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Meccano Double FlyboatsThe Christchurch Meccano Club was asked to supply some models for a Christmas window display in the local department store. Now, the most important thing about a window display is that you must have movement, and you must have lights. We have models with one or the other, but this display was intended to run unattended for a month or more. We certainly didn't have anything that reliable!
What you will needA very simple build, this one, and mostly it has only very common parts. The model plan can be downloaded by clicking on the image above – it's about 3Mb and contains eight pages as a compressed folder. Open it up and drag the contents to another folder on your computer, then print them out.
The cars themselves use very common parts, but since there are sixteen of them in the double flyboats even they can cause concern! You will need 64 each of parts 4, 5, 6a, and 90a. And a faintly ridiculous 96 of part 48a (2½''x½'' double angle strip). These are extremely common, but it can still be tough to find quite enough in good condition. I spent the first morning stripping and repainting these parts to make sure I had enough good ones.
You'll find most of the rest of the parts in a 10-outfit, although you will see later that I modified the model making it require 32 of part 48b (3½''x½'' double angle strip) instead of the original 16. Add in six of part 113 (girder frame) and you're ready to go.
Building the modelThere are four simple parts to the model:
- The base, which is shown in the plan with all flat plates but can easily be made using strip plates, provided you reinforce at appropriate places with 12½'' angle girders underneath.
- The main supports, of which you will need three (or two if you are building single flyboats).
- The wheels themselves – one or two needed depending on your preference.
- The cars, of which there are sixteen (eight on the single flyboats). These drove me mad, but with a production line it's soon over with. You can see from the photo below that I added three curved plates (part 200) on each car to close them in, and add some red to the all-green wheels.
It would be quite possible to extend this further, by perhaps three or four more holes. Clearance at the bottom could be created (if you're using strip plates) by curving them such that the base under the wheels was concave. Adding this much extra length to the arms caused them to be visibly too far apart, but there is then room to add intermediate arms reinforced by more 5½'' strips to give 16 cars per wheel. This really would make the model a giant, and it might be something to attempt later. For now, making 32 cars was beyond what I had time for!
The photo to the right shows the drive mechanism I ended up with. The model is driven from one of the fine small geared motors available from Meccparts, this is the 167rpm model. It's ridiculously small, so can be mounted vertically underneath with the worm gear on the drive shaft. The two plastic pinions are driven in opposite directions, balancing out much of the force on the worm gear, and the two small sprocket wheels drive the wheels directly through 3'' sprocket wheels at the top. This 4:1 reduction added to the 19:1 reduction of the worm/pinion gives a final speed around 2rpm, just under 30 seconds per revolution.
The plastic pinions keep the noise down, and are designed to be sacrificial – if any gear is going to fail it should be these ones. However, they've lasted well so far! The two 1'' gears on the far end are also in mesh, and appear superfluous. They balance the driveshafts and in doing so prevent the drive from failing due to either pinion slipping on its axle. I have no idea whether this is worthwhile, but it does seem to quieten the drive quite significantly.
A short piece of spring cord with hooks at each end maintain the tension on the jockey wheel. This wheel is installed on the 'slack' side of the chain, near the top. That way, the jockey wheel guides the chain back on to the large 3'' sprocket at the top of the wheel.
When wiring LEDs, you should have them in parallel with a resistor next to every LED. It's naughty but possible to wire identical LEDs in series, which is what has been done here in order to reduce the amount of wiring on the back of the arms. If you're going to do this, make sure all LEDs are from the same batch.
In this model, four LEDs in sequence are wired in series, across 12V. These ultra-bright white LEDs have approximately 3.5V drop across each one. Check the voltage for the LEDs you use – many LEDs only use 2V which will mean you'll need more of them.
The positive wire is run through a hole in the 3'' drive sprocket to an electrikit commutator mounted on the same axle. You can see the contact on the commutator in the picture to the right. The negative supply is bolted to the boss of a crank mounted on the support, with a nut preventing the bolt from going too far into the crank and stopping the axle turning.
While we're here, I'll also mention that the original design calls for the entire weight of the wheels to be held by the girder frames on top of each support. To reinforce these bearings, I've installed a crank (boss inwards) on one side of the girder frame, and a 2'' strip on the outside of the girder frame, bolted together and bolted to the 5½'' strip below, transferring some of the load.
The LEDs and the small motor give an almost unbelievable final load of only a little over 100mA. It runs happily on a small plug-mounted transformer, and the LEDs are surprisingly bright. So far, the model appears fine after a few days continuous running. We shall just have to see how it lasts for an entire month on show!
Update: The model happily ran for around 8 weeks continuously (night and day), with only one instance of the sprocket chain falling off. This might well have been caused by someone bumping into it. It was then parked in a room for most of the year, and performed for around 10 weeks continuously the next year. The only "repair" work required was to take a link out of each chain – such a long length will always tend to stretch with use. However, I can report that the model is extremely reliable and can be run for weeks on end without attention.