Bringing the Siku Bombardier tram to life in Casualized HO-9

I've had it in my mind for a long time to motorize Siku's Bombardier toy tram (SIKU 1895). In Toronto it seems to be marketed as a toy version of the TTC's iconic streetcar manufactured by Bombardier.

Siku Bombardier tram, SIKU 1895, straight out of the box

The box says it's HO scale, and I believe it, but it is a casualized representation of the vehicle. Ok, it is a children's toy so play value down on the carpet is more important than the fussy desires of an adult modeller. However, the shells are nicely detailed, and I thought they'd make for a rather decent casualized HO-9 vehicle for running around the Centennial Experimental Farm layout, or simply posing for scenic photos.

A TTC Bombardier streetcar as seen in Feb 2019

I started the motorization and casualization back in the fall of 2022. I thought it was going to be a rather easy conversion, but I was very wrong. There was a lot of trial and error before I even came close to getting it to run trouble free laps. At one point I was so frustrated I parked the project and only gave it another go just after last Christmas. Even though it now runs, and doesn't look too bad, I'm not completely satisfied with the approach I've taken. I'd say it's good enough for what I want, but it could be much better. What follows are some rather loose notes on how the build proceeded so I have a record in case I try this conversion again, or someone else is interested in learning from my mistakes.

The Siku toy taken apart

The toy is held together with 2 screws on the bottom of each chassis. Once removed the shells and baffle are easy to pry off the chassises. Now the fun begins.

Preparing the shells for re-spraying with white paint

I decided to work on some cosmetic changes first. The oversize Bombardier logo was the first thing to go. I rubbed it off with an abrasive track cleaning block and an assortment of fine sanding sticks. The damaged areas were then masked off and resprayed with white paint.

About 1/3 the way through construction

The above photo is a bit deceiving because a lot of work has been done at this point besides re-painting the shells. As I mentioned in the beginning, there was a lot of trial and error during construction and I didn't photograph many intermediary steps. I'll note a few things in the above photo:

1. A big rectangular hole has been cut into the forward chassis for accepting the Kato 11-109 drive unit that powers this thing. It was cut out with a disc cutter in my Dremel motor tool. If you're going to do this wear safety glasses, and go slow. Once the hole is cut it needs to be cleaned up with files.

2. The forward interior insert needs to be cut up to match the hole in the chassis. At this stage both interior inserts were painted black.

3. There's a long and complex story about the trailer's wheels. I'll try and be brief. Although the model is more-or-less HO scale, the wheels aren't even close to standard HO gauge, or standard 9mm N gauge either. There was going to be lots of work fitting standard HO-9 or N gauge wheels to the trailer, and after much head scratching I decided just to grind off the wheel flanges and pull the trailer along the road with the power car as if it were a truck's trailer. For running on Kato Unitram track this works ok. And it turns out since the wheel sets are close to N gauge, the track rails inadvertently help keep the trailer more-or-less tracking the power unit when in motion. That does increase rolling resistance, but the power unit appears to have more than enough umph to handle it. More on wheels, tracking, and turning radius a little further on.

4. Speaking of wheel sets, the toy wheel set that would go into the back end of the power car was eventually left off. Only the trailer incorporates those ground down toy wheel sets. The only wheels on the power car are those on the Kato drive unit.

There's a lot of equipment on the roof

5. The shell roofs were enhanced a little with a few extra mechanical looking boxes glued on and everything up there was painted with some greys and blacks. There probably needs to be a bit of weathering applied.

Styrene blocks were used as motor supports

One of the trickiest parts of construction was installing the Kato drive unit. Obviously the couplers and their supports were cut off before starting. Again, there was a lot of trial and error in measuring and fitting styrene blocks to the chassis and power unit until I got the heights and positions just right. In the above photo those blocks numbered 21 and 25 have been previously glued to the power unit and the resulting structure is being epoxied into the chassis. Those styrene strips on the track are there to temporarily lift the chassis to the correct height until the glue dries. Ground clearance is something like 1.5 mm - very low.

The forward power unit is loaded with weights

From this point on there was lots of testing on the track. Again, lots of trial and error, but here's what I hope is a summary:

1. The power unit was loaded down with 'a lot' of weight: a strip of chicklet style 1/4 oz weights plus an old lead fishing weight (which can't be used to fish because of the lead) pounded a bit flat. The trailer has a bit of a bumpy ride and the extra weight up front helps keep the power unit's wheels in contact with the track in the presence of this transferred shaking motion. I probably should have added a little extra weight to the trailer - not as much as up front - to help it roll a little better. Maybe next time.

2. The only strong - aka, metal - 'connection' between the trailer and power unit are the two flaps sitting one atop the other. Note that there's no positive mechanical connection. It's the weight of the power unit that maintains the connection through the flap to the trailer.

The trailer connection casting is discarded

The reason for this setup  is the trailer has to be loosely connected to the power unit so that trailer motions don't transfer to the power unit and cause it to lose contact with the rails.

This also meant that the metal castings in the toy that connect the two shells had to be discarded because they made the connection between the two far too rigid. The tail would literally wag the dog when this thing was in motion with the metal connection castings in place and locked together.

Ok, well as you see in the photo on the side the trailer casting was discarded, but I kept the one on the power unit as it provides just a little weight over the flap connection to hold things in place. 

Toy's baffle is not very flexible at all

The other piece that had to go was the baffle that covers the connection between the two cars. It's far too rigid and prevents the cars rotating with respect to each other. 

Again, after lots of trial and error, I improvised a new baffle by slicing the ends off the old one and replacing the middle with a piece of micro fibre eyeglass wipe. The wipe was blackened with a Sharpie pen, glued over the baffle ends, and then whole thing was inserted and glued between the cars. 

Before running, the new baffle needs to be carefully folded so it will open and close cleanly as the vehicle goes around curves and doesn't prevent the cars from freely rotating. After a lot of test runs I'm thinking the micro fibre baffle might be replaced by either a silk, mylar, or very thin plastic one to further improve the baffle's flexibility. I like the visual texture of the micro fibre, so maybe it'll be a silk one to try and retain some of that look.

Underside of the power unit

All these special provisions - removal of the toy's cast metal shell connector, replacement baffle, wheels with ground off flanges that run on the road surface, flap only connection between the cars - are needed because I'm trying to make the little vehicle run over curves that are far to tight for it, and because the connections between the cars, and between the cars and rail, are too numerous and too rigid. A moving vehicle needs flexibility to negotiate its travels and deal with upsets. A moving model needs that too. The basic toy doesn't because it's designed so junior can't break it - in that regard, it's a champ :-)

I know, I've skipped over some items like arms to the overhead wiring and new decals as they're relatively straight forward compared to the mechanical work.

Operationally, it's finicky to get set up and running. It has to be handled very gently when placing it on the track because the cars aren't really connected together by anything other than a thin piece of cloth. And that cloth has to be carefully folded so that it flexes in just the right way and doesn't cause the streetcar to stall on curves. But, once those are dealt with, it's smooth running, and I like the way it looks on the farm.

Overall, it's ok, but needs a lot of refinement: more flexible baffle, smoother running wheels in the trailer, and some sort of secure mechanical connection between the cars just to name a few. Another job for the future :-)