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joe greiner
9th Apr 2010, 11:35 PM
Our WT club meets at a building adjacent to a railroad siding. The railhead is currently being used to off-load 100-foot-long sections of steel pipe for construction of a trans-continental gas pipeline. The pipe is approximately 3-4 feet in diameter. Three pipes are loaded onto each trailer, for subsequent transfer to a holding area about 20 miles East of Tallahassee. Past and future holding areas are located at 100-mile intervals, each to hold 100 miles of pipe, reminiscent of Amundsen's and Scott's expeditions to the South Pole. Other railroad depots are used for other holding areas.

Using 100-mile intervals, and 100-foot-long pipes, simplifies the arithmetic, i.e. 5280 pieces of pipe. At three pipes per trailer, 1760 round trips are needed. I think there are about 6 truck/trailer combinations employed. Maneuvering such combinations through city streets, and in the holding area, is a formidable challenge, even with police escorts. The trailers, however, have elegantly simple articulated mechanisms, whereby the rotation of the trailer at the fifth wheel urges a similar rotation of the rear wheel set with respect to the trailer. Thus, the turning radius is significantly reduced. The simplicity of the apparatus is remarkable: Drawbars connecting opposing sides of the fifth wheel and the rear wheel dolly cross at mid-length, through a supporting frame. The drawbars are tightened with turnbuckles.

I spoke with one of the drivers. He informed me that using these trailers is quite easy; the trailer simply does double what would otherwise be expected, in forward or reverse.

I found no patent number on one of these trailers, probably because it's so simple. US patent class/subclass of 280/426 is concerned with Land Vehicles (280) and Steering by Articulative Movement (426). I found 161 patents conforming to this; the oldest was issued in 1917; the newest was issued last month. There's an amazing variety, including hydraulic devices, microcomputers, and who knows what else, to accomplish more movements than needed here.

Moving big stuff has many applications. I thought this one was pretty cool.

About 12 years ago, I witnessed a driver of a tractor and flatbed trailer execute a reverse T-turn into a driveway off a narrow road in the Netherlands. It was executed too rapidly for me to note how he did it, but the trailer must have been remotely steered to some extent. And about 25 years ago in Washington State, long prestressed-concrete girders were transported with manually steerable rear bogies, similar to large fire trucks. On at least two occasions, gravity and/or centrifugal forces became mis-aligned with the upward (more or less) direction of the prestressing, subjecting the girder to lateral-torsional buckling, and the girder exploded.

Cheers,
Joe

zuffen
11th Apr 2010, 09:31 AM
That steering system on the trucks is a larger version of what you see on airport container trailers.

Their axles are linked so the rear steers the opposite way to the front.

This is so the "train" of trailers will follow a set path rather than cutting off the inside of the turn.

Wouldn't do cleaning up a Rolls Royce engine because the trailers didn't all follow the same track.

You will find a lot of semi trailer set ups in Europe have a steering rear axle (on tri-axle trailers) to help them around tight village streets.

Not sure how they steer them but they can get quite some articulation in them

I don't think we're allowed to use rear steer trailers over here. All rear steer's I've seen are crewed by a second "driver/steerer".

joe greiner
11th Apr 2010, 10:47 PM
The rear bogies here also had a second driver. I haven't had to look into it for a while, though. There might be some later developments.

The one I saw in Europe had a single driver. I had the impression the rear axle was controlled from the cab, but it might have been more automatic, like the ones I saw recently.

I think the airport trains have more pivot points, but I haven't looked closely at them either. IIRC, one or both axles turn, and there's also movement at the pintle.

Some (or all) of the states here allow double trailers, and a few allow triples. In Australia and Brazil, the only limit seems to be tractor capacity for hauling, subject to grade incline and stopping ability. I'm pretty sure none of them can be operated in reverse, except for short distances - too much likelihood of jack-knifing.

Weekends are awkward for study much deeper. Possibilities include the patent list I found, and forum members Gil Jones (retired aircraft mechanic), and Ad deCrom (retired mechanical engineer). During the work week, I can contact the trailer manufacturer, my niece (a mechanical engineer technician - I only have her work email), and some former mates in civil engineering. There's a computer program, AutoTurn, which simulates vehicle movement; I think some of its later versions allow user-defined apparatus. Previously, we just used templates for simpler machines, for roadway layout; tracing paper (or brute force CAD) for other stuff like construction equipment and ships, with generous allowance for error.

Cheers,
Joe

Wahoon
11th Apr 2010, 11:04 PM
Kurt Johanssen, who pioneered cattle trains in the NT used self steering trailers to his own design. Some of these trailers are at the Road Transport Museum in Alice Springs, and are used on special occassions.
Cheers,
Dion

zuffen
12th Apr 2010, 08:39 AM
I understand the original haul unit or prime mover for the first road train had a steering rear axle as well. And to add it was built in the UK. I think it was a Thornycroft.

If you folow a road train B double or C double around a tight turn they can use a lot of road as they have no self steer.

I'd be most interested in knowing how they steer the rear bogie in Europe.

I know some rigid busses in Sydney have steer on the back axle in the rear bogie.

The airport units are simply linked fron one corner of the front axle to the opposite on the rear. As the draw bar pulls the frot axle around the rear follows in the opposite direction. Simple and effective.

malb
12th Apr 2010, 06:06 PM
There are some quad axle low loaders around melb for transporting large earth moving machines. These trailers have some form of self steer on the front two axles which are maybe 2 to 3m ahead of the rear axle sets. Allows the trailers to turn without excessively scruffing the road surface. No idea how its controlled though.