PAPERS

IN

MECHANICS.

The GOLD ISIS MEDAL, and TWENTY GUINEAS, were this Session voted to Mr. WILLIAM WYNN, of Farnham, for a Time-keeper and Compensating Pendulum. The following Communications were received from him on the subject, and Models of the Inventions are preserved in the Society's Repository.

I

SIR,

BEG leave to lay before the Society for the Encouragement of Arts, Manufactures, and Commerce, a time-keeper, and a compensating pendulum, on a new construction. They are of my invention. I also forward the description.

Description of and Observations on the Time-keeper.

IT has ever been my opinion, from the experience I have had, that friction is one of the greatest enemies that clock-makers have to contend with in the construction of a perfect time-keeper; because it is a resistance which continually increases as the movement becomes foul, and varies as the oil is more or less liquid by the change of temperature of the atmosphere. I have, therefore, for some years, been endeavouring to form a plan to reduce it, and I flatter myself I can demonstrate by the one I have the honour to exhibit a very material diminution of friction in every part where it is to be met with in time-keepers of a common construction, and in some of the parts have entirely done away with it.

I have made the pinions to consist of cylinders which run freely round on small pivots, of one-fifth of their diameters, between two brass collets. When the tooth of the wheel comes in contact with each of those cylinders, it will run round on its pivot instead of suffering the tooth of the wheel to rub round a part of its circumference, or, as in common pinions, round the pinion-leaf. This will cause a diminution of friction in proportion as the diameter of the cylinder is to its pivot, and four-fifths of the friction will be lost.

I have placed friction-wheels in contact with all the pivots in the frame, which will reduce the rubbing friction of them as the diameters of the rollers to the diameters of their pivots, which cannot be less than twenty-five or thirty to one. The application of friction-wheels to pivots in many machines is by no means new; but I think it is new as applied to clock-movements.

The

The pallets are constructed of two segments of cylinders, which come in contact with the teeth of the swing-wheel, and go round on very small pivots immediately as the teeth strike each of them; and therefore they suffer the pendulum to vibrate after it has received its impulse with the smallest possible and most equal resistance; as the propor tion of friction with these pallets, compared with the common dead scapement, is as the diameters of the cylinders, provided they were whole, to the diameters of their pivots, which is not less than twenty to one. When the pallet returns to give the impulse for the next oscillation, it still acts upon the rolling cylinder, slides along the curved inclined plane, and causes an equality of impulse, which must contribute to preserve a more equal arc of vibration than any time-keeper I have seen or heard described.

Besides the advantages gained by these diminutions of friction, I shall be able to make the movement go without oiling any of those parts which are usually oiled; as it will be necessary to oil only the pivots of the friction-wheels and cylinders, and not any of those parts in contact which are usually oiled; for as all the parts in contact will have a rolling and not a rubbing friction, (I know no better way to` express the difference), there will be no necessity to oil them.

The parts which will require oil will be so very remote, in point of influence, that its maintaining power, and the resistance of the friction of the scapement, will be always equal in all variations of temperature and foulness. The pendulum must therefore oscillate at all times in an equal arc of vibration, which will prevent the necessity of using any artificial means to preserve the isochronism of unequal

I intend entirely to dispense with the wheels called motion wheels, which give motion to the hands. As three of the wheels of the movement revolve in the times which are necessary to give motion to the hour, minute, and seconds hands, they may as well be fixed to their several axes, as to be under the necessity of loading the movement with three extra wheels and a pinion for that purpose. The wheels which are destined to carry the minute and seconds' hands, will naturally have their motion in a forward direction, as there is a wheel in the movement between the two; but the wheel for the hour hand, viz. the great wheel, has a retrograde motion, which difficulty is obviated by having the hour figures engraved on a small circular plate instead of the dial, and fixing this plate on the axis of the great wheel instead of a hand. A hole is cut through the dial plate to let the hour figures appear through, and an index fixed to the dial to point to the figures. By adopting this plan the hour figures will not be retrograde,and consequently there will be no difficulty for the most ignorant to understand the hour the same as on a common clock. The only objection which can be made to leaving out the motion wheels is, that when the piece is to be set, each of the three hands must be set to the hour, minute and second of time; but that is a trifling objection compared to the advantage gained by the annihilation of friction and resistance which will be found in dispensing with them.

As the hour circle is fixed to the axis of the great wheel, the weight cannot be wound in the usual way through the dial plate. I have therefore cut the barrel-cap as a wheel of the bevel gear, and placed another wheel of the same sort with its axis at right angles to the axis of the barrel, with its teeth to run in the barrel wheel; and by having its