I see references to locomotive trucks often (diesel-electric mostly), but nothing about the differences among the types and the reasons why they are constructed differently ('Type A', 'Type B', 'Blomberg', 'High Adhesion', 'Radial', etc., etc.). Are there any references that would be comprehensible to a layman that explain and illustrate truck construction? I see scattered articles on truck types on Internet searches, but nothing like a comprehensive discussion. Suggestions welcome. /LEJ
PM Dave Goding. What he doesn't know already, he can point you toward.
A good general introduction to diesel locomotive trucks is contained in a book, "Model Railroader Cyclopedia Volume 2 - Diesel Locomotives" starting on page 18. This dates to 1980 and has little past the introduction of EMD "Dash 2" locomotives in 1972. But it should be possible to find a used copy somewhere (possibly on line).
This has good clear photos of most locomotive trucks up to the date of the book.
It has a good if small drawing of the EMD Blomberg two axle truck, including a section that shows the secondary full elliptic springs, the swing hangers and the spring plank, which is the hardest thing to visualise without drawings.
It is worth noting that AAR type B trucks have similar swing hanger scondary suspension, but this is not as visible as on the Blomberg.
The collection of photos shows the external appearance of the trucks up to about 1972. With the three axle trucks, the EMD Flexicoil, the EMD HT-C and the GE three axle Floating Bolster trucks all look generally similar in appearance, and they all have a central pivot on a bolster.
The Flexicoil has coil secondary suspension (between the truck frame and the bolster) while the HT-C and Floating Bolster have rubber pad secondary suspension. The rubber is stiff vertically but allows lateral movement. One result of this is that the primary coil suspension (above the axleboxes and below the truck frame) must be softer than in the Flexicoil, where the secondary coils provide more vertical flexibility.
EMD built some trucks to the HT-C design for use in Australia from 1967 (so five years before they were adopted in the USA. Some of these locomotives developed frame cracking around the bolster pivot, at least partly due to the harder ride from the rubber secondary suspension. The frames were lighter than USA frames due to weight limitations.
Interestingly, the Alco three axle Hi Ad is basically similar to the EMD Flexicoil with the exception that the "flexicoils" are outside the truck frame rather than inside.
Sadly, one of the most important trucks of the period, the Canadian MLW/Dofasco was not covered in this book. This was like the EMD HT-C but had no bolster, the rubber secondary pads supporting the locomotive frame directly with a non-weight bearing pivot point.
This truck led to the GE "Roller Blade" trucks after GE obtained MLW design data, and less directly to the EMD steering trucks and their rigid decendants which also used rubber secondary suspension directly to the frame and a non weight bearing pivot.
But the Kalmbach book is a good place to start. Similar photos appeared in the "Second Diesel Spotter's Guide".
Peter
Many thanks, Peter, for the detailed discussion.
I have Louis Marre's Diesel Locomotives: The First 50 Years (a guide to diesels built before 1972), which has a section at the end on diesel trucks, with photos of the main types. That's what sparked my interest, as the side views don't show the components or what they do. I'll look around for the Modeler's Guide; used copies seem pricey.
It's funny—I have a number of books on diesel locomotives, but aside from Marre's book, none spend any time on the construction of trucks. When you figure that they carry the traction motors that really move the train, this seems like quite an oversight. —LEJ
MrLynn I'll look around for the Modeler's Guide; used copies seem pricey.
My complaint with most of these is that they are precisely what they were written to be: railfan guides. You get railfan terminology, and railfan spotting differences, not the engineering as to why the designs were made as they were, or the course of sometimes surprising improvements... or blind alleys. I loved the hell out of Alco's three-axle Hi-Ad design as a kid -- there might be no more Big Locomotive Means Business! Truck frame design than that -- but it had a nasty harmonic-rock resonance disturbingly near that produced at common '60s and '70s road speed on poorly maintained jointed rail. Which was most of what people running big Alcos increasingly had...
The Internet is such a good place to put 'enthusiast' discussion of favorite detail design, and the actual technical interest in differential design of various trucks do specialized, that I wouldn't be surprised to see many actual detail books or textbooks on the subject ... especially with publication costs rising and the 'used' market for specialty texts so ruthlessly exploited.
Overmod PM Dave Goding. What he doesn't know already, he can point you toward.
Don't see a PM button anywhere. . .
Overmod My complaint with most of these is that they are precisely what they were written to be: railfan guides. You get railfan terminology, and railfan spotting differences, not the engineering as to why the designs were made as they were, or the course of sometimes surprising improvements... or blind alleys. I loved the hell out of Alco's three-axle Hi-Ad design as a kid -- there might be no more Big Locomotive Means Business! Truck frame design than that -- but it had a nasty harmonic-rock resonance disturbingly near that produced at common '60s and '70s road speed on poorly maintained jointed rail. Which was most of what people running big Alcos increasingly had... The Internet is such a good place to put 'enthusiast' discussion of favorite detail design, and the actual technical interest in differential design of various trucks do specialized, that I wouldn't be surprised to see many actual detail books or textbooks on the subject ... especially with publication costs rising and the 'used' market for specialty texts so ruthlessly exploited.
I'm not a modeler nor a technician, so my interest is mainly fan curiosity. Naive questions come up, like "How could one RR truck provide better adhesion than another?" "What's the difference between 'road' and 'switcher' trucks?" I see references to things like this often, but no explanations.
Guess I should do more research on the Internet. E.g. a quick search finds some good photos here: https://condrenrails.com/Diesel-Locomotives/trucks/index.html But it's a photo site; no discussion.
Thanks for the response(s). —LEJ
MrLynn Overmod PM Dave Goding. What he doesn't know already, he can point you toward. Don't see a PM button anywhere. . .
Click on bogie_engineer's avatar then click on "Start conversation".
_____________
"A stranger's just a friend you ain't met yet." --- Dave Gardner
One of the best resources, in my opinion, are patent drawings and text to understand the details and the designer's intent. The claims are often indecipherable to a layman but the descriptions are usually good reading. Here's some references you can look up on the US Patent Office search site: http://patft.uspto.gov/
Blomberg's E truck design: 2,189,125
Blomberg's Rigid Switcher truck: 2,137,074
EMD DD truck: 3,313,244
EMD HT-B truck on some GP40X's: 4,075,950
EMD HTCR radial truck: 4,765,250
GE Steerable truck: 5,746,135 & 6,006,674
A great reference for trucks and other RR related topics is Don Strack's Utah Rails site, specifically for trucks: https://utahrails.net/loconotes/loconotes-trucks.php
Dave
Overmod MrLynn I'll look around for the Modeler's Guide; used copies seem pricey. I bought mine (very belatedly!) for $8.50 last month off eBay, together with an equally-used copy of the hardbound 'Volume 1' for steam locomotives. If you are patient and set automatic search you will find reasonable prices. My complaint with most of these is that they are precisely what they were written to be: railfan guides. You get railfan terminology, and railfan spotting differences, not the engineering as to why the designs were made as they were, or the course of sometimes surprising improvements... or blind alleys. I loved the hell out of Alco's three-axle Hi-Ad design as a kid -- there might be no more Big Locomotive Means Business! Truck frame design than that -- but it had a nasty harmonic-rock resonance disturbingly near that produced at common '60s and '70s road speed on poorly maintained jointed rail. Which was most of what people running big Alcos increasingly had... The Internet is such a good place to put 'enthusiast' discussion of favorite detail design, and the actual technical interest in differential design of various trucks do specialized, that I wouldn't be surprised to see many actual detail books or textbooks on the subject ... especially with publication costs rising and the 'used' market for specialty texts so ruthlessly exploited.
I bought mine (very belatedly!) for $8.50 last month off eBay, together with an equally-used copy of the hardbound 'Volume 1' for steam locomotives. If you are patient and set automatic search you will find reasonable prices.
I am also a big fan of the Alco Hi-Ad truck. I've traelled hundreds of miles in those locomotives and never experienced any harmonic rocking, although I was riding on 132lb rail continuously welded from new all on 24 inches of crushed rock ballast.
BHP Iron Ore really liked them and had 27 M636 units built with the Alco Hi-Ad truck rather than the Montreal/Dofasco design. Eventually they bought units with MLW trucks but only because the Alco licensee refused to build any more trucks to that design.
BHP Iron Ore rebuilt 32 C636s and M636s as General Electric Dash 8s but no units with MLW Dofasco trucks were rebuilt, only units with Alco Hi-Ads were modified.
Eight Dash 8 units were built new with GE Floating Bolster trucks. When BHP took over the Mount Goldsworthy line, which had jointed light (94 lb/yd) rail (subsequently welded) they soon found that they needed to use the units with GE trucks on the light rail and this showed up in my photos of this operation.
But thanks to BHP, more units with Alco Hi-Ads were built in Australia than in the USA.
The Indian Railways built some high speed prototype electric passenger locomotives. Two used Alco Hi-Ads (or a copy thereof, since no Hi-Ads were built for 5'6" gauge) and two had EMD export Flexicoils from retired GT16C locomotives (an export version of the SD24).
The high adhesion feature of the High-Ad is clearly visible. The large and obvious traction rods between the truck frame and bolster mean that the traction forces are transferred to the bolster at axle level, which avoids any tendency for the truck to lift at the front, which would happen if the forces were transferred above the axle level. This avoids the lead axle unloading and possibly slipping.
MrLynn Overmod My complaint with most of these is that they are precisely what they were written to be: railfan guides. You get railfan terminology, and railfan spotting differences, not the engineering as to why the designs were made as they were, or the course of sometimes surprising improvements... or blind alleys. I loved the hell out of Alco's three-axle Hi-Ad design as a kid -- there might be no more Big Locomotive Means Business! Truck frame design than that -- but it had a nasty harmonic-rock resonance disturbingly near that produced at common '60s and '70s road speed on poorly maintained jointed rail. Which was most of what people running big Alcos increasingly had... The Internet is such a good place to put 'enthusiast' discussion of favorite detail design, and the actual technical interest in differential design of various trucks do specialized, that I wouldn't be surprised to see many actual detail books or textbooks on the subject ... especially with publication costs rising and the 'used' market for specialty texts so ruthlessly exploited. I'm not a modeler nor a technician, so my interest is mainly fan curiosity. Naive questions come up, like "How could one RR truck provide better adhesion than another?" "What's the difference between 'road' and 'switcher' trucks?" I see references to things like this often, but no explanations. Guess I should do more research on the Internet. E.g. a quick search finds some good photos here: https://condrenrails.com/Diesel-Locomotives/trucks/index.html But it's a photo site; no discussion. Thanks for the response(s). —LEJ
Mr. Goding is the expert around here, but I am buzzword enabled on this.
Improved adhesion comes from controlling weight transfer when the traction motors and in turn the axles are pulling hard against the whole truck springs and linkages leading back to the locomotive frame.
The slipping of the front engine on the Duplexes, Mallets and simple articulated locomotives is explained as a weight transfer problem.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
MrLynnquestions come up, like "How could one RR truck provide better adhesion than another?" "What's the difference between 'road' and 'switcher' trucks?" I see references to things like this often, but no explanations.
The explanations are there but you have to dig for them (and know what you're looking at sometimes, and take careful cumulative notes). Some of the better material has a nasty habit of disappearing over time, as interests change, sites die, or people try to eliminate bad ideas...
Remember that a locomotive bogie has to do a number of things simultaneously, ideally without one of the functions severely upsetting others. The locomotive has to follow the track, which may not be level or in good shape, and sometimes has very restricted ability to handle vertical or transverse loads. It must also be capable of negotiating curves, and both accommodating and absorbing road shocks of various kinds. Since it provides tractive effort, the methods of motoring the axles, and consequences of supplying traction via the wheels and bearings, become important. Cost, including cost of maintenance, relative ease of maintenance, and immunity from failure of key components (as notably found in the unpowered Allied Full Cushion truck, otherwise an excellent high-speed design) are also factors.
We've covered a number of these things in various posts. The key with this mysterious 'weight transfer' is that in order to get tractive effort from the turning wheels to the drawbar at the end of the locomotive, it has to be transmitted, and where this transmission isn't in a straight line it can tend to 'cock' or lift part of the truck in a way that unloads some of the wheels in a way the equalization poorly accommodates. The simplest example of this is some of the early 'trimount' trucks, with unequal axle spacing to get all the motors 'inside' the truck wheelbase to keep it short. These are usually nose-suspended motors, meaning that the actual motor torque is exerted away from the wheel, via a pinion and bull gear, and the torque reaction between the pinion and gear tends to rotate the suspended wheel away as the motor pivots on its 'nose suspension'. When all three motors rotate the same way, the result is to lift or depress the truck frame equally, but if they counterrotate, one tries to lift while the other drops, and this confuses any drop equalization. In the relative absence of good antislip control on traction motors, as on (say) early Baldwins like the Gravel Gerties, or RSD4/5s, this could cause all sorts of slip at the treads of the wheelsets 'jacked up' by high torque.
Assuming no further fun from the motors, the tractive effort from the wheelrims has to be transmitted to the truck frame, while allowing the wheels proper suspension action. Ideally this involves taking thrust in a plane measured relative to the axle centers or journal-box centers of contact; if there are any levers or struts they should act in or below this plane for stability. Some trucks carefully put a traction strut from the truck frame to the carbody independent of the truck pivot arrangements (or axle steering arrangements) which prevents any effects of trying to take TE through the truck bolster arrangements or the physical pivot point between truck and locomotive frame -- look carefully at your patent drawings to see how different designs provided the bolster and pivot, and how some later designs have 'centerless' or shear-member secondary suspension without a physical pivot taking load and rotation together at all. (There at one point was a good technical explanation of Henschel "Flexi-Float" bogies in conjunction with the GE "Blue Tiger" export locomotive design ... but I think it is now gone from the Web, another victim of robots.txt paranoia...
Find and read some of Mr. Goding's discussion of steering in trucks, from the experiments in the '80s forward to the current recognition that formal steering levers a la Klien-Lindner are not really necessary with proper detail design and geometry.
Technically, a switcher truck should have more flexibility, be capable of exerting more starting TE effectively, and handle very rapid acceleration and braking without upset. In practice, cheapest cost often seemed to rule the day. In some cases (as Don Strack relates for the TR units UP bought to be road helpers) the poor high-speed suspension and damping in cheap switcher trucks was a major problem. There is also the consideration when switchers have to be moved over regular lines for service or other assignments -- while they can usually be more or less happily MUed or carried isolated or even dead-in-train, if they have AAR switcher trucks or equivalent the whole train will be limited to the speeds the trucks can safely handle.
Many thanks for the scholarly discussion, Overmod, and apologies for the late response.
I read through Dave Goding's history of his role developing EMD's radial truck and the ensuing discussion in the thread from earlier this year,
http://cs.trains.com/trn/f/741/t/281717.aspx?page=1
It is fascinating to read engineers' reports of their own work, even when much of it is over my head. I really had no idea of the complexity of locomotive bogies (trucks), which have to deal with multi-directional forces resulting from power being applied to the wheels—I had generally imagined simple freight-car trucks with a couple of traction motors stuck on them, happily swiveling along.
I'll look further at the Patent Office diagrams and try better to familiarize myself with the names and functions of all the parts. I did find one site that is more or less the kind of primer I was looking for, albeit from Japan, "How Bogies Work":
https://web.archive.org/web/20070927202523/http://www.jrtr.net/jrtr18/pdf/f52_technology.pdf
This will be of interest to others as new to the subject as I am. I wonder if Mr Goding or others as expert would consider writing an introductory article on bogies for Trains—if they have ever done one, it doesn't show up on my Internet searches.
One surprise from Mr Goding's posts: I would never have suspected how great a role rubber seems to play in bogie suspensions. One would think that rubber bushings, etc. would wear too quickly for such heavy industrial applications. But then, my little Casita travel trailer's Dexter axle contains essentially rubber bands. /LEJ
With respect to the rubber - the French were early pioneers of the use of elastomer, often using the 'Silentbloc' name (or variants).
Note Dave Goding's post about the HT-BB on this forum in 2009; the four-wheel HT-B truck (as seen on the GP40x and offered on the GP50s) used a composite spring for secondary compliance at multiple angles. The resulting lateral compliance was just awful at the time (perhaps seen as particularly wanting compared to the over 2" of controlled lateral in the swing-hanger 'Blomberg' it was to replace) but I suspect that could have been addressed either by re-angling the composite secondary springs or making them more anisotropic. The fact this wasn't done in practice for the GP50 and GP60 lines does indicate it was not a simple solution.
The GE FB-2 ('floating bolster) has a great many elastomer rubber blocks in its construction, and a couple of examples I've observed show these collapsing like Mercedes-Benz rubber mounts of comparable vintage (and perhaps comparable oil and grease exposure). I was told this deterioration does not materially affect the weight-transfer characteristics of this truck under load, although I'd be interested to hear from railroaders over how well these do in service.
The great advantage of rubber in the ways the railroads generally use it is that it does not exhibit a resonant spring-rate effect -- the thing 'snubber' springs were designed to help break with leaf or helical suspensions. This makes them ideal for, as an example, providing the 'centerless' truck rotation on many recent locomotives. On the other hand there have been complaints about some of the early GM isolated cabs (the ones with the black line of visible elastomer) -- supposedly these start sagging with age and it doesn't take much to make them into thundercabs...
Elastomer springs came in to use at EMD in the mid-1960's first with the GL-C and GH-C 3 axle high adhesion trucks for export lower axle load applications and finally the HT-C which is a scaled up version of the GH-C for NA axle loads (it was designed for up to a 450,000 lbs. loco but never sold at that high a weight). In those trucks, a secondary suspension that was stiff vertically, but softer laterally, was needed to keep the truck frame from pitching relative to the bolster to minimize weight shifting within the truck. The first HT-C springs on SD40-2/SD45-2/SDP40F locos were too stiff in the lateral direction and gave a very rough lateral ride, after a few years production a softer lateral spring was developed which was used through the SD60 production. A nice feature of rubber springs is the ability to shape them and adjust rubber durometer to optimize the stiffness in each direction. As OM notes above, the HT-B suffered from poor initial ride performance and would have been fixed had there been a continued market for that truck; instead, after the GP40X's it was never used again. Although some say it was offered on GP50's, by the time that model came out it was discontinued in EMD's eyes.
The main problem with rubber springs is they suffer from set and drift under load. Set is permanent deformation, drift is deformation over time that recovers if the load is removed. The cab isolators suffered from the long term set and drift both as they never are unloaded vertically and eventually the isolation they provided was short-circuited. The rubber truck springs at EMD have proven to be highly reliable and I am sure many SD40-2's are in service with 50 year old springs, although the maintenance instructions say change at 10 years.
Elastomer springs came in to use at EMD in the mid-1960's first with the GL-C and GH-C 3 axle high adhesion trucks for export lower axle load applications and finally the HT-C which is a scaled up version of the GH-C for NA axle loads - Bogie Engineer
I don't think I've ever heard the name GH-C before.
Hovever, from what I know about EMD Export units, most if not all GH-C bogies must have been used in Australia. The first of these appeared in 1967 on 25 GT26C units of 135 long tons for Western Australia and on 20 J26Cs of 108 long tons for New South Wales. There are references in the ASME Paper on the development of the HT-C truck to prototype testing in Australia.
It has recently been mentioned on this Facebook site
https://www.facebook.com/groups/1261157917311429/
that the J26Cs suffered from underframe cracking around the bogie pivots when new. I suspect that this was due to the primary springs being too stiff since there was very little vertical flexibility in the rubber secondary pads. It is possible that if the same springs were used as in the heavier GT26Cs, the lighter units ended up with a much harder ride.
About this time the Victorian Railways decided to replace the Flexicoils (which had been cracking and failing on the VR's fairly ordinary track) in their older trucks with rubber pads (I was told standard EMD pads from SD40-2s) . This caused significant frame cracking around the pivots, but they never changed back to flexicoils, nor to my knowlege, fitted softer primary springs.
There were many more GH-C bogies built, 17 sets for AT26Cs in 1970, 8 sets for JT26Cs and 10 sets for GT26Cs in 1976-77 and 84 sets for JT26C-2SS in 1981-82. By this time a new EMD Trimount design had been adopted, much like the GH-C in appearance (and dimensions, these being 12' 6" wheelbase). As the name suggests, they had an offset pivot sitting on rubber pads with the body directly suupported on two pads between the two inner axles. Most later JT26C-2SS had these Trimounts, as did most of the later narrow gauge GL22Cs and GL26Cs but the GH-C had a last outing on 25 JT22CH-2SS passenger units.
Most of these units still exist and many are still in service. All the JT22CH-2SS units are still in service with their original operator, the only change (apart from paint) being the substitution of D43 motors by D77s (because they are cheaper to buy as unit exchange).
M636C Hovever, from what I know about EMD Export units, most if not all GH-C bogies must have been used in Australia. The first of these appeared in 1967 on 25 GT26C units of 135 long tons for Western Australia and on 20 J26Cs of 108 long tons for New South Wales. There are references in the ASME Paper on the development of the HT-C truck to prototype testing in Australia. It has recently been mentioned on this Facebook site https://www.facebook.com/groups/1261157917311429/ that the J26Cs suffered from underframe cracking around the bogie pivots when new. I suspect that this was due to the primary springs being too stiff since there was very little vertical flexibility in the rubber secondary pads. It is possible that if the same springs were used as in the heavier GT26Cs, the lighter units ended up with a much harder ride. About this time the Victorian Railways decided to replace the Flexicoils (which had been cracking and failing on the VR's fairly ordinary track) in their older trucks with rubber pads (I was told standard EMD pads from SD40-2s) . This caused significant frame cracking around the pivots, but they never changed back to flexicoils, nor to my knowlege, fitted softer primary springs. There were many more GH-C bogies built, 17 sets for AT26Cs in 1970, 8 sets for JT26Cs and 10 sets for GT26Cs in 1976-77 and 84 sets for JT26C-2SS in 1981-82. By this time a new EMD Trimount design had been adopted, much like the GH-C in appearance (and dimensions, these being 12' 6" wheelbase). As the name suggests, they had an offset pivot sitting on rubber pads with the body directly suupported on two pads between the two inner axles. Most later JT26C-2SS had these Trimounts, as did most of the later narrow gauge GL22Cs and GL26Cs but the GH-C had a last outing on 25 JT22CH-2SS passenger units. Most of these units still exist and many are still in service. All the JT22CH-2SS units are still in service with their original operator, the only change (apart from paint) being the substitution of D43 motors by D77s (because they are cheaper to buy as unit exchange). Peter
EMD used the GH-C on quite a few locomotives around the world, I know South Africa got a quite a few equipped with inter-bogie control, a linkage beneath the fuel tank that connected lead and trail bogies with a spring-loaded link to try and force equal and opposite yaw, I think this was at Dr. Scheffel's doing. I have part numbers of bogie frames for meter, 3'-6", standard, and 5'-6" gauge so there were many uses over the years. It was designed for locomotives weighing 190K to 315Klbs and offered with single shoe or clasp brake rigging and optional truck-mounted sandboxes. Wheelbase is 143", compared to 163.4" on the HT-C so the motors are really tight to the transoms.
For comparison, the GL-C had a wheelbase of only 129.5", made possible by the use of close-coupled D29CC traction motors (axle to armature distance shortened) and only offered single shoe brake rigging. It was designed for 156K to 210Klbs. locos and was made in meter, 3'-6", and standard gauge.
The other popular EMD 3-axle export truck was the GC truck from the 1950's, which had a flexicoil secondary suspension with versions for 3'-0", meter, 3'-6", standard, and 5'-6" covering a loco weight range of 180K to 263Klbs. I believe the first use was G16's for India in broad gauge. This was the truck used on the SDL39's for the Milwaukee.
I'm not familiar with an EMD tri-mount design, must have been designed by Clyde or EDI as I know we didn't do it in LaGrange.
Substituting rubber springs for longer travel coils or elliptics can definitely cause problems if the primary aren't softened. EMD had a bad experience with the conversion of the GP (Blomberg) to rubber secondary springs to fit single shoe rigging with introduction of the -2 line. Eventually mostly solved with the low profile elliptic springs released in the mid-80's.
I was impressed from early in my career with some of the Clyde designs for the unique Australian requirements. IIRC, the chief engineer was a really great engineer named Dave Butters who visited LaGrange often looking for information or to convince EMD to design some unique parts for their use. Perhaps you know him.
Of course I know Dave Butters. I last saw him at a rail conference in Sydney, maybe two years ago. He looked a bit frail due to his age, but I had a chat to him about locomotive topics. I remember speaking to him about design variations in Clyde units, maybe as long ago as the early 1980s. I was very impressed by the JT26C-2SS as built for NSW, the "81 class". This had a heavy side girder underframe with a cowl body removable in sections, which gave ready access to the engine if required. These were the units with the 12' 6" HT-C style truck. All the other JT26C-2SS units had a carbody structure with full height trusses in the sides and they also had the Trimount bogie.
Dave indicated that he wasn't impressed with the cowl units. The structure was heavier, resulting in a smaller fuel tank and a restricted range to keep within the allowed 128 long tons.
Those were the first standard/broad gauge Trimounts and that design might have been a further weight saving.
They built 80 of the cowl units and 43 of the carbody units. The carbody units aren't as strong and suffer from deformation from rough handling. Two were scrapped after a collision.
The first 95 JT26C-2SS units had the AR16 alternator, and these are popular with crews since there is no transition with the accompanying loss of power.
As well as the 80 units, NSW purchased four full sets of equipment as spares. After ten years, they found they had only used the traction motors, so they had Clyde build four new frames and assemble four additional units.
These were used for many duties, but they have hauled grain on the main south line up 1.5% grades for nearly forty years. We now have a very good grain harvest this year, and the trains have sometimes been overloaded.
It seems that the 12'6" truck may not really be a GH-C, but is definitely a scaled down HT-C.
I think I should post a couple of illustrations of the truck types I've described.
First the Clyde Trimount on a JT26C-2SS...
Scroll down through the photos and data for the diagrams.
https://www.victorianrailways.net/motive%20power/gdiesel/gdiesel.html
The HTC analog is at:
https://www.victorianrailways.net/motive%20power/pics/N-1.gif
The truck sidrframes look very similar and I'm sure that most railfans think they are the same.
To understand my point about paint on the passenger units, see:
https://www.victorianrailways.net/motive%20power/ndie.html
For any diehard steam fans that have read this far...
https://www.victorianrailways.net/motive%20power/ssteam/ssteam.html
Engineers might appreciate the photos of the moulds for and one piece castings for the three cylinders. There is a link for locomotive diagrams.
M636C I think I should post a couple of illustrations of the truck types I've described. First the Clyde Trimount on a JT26C-2SS... Scroll down through the photos and data for the diagrams. https://www.victorianrailways.net/motive%20power/gdiesel/gdiesel.html Peter
What are 'automatic staff exchangers'?
Never too old to have a happy childhood!
BaltACDWhat are 'automatic staff exchangers'?
The idea is to have a mechanical piece that confers route authority on its possessor, perhaps by insertion into a device that then works with some version of automatic train control.
If a train is moving quickly, you have some of the same problems as in relay races, with the physical staff 'slapping' into the fireman's (or whoever's) hand with what can be severe force. Therefore arrangements like those used for high-speed mail cranes can be used to let the staff be 'picked up' at any speed, retrieved from its catcher, and inserted or used appropriately. (There is at least one episode of the old TV show "Railway Roundabout" that specifically shows one of these in use...)
I suspect there may also be devices that automatically register the staff as well as exchange it -- I'll hand that to Mr. Clark to describe in detail.
BaltACD M636C I think I should post a couple of illustrations of the truck types I've described. First the Clyde Trimount on a JT26C-2SS... Scroll down through the photos and data for the diagrams. https://www.victorianrailways.net/motive%20power/gdiesel/gdiesel.html Peter What are 'automatic staff exchangers'?
As noted in the text at the link the G class were "the first locomotive delivered without staff exchangers", hence the question.
Looking here
https://en.wikipedia.org/wiki/Token_(railway_signalling)
The token, or staff is effectively a permanent "train order" between two locations. Variations in the system are described in the Wikipedia article. The name "staff" is used for the cylindrical version of the item used in the interlocked machines.
The electric staff system consists of two machines electrically interlocked, so that only one "staff" can be removed from either machine at a time. While there is an illustration in the article, the operation can be observed in this video:
https://www.youtube.com/watch?v=-uFJs-xoTMM
This, at 16.00 in the video, shows a manual exchange, but an "automatic" or more correctly mechanical exchange is similar. The video shows the electric staff machines in use.
Clearly, it is better to describe the system on a locomotive that actually has the system fitted. Checking
and the photos at
the device can be seen immediately above the leading axle on the left hand side of the locomotive (only in the photos in the orange and grey colour scheme) and is a rectractable hook device with a curved helical section (sometimes called a "ram's horn") intended to retain the hoop with the attached staff. This is recovered by a crewman through a hatch in the recess or replaced for dropping at the other end of the "section".
The system had been abandoned on the Victorian broad gauge by the time the maroon and blue colour acheme had been adopted.
Doesn't anyone have a comment about the trucks?
M636CDoesn't anyone have a comment about the trucks?
I presume that the thing at the extreme inboard top of the trucks is an 'enhanced' traction-motor blower duct. I'd be interested to see detail pictures and a description of what that feature does, as there's nothing like it at the 'leading' end of the trucks.
Can someone explain the rationale for terming these "Trimounts"? They have equal axle spacing, presumably all the traction motors 'face the same way' in the frame, and they have no external drop equalization... I considered the offset bolster in a North American Trimount to be a matter of necessity, not choice.
I've always associated the term Trimount to indicate a truck with a pivot on or near the transom between motors 1 and 2 and a pair of secondary springs on the sideframe between axles 2 and 3, either with a fixed or sliding interface, resulting in 3 points of support with little secondary spring travel. I welcome any correction to that thinking.
bogie_engineerI've always associated the term Trimount to indicate a truck with a pivot on or near the transom between motors 1 and 2 and a pair of secondary springs on the sideframe between axles 2 and 3, either with a fixed or sliding interface, resulting in 3 points of support with little secondary spring travel. I welcome any correction to that thinking.
It also explains something about why the pivot would be spaced opposite and at equal distance from the two support pads, with the geometrical center of the truck in plan in the 'center' of the triangle, to make the best use of the three-point support so provided.
Thank you.
bogie_engineer I've always associated the term Trimount to indicate a truck with a pivot on or near the transom between motors 1 and 2 and a pair of secondary springs on the sideframe between axles 2 and 3, either with a fixed or sliding interface, resulting in 3 points of support with little secondary spring travel. I welcome any correction to that thinking. Dave
Firstly I should state that the drawing reproduced is a railway drawn diagram, not one from Clyde Engineering, and it is quite possible that the draftsman is just tracing the builder's diagram without understanding any of the content. However, that's what we have on line and it shows the main features, if a bit oddly.
AS pointed out by Overmod, the traction motor blower ducts show up with more prominence than they deserve, and all three are visible, the other two being partly concealed by the three suspension points.
The really sad part is that in this version of the drawing no body bolster is shown over the designated bogie pivot.
However, by comparing the "G class" drawing with the "N class" drawing, it can be seen that the bogie frame itself is very similar. The HT-C analog on the N class has a bolster with four point support on the bogie frame, each with a rubber/metal sandwich support pad.
On the "G class" the "bolster" is a simple plank with a central pivot carried on rubber pads. Thus the pivot is offset towards the locomotive headstock compared to the older design. The two body support springs completing the three trimount points are located where the bolster pads would have been on an HT-C.
It is possible that the same wooden moulds could be used for the casting for both the Trimount and HT-C analog versions with minor interchangeable sections of mould.
On the Alco Trimounts the two supports away from the pivot were locally called "elephant's feet" and were very stiffly sprung and subject to uncertain sliding movement in curves. On the larger units, the DL541, this gave a very poor ride, particularly at speed. On a few units rubber pads as used on the MLW Dofasco trucks were substituted and this was said to give better rotation in curves and better vertical ride.
The Clyde/EMD Trimount was used on around 250 3'6" gauge locomotives, in place of the GL-C.
That is a fantastic film. Beautifully done. Thanks for the link!
Overmod BaltACD What are 'automatic staff exchangers'? Google 'electric train staff' for the basic details of the train-staff system. The idea is to have a mechanical piece that confers route authority on its possessor, perhaps by insertion into a device that then works with some version of automatic train control. If a train is moving quickly, you have some of the same problems as in relay races, with the physical staff 'slapping' into the fireman's (or whoever's) hand with what can be severe force. Therefore arrangements like those used for high-speed mail cranes can be used to let the staff be 'picked up' at any speed, retrieved from its catcher, and inserted or used appropriately. (There is at least one episode of the old TV show "Railway Roundabout" that specifically shows one of these in use...) I suspect there may also be devices that automatically register the staff as well as exchange it -- I'll hand that to Mr. Clark to describe in detail.
BaltACD What are 'automatic staff exchangers'?
Google 'electric train staff' for the basic details of the train-staff system.
So the meaning of "staff" is from a "swords and sorcery" game or novel of a cylindrical object granting the the bearer status, power, authority or the ability to cast spells as opposed to the group of workers who have to answer a politician's mail?
Could this granting of track authority be exchanged with some kind of electronic token, using encryption to make it secure?
Paul Milenkovico the meaning of "staff" is from a "swords and sorcery" game or novel of a cylindrical object granting the the bearer status, power, authority or the ability to cast spells as opposed to the group of workers who have to answer a politician's mail?
The original system involved a piece of unfakable wood, possession of which (like the gavel at a meeting) conferred authority to occupy a piece of track -- anyone else approaching the track wouldn't have it, and therefore couldn't proceed. There was nothing special about the baton shape except that it was easy to pass back and forth between a train and the ground. Other railroads utilized a 'tablet' system, which was kind of like a flat disk or purse-shaped object with a ring handle that could be put on a hook or, later, exchanged with mail-crane-like equipment. If I remember correctly, some of these were made with wards or other special enablement to unlock specialized signal equipment when inserted -- so that no 'other' tablet could be used where access was to be restricted specifically. By inserting the staff into a ground-based device, for example, a counterpart staff could be released from its ccarefully-tamper-proofed counterpart device at the 'other end' of a block...
I don't recall this being used extensively in American practice; we went to electronic communication of written or verbal orders instead of possession of a device.
A better analogue would be to pass a handheld device with the equivalent of a thumb drive, or short-range RFID, that would serve as an access device or 'dongle' to activate safety or signal equipment. In a sense, the old QNS&L 'radio proximity' system that told any two engines how far they were from each other was a perfectly good equivalent to a 'multistaff' system that could identify continuously where the staffs were and that could at least warn when they were 'disturbingly near' each other in absolute terms... thus neatly getting around the often-mentioned difficult GPS systems have discriminating between track centers and the like. Of course a simple transponder-based system no more complicated than that for EZ-Pass would neatly extrapolate "staff" functionality to a handheld passive device, one that could be read by onboard equipment as well as external sensors.
This is a description of the system that replaced electric train staff on the Goulburn Canberra line...
ARTC Corporate Policy and Procedure Template
Note that there are electronic interlocks and the orders are not transcribed by the train operator.
End of section signals are flashing white.
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