I'm not so sure that this would be an OP engine, FM also has the rights to the 251 engine.
Suspect it is a radial device with three cylinders each 120-degrees apart with a very short crankshaft
The FM opposed=piston scheme means an even number of cylenders, 2, 4, 6, 8, etc. How do you do it with three? If it is not the Wankel arrangement, then possibly Delta, with three cranksafts? Far too unnecessarily complicated, in my opnion.
daveklepper The FM opposed=piston scheme means an even number of cylenders, 2, 4, 6, 8, etc. How do you do it with three? If it is not the Wankel arrangement, then possibly Delta, with three cranksafts? Far too unnecessarily complicated, in my opnion.
In MY understanding of the FM opposed Piston engine, there could be ANY number of cylinders, with each CYLINDER HAVING TWO PISTONS inside of it, with the pistons moving TOWARDS each other on the compression stroke, and AWAY from each other on the power stroke. There are TWO crankshafts that are geared together. The number of CYLINDERS does not need to be of an EVEN denomination, but it sure helps if the number of PISTONS is
Doug
May your flanges always stay BETWEEN the rails
OP itself stands for 'opposed piston' - one famous automobile version developed in recent years is the OPOC.
The FM engine, first developed in the '30s, is notable for having no valves to burn or cylinder head to warp; injection is easy and direct without need for fancy prechambers and quench, and combustion is good in the 'chamber' between shaped piston crowns. It is a two-stroke engine with scavenge ports that 'sweep' from one end of the cylinder volume to the other when the pistons are mutually apart. On the flip side, there is that whole upper crankshaft, on the top of an already tall engine, and oil cooling of the upper pistons, leaks from the bearings, etc. all find their way down where you don't want them. As FM locomotives got older, this could result in some terrific smoking at idle - I think there was a story in an old issue of Trains about a FM that was given a block heater so it could be shut down over the weekend in winter ... idling it smoked out the whole area downwind!
On an EMD, you pull a power assembly if there's a piston problem like worn rings. GEs and Alcos are more involved, but still manageable. On an OP, you have to unbolt and remove the whole top of the engine, and then resynchronize the bevel-gear shaft, blower drive, etc...
The number of pistons is determined by the horsepower requirement and the crankshaft balancing/harmonics. Note that balancing is complicated a bit by the fact that the upper crankshaft is phased a bit differently from the lower one (about 15 degrees).
Many people think of the OP as being predominantly for freight service, but some of the fastest locomotives built in America had them (the Speed Merchants).
Sand corrected. I understand now that a 3-cylinder OP is possible, in that with two pistons it is still one cylinder.
The British "Deltic" from the 1950s had a setup where three pistons shaerd one combustion chamber. Obviously not a single cylinder, as the pistons were 120 degrees apart. Like the OP, multiple crankshafts and associated synchronization problems.
rcdrye The British "Deltic" from the 1950s had a setup where three pistons shaerd one combustion chamber. Obviously not a single cylinder, as the pistons were 120 degrees apart. Like the OP, multiple crankshafts and associated synchronization problems.
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Oh, wow. And I thought the OP was wild. There was a different British design which was like the one I described, which I interchanged with the Deltic. The Deltic was successful in the sense that it was used for quite a number of years. It must have been a maintenance nightmare.
rcdryeThere was a different British design which was like the one I described, which I interchanged with the Deltic.
What is that? You've piqued my curiosity...
About the weirdest setup I know is the Doxford/Commer-Knocker setup where all the opposed pistons work on a common crankshaft. It's hard to believe these things run very long at all, let alone can be reliable for extended periods of time compared to more conventional contemporary engine designs.
Wizlish . . . As FM locomotives got older, this could result in some terrific smoking at idle - I think there was a story in an old issue of Trains about a FM that was given a block heater so it could be shut down over the weekend in winter ... idling it smoked out the whole area downwind! . . .
As I recall, the plug-in was more to keep the engine warm without using fuel, rather than smoke reduction (though that certainly would have been an added benefit. It was at Mullens, W Va., too, as I recall.
Now that many rail routes have much higher vertical clearances for double-stack container and multi-level (auto-rack) trains, I've wondered if there would be room (pun intended !) for an FM Opposed-Piston locomotive to make a comeback. It might be able to use that added height to good advanatge - how would it compare in fuel useage and pollution emissions to today's locomotives ?
- Paul North.
Wasn't there something in that story about a blue haze of oil smoke over a wide area? I can't get to the Complete Collection at present (Mac issues) to be sure, but someone might check it...
Paul_D_North_JrNow that many rail routes have much higher vertical clearances for double-stack container and multi-level (auto-rack) trains, I've wondered if there would be room (pun intended !) for an FM Opposed-Piston locomotive to make a comeback. It might be able to use that added height to good advantage - how would it compare in fuel usage and pollution emissions to today's locomotives ?
I'm not actually sure a modern version of an OP engine would need to be excessively high - did the Speed Merchants have 'downsized' versions of the powerplant? I have not calculated whether there are added stability concerns from the mass or momenta of the upper crank arrangements -- but they would surely be less than the effect of loaded doublestacks on low-bolstered 3-piece well-car trucks...
My father has noted that stack clearances are potentially advantageous both for modern OP engines and for steam engines using something like the Donlee multiple-pass boiler (see for example the TurboFire XL tests). The potential 'fly in the ointment' is that the same argument applies to putting Tier 4 final, or enhanced mufflers, or whatever, in the higher clearance spaces, and we have not seen (to my knowledge) designs or even proposed variants of production locomotives that do this.
In my opinion at least, a greater problem is that the company with current rights to the OP engine explicitly forbids its use or adaptation to railroad service. I have seen drawings of a turbocharged version developing higher than 8400 hp from a single engine, if there were to be an application (probably involving multiple road slugs) that 'valued' that level of output. But at least until recently it was the 251 family for locomotives, or nothing.
I suspect that fuel usage and at least some of the emissions problemswould be solved with better injection technology, ceramics on the piston crowns, etc. The design is fundamentally strong in a way that permits higher charge-air preheat (to do this, the required turbocharging pressure becomes very high for the same reasons that intercooling, at lower thermodynamic efficiency, addresses). However, I'd also expect the NOx emissions of such an engine to increase, meaning that appropriate abatement (at least comparable to that for GM 2-stroke power) would ALSO need to be mounted above or around the engine, and designed to be modularly removable to expose the upper crank stuff for maintenance...
Wizlish - that 1973 article (pgs. 46 - 47) said: "The branch runs through a residential area, and as the monster idled by the station, the sound of the opposed pistons churning away through the nights and on the Sabbath disturbed many. Noise pollution control, late 1950's-style, demanded that the engine be shut down in the off hours." No mention of smoke or air pollution concerns of any kind.
That entire Aug. 1973 issue was pretty much an all-Train Master one" "THE TM: BORN TOO BIG TOO SOON", though that's also the issue in which the Editor announced no more 'single-topic' issues.
Thanks for the response to my question about OP engines in double-stack clearances. I was able to follow it as far as the "intercooling" part . . .
FM OPs were quite successful in places where they existed in reasonably large quantities, and were locally maintained. SP's Trainmasters were surrounded by a reasonably large group of H-12-44 switchers, all maintained at SP's Bayshore shops. MILW also had a large group that lasted into the 1970s. Even C&NW's units worked well after they were concentrated in Wisconsin and Michigan.
Where OP's (and Baldwins, if it came to that) did not do well was where they were roster minorities. Early GE U-Boats suffered the same way, getting less maintenance than they needed.
Many FMs and Baldwins were withdrawn for electrical rather than prime mover reasons. Westinghouse parts became fairly hard to get, or at least fairly expensive, after the mid-1960s.
In my neck of the woods, we had FM yard power - all maintained locally, and blew oil all over the place. Crews appreciated when the FM's were replaced with EMD power.
One location was required to have U Boat GE power account servicing a GE plant. Crews hated them with a vengence.
Never too old to have a happy childhood!
Paul_D_North_JrThanks for the response to my question about OP engines in double-stack clearances. I was able to follow it as far as the "intercooling" part . . .
Ah, so...
An older approach to "better" diesel performance is to retain as much of the compression heat in an intake charge as possible, rather than intercooling to get higher oxygen density. This requires substantial pressure, 60 psi or better, and 'traditionally' the use of staged compression ('twins', etc.), and in turn this produces very high peak temperature during combustion, enough to endanger valves ... in engines that have them ... and I think enough to increase the amount of NOx from compression ignition.
In practice, I suspect there would still be intercooling, probably using split cooling, combined with active wastegating. VERY competent FADEC would then determine the appropriate mix of efficiency vs. power vs. 'turbine inlet temperature' to the first stage of turbocharging.
I suspect NOx generation during high temperature, high pressure operation would be high enough, even with substantial EGR, to require some form of urea treatment to achieve Tier 4 standards (or better). On the flip side, I'd expect much lower effective nanoparticle generation, no need for an already dubious oxidation catalytic converter, and perhaps -- hopefully, in fact -- no need for an idiotic regeneratively-cleaned DPF (except insofar as you could recover the added regeneration heat for useful purposes, for example in the pressure-charging turbines or in an absorption refrigerator or ORC bottoming system).
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