"Overhead" essentially means that you have to lift the container off the pins or twistlocks that hold its corners from sliding. The required 'lift' is only a few inches, and doesn't need to be exactly straight up or untwisted, but unless you've arranged for the pins to drop or hinge down (as they did in my 1970s side-loading proposal) you can't load them Flexi-style (or, as indicated, circus-type although how or why you'd want to do this directly with containers is a bit mysterious to me... ;-}) without some additional steps to raise the corner castings over the pins.
You can lift any of these containers if you have a long enough 'spreader' to engage the four top castings: that is why you see the long, elevated, usually adjustable-length frame attached to the handling equipment. In the old days, quite a few 20' boxes were forkable, but that's not as good an idea on longer boxes, and it is not pleasant to think of all the things that could go wrong forking a loaded 53' box.
Not quite as 'mentioned' but still important is how you subsequently put the container on a typical truck underframe, which has fixed pins and considerably less mass and 'lateral resistance' than even a lightweight railcar. All the chassis I have seen recently have fixed pins and are 'overhead' load; it is relatively easy to arrange to align and lower the container with a Mijack or to align the trailer straight under a traveling crane... but it still has to go down, not slide, to go on.
As an aside: If you have the analogue of a lightweight spine car, with 'kangaroo' pockets down to near rail level, loading trailers is an 'overhead' exercise in most practice. THAT is an interesting design problem for all those trailers that aren't made to be lifted at the corners or the quarter points...
RME
andyb Thanks for that - please excuse any ignorance that is apparent in my next question but what form would the overhead loader take? Would it be a travelling gantry crane? or maybe a mobile vehicle similar to the Mi-jack translift? or something smaller such as the Kalmar container crane? or maybe all of these dependant on the size of the terminal? Being in the UK it's not always easy to find these things out - and y'all know how the rivet-counting community can criticise if you don't represent something correctly! Thanks in anticiaption Andy
Thanks for that - please excuse any ignorance that is apparent in my next question but what form would the overhead loader take? Would it be a travelling gantry crane? or maybe a mobile vehicle similar to the Mi-jack translift? or something smaller such as the Kalmar container crane? or maybe all of these dependant on the size of the terminal?
Being in the UK it's not always easy to find these things out - and y'all know how the rivet-counting community can criticise if you don't represent something correctly!
Thanks in anticiaption
Andy
All of the dependent upon what equipment each individual terminal used. It was not common for each terminal to have more than one type of loading equipment.
Never too old to have a happy childhood!
andyb Were front runners only 'loaded from overhead only'? or were there alternative methods? I have anumber of these in HO scale (Walthers) and would be interested to find out how it was done. If anyone could explain or point me toward an image somewhere I'd be grateful. cheers Andy
Were front runners only 'loaded from overhead only'? or were there alternative methods? I have anumber of these in HO scale (Walthers) and would be interested to find out how it was done. If anyone could explain or point me toward an image somewhere I'd be grateful.
cheers
Overhead loading just means that you could not "Circus Load" the cars by backing the trailers up a ramp, as the cars lacked a continuous deck. With the exception of "Expressway" (and of course Roadrailer) all Intermodal is Overhead loading only.
overhead loading.
We don't have trailer piggybacking in the UK as such due to the low loading gauge clearances (and a lot of 25Kv overhead wires) - reading about the problems the US rail users had with these perhaps it's just as well...
In addition to their sensitivity to wheel climb derailments, especially when empty, a major reason for their retirement is that they could only handle trailers up to 48' long. As 53' trailers replaced 48' trailers in TOFC service, the TTUX, later TTOX, cars became less and less useful. The 48' TTAX all-purpose spine cars could carry a reduced number of 53' trailers by overhanging adjacent units, but that was not possible with the TTOX cars. With the overall decline of TOFC traffic, the 48' TTAX cars are starting to be retired now as well.
Dick Dawson
Retired Chief Engineer, TTX Company
anb740 Yes....and yes. They sometimes had "hunting" problems after reaching a certain speed with the car wobbling violently from side to side. They were also extremely lightweight when empty and any slack action could (and would) cause them to pop right off the track. And that happened on multiple occasions. My last encounter with these was back in 1999. I caught a 53-car cut of them headed to the Trailer Train plant in Augusta for scrapping. http://anb740.rrpicturearchives.net/showPicture.aspx?id=91940
Yes....and yes. They sometimes had "hunting" problems after reaching a certain speed with the car wobbling violently from side to side. They were also extremely lightweight when empty and any slack action could (and would) cause them to pop right off the track. And that happened on multiple occasions. My last encounter with these was back in 1999. I caught a 53-car cut of them headed to the Trailer Train plant in Augusta for scrapping.
http://anb740.rrpicturearchives.net/showPicture.aspx?id=91940
To add a little to the story of the TTX 'Front Runners':
Part of the story of what happened to the fleet of front runner cars is told here; The tracking issues as explained by Posters above.
They (specifically, The Front Runners) developed a pretty bad reputation within the Rail Industry for their abilities to spontaneously derail; to the extent that for a time, the tale about how the Southern Pacific would accept them for delivery, but immediately unload them and return them to the Carrier they were received from, is mentioned in some of the information.
In the early 2000's they were accumulated and stored in Iowa, in large numbers. About 2002/2003 they were moved down to the St. Louis area and ultimately scrapped.
The National Museum of Transport ( in Kirkwood, MO.) St.Louis, Mo.
@ http://www.transportmuseumassociation.org/
Has a Front runner in their collection:
TTOX #130059 "Piggyback" Flatcar 1984 Builder: United-American Car Company Four-wheel ¦Front-Runner² car; partial deck and fixed trailer hitch; loaded from overhead only; 28-inch instead of standard 33-inch wheels to lower car for better clearances.
The story was that one of the folks from the Museum saw the Front Runners stored over in E. Saint Louis and asked Trailer Train and one was donated to them. This was about 2002/2003.
Thanks for the reply. I've wondered about this for a long time.
Bad idea , thank God they are gone !!!
Good Ridence - train building nightmares!
Joe H. (Milepost S256.0; NS Griffin District)
Pictures: http://anb740.rrpicturearchives.net
Youtube: http://www.youtube.com/anb740
Whatever happened to the two-wheeled truck front runner intermodal cars? Were they removed from service for design flaws? Were they prone to derailments?
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