[MOC] Umbauwagen 3yg

[jtlan]

Greetings, Train Tech!

About a year ago, I posted my Umbauwagen 4yg. Here is the 3-axle variant, the 3yg:

The name Umbauwagen means "rebuilt coach" -- these coaches were built after World War 2 by modernizing prewar compartment coaches. More accurately, this is an AB3yg (first/second class) + B3yg (second class) pair -- these cars were nearly always found in close-coupled pairs. A few survive as single units in work trains, painted yellow.

The body of the model is essentially constructed the same way as my 4yg model: studs-up construction for the main body (leveraging the train window and the 2x8x2 curved slope), SNOT construction for the doors, the details around the buffer, steps, and corridor bellows. Of course I designed new side frames, and there are a few minor details that are different such as the lights above the end doors of the pair. These cars were painted green in DB service, but as the train window does not come in green I elected to build the 3yg in a different color scheme. I believe that this livery corresponds to 3yg cars used as trailers for the ET 85 electric units -- someone with more knowledge of German railways may be able to shed more light on this.

At the time I built the 4yg I also built some test models to research how feasible it would be to build the three-axle variant. However, I ran into difficulties designing the chassis and moved on building the 4-axle variant instead (which had none of these challenges). Earlier this year I circled back and spent some time looking into the problem. The first attempt was to articulate the chassis as 4+2, pivoting the body to reduce the overhang -- a technique I previously used on the tender for my model of the Gr670. However, the Umbauwagen 3yg not only has a long 3-axle wheelbase, but also has a long distance between the outer axles and the buffers:

Articulating the chassis as 4+2 would allow the car to negotiate turns, however it would also derail any vehicle attached to it as the buffers swung out widely. Further iteration yielded the general outline of my eventual solution:

The center and end axles are connected together with a 6-bar linkage, rather than a rigid frame, allowing the chassis to change shape when traveling through curves.

It's important to note that the center axle is actually what actuates the system. As the car enters a curve, the center axle is pushed sideways to follow the curve, which in turn angles the outer axles to follow the curve as well. The track cannot apply rotational forces through a single pair of wheels on one axle, and so a similar design to this one without the center axle would not work.

You can see the mechanism here:

The outer axles are mounted on 2x2 round bricks riding in a 2-stud-wide channel, allowing them to turn and slide slightly towards the center of the car in turns. I experimented a bit to find the best places for the pivots and a construction that would be light and reliable. In the final model I removed the blue tiles shown in the screenshot, to avoid additional friction and binding in the mechanism.

Thanks for following along! As usual, I've uploaded some additional images to a Brickshelf gallery, including some notes on and prototypes of the linkage mechanism. Thanks for reading, and let me know if you have any questions!

Edited September 13, 2017 by jtlan

[baard]

Nice mechanism for the wheels. How does it handle the points?

[ReplicaOfLife]

7 hours ago, jtlan said:

 These cars were painted green in DB service, but as the train window does not come in green I elected to build the 3yg in a different color scheme. I believe that this livery corresponds to 3yg cars used as trailers for the ET 85 electric units -- someone with more knowledge of German railways may be able to shed more light on this.

That is correct, though I think they only used the second class only version there.

Btw, the same thing applied to some 4yg, which were used as middle coaches in ET65 units, and also were found coupled with ET85 units.

Some of these coaches were later sold to private train companies and heritage railways, where some were painted in other, sometimes quite unusual color schemes.
Another use was the conversion to track maintenance cars, usually painted a dark blue, and often with some conversions to the body (usually they had fewer windows).

[jtlan]

6 hours ago, baard said:

Nice mechanism for the wheels. How does it handle the points?

No issues whatsoever that I could find. After I worked out the basis I built a test chassis and sent it around a test track as fast as I could. A 9V train motor could pull it at its top speed without derailing. In reverse, the car could be pushed up to very high speeds before coming off the track.

1 hour ago, RogerSmith said:

That is correct, though I think they only used the second class only version there.

Btw, the same thing applied to some 4yg, which were used as middle coaches in ET65 units, and also were found coupled with ET85 units.

Some of these coaches were later sold to private train companies and heritage railways, where some were painted in other, sometimes quite unusual color schemes.
Another use was the conversion to track maintenance cars, usually painted a dark blue, and often with some conversions to the body (usually they had fewer windows).

Thank you for that information, @RogerSmith. Most of the maintenance cars I found were painted yellow, with the blanked-out windows you mention here. The Deutsche Weinstrasse color scheme is another possibility ... but tan windows are extremely expensive!

[LEGO Train 12 Volts]

Very sleek solution! Lovely work! 

[kieran]

Nice solution, how robust are the wheel sets?

[Man with a hat]

Very nice work. The coaches look really nice. And that mechanism is briliant!. It not only works. It looks great as well.

[jtlan]

On 9/11/2017 at 1:18 PM, kieran said:

Nice solution, how robust are the wheel sets?

Not sure what you mean by "robust", but the linkage features Technic axles reinforcing the sections above the outer axles and three stacked hinges in the joints. It's extremely unlikely to break under normal operating conditions.

 

14 hours ago, Man with a hat said:

Very nice work. The coaches look really nice. And that mechanism is briliant!. It not only works. It looks great as well.

Thanks! I'm really proud of the mechanism. This model has been over a year in development, if you start counting from the first experiments with the 4+2 arrangement...

[kieran]

That sounds very strong or robust, thanks for the details 

[M_slug357]

On 9/11/2017 at 9:45 AM, jtlan said:

...The Deutsche Weinstrasse color scheme is another possibility ... but tan windows are extremely expensive!

Does sun exposure still cause white pieces to get 'yellowed'? I don't know how long that process would take though, but it could be worth a shot?

There's always spray painting, but color matching & consistency can be a pain....

 

Also, have you thought about doing a 'wartime' dark grey color scheme for another 4yg or pair of 3yg's?

[jtlan]

10 hours ago, M_slug357 said:

Does sun exposure still cause white pieces to get 'yellowed'? I don't know how long that process would take though, but it could be worth a shot?

There's always spray painting, but color matching & consistency can be a pain....

 

Also, have you thought about doing a 'wartime' dark grey color scheme for another 4yg or pair of 3yg's?

Not much of one for painting or discoloring. If the Weinstrasse variant is out of my budget, so be it.

The coaches were built after WW2, so a wartime paint scheme would be highly anachronistic. Dark grey is also a very rare color for the window.

[Brickwolf]

Beautiful 3yg Umbauwagen!

[M_slug357]

On 9/14/2017 at 9:10 AM, jtlan said:

Not much of one for painting or discoloring. If the Weinstrasse variant is out of my budget, so be it.

A pair of Weinstraße 3yg Coaches,

Deutsche Weinstraße Coaches by Nick Jackson, on Flickr

(plz excuse my finger in the frame)

Deutsche Weinstraße Coaches by Nick Jackson, on Flickr

Deutsche Weinstraße Coaches by Nick Jackson, on Flickr

Close-up of the AB3yg.

Deutsche Weinstraße Coaches by Nick Jackson, on Flickr

Close-up of the BD3yg, I chose to go with this so I could avoid buying more of those dastardly tan windows.

Thoughts?

 

[zephyr1934]

That is a brilliant mechanism (I'm still pondering the original post), looking sharp.