Synchromesh Coupling

by Michael Adler


This gearbox is based on the Rod with Keyway (a). A Socket Coupling (b) holding two 1/2" Bevel Gears 30a (c) is free to slide on the rod, but a special keyway bolt prevents it from rotating on the rod.

Each bevel gear engages a similar sized bevel gear (d) attached to a 57 tooth gear (e), both free to rotate on the rod with keyway. Attachment is obtained using the threaded holes of short couplings (f). Each 57 tooth gear is driven from a single motor, but in opposite directions.

The socket coupling is controlled through its middle groove. A selector mechanism holds the mid-position where neither bevel is engaged.

Moving the selector to each side engages pairs of bevels, and gives the output shaft the appropriate rotation as required.

As many output shafts as desired can be linked or stacked.

The use of small bevels as dog clutches is highly unusual. The advantage is that only a very small rotation of the input shaft is required before engagement occurs, unlike the conventional dog clutch where up to half a rotaion may be required. Also the depth of engagement is very much reduced, and tooth profile is advantageous. It seems that possible tooth damage is minimised by their very low profile.

The gearbox could be used where multiple drives are required, and also in constant mesh vehicle gearboxes.

I would be pleased to learn about applications of this gearbox. Also any ideas for improving the linkage between the bevels and the 57 tooth gears.


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