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25th February 2010 Flying Bi-planes 2

The finished model

My first working mock-up (see HERE) proved that a bit more thought was needed to make this simple looking model perform smoothly. The method of suspending the planes was just not up to the job and the rise and fall mechanism needed some work.

Mk1 not good

Getting it to work

Initial experiments with a wheel disc and rod and strip connectors resulted in a very uneven ride as the joints were strained. I decided that a better form of joining the lifting rods was required.

Mk2 not much better

A solid cross with universal joints was made up from a couple of double angle brackets and although this did improve the situation it was still not good. Another problem was the rise and fall had limited travel and was hardly effective at all. After a lot of head scratching and a bit of experimentation I discovered that there is a lot more movement going on at the joints especially after I decided to move the point at which the rods connect to the arms in order to increase the lift. It was clear that the union of the rods had to be fairly substantial and each joint had to be capable of movement in two axis.

A rummage through the parts and a discussion with Sue resulted in a new compact union being constructed around an eight hole bush wheel. Four rod and strip couplings are bolted to the wheel. These will not tighten up on the wheel as the holes are through threaded and tightening the bolt will not close the slot in the coupling. To hold the couplings solid on the wheel a washer needs to be bolted into the free holes of the bush wheel to hold everything square. The plastic washer and second metal washer are purely cosmetic.

With the union assembled into the model and a second Marklin crank added to the top to support the Meccano sign.

Motors and drive

Now the mechanics are sorted out it is time to power it. A simple drive is all that is needed the motor that provides the rotation is a very slow running meccparts motor (Supplied by Michael Threlfall) to avoid damaging the motor or gearbox the drive is interrupted by a plastic rod connector this provides enough grip to drive the model but will slip, and act as a clutch, if the arms are stopped. The rise and fall is driven by an EM1 motor supplied by Dave Taylor very simple gearing directs the drive up the tower.

Cosmetics

A test run proved the theory and it was time to finish off the rest of the model. Narrow strip bracing was added to the tower and the base-plate was clad with flexible plates, strips and short girders in the corners. Two additional plates were added to make the base square. Now it is ready for its first outing to the TIMS meeting this weekend.

Narrow strips add strength and look better than the full width versions

Ralph.

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