Given this gem of an understatement … I would think even two bearings might present a challenge to some in the original cohort of builders !

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Assuming you have the tools and the skill to get it all aligned … adding a third bearing seems a valid improvement.

MichaelG.

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Edit: Maestro Jason beat me to it

Not only starting.

The 90º crank-setting was normal for twin-cylinder steam-engines, to aid starting in use albeit making balancing in manufacture, more difficult.

Its other reason was to give more even torque per revolution.

The maximum torque from one cylinder comes around mid-stroke, during the minimum, dead-centre, point for the other.

Since the engine is both double-cylinder and double-acting the resultant torque approaches some constancy through the full 360º: a polar plot of effort against angle looks a bit like a four-leafed clover. The flywheel inertia smooths the curve to some extent, making such engines very good for driving directly-coupled dynamos and similar duties.

Apart from making the engine self starting having the cranks at 90 degrees doesn’t increase torque. What it does do is spread the torque impulses around the circle. First, consider that the rotational inertia of the flywheel means that the flywheel is essentially a lowpass filter with respect to torque impulses on the crankshaft.

With the two cylinders in sync there are two impulses per revolution. With the cranks at 90 degrees there are four (smaller) impulses per revolution. Given that the impulses are smaller and there are double the number (double the frequency) the flywheel is more effective at ironing out the torque fluctuations.

Julie