Thanks.  I figured that early revolver cannons would stop the cylinders but wondered if improvements in ammo components, especially primers, had allowed sufficiently accurate ignition timing to keep the cylinder spinning.   As the size of the cylinders increase, the forces needed to stop and start their spin would get pretty large.   Is the barrel assembly held essentially rigid, or does it rotate over a relatively small arc each time the cylinder is locked up and then return to its original position?

anybody know the ROF?

mpopenker said...

yes, i believe in most revolver systems cylinder has to stop to ensure proper alignment with the barrel

Only the Gatling guns can fire during continuous rotation, I think

That is not correct, at least for the Rheinmetall 35 mm KDG.  This weapon can fire up to 1,000 RPM.  At that speed, it would be impossible to start and stop 1,000 times a minute.  Instead, what the designers did is have a wider barrel section between the revolver and the start of the rifling which accommodates the projectile's sideways travel as it exits the revolver and enters the rifling of the barrel.  The timing of the firing is such that the projectile is nearly centered in the bore as it enters the rifling.

You can see this wider section in this illustration which shows the firing sequence.

TonyDiG said...

At that speed, it would be impossible to start and stop 1,000 times a minute.

Perhaps more difficult for the size of the 35mm rounds, but there are a number of single barrel, single breech, weapons with higher rates of fire than that.

There are also faster firing revolver cannon. Most of them, in fact.

If I remember correctly Oerlikon had to tailor the cartridge case and crimping of the KBB round to withstand the "rock crusher" forces of chambering the round at high rates of fire. Some of that knowhow went into design of the 35mm case and crimp.

TonyDiG said:

At that speed, it would be impossible to start and stop 1,000 times a minute.

That is not true.
Its absolutely possible to start and stop a mechanism 17 times per second. Or even more often.

TonyDiG said:

You can see this wider section in this illustration which shows the firing sequence.

This illustration strongly suggests that the mechanism is stopped and there are four steps that are taken when the chamber is stopped in the right position. Nowhere does it say its a continous movement.

The Mauser BK27 for example does stop. The gas piston moves the revolver one fifth of a full turn with each stroke. Moving it one position with each shot. It does that 28 times per second.

Just looked the description of the KDG up. It says the gas piston moves the revolver 90° each stroke. So it does stop. Each shot it moves 90°.
Even though the dwell time is short its more than enough for the cartidge to fire and leave the revolver.