Saddle Key

[Alan]

Can anyone give advice on how a "saddle key" works I am going to build the McOnie engine serialised in the ME However Anthony Mount who is serialising the build says the Flywheel is held in place with a saddle key. This key needs a slot in the flywheel but not in the crankshaft ! Any ideas ?

[jgb7573]

I believe there is a flat on the shaft and the key sits on that. It saves cutting a keyway in the shaft.

[circlip]

Key tapered in side elevation with a gib head, like the nails used inthe past for holding floor boards down.
Regards Ian

[jasonb]

He uses then on most of his engines. Does them by boring a hole in a piece of steel to suit the shaft, then turns down the outside with 2degree taper to form a flange which becomes the gib head, then parts off.

You now have to saw out a section of the "tube" the width of the key.

Flywheel is keyed with a slotting tool or using the lathe carrage then the last few strokes are done with a matching angle to the key.

There are no keyways or flats cut on the shaft, the concave inner face of the key sits on the curved face of the shaft, the taper holds it tight.

Its a nice engine to watch ticking over, saw it at the London Model Ehibition earlier this year, lots of fine work in the valve linkages

Jason

[paul]

Maybe something like this (photographed on the mighty Bratch engine last Sunday)...

[jasonb]

Jun 19, 2008 20:47:18 GMT paul said:

Maybe something like this quote]

The one in your picture has a shallow keyway in the shaft, The ones he uses do not have any keyway or flat on the shaft, also the gib faces away from the shaft and the key has a curved face to match the shaft.

If you don't want to wait until he describes how to make them in the ME articles, they are described in his book, comes up about 3 or 4 times and is almost an identical paragraph.

Jason