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Zonker's LEGO Round House

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(updated: 99.7.15)

During our summer trips to Europe, I have visited a number of train yards in Spain, France, Poland, Germany, and the Czech Republic. When it was allowed, I took photos and/or video of the trains, train yards, main station houses, and work trains. In Poland (1996), I took some good video of a working round house in action. Because of this round house visit (and the good luck of finding the discontinued Load n' Haul freight railroad in Poland), that I decided I would try to make some models based on trains I have seen in Europe and at home in the U.S., including a working round house. To that end, I bought all of the rail-wheel sets, magnetic coupler sets, and the boggie plates for the rail wheel sets from one small shop in Prague which carried a large collection of Service parts. I also bought some interesting Technic gearing sets with the intention of using them to build switching and signal models.

My first train creation (while waiting for the freight train model to arrive from Poland by postal mail) was a large, yellow diesel engine, ala the Union Pacific Railroad. After building the big diesel, I also built a smaller freight-yard engine. (You can see both engines on my engines page.) About the same time, I finally decided that my next Big Project would be a working round house for my LEGO trains. This would require destroying the large Fire Station project that had been my labor for over a year, in order to use the roll-up doors for the five diesel engine bays.

I've discovered that the roll-up doors have their limitations...for example, you can only have 12 window segments in the overhead rail. Since most train cars are longer than this overhead rail, I can't let the door come down from the back. If I used 13 or more segments, the door would hang down from the overhead rail, and impair the clearance in front or in back of the overhead rail. Also, given the constraints of the overhead rails, there is a limitation of 10 of the 1x2 slotted bricks that form the vertical rise. (If you have 11 vertical bricks, the door will have a gap at the top.) On my mock-up of a garage bay door, I use a plain 1x2 brick at the foot of each front pillar, so that the door segment does not rest on the rail. This is equivalent to the height of the track tie and rail, leaving 10 bricks for the vertical rise for the doors. The links below show the first mock-up of the bay doors and supports.

I have already created the basic turntable, using a large, blue technic gear, so that the turntable can be run by a crank or a motor. There is a separate turntable page that documents how all of this works.

I built a version of the round house with 3 studs between the hinges and the door frame, to see how close I would need to be to the turntable. I tried 4-studs, and 5-studs spacing as well, to determine the best spacing for me. (The more stud spaces between the hinges and door frame, the farther back from the turntable the front walls will need to be.)

Here is what the first version of the roundhouse and turntable were going to look like. The turntable is about 15 inches (three straight track segments) across, and the five bays span 90 degrees of arc. This leaves a 22.5 degree angle (1/16th of a circle) difference between each of the bays. This works well, since LEGO curved train track segments are also 1/16th of a circle. The red outline shows the basic layout of the roundhouse, as I originally planned it. The track layout artwork is courtesy of Matthew Bate's Track Designer program, available from Matt's Train Depot. Sadly, the program is only written for Windows. :-(

Unfortunately, this setup is too big to fit on a Modular Train Table, even a large module. I hope Matt will add the table outlines to Track Designer. :-)

After the first couple of attempts, I began working on the round roundhouse in earnest. The results are shown in the next few photos. I have installed red and green transparent 1x1 round plates (lenses) on the frame of each door. I have the ability to put small LED indicators behind these, shining through the 1x1 brick that supports them. My plan is to use a single switch to connect one rail to the train controller, and have the same switch connect the LEDs to a blinker circuit. (The other rail would be connected to the train controller directly.) This way, I will have a visual indication of which track(s) are 'live' at any time. Someday, I'll even be able to switch from the green LED to the red LED when the train reaches the end of the track!

I have also managed to acquire a matching gear to the old, big, blue gear I picked for the turntable base from Fred Yokel in San Jose, CA. Pictures of the gears are on the Turntable page. Basically, the big gear is sitting on a 4x4 swivel brick. The next gear assembly is built up as follows: 2x2 swivel plate on the bottom, 2x2 round plate on the swivel, small white gear (to mesh with the big blue gear) on top of the round plate, and finally a 2x2 technic gear on top of the white gear, to make the connection with the gear drive assembly.

I've used a 2x4 brick, with side studs, to hold a technic worm-gear drive unit sideways. (You'll need to see the pictures.) Then I use two technic plates to suspend a small and large technic gear, as the interface between the worm-gear unit, and the small gear described in the previous paragraph. A long technic cross-axle is currently used to turn the worm gear, but the 8720 motor could be used as well. The walls of the turntable pit will support either method (manual or motor drive).

The Rectangular Roundhouse

When I saw what looked like a lot of wasted space between radials, I thought about using some curved track, to try to make the tracks within the roundhouse parallel to each other. This experiment resulted in the following notes.

Overhead view of Straight HouseBased on a 5-bay design (because I only have enough parts for five doors), I decided that bay 3 would be a straight radial from the turntable. The tracks to bays 2 and 4 would have one curved segment that meets the turntable, and then they become straight segments. Bays 1 and 5 would have two curved segments, and then they become straight tracks.

With this design, the separation between the ties between bays 2 and 3, and between 3 and 4 would be 5-studs. The separation between the ties for bays 1 and 2, and bays 4 and 5 would be 8-studs. Because of the curved track, the front edge of the bays would need to be at least 21 studs from the turntable edge of bay 3. However, if I want to get long-frame cars and engines into bays 2 and 4, the setback moves to 23-24 studs, and if the long cars go into bays 1 and 5, the setback moves to 28 studs from the turntable!

Now, figuring that I need at least 2.5 straight track segments within each bay, to allow for the longer cars, that means that the back of the bays would be at least 28 inches from the edge of the turntable.

The track spacing (with ties being 8-studs wide) looks like this;

 [TIE]<8 studs>[TIE]<5 studs>[TIE]<5 studs>[TIE]<8 studs>[TIE]

That makes the track area 66-studs (20 inches) wide. Add at least 1-2 more inches from wall to wall. Suddenly, this thing started to look B-I-G!

Advantages to the rectangular roundhouse (so far)
+ design seems easier and neater (more compact)
+ it will be easier to make the roof (maybe use large building plates?)
+ a service crane could slide over many tracks, instead of just one

Disadvantages to the rectangular roundhouse
- curved tracks impose added distance between turntable and bays.
- the curved sections also change the length of bays (2 and 4 are the
deepest, bay 3 is shallower, and bays 1 and 5 are shorter still.
(With a roundhouse, straight radials mean bays will be the same depth)
- it's a bit strange (aren't roundhouses supposed to be round?)

I decided that I liked the challenge of building a curved face to a building, and the use of hinges and roll-up doors made this pretty easy. I wanted to build a round house, and not a straight house.

About June of 1998, the round house construction came to a halt. As work had been progressing, I would fold the round house up (see photo to the left) using the hinged walls, and carry it outside to take pictures of the progress. Unfortunately it was finally getting so big that it was starting to sag under it's own weight as I moved it.

I decided that I needed to build a table for it, and install the turntable into the table, before I could continue to build more of the round house. Up to this point the round house and turntable had been separate projects. Now, they needed to be merged.

I had originally used a 4' x 4' piece of 5/8" particle board for laying out the round house. I figured that was a common size, and I could attach it to a 4' x 8' layout later. I hadn't thought about legs, since I didn't have space for a permanent table. I picked a turntable location at random, and figured out where the radials would go from there, tacked some track down, and then put the building face around the tracks, to see how things fit, and take pictures in bright daylight.

Later, I read about the modular tables used by the PNLTC. They used a non-standard size (i.e. 'not even U.S. feet or inches'), which was chosen to fit LEGO part widths (i.e. 'studs'), rather than inches and feet. The table heights were also set, picked so that it was a good height for kids to look at them, and so that various members could build these tables independently, and then bolt them together at train fests! The design included a square and a rectangle (two squares side-by-side), allowing lots of possible combinations.

I decided to use the modular tables, designed by PNLTC member Ben Fleskes. I chose to use the modular tables so that I could mate my roundhouse to other layouts later, when I find a few more trainiacs in the S.F. Bay Area. You can find the building instructions for the modular train tables here on

In November of 1998, I had built a large and small table module, only to find that the turntable and the original round house would not fit on the large module at the same time. (you can see how the roundhouse seems to stick out over the far side of the table in the photo to the left.) And, due to the overlap needed between the round house and turntable, the two models couldn't be built on separate tables without a major redesign of the buildings or track layouts. I also didn't want to have to bolt two tables together all of the time, since the overlap didn't take much space. I realized that I couldn't count on having enough space on a nearby module, and I also didn't want to have a portion of the building unsupported. Occasionally, I'd try to find a way to make them fit on the large module, without success. Again, building was halted, until I could solve this puzzle. In the meantime, I also designed a small electronic circuit for LED-based train signals., and some rolling stock, helped get BayLUG started, and launched the BayLUG website.

In May, 1999, I finally had the breakthrough I needed. After the first 'Official' BayLUG get-together, I invited a few members to visit my home, and see my LEGO building area in my badly cluttered garage. During the visit, one member accidentally bashed part of the round house wall with his elbow as he was turning around. Later, when he turned to show the others the damage he had caused, he accidentally bashed it again, this time with his hand. He left that day feeling a bit like Godzilla! I didn't really survey the damage for a week, after all, bricks go back together, and I had photos to work from! While the damage wasn't catastrophic, it was significant enough that I could choose to rebuild it the way it was, or I could save the bay doors, and redesign the rest of it.

While considering the redesign option, I decided that I really wanted the turntable and the round house to both live on the same large module. Having decided that, I needed to consider placement of the turntable, because I didn't want this below-the-surface construction to weaken the table frame, or to interfere with the structure for bolting it to other modules, since the turntable would also be connecting to the train tracks from those neighboring modules/tables.

I chose where the turntable would live, without interfering with the table frame structure, and tried setting out a few possible track layouts on the tables surface. Early in June 1999, I finally made a bunch of sawdust, cutting the hole for the turntable to pass through, and made a mounting system, so I could easily remove the turntable. (The LEGO parts in the photo were used to align the marker track to the 22.5 degree angles to lead into the Round house bays, and to mark the radius of the hole for the turntable!) Later that week, I began working on the track layouts, and on putting the face of the round house back on the table. I took pictures along the way, but the negatives somehow turned out all white for the LEGO pictures, even though other shots on that roll were fine.

Here's a look at the basic track plan for the new roundhouse The Office/Shop area is about the same size as before, but the opposite wall has been moved in quite a bit. Bay 4 and Bay 5 are very shallow, so I can only fit a small transfer engine or other short wagon in these bays. (That back wall is actually on the edge of the module. No overhang, but tricky none the less.)

This illustration was made with Matt Bate's fine Track Designer 2.0 program for track layout, run through MS Paint to add the colors and show the building footprint and saved as a bitmap, then strained through Adobe ImageReady to make the colors web-friendly and add the text.

I decided to use a couple of curved track segments within the round house, so I could have some parallel tracks under a service crane. I've tucked two 15" x 15" large grey base plates under the three parallel tracks, to support a work area, and give me a base to create a service crane within the roundhouse. To make the crane simple, I actually turned the second and third bays a bit (1-curve, and 2-curves, respectively), to make them parallel to the first bay. But, this creates an odd height problem, since a base plate is about 1/2 as thick as a plate. I can't use base plates under all of the round house without cutting up a few base plates, since there are odd-angled track, curved tracks, and the odd angles of the face of the round house being made of hinges.

Photos of the new design, on the train table.

I've made a lot of progress over the past few weeks, and I've made some interesting adjustments along the way. Since a couple of the bays are relatively short, I've modified the windows along the long back wall, adding a ventilation system, work bench, and sink and shower (for chemical accidents). I've also had to redesign the shop area, and changed the roof access a bit. I'm working on those safety features that a U.S. OSHA inspector might want to see, and I've used some older rail ties along the base of the long walls, so I can help anchor the walls to the tables, to keep things from sliding while shipping. I also need to track down another freight loading station, to get the elements for the overhead service crane.

I still need to work on the vertical alignment of the turntable. The cradle for the turntable is between 2-3 plates too shallow, so there is quite a drop onto the turntable, even when the radials are aligned. I'm going to try to use a sheet of rubberized canvas below the grey baseplate under the turntable. (Folks with small boats may know this stuff, since they use it to keep stuff on the shelves while under way.) The height should be close, and it'll help keep the turntable in place without needing to use glue or screws. I may still need to redesign the turntable supports to help get the track heights to match.

During the beginning of July, I mounted the track power contacts, and drilled holes near the contacts, so I could drop the wires under the table. Of course, that meant cutting the power cables. I still need to decide where I'll control the track power from, so that I can run cables there. I'd better get to work on my track power switching board, and my timer board. I'll also need some LED signals pretty soon after the the round house is done. I also need to drill holes for the LEDs that will be mounted in the lenses along the front wall, and connect the wires for the LEDs for each bay into the same connector as the track power for that bay. I also need to redesign the turntable a bit, to allow me to pass power cables for the trurntable track safely out of the turntable bed area. Then I need to route the power to the motor that will turn the turntable...

I also want to build a few more table modules in August. If anyone in the S.F. Bay Area is also interested in taking part, they should contact me by email, or by posting to the LUGNET S.F. newsgroup. I'd love to have a bunch of tables that could be mounted together for a static display somewhere!

These pages are NOT sponsored or endorsed by the LEGO companies.
They are the creation of an enthusiast of LEGO bricks.
The official LEGO home page is
(The LEGO companies have their own pages. This page is mine. :-)

Copyright 1996-99, David K. Z. Harris, N6UOW
Questions? Comments? Additions? Email
frenezulo at

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