cyclic steering

Cyclic steering is used by helicopters (when flying sideways), by industrial robots and by minesweepers. It has the advantage that a vehicle can move in any direction regardless of its orientation.

Although they are quite involved to make the result can be quite satisfying, the steering linkages create a very baffleing effect as they rotate.
It consists of a circular wire frame mounted on three castors, one of which is motorised so the whole frame goes round and round. Each castor is steered by a wire hairpin which bears on a crank,which is orientated by a radio controlled propellor. As the frame rotates and the crank stays still each castor is steered cyclically according to its position in relation to the crank.
This produces an overall motion at right-angles to the crank. The vehicle can be steered with the propellor rather like the tiller on a boat or the tail rotor on a helicopter.

Only one wheel shown on animation for simplicity.

This is one which uses a trail wheel to control the orientation of the crank, it only goes in straight lines

This is a movie of it. It uses three drinking straws attached to the castors by cardboard hinges. Each straw points at the off-center bearing

It is important that this bearing has as little friction as possible.

This one has a modified trail wheel that allows it to be steered

It is a motorised plastic bead that normally skids sideways

This is a movie of it moving its steering arm with the propulsion motor off. Another movie this time with the propulsion motor on.

This one has two contra-rotating turntables. It was made by Leonard Charley.

Originally these were driven by two electric motors mounted in the metal brackets at the corners. The off-centre pegs were controlled by a central joystick with mechanical linkages.

This is my version

It's two of the other ones joined together, the steering arms are linked with two connecting rods & driven by rubber bands from a central control motor. You need two connecting rods offset by 90 degrees because otherwise they stick at top dead centre.

lego holonomic drive

back to main site
my email is