Will it go 'round in circles?

Yes it will.

Will it fly high like a bird up in the sky?

I sure hope not*

In this 3rd wave lockdown I seem to have the attention span of a squirrel, running all over the place with no rhyme or reason. I've been thinking about track plans, and have been wondering about adding a small streetcar turntable to the layout. Having temporarily lost my motivation to install a roof on the HQ model, I thought I'd see what was around the workshop that I could use to build a simple, manual turntable.

I've got a build, I ain't got no steps, no.

I'm gonna let the components move me around.

So, I got started by searching the internet and old magazines for ideas, as well as looking through my parts stash. I'm not saying that what I settled on is the best, but it seemed workable with what I had on hand and my current temperament.

Some design considerations in no particular order:

1. I had a cheap Lazy Susan bearing from 30 or so years ago that I was keeping around to use 'one day'. 'One day' arrived last week. Its square metal base measures 4" on each side.

2. All the turntable has to do is rotate a streetcar 180 degrees. There's no track indexing or massive roundhouse to be serviced.

3. I'm perfectly happy with it being powered by pushing it either by finger or stick. Motorization isn't needed. Cheap and cheerful is the name of the game.

4. Its track has to fit streetcars with the longest wheelbase in my fleet, which are PCCs. The body can overhang the turntable.

Soldering the plug to the rail.

The part that concerned me most was how to get power to the track?

The method I used is based on the one presented by Bob Hayden in an article called An inexpensive, easy-to-build turntable, in the Feb '87 issue of Model Railroader. It used a 1/4" headphone plug as the turntable's rotational mechanism and method of transferring power. I used a much smaller 2.1mm x 5mm plug instead as I had some on hand, and since I was using a bearing for rotational motion, I didn't need a 1/4" plug.

I've got a story that's got a moral.

Don't use two axes ever again.

I should mention there's a problem with my design. There are two axes of rotation: the bearing has one, and the plug has one. These two axes need to be perfectly lined up, one on top of the other, for the turntable to freely spin. 

It turns out because I eyeballed the installation, these two axes aren't perfectly aligned, so there is a little bit of binding when you turn the thing. This isn't a big problem because there's no motor that'll burn out, and no large number of tracks to be indexed, but eventually something will wear out or break: likely the plug, or its supports. Given how little use this thing will get I'm betting wear out will happen long in the future. But, we'll see.

A better scheme would likely have been to solder wipers to the rail bottoms and have them rub against contacts from the fixed layout track when rotated into position. This gets rid of the plug's axis and eliminates binding, although you'll need to make sure the wipers have sufficient spring to make good contact - I didn't have components on hand for that kind of system, so I didn't pursue it.

The top and bottom circular plates are cut from 0.080" sheet styrene.

In this photo I've inserted the plug into a whole drilled into the centre of the upper plate after the plug's leads have been soldered to the underside of the rail. 

The track has been attached to the plate using plastic solvent. 

I'll probably have to adjust the rail lengths when installing the turntable into the layout. I cut them a little long so fine tuning can be done.

The plug to plate connection was stiffened with four gussets, each cut from 0.080" styrene. I spent a lot of time trying to get the plug dead centre and as perpendicular with the plate as possible, but as I noted above, it wasn't quite good enough.

After drilling a matching hole in the bottom plate, the turntable was glued on with epoxy and left to dry for a few hours.

One thing I should point out before I forget is that I was checking the electrical continuity after just about every step. 

I'd hook an old 9v battery to the track, and then use my continuity checker to make sure the light came on. The light is quite faint in the photo, but that's because I'm using an old battery.

I don't have any photos of the struggle to align the two plugs, but basically once the plates were epoxied to the bearing, I pushed and persuaded the joined plugs until the turntable seemed to rotate back-and-forth without much friction. The bottom plug was then epoxied into place along with 2 torsion supports cut from 0.080" styrene. 

And this is what it looks like once everything was glued in place. 

I applied a little light oil to the bearing to help smooth its operation.

From here on the rest was painting and decorating to make it sort of look like a turntable.

Styrene sheets were used to build up the upper surface so styrene brick sheets could be used to panel the top. 

I took care to make sure the brick sheets were below the rail head, because if they're level with it, it's often possible for wheels to ride up on the plastic and lose rail contact. 

Some 0.040" x 0.060" styrene strips were glued to the perimeter to neaten the edge. Then it was on to painting. 

I continue to dabble with Revell Aqua Color. The basic brick hue is mixed from their #37 Reddish Brown and #39 Dark Green using the same technique applied to both the Weekly Herald and the HQ. Alternating thin layers of the brick mix, #75 Stone Grey, and Tamiya flat black were used to build up the final colour. The edge trim was painted with Stone Grey.

I'm finding I rather like those little blue cubes Aqua Color comes in. I often use them as supports for work-in-progress.

Those Ls for rotating the turntable are cut from piano wire and inserted into holes drilled through all the top layers.

*Well, that's that. Given how I've mangled Billy Preston's lyrics, I should leave you with the legend so you'll know how great the song is.