John Dowding's Meccano Projects

Here are some of the many projects that I've built using components made by Meccano, Erector, Ashok (high quality replica parts), etc.
 

Tower Crane	Trebuchet	Cars

Tower Crane

This is an ongoing project that I work on from time to time.It stands just over 6 feet tall an is designed to pick up a brick from the floor and put it on the kitchen table

Detail Shots (click on the thumbnails for larger JPEG images)
 

1. Main Bearing - Side View	2. Main Bearing - Top View	3. Bridge Drive - Upper Part	4. Bridge Drive - Lower Part	5. Trolley and Block

1. The main bearing uses circular girders and flanged wheels.
2. Another view of the main bearing. Note in this image, the small (3 1/2") circular girder is not a Meccano part. This was manufactured by Ashok K. Banerjee and he has other sizes (and other parts) that were not made available by Meccano. To see what parts he has available, do a search in your favourite search engine with the keywords: Ashok, Meccano, replica. For Meccano modelers, it's well worth the effort.
3. The bridge will be driven by a motor (not shown) mounted in the tower structure just below the bearing and it is geared to rotate the bridge at less than 1 revolution per minute to prevent the load from flying outward. The two spur gears seen in image 3 are mounted on 11 1/2" axle rods that have 19T pinions on the other end. These pinions will mesh with the inner edge of a gear ring mounted on the underside of the bridge. I use two shafts here to divide the high torque that would otherwise overwhelm a single shaft. (gears and pinions are only set screwed onto the shafts - not keyed as they would be in real industrial applications - they have a tendency to slip when under high torque)
4. Gearbox for the bridge drive. Notice in this image, that the output shaft of the gearbox is spring loaded to push it upwards. The upper end of this shaft is designed to mate with the centre bush wheel of the bridge drive upper part aligning the 25T pinion with the two 50T spur gears. Having the shaft spring loaded allows easier mating of these subassemblies of the drive when they're mounted in the tower structure.
5. The trolley and block shown here are not seen in the main image above because the cable was not threaded through the system when the photo was taken. As I develop the crane further, I'll take more pictures and eventually, I'll have one with all of the pieces in place.

There are a number of other subsystems not shown and they will be displayed at some future date.
First is the cable winding drum and its drive. This subsystem includes a cable guide similar to that in a fishing reel.
Second is a mobile counterweight system in the rear section of the bridge which will react automatically to luffing movement of the load (and when the load is lifted off the ground). This will make sure the bridge maintains a continual balance over the tower.
Third is a slip ring commutator which I am developing and making myself. This will allow the bridge full rotational capabilities without tangling any power and control wires between the tower and bridge. If you look at image 1, you can see a black plastic cylinder at the centre of the system. This is actually the cap from a can of spray paint. I have two of these (the other is above the top edge of the picture). The commutator slip rings, which will be made of a flexible plastic sheet with conductive traces on it, will be wrapped around these cylinders.  The wiper arms which contact the traces will be replicas of parts from the Meccano Elektrikit and will be mounted on the support collumns (blue and green angle girders).
Fourth is the trolley drive. It will be tucked in with the cable drive on top of the rear section of the bridge and is only partially developed at this time.

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Trebuchet

The trebuchet was a seige weapon used in mediaeval Europe till it was rendered obsolete by the introduction of reliable cannons. These weight-powered slings were used by armies to throw boulders at castle walls in an effort to smash their way in. Like their cousin the catapult, they were also used to hurl diseased bodies, the heads of captured enemies and other horrors into the castle itself. Nasty stuff.

My model will not be used for anything nearly as neffarious as that.

This was an extremely enjoyable model to build and is even more enjoyable to demonstrate for people. This machine has 10 pounds (4.5 kg) in counter weights and can throw a hackie sack over 40 feet (12 m) with incredible accuracy. Three or four shots in a row at the maximum range will almost always land within a couple of feet (0.6m) of each other, usually within one foot (0.3m).

For a small video (795 kB AVI file) of an early version of the trebuchet, click here. Notice that the earlier version has a much smaller counter weight and a thicker throwing arm. As I tried to achieve longer ranges, these parts were changed again and again.

Detail Shots (click on the thumbnails for larger JPEG images)
 

1. Counter Weights	2. Release Pin and Trigger	3. Main Bearing	4. Winch	5. Other Details

1. The Counter Weight section includes both fixed and hinged counter weights. The hinged counter weight consists of 500 perforated strips ranging from 2" to 5.5" in 10 bundles of 50 each.
2. The release pin is adjustable to change the release angle. This, combined with how far the throwing arm is winched down, can give a variety of heights and ranges. This can be useful for lobbing a projectile high over the castle wall or relatively horizontal at the wall.
3. The main bearing includes a number of bush wheels for added strength. Compare this to photo 1, which was taken before the extra bush wheels were added. I had some trouble with the axle rod flexing under load.
4. The winch was added to give it a little authenticity. After all a mediaeval warrior could hardly be expected to pull the throwing arm down by hand.
5. In this image of other details, you can see the sling and pouch. The pouch is a piece of leather from an old glove. In order to give it a cup-like shape, I pulled it tight over the end of a shovel handle and hammered it into shape. In this photo, you can also see details such as the outriggers (lateral support), the trough (slider for projectile) and frame base (below the trough - everything sits on this). Note that the trough and frame base are each made with a pair of Erector parts (part MN - 12" base plate)

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Cars

I build very few models from the plans supplied with Meccano sets these days, but I had some really nice red 1" pulleys from the 1937-41 era so I thought I'd build a couple of cars with them. The top car is  model 3.4 from the 23/69 model book and is not built with authentic colours The green and red are from a different era but these parts were relatively scratch-free. This model is also built with brass nuts and bolts. I don't have many of these so I thought a small model would be their best use. The bottom car is model 3.7 from the 162163 model book and other than the wheels, it is built with authentic colours of the period ('70's). Other than the colour of the wheels, there is one other deviation from the model plan. Instead of using two overlapping  2 1/2 x 2 1/2 flexible plates for the body just in front of the driver, I used a single 2 1/2 x 3 1/2 plate. Because of the lack of bolt holes where I needed them, this prevented me from installing the windshield. Oh, well. The driver can wear goggles. The models are photographed on a gloss black coffee table. Click here for a larger picture.

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