by 'hinged', do you mean 'articulated'

i.e. some form of frame-flexing of a single truck?  I've never seen one, though I've learned to be careful with that 'never' word.  Generally, a 2-axle truck needs no such feature, and rather than articulate a 3-axle truck, the center axle either

- has the center axle's wheels slightly 'under gauge', such that the flanges are set inside the line defined by the flanges of the wheels on the outer two axles, or

- has the axle tips shortened such that the whole axle can 'slop' back and forth a bit in the truck.

Both the above options, of course, apply to the model, not the prototype.  I have no direct knowledge of how a real 3-axle diesel truck accommodates tight radius curves - though many RRs simply restrict locos with 3-axle trucks from tight-radius industrial trackage, mandating crews to utilize 'reacher' or 'pusher' cars to access other cars on the tracks.

YMMV.  Merry Christmas, Brian!

Blair

It does look like,

at the site you linked to, there is a "steerable" 3-axle truck; the image shows what appears to be a mechanism to shift the center axle left or right of the centerline of the truck, which would accommodate what you're asking, without compromising the main frame of the truck.  (and also approximates one of the two modelling options I suggested above). That doesn't make the truck articulated, it just allows it to relieve the stresses on the truck that otherwise result from a tight radius curve.

Blair

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.

Equalization

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

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.

Equalization

Interesting point of view on this subject of equalization,..

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.
 

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,...(edited: derail prone on uneven track, and certain smaller radius tracks)

(previous layout,...  the Central Midland,.. https://forum.mrhmag.com/post/the-central-midland-layout-by-john-armstrong-atlas-plan-29-12207702)

Radial Steering Truck

...very interesting video offered by a gentleman on another forum,...

Collection of Locomotive Truck Photos

again a reference link from the other forum,..

https://donstrack.smugmug.com/UtahRails/Locomotive-Details/Locomotive-Trucks/i-zHwNWJd/A

I Think What You are Seeing

On the P2K model truck, appears to be a model engineering solution to the tight radius curves of modeling. It would allow for a "hinging effect", to use your terminology to allow the truck to "bend" around a tighter radius curve. But, I had to look at one of my own P2K units to confirm this. On the model the separation in the truck allows for some VERTICAL accommodation to uneven track structure; it flexes up and down slightly  This design does NOT allow for the "bending that you are looking for. The additional lateral accommodation of the model truck to curves is handled by the excess side to side movement of the wheels within the truck. Try moving your own truck and you will see what I mean.

I hope this helps

Espee over Donner

I wasn't looking for bending

I wasn't looking for bending around curves . I was looking for vertical accommodations,...that hinging of the third axle to stay in line withe the other 2.

I brought that other video/quote over to the discussions as I though there might be interest in this aspect of truck design.

Surprised

I'm surprised at the lack of interest (comments) on this 3 axle truck design that Proto2K utilized for a while. I'm not sure that any other model train manufacturer made use of such an idea??

Can’t say that I’ve ever heard of a hinged locomotive truck

I think that’s what the springs are for, to keep the wheels on the track.

Am most intrigued.

Model trucks

Brian,

The truck design your showing is essentially the old Athearn inside frame design, with some improvements.  The bearings have some vertical play in their slots.  The hinge may allow the other two wheel to move relative to the fixed four. 

There is nothing to force the wheel impact to be equal.  Thus, three points will support the the weight.  This will likely be on the fixed four.  The other three may contribute depending on the amount of contact, the flex point will help some.  This situation will vary from truck to truck and with age of the trucks.  These trucks have two sides that are aligned by plastic pins that the gears fit on.  There is a fair amount of variability in this alignment overall, so how effective the six wheels are will vary.  This situation would be true for 4 wheel trucks as well.  The difference is that only one wheel would not be 100% effective.

This can be said about most of the trucks that come with these models.  There are designs that will force the wheels to be nearly equal in contact force.  Prof K gave some references in my draw bar force post some years back of some interesting work done to improve this situation.  The designs are complex and would likely add to the cost of the engine.  Plus increased opportunities for problems with assembly.

In real engine trucks, there are many techniques that can be applied to improve on this problem.  For these models, it is best to keep it simple.

Wheel Diameter

One thing I haven't seen in this discussion is wheel diameter. How close are the diameters of the 6 wheels in relation to each other on one truck? With no vertical movement of the axles, if the center wheels are -.002" smaller than the end wheels, there will be no contact of the rail head, thus no traction or possible electrical contact.

Bernd

Hinged trucks

There are no hinged trucks in modern usage and the last prototype "hinged trucks" I saw pictures of were on some early Westinghouse and Baldwin diesels of the 1920's and 30's.

Steerable trucks aren't "Hinged", they have a lateral equalization that allows the axles to skew in relation to the curvature.

In the P2K truck, its not "hinged", its just the gear cover is in two pieces.  Probably the larger piece is the same as in some other P2K model so they recycled an existing cover and then added a filler.

Vertical movement in a prototype truck is accommodated by springs in the frame above the journals.  The journal is in a box that rides up and down in the frame and there are springs above it that allow the axle to move up and down.  The truck frame in a 6 axle truck is a huge, one piece, rigid steel casting that does not bend, hinge or articulate in any way.  In addition some designs may have a bolster that also rides on springs resting on the truck frame. The journals are on springs in frame and the bolster is on springs in the frame.

The center axle of a prototype truck allows some lateral movement to accommodate curves.

In the vast majority of model trucks, there is no springing, hinging or articulation, it is a rigid frame that holds the wheels in constant line to each other and the frame.  If the truck goes over a dip or bump in the track, wheels come off the rails.  That's why model engines derail on bad track where a prototype wouldn't and why model engines lose pulling power on rough track where a prototype wouldn't.

I have a number of these HO

I have a number of these HO scale Proto 2K with 3 axle trucks like the one I posted earlier. And if I recall properly they definitely have a truck that appears to hinge at that location. I will try to get a few out tomorrow and look closer.

Meanwhile can anyone find some other photos / illustrations /  drawings of these trucks. (I guess I am using the wrong search terms to find them?)

Any chance of a video?

Brian,

If you retrieve your models it would be most useful to see a video of the hinging mechanism in action.

I was taught very early in my engineering training that shocks and springs on vehicles serve one purpose: they help keep the wheels on the road. The nice soft ride is a side benefit.

A rigid frame with no springs, as we often see on our models on rough track can result in wheels lifting completely clear of the surface.  Some of my G Scale Diesels have sprung trucks and they make a big difference on rough garden trackage. 

We always spring the axles on live steamers, and a great deal of satisfaction is achieved pushing here and there on the locomotive frame seeing how the wheels stay glued to the track.

Okay here are a few of my

Okay here are a few of my Proto 2K locos with those style trucks.
 
 

….and here you can see that the journal bearing for that axle has moved down in its slot
 

The next two photos are where I pressed the hinged axle down then let it up. You can see the change in the size of the slot there.

These next photos are probably most illustrative of all

This appears to be the rotation 'shaft' around which that single axle portion of the truck rotates.

Sorry for the several different size photos,..i tried making some of them larger so you could see the details.

Time for...

Time for a dive thru HOSeeker.org documentation archive methinks...

Prof K

PS Now that we know what we're discussing, this "truck and a half" system is obviously a _model_ thing, not a _prototype_ thing...

...although an astute observation of _prototype_ trucks in action would reveal the 12"/1' scale "axlebox U/D movement" and related spring/equaliser beam/sideframe/bolster configuration, esp over rough track... (Maumee Western anyone?   )

Prototypical Diesel Locomotive Truck Linkage

And no, there is no pivot existing. The linkage of this H0 scale model is just like the prototype performed and is acting like the prototype.

Lutz

Hinged

Now I see what you mean by hinged.

Unless its sprung or equalized in some way to force the hinged axle down, I don't see where it would help traction.  Then it would only add traction to the extent of the downward pressure of the spring/equalizer.

Since nobody else picked up on it, its probably either very expensive to make/assemble or ineffective.

Neither of those videos

Neither of those videos addressed the same style truck,...at least from what i see??

And I don't speak German,.... even while I don't think that would help considering how short the videos are?

Unless its sprung or

This is my thoughts on its usefulness.

1) It's flexibilty really helps to prevent some derailments

2) Perhaps the fact that most of the locos weight is now 'officially' supported on fewer wheels (4 rather than 6 on any truck) might increase the tractive effort?