"Dyno" for Locomotives




Introduction: "Dyno" for Locomotives

About: Hungarian guy in Switzerland (after 9 years of Netherlands). Check my website for nixie clocks!

“If you want something done, do it yourself. Yep!” says Mr. Zorg in the Fifth Element. Probably motivates us to start our projects.

I am a big fan of model trains but unfortunately I do not have a permanent room but what can I do if I already have a nice collection of trains especially steam engine models?
It is so nice to see the spinning wheels and moving rods. I was looking for a nice solution to display some of my collection and also run the engines. On the market there are a several products available for high price, with limited ways to place a large American steamer. So here comes again, I have to do something better and nicer myself. :)

The Broadway Limited came out once with a display bridge designed for the expensive brass Big Boy, but there were only fixed bearings and only for the Big Boy wheel arrangement. The basic idea was there I just needed to re-think and modify my display to serve different axis arrangements and have a nice look.


Lately I found this very interesting photo about a steamer dyno. So they actually existed in a kind of similar way as my design. Nothing new under the sky. :)

I already have plans to build a real loco dyno with measuring feature.

Step 1: The Displays

Bridge I., ( I call: the cherry bridge) has a cherry wood base and hand cut hard wood structure. I used ready made 4 x 4 mm and 2 x 2 mm hardwood rods from the local model shop. Cut all the elements and glued them together. The bridge structure is painted to very dark brown color.

Bridge II., (I call: the wenge bridge) has maple and wenge wood base and laser cut wenge structure what I only nailed, except the top of the bridge where the tracks are, there I had to use some glue. The finishing is only tung oil, amplifying the beautiful color and the wood grains of the wenge.

Both bridges are capable to handle the Big Boy as the biggest loco. The wenge bridge has lighting separately switchable on both side of the display. Both can be used under analog or DCC (digital) mode, only need to plug the 2 track wires.

These bridges at this stage can not handle 3-rail system models, such as a Marklin. For that a little tweaking is necessary.

Videos of the bridges:

Let’s see the details...

Step 2: Bridge I. (cherry) - Woodwork and Tracks

There are some bigger engines than the Big Boy but for the bridge I took the 8 driven wheels as the largest to serve. This loco is 45 cm long so the bridge had to be a little bit longer.

I have made the prototype bridge years ago, but never completely finished it. Now I had a chance to redo it in a better way.

This bridge has a cherry wood base with 45 degree sides and grooves for the acrylic box, all cut using a table saw. After planing, sanding and lacquering it, the base part was done. I added four legs from the same cherry wood and cut a piece of black plastic for the bottom to hide the wires.

I really like those old wooden bridges therefore I followed that structure. The architecture under the tracks are based on some research on the Internet. It has been optimized to easily make use of existing modeling components and not  over complicate it. My goal was to give a close enough realistic look but nothing more ...no rivet counters please. :)

For the bridge I have used 4 x 4 mm and 2 x 2 mm hardwood that I bought in the local hobby shop. To ensure that all the pillars will be the same I made a template by printing out the plans and built the place for the legs and the cross bars.

First I sanded all the long wooden rods then cut all the individual pieces for the pillars with a mini table saw, than I  assembled each of them using the template. The bars are glued together and each cross section is supported with 0.6 mm x 6 mm nail. To avoid cracking these thin bars I pre-drilled all the holes for the nails.

Once all the pillars were done I painted them because after assembling the whole bridge that would have been more difficult.

(On the previous prototype I made a mistake with the painting by choosing the wrong method and paint. The normal paint was not a good choice because all the wood grains, little sharp corners disappeared when I sprayed that thick paint.)

On this bridge first I used dark wood stains and then brushed it with plain black ink which really soaked into the wood, then again brown wood stain and ink. This way the grains and little lines on the wood structure remain visible, only the color has been changed. Last but not least, the ink gave a very soft satin shine to the wood like the tar on the real railroad wooden structures.

Every third pillar had longer middle legs to attach them to the base and the rest of the pillars are connected to each other with the connection bars what are painted the side bars the same way as the pillars. 

I used the Tillig Elite track system because those are really nice pieces with darkened tracks and fine details. As I have seen on the pictures of similar wooden bridges, the railroad ties are placed more densely, therefore I had to duplicate them. I opened a spare track and cut the ties individually and placed them to my designated bridge track between the existing ties.

Because there are footways on both side of the tracks I extended the ties under the footway. I cut the sides from a normal track ties and glued them to the bottom of the footways which hide the joints of the extensions.

The inserts are there to extend the normal track when shorter loco goes to the bridge. If both inserts are in place the remaining space is enough to run the Hudson steamer which has 3 driven axes.

Step 3: Bridge II. (wenge) - Woodwork and Tracks

While I was making the Bridge I. I had an idea to make another bridge from wenge wood. The properties of that wood is just perfect to make small parts out of it. It is very hard, has very fine grains and dark color. With oil finish looks excellent.
A unique wooden bridge needs a nice surrounding, so I made this layered maple and wenge base for it.

I planned and glued the wenge and the maple timber and then planned again to finalize it. The same way as for the cherry base I cut the sides and the groove for the acrylic top. This base got a shiny lacquer finish.

I cut 2 mm and 4 mm wenge sheets from a bigger piece of timber sanded them until I had a very smooth surface. Using my computer I designed the structure and made the files for the laser cut. After having some experiment with the wenge wood and the laser cutter I have realized that I can do very thin parts from that wood. It will not break or damage, even the very thin square “shoes” for this bridge are strong.
The blackened, burned surface after the laser cut is easily removable by using fine sandpaper.

I cut all the tiny holes for the nails by laser therefore I did not have to use glue at all or just very rarely. The structure just holds itself very strong.  Of course on the side of the legs I had to drill those holes by hand, I just had to follow the pattern and use the pre cut side rods to mark the nail’s positions.

The tracks are the same as on the cherry bridge, Tillig Elite and on the middle of the tracks I duplicated the ties the same way as on the other bridge but the extended ties are from only wenge under the footway.

The bearings and frames are also same and this bridge also has the track insert pieces to allow it to run different engines with different wheel arrangement.

Step 4: The Dyno

I have studied lots of images before I designed this system and I think it is an easy way to run my locos. Setting up a new wheel arrangement only takes a few second. Some of my locos are collector’s editions and other high quality pieces so you can believe me I would not put them to a display I do not trust. The bearing frames are sitting tight, the bearings are running smooth.

The individual frames are made from laser cut acrylic sides connected by 2 mm rod and hold 2 pair of bearings.
The bearings are very small size 2,5 x 5 x 2 mm. I used 2 mm brass rods as the fixed axis. Under the dyno frames are additional tracks and the axis of the bearings are sitting on them. The wheels of the loco pick up the electricity through bearings. The track system under the tender is also powered.

The dyno tracks are just  simple brass bars, and the weight of the loco holds the frames on them and also give a possibilities to the frames to slide on the track a little to compensate the miss-centered wheels, or jerky, bulky movements, what very sad, but occurs sometimes even on an expensive loco.
To set a new wheel arrangement I just simply remove the model, move the bearing frames roughly to the desired position and place the new loco. If some of the frames are not perfectly under the wheels just need to lift up the loco a little and move the frames.
If I want to run a smaller loco I just place the necessary frames and place the track inserts if required. There are two inserts, a shorter and a longer one to extend the normal track to fill the empty dyno section.

The power source can be analog or digital. At the end of the base there are two mini plugs where the controller cables go.

Step 5: Assembling, Acrylic Top, Some Electronics

The displays have a removable acrylic top. I decided to cut by laser and assemble them with screw instead of gluing it. To be honest, I tried to glue the boxes but I always messed up the acrylic, that is why I switched to this method.

The bridge structures are glued to the base by those longer legs of every third pillars. There is a tiny square “shoe” on every leg  of the pillars, just to look some continuity between the base and the bridge and hide the little gap on those legs what are not connected to the base.

The tracks of the cherry bridge are just simply powered, running the wires from the power points to the tracks.

The wenge bridge has got some electronics, because it has a switchable lighting. There are 2 switches next to the power plugs to light up each side for convenient photo taking.

There is a small panel to regulate the power and gives constant 3 V for the spots. If you connect 16 V,  AC, in DCC mode it can rectifier and reduce the power for the lamps.  If you connect analog 3-12 V DC then it controls and keeps the power as low as 3 V for the LEDs.

The spots are from Brawa, I have changed the original 12-16 V light bulbs to LEDs, which in analog mode would not work but only when you run the loco close to full power.
The average minimum starting power for analog models is around 3 V and that is enough to power up the LEDs.

Step 6: Bridge I.

I have run one of my loco for 8 hours on one of the bridge to test the durability. I did not experienced any problem from the bearings, all run smooth and quiet.


Scale: Ho (1:87) Two track system

Display length: 57,3 cm  (22,55")
Display width: 19 cm  (7,5")
Display height with acrylic: 23 cm  (9")

Bridge length: 51 cm  (20")
Bridge height: 7,3 cm  (2,87")
Bridge width at track level: 4,5 cm  (1,78")
Bridge with at the base: 6 cm  (2,36")

Length of the dyno track: 18,5 cm  (7,28")
Number of dyno frames: 8
Lights: no
Power source: digital or analog

Step 7: Bridge II.


Scale: Ho (1:87) Two track system

Display length: 56,6 cm  (22,28")
Display width: 16,5 cm  (6,5")
Display height with acrylic: 21 cm  (8,26")

Bridge length: 52,5 cm (20,65")
Bridge height: 6,5 cm (2,56")
Bridge width at track level: 4,8 cm  (1,89")
Bridge with at the base: 5,5 cm  (2,16")

Length of the dyno track: 18,3 cm (7,2")
Number of dyno frames: 8
Lighting: yes
Power source: digital or analog

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    8 Discussions


    Question 1 year ago

    So, do you get the locomotives only to keep up at the display or you run them in your layout?


    4 years ago

    That's sweet.


    Reply 7 years ago on Introduction

    No, they are very fine models from MTH and Broadway Limited.
    I wish to make this kind of engines :)


    8 years ago on Introduction

    I've not been into model trains for several decades, but this instructable caught my eye for some reason. I have to say I'm glad I took the time to read it! Excellent photography, very well written, and showcasing some masterful craftsmanship


    8 years ago on Introduction

    When I first saw this, I said, "Wait, isn't there something out there like this?" If so, it certainly cannot be of this quality or precision. This is a work of art. Craftsmanship is still alive, as well as love of a project.