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 o
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
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.
Don’t see a PM button anywhere. . .
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
Click on bogie_engineer’s avatar then click on “Start conversation”.
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
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.
[quote user=“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&#
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 ’
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.
Dave
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
[quote user=“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 fo
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.
Peter
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.
Peter
What are ‘automatic staff exchangers’?