Diesel Locomotive Truck Design


B

beiland

Well-Known Member
A recent posting brought this subject of diesel locomotive truck design back to my mind. I went looking in the search box, but was not coming up with some of the info I was seeking,...perhaps I just entered the wrong search words?


I did arrive at this 'pictorial site' which was interesting but still didn't answer some of my questions.
https://condrenrails.com/Diesel-Locomotives/trucks/index.html


My primary question(s) is how are the truck axles 'hinged' (I guess that's the correct term?). I've wondered about this before, particularly with many 3 axle trucks we see on many of the larger diesel locomotives? I recall seeing some hinged trucks on a few of our model engines, but not as many as I would have expected? Do some of the prototypes not have hinged trucks??
 
I went out to my display case and picked up a couple of Proto2K E-units. They have these hinged 3 axle trucks I was speaking of.
 
If you are referring to how the trucks pivot under the frame to permit the locomotive to negotiate curves, the whole truck pivots on a "kingpin", at least on our models. I am not sure about on the prototype, as there was provisions for the axles and journals to swing laterally to some degree. That may have just been to allow for small variation in the track. One of the prototype trucks shown in your referenced pictorial site did show a hinge in the middle of the truck frame, but that is an exception.
The other thing is that the three-axle trucks on the old E-units, had only the end axles powered with traction motors. The center axle was an idler, resulting in the designation A-1-A. Two-axle trucks were designated B-B. Trucks with all three axles powered are designated C-C.
 
hinged vs articulated

I'm changed my wording from articulated to hinged. I think the word hinged is a better description of what I am asking.
I'm questioning NOT how the truck articulates around a curve, but rather how it tries to keep all 3 wheels on any one side of the truck frame in constant contact with the rail that might have a few vertical high and low spots.
I went out to my display cabinet and picked up a couple of the Proto2K E-units. They have these 3-axle trucks that are hinged in such a fashion that 2 of the axles act in unison, while the third axle can hinge.


Proto 2K E-unit trucks

I was surprised that I couldn't find many images of these trucks on the internet?
This is what I am speaking of when I called them hinged trucks,...you can see the dividing lines on the truck covers.
image-20201226065311-1.jpeg


image-20201226065339-2.jpeg


Are there problems with these truck designs,..other than the well known cracked gears on Proto 2K locos??


NOTE: These 6 axle locos did NOT have any problems with my trackwork on my original layout, whereas I had a Spectrum 6 axle loco with very small flanges and rigid truck frames that I would bring out when searching for my track laying problems.
(previous layout,... the Central Midland,.. https://model-railroad-hobbyist.com/node/31007 )
 
Equalization

Fri, 2020-12-25 12:09 — blindog10

The term you're looking for is equalization. On diesel trucks it is accomplished by either having springs over the journal boxes or by heavy weights draped between the boxes. The weights are thick steel plate and are called "drop equalizers". The "AAR-A" switcher truck, "AAR-B" road truck, and "Tri-Mount" 3-axle truck all use drop equalizers.
Scott Chatfield


Equalizer

Fri, 2020-12-25 16:16 — dave1905

They aren’t weights, they are more or less levers, when on axle is pushed up, it pushes the others down (sorta). Steam engines have a similar arrangement in their drivers.

Dave Husman
 
Interesting design. Obviously created to overcome the 3 axle trucks propensity, if rigid as most are, of the center wheel's habit of where there might be a high point in the track of it pivoting around those wheels and derailing via, the front wheels loosing directional flange contact with the rail. Worse with the shallow flanges used now. I have seen trucks so derailed sliding along straight track and only derailing when hitting a turnout or curve entry. I don't believe my P2K Alco PA/PB's have that hinge and they are long trucks. I would think that hinge would help a lot. They look as though they might be shaft driven too.
 
@ Tootnkumin,
I was looking on the internet trying to find pics and discussions of these P2K trucks and wasn't finding much,..surprised.

And I think you are correct, they do not exist on the other P2K locos,...just on the E series,...and I am not even sure if its on all of those??
 
Ah, I see what yer talkin' bout.
I can’t think of a prototype locomotive truck like that but a buckeye freight truck would be considered to be hinged.
Loco axles move vertically in the blocks against springs but there are A1A arrangements with air actuated lifts on the center axle.
I'm unaware of any other HO loco that has hinged trucks like you’ve shown.
Still might not be the answer youre looking for but way cool subject!
 
beiland said:
@ Tootnkumin,
I was looking on the internet trying to find pics and discussions of these P2K trucks and wasn't finding much,..surprised.

And I think you are correct, they do not exist on the other P2K locos,...just on the E series,...and I am not even sure if its on all of those??
Click to expand...
I'm wondering if the chassis-drive-line-trucks are not P2k with a Proto shell fitted. I remember seeing an Anjin chassis and drive that the 6 wheel trucks were shaft driven with an Athearn shell on it. They weren't hinged like those, but the gearing was worm and pinion on each axle with the lengthwise shaft carrying the pinions above the axles and the crown gears on them. Are they the flywheels at the inner end of the truck, possibly on the end of that shaft. To allow the hinge to operate that shaft would also need to "bend" above the hinge with some sort of slip jointed universal. Quite complex.
 
I just looked at one of my P2K chasis with the 2-piece cover plates. I see no sign that the trucks are hinged between the long and short cover plate. Rather, the center axle has a fair amount of sideplay, allowing it to shift laterally as the truck goes around a curve. On some old Athearn Blue Box Alco PA trucks, which I used to kitbash some GM E7's, I removed the wheels from the center axles, leaving the axles themselves with the gears in place because I did have some problems around 18" radius track and #4 turnouts. Some later six axle E6's from either Walthers or Bachman (I forget which), seem to have no problem negotiating 18" radius, but I haven't looked at the truck construction.
Happy, Healthy and Safe New Year!
 
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