reasured me that the frame was more than sufficient for the job.

So, how would the rear receiver be constructed?

[Steve R.]

...Again, I think the Oliver construction is fine... I just don't see any real structural benefit to the leaf springs.

Maybe not but it makes sense why they chose the longer bracket design. I agree that they could've done something similar with a Torflex axle. In fact, a fairly new Casita that I recently saw had small square tubing running along the frame between the Torflex axle bracket. It was a little longer than the bracket.

Jim Oliver, or maybe it was their sales manager, mentioned that they did extensive testing with both the Torflex and conventional spring/shock axles and the later performed the best in their opinion. I would be curious to know what led them to that conclusion.

I don't know if this is related but most of the serious off-road trailers use a conventional spring/shock axle setup. The Canadian M101 that I have is no different. It's virtually indestructible.

[Anders Laurits]

So, how would the rear receiver be constructed?

It would be mounted directly to the frame, not the bumper. The bumper would swing up and down in the regular way. There would be a shallow notch in the bumper, so it could surround the reciever, without being attached to it. The compartment behind the bumper would not be effected by the reciever. The clean look of the rear of the coach would not be effected. The reciever would be under the fiberglass spare tire cover and at the top of the bumper. The bumper is the same 2" X 5" material as the frame. Or it seems to be. I didn't ask. This was something that hasn't been tried before and would be subject to approval by the staff engineer.
The sole purpose of this reciever would be to carry less than 200 pounds of weight, cargo rack and all. It would never be used to tow anything.

[Anders Laurits]

While looking over the "innards" of the Oliver, I paid particular attention to the wiring. I had noted that the 07' Oliver I looked at, in Vanburen Arkansas at the River Valley Egg Rally, had a circuit breaker panel near the door. I liked the idea that in an emergency, smoke for example, I could rapidly exit the coach while turning off "stuff" on the way out. Once safely outside, the next thoughts would be to further shut things down, disconnect the battery and turn off propane, before picking up a fire extinguisher.
The propane shut off was in the usual place. I asked about a battery disconnect and sure enough the response was , "in the battery box". The battery box's slide out tray has room for two optional Opitma batterys and has a courtesy light in it.
The wiring is not simply "strung" from point to point, it is in a mesh wire loom and color coded well. While at the station where the wiring was being done, I talked to the technician who stopped referring to his "hook up" sheet and answered my questions about wire sizes, ect.
Because each build sheet is different according to the owners requirements, he had to follow the sheet carefully, before the inside bottom shell is added to the coach. For example: the Ground lighting in it's extremely low location for better visibility, cannot be added at a later time.
Standing quietly in a completed Oliver coach I listened for converter noise. Though all available lighting was turned on, there was no disconcerting humming sound from the converter.
The 08' Oliver had a smaller in appearance roof air unit on it. I asked and it wasn't smaller, but the Oliver staff had discussed a smaller unit because of their insulation R value, the coach just didn't need such a large unit.
If the size of the air unit is reduced, then a boondockers generator size could be reduced. Resulting in greater fuel economy, as well as initial generator purchase cost, and allowing the owner to reap some of the rewards of investing in the latest in technology.
The shore power cord, 45' long, was on a very quiet power reel and the access door had a fairlead roller built into it !
The fiberglass propane tank cover fit well and there was enough room in there that the tanks could be replaced with 30 pounders and still fit well, another great boondocking possibility !
The location of the propane supply line to the coach would lend it's self well to adding an outlet for an outside grill or even a oven to be hooked up. The propane tanks enclosure on the tongue is open on the bottom so no explosive vapors can accumilate in the event of a leak.
I think that the Oliver tour was a look into the future of the industry.
Serious time has been spent thinking about the needs of the end users.

[Brian B-P]

Jim Oliver, or maybe it was their sales manager, mentioned that they did extensive testing with both the Torflex and conventional spring/shock axles and the later performed the best in their opinion. I would be curious to know what led them to that conclusion.

I was curious too, and while the Oliver people were responsive, I didn't get a very specific answer.

I think that the key is the use of shock absorbers; they are readily added to leaf spring axles (and stock on the Oliver Legacy), but it seems that the Oliver people did not try a rubber torsion axle with shocks, which are less readily available.

JI don't know if this is related but most of the serious off-road trailers use a conventional spring/shock axle setup. The Canadian M101 that I have is no different. It's virtually indestructible...

...and many modern military vehicles use various types of independent suspension. A sturdy and effective system can be built in a number of ways.

[Steve R.]

... I think that the key is the use of shock absorbers; they are readily added to leaf spring axles (and stock on the Oliver Legacy), but it seems that the Oliver people did not try a rubber torsion axle with shocks, which are less readily available...

Wouldn't that be redundant though? I thought the Torflex had damping capabilities?

[Steve R.]

I'm having second thoughts about the rear bumper fold down storage. On the surface it seems like a great idea but wouldn't there be a concern about leaving the bumper in the down position all the time and exposing what is stored inside? I understand the bumper has to be in the down position while the drain hoses are being used. The problem seems complicated by the fact that this is the only outside storage (me thinks).

[Brian B-P]

Re: Shocks with Rubber Torsion Suspension

Wouldn't that be redundant though? I thought the Torflex had damping capabilities?

No, and yes... all springs used on trailers have inherent damping characteristics:

• multi-leaf spring packs have friction between the leaves
  • this is inadequate for most applications, which is why all those leaf-spring pickup trucks have shocks
    
  • friction is poor type of damping, so in vehicles which have shocks low-friction materials are often used between the sheets to minimize it
• "slipper" type leaf spring installations have friction between the spring tail and the frame mount
  • this method is routinely used on cheap single-leaf trailers since they don't have inter-leaf friction
• rubber springs have hysteresis inherent in the rubber material
  • "hysteresis" means that energy is absorbed with distortion and turned into heat, damping motion
  • this damping helps, but was judged inadequate for even the old Mini, which had hydraulic shocks in addition to the rubber springs
    
  • European travel trailers very commonly use a rubber torsion axle, and shocks are a routine option from the axle manufacturers
    
  • reportedly, trailers (even with rubber springs) licensed in Germany must have shocks as well to be allowed operation over 100 km/h (62 mph)
    
  • Airstream has used Henschel Dura-Torque axles (functionally identical to a Dexter Torflex) for decades, and includes shocks as standard equipment... they apparently consider the inherent rubber damping inadequate

[Anders Laurits]

I'm having second thoughts about the rear bumper fold down storage. On the surface it seems like a great idea but wouldn't there be a concern about leaving the bumper in the down position all the time and exposing what is stored inside? I understand the bumper has to be in the down position while the drain hoses are being used. The problem seems complicated by the fact that this is the only outside storage (me thinks).

I have seen the bumper in the up and the down position. Having it in the down position at the River Valley Egg Rally didn't seem to be a problem while hooked up to the septic line. I would not have anything except some sewer related items in there any how. For example, a box of latex gloves, a black water rinse down wand, a short black water garden hose, a slinky type drain hose support system and some other related items. Security for those items, likely will not be a issue.
However for most of my use ( boondocking ) the bumper would be down only at a dump station.
I think the dump hose might be able to stay hooked up on the tank end making the dump procedure easier.
A 90* fitting and a hole saw would put the drain out of the bottom through the aluminum bottom of that compartment, for those that wanted the bumper in the up position in a RV park.
Because my main use would be boondocking I would want nothing exposed under the coach however.