Why do most multiple unit trainsets have transit couplers instead of knuckle ones? What are the ins and outs regarding knucke couplers or transit couplers in multiple units? why can’t passenger cars adapt to this standard?
Every time we coupled up locomotives into a multiple unit, we use the knuckle couplers provided…care to define or explain what an “MU coupler” is?
Yes i am waiting also as i dont want to be calling things by the wrong name.
A transit coupler. Looks like this: http://en.wikipedia.org/wiki/File:SEPTA_budd-coupler.jpg
They have air and electrical MU connections all in one. Makes it simple to build and separate trains. One man can do it by himself.
Interesting Wikipedia article on coupling:
http://en.wikipedia.org/wiki/Coupling_(railway)
Not nearly as much fun as the coupler thread was a while back, but informative enough.
Don,
I have never seen that type of coupler, but I remember David P. Morgan bemoaning the fact that the vaunted automatic coupler was not really automatic because it does not automatically make the air connection. So I set out to solve that problem by brainstorming and building a prototype of an automatic air coupling that would hang below the knuckle coupler.
It is interesting to see the cone and pin system that guides the coupler together in the photo of the transit coupler that you posted above. That is exactly the method of guidance that I settled on for my invention. Then I did a patent search and found several prior inventions that were intended to automatically couple the air lines. Some looked like they would have worked, and some did not. Oddly enough, the cone and pin system that I had developed was precisely included in one of the patents from the very early 1900s, so somebody had gone do
I would be concerned about the draft/ tension strength of the transit-type couplers when used in mainline freight service. They work just fine in comparatively short commuter car trainsets - which are often the ultimate in Distributed Power, since each and all cars are powered ! But I don’t think they’re rated for as much as the Grade E AAR couplers, which are good for 330,000 to 500,000 lbs. per Al Krug at - http://www.alkrug.vcn.com/rrfacts/drawbar.htm So unless something else is done to limit the in-train draft gear forces - such as widespread use of DP locomotives, short trains, or a closed and controlled service such as one of the mine-to-power-plant operations - I would worry that they would fail under even typical loadings.
However, there’s nothing to stop a beefed-up design that could cope with those forces from being manufactured and implemented, and I’ll even suggest where it would be most useful without getting ensnarled in the whole compatibility/ interchange issue - the ECP trains now being tested by NS and BNSF. That would solve the occasional problems with the wire connections that seem to occur - kolevchoski (sp ?)
In the first generation diesel era as well as with multiple unit electric cars in rapid transit, and with stack train platforms, there are often other than standard couplers. This is to maintain a unit configuration in many cases. Also, as in rapid transit, it might also be for electical and other connections. Sometimes this was used so that the unit(s) could not be used in any other service that for which it was assigned.
Edit add: of course all steam locomtives were semi permanently attached to their tenders, too.
I remember back in the 50’s when the DL&W was moving a lot of NYC (BMT?) subway cars from either ACF in Berwick, PA or from St.Louis Car in St. Louis, MA there had to be some kind of idler at both ends of the cut of cars to couple to the rest of the train and to the caboose. Hieght and weight restrictions on contemporary rapid transit couplers, plus air and other electrical message lines, is why these cars today are either on flat car or highway trailer.
With stack platforms, there are usually five platforms per “car” which are semi permanently coupled with other than standard couplers for very much the same reasoning. Plus I believe there is a marketing value applied to the 5 platforms per car configuration.
I agree that a coupler with an electrical train line (or even a reliable infrared link) would go a long way toward getting ECP to work well. But, if you are doing ECP, you might as well do distributed power - with the communications via the same trainline, and then there is no need to beef up the buff and draft strength of the couplers.
Say WHAT??? What does buff and draft haft to due with distributed power???
Not as it’s being done now…
Think one locomotive for every 30 cars more or less evenly distributed throughout the train. The trainline for the ECP replaces the Locotrol radio. GE (and others) have been talking about this for 20 years - or more.
Can you imagine all the extra work at terminals that you would have to do if you had multiple engines scattered throughout the train? It would take a lot longer to build/unbuild a train.
The current coupler system works well. It is standardized among all USA railroads, and all freight car owners. To start sprinkling a new design will just create hassle and cost. The current design also keeps electronics out. The only time couplers/drawbars/knuckles get any kind of mechanical attention is when they break. Usually it’s just a knuckle pin or knuckle, which is usually easily replaced. Sure, you have to reach in and tie the airhose, but that takes a few seconds, and if the hose is damaged? Well, even a conductor is capable of replacing that if need be.
I know some people just have this urge to introduce electronics into every aspect of life, but I think this is one place where it is NOT needed for maximum efficiency.
And I always thought MU-trainsets could have those funky couplers since they don’t need or have that wonderful little thing called slack. Even in my limited PlayStation (RCO) engineer jobs, I could not imagine freight trains without slack. (well, except toadtailers that don’t have slacks, but they are a different beast in their own separate category - where they should stay!)
I think you could develop an automatic air coupler, and the goal of eliminating the need to go between cars and couple the air hoses would be a valuable improvement. However, I don’t think the value of achieving that goal would justify the price. There are too many couplers out there to change them to a new design overnight. So anything added to or modified on the standard coupler has to be able to mate with other couplers that have not yet been modified. This ability to work either way imposes more cost on the new design improvements. The standardization and widespread use of couplers makes it hard to revise the design. So I would bet that the standard couplers will remain as they are, and never incorporate an automatic air connector.
However, if anything were capable of causing a redesign of coupler systems for freight, it would be the ECP brake system. It seems as though the most difficult part of ECP brakes to perfect is the electrical couplers. I think we will see a lot of continuing development on the electrical component of ECP brakes. Most of this development will be with more or less dedicated trainsets and equipment. This will eliminate the burden of making the ECP system entirely compatible with existing brakes as development R&D continues.
You wouldn’t build your trains and then apply the power. You’d build the train with the power - by the block. The power goes with the block. When you set out the block, the power stays with the block. You build and switch the train with the road power that goes with that block. A set out or a pickup takes 10 minutes - even if you are setting out or picking up some cars w/o power attached. ECP and distributed power mean you don’t have to tie down any hand brakes. You don’t have to worry about air leaking off. You don’t have to spend 40 minutes after working a location to get the air back. You just do your work an go.
You do realize, of course, Don, that we’re both kind of ‘channeling’ John G. Kneiling on this, don’t you ? You’re quite right, as I see it - it’s just that I was applying Railway Man’s observed principle of ‘‘only 1 big change at a time’’, starting with the couplers and then progressing from there.
zug, this would be mainly for unit trains such as coal and grain that pretty much stay together for the entire round-trip, and intermodal which are often built-up with longer cuts of multiple-platforms anyway, so once the power is cut in, it can stay there. It would indeed be a pain for loose-carload/ assembly of random individual cars into trains. Your point about slack is well-taken, but one result of these MU couplers is virtually slack-free couplings, and with power distributed throughout the train and a generally higher HP/ton ratio, there isn’t as much need for free slack to get the train started.
The next step as planned by Kneiling would not be separate big heavy independent locomotives cut into the train as we do n
There is slack and then there is slack. There is the free motion, or slop, between the moving parts of the draft arrangement (coupler, knuckle, yoke draft gear) , and then there is the springiness in the draft gear itself.
The free motion is totally unneeded. It’s just the result of a really old design and wear and tear. Nobody would vote to keep it if it could be done away with by the wave of a magic wand.
The draft gear is there to allow you to slam cars into each other at 4mph without destroying the car and/or the lading. It also helps when all the free slack runs in and out. You don’t HAVE to have either.
In fact, if you don’t switch without power attached, it would be better to do away with all slack. The closest thing to a slackless train would stack trains of 5 wells each. The articulated connections are slackless (and stay that way as they wear). There was an interesting demo of exactly how smooth handling these trains were. They set a table in the rear container of a train in Seattle with a table cloth, china and glasses and closed the door. They opened the door in NJ and nothing had fallen off the table.
For instance - the MILW’s light axle-load 2300 HP SDL39’s - which were specially built for granger branch-line service - can be used to define what is really needed for the basic locomotive, and how much extra weight is just ballast.
The 6-axle SDL39’s weighed in at 250,000 lbs. or 125 tons per http://www.thedieselshop.us/Data%20EMD%20SDL39.HTML - that’s 41,700 lbs. or about 21 tons per axle.
Compare that to a 4300 HP SD70M at 407,000 lbs. or 203.5 tons per http://www.thedieselshop.us/Data%20EMD%20SD70M.HTML = 67,800 lbs. or about 34 tons per axle.
The difference in weight is 157,000 lbs. or 78.5 tons (26,200 lbs. or about 13 tons per axle
Paul,
In your thinking about a new train that spreads out the power and reduces tare weight, are you considering incorporating this concept with conventional loose cars, or are you considering it for a dedicated consist of permanently coupled rolling stock?
If the latter, you can also take out tare weight in the car structure no longer needed to transmit pulling force through a car that might end up first out on a 200-car conventional train, for instance. Kneiling was always promoting that method of reducing tare weight. If the dedicated consist were say 20 cars, then none of them need to be any stronger than it takes to transmit the tractive force needed for 20 cars. And even with just 20 cars, if you spread the power out, you can further reduce the tare weight of the cars themselves.
First, 4mph? Those springs on the draft gear are good for up to 10mph! (or so I’ve heard…[:-^] )
Maybe if you switched with the locomotive attached, you wouldn’t need slack. But that style of switching is S-L-O-W. The yard I work with has a good grade, so it is a lot easier to cut em off, and let gravity do the rest!
Maybe on a road train
Bucyrus - It would be the latter, as you indicate. I know you’ve mentioned this before in another thread around a year ago. If we can reliably know that the car will never be used or included in any other kind of train - then yes, I suppose that we could reduce the required structure and hence the tare to reflect the lessened exposure to lighter buff and draft loads.
A couple weeks ago I was considering this in the context of one of our tank car threads here, and estimating the forces and stresses on the short cylinder of the kinds without a center sill. Perhaps somewhat surprisingly, there’s not that much weight involved with the steel that’s needed to purely transmit the longitudinal train forces. Here’s pretty much how my simplistic and ‘‘quick-and-dirty analysis’’ ran:
Consider the deisgn load as being the same as the maximum ‘shock load’ for a Grade E coupler, which is a ‘draft’ or tension force of 500,000 pounds, such as from a train starting or a slack run-out.
Figure the steel has an allowable tensile ‘working stress’ of 20,000 psi - I know, that’s probably not the currently accepted analytical method, and is also a really low stress value, but bear with me here for a moment - substitute your own value if you like.
So, the required cross-section area to accomodate that load is 500,000 / 20,000 = 25.0 square inches. If we estimate the bottom to be about 10 feet across and each side to be about 12 feet high, then the total perimeter of that U-shape is about 34 feet. Spreading that 25 sq. in over that 34 feet x 12 = 408 inches or so means that an average thickness of about 0.06 inch = 1/16 inch of the skin thickness would be nee