Why cannon balls climb

[longcaribiner]

I was trying to describe why cannon balls fired from smooth bore cannons climb above the bore line for a part of their flight.  And got stuck. This is for the Mrs college speech class, she needs to give a speech explanaing an apparent contradiction of science.  She can have help with the research, the grade is in her ability to explain it so that lay persons understand.   I think Ben Robins and Magnus may have explained the concept, but I can't find any reference to the explanation.  Help? 

[Double D]

If the gun is fired perfectly lever they do not climb.  Only if the barrel is elevated will the ball climb above the bore line.

[moose53]

If you check out the Tippmann flatline paintball guns you will find a good explanation . Under certain circumstances a cannon ball with appropriate back spin will climb out of its normal trajectory , much like a golf ball .

[longcaribiner]

Back when I got my first muzzleloader cannon, a 10 gauge, I read about cannon ball climb.  I thought it had to be a crock, so I went out to the range and tried it.  firing unpatched steel ball bearings over thick cardboard wads, the ball climbed at least 10 feet over the bore line by the time they reached 100 yds.  They were going over the back stop, even when the bore was pointed at the ground at the base of the back stop.  I thought perhaps I had an off center bore and checked it all kinds of ways.  Hearing those ball bearings ricocheting off tree trunks was something else too.    I repeated it at least a dozen times after checking the bore.  Even had spotters checking to make sure the balls were not hitting the ground and bouncing up.  They definitely climbed.  

And BTW, the trees were quite some distance beyond the back stop and from there, the back range went up a steep mountain. I definitely was not bouncing balls into the next county, housings developments etc.

I understand what you are saying Double d, but I did find a reference to a Magnus explanation of bullets deflecting above normal trajectory due to spin rotation and cross winds.  Also.  a bullet fired from a rifle spins on an axis that is parallel to the flight.  A cannon ball fired from a smoothbore can spin on an axis that is perpendicular to the line of flight.  Which creates two distinct aerodynamic effects.   

[subdjoe]

Instruction for Field Artillery

that should open to page 27 and tell you what you want to know.

[Cat Whisperer]

I was trying to describe why cannon balls fired from smooth bore cannons climb above the bore line for a part of their flight. 
...
 Help? 

As subdjoe's reference illustrates it climbs above the LINE OF SIGHT.  The bore line and line of sight cross.  So in hte first part of the flight the ball appears to rise, crosses the line of sight (that's  the 25yard zero for your M16) appears to rise and fall, crossing again the line of sight (that's the 100yd zero for your M16) and continues to appear to fall.  The trajectory is (or is close to) a parabola.

Does spin affect 'climb'.  Yes.  It's affect is MUCH less dramatic.  Does velocity affect it. YES.  A lighter round shot with the same charge will shoot in a MUCH 'flatter' parabola -  hitting much higher. down range. 

[Double D]

The ball will not in normal flight rise above the bore line.  It may raise above line of sight if the bore is elevated.

[Rickk]

Any chance that the gun has recoiled slightly while the ball is still in the barrel? If the barrel is pointed above the horizon, the recoil pretty much has to push the muzzle up.

With handguns the effect is very dramatic, which is why a repeatable grip is so important. Also, in a handgun heavier bullets typically hit higher because the time in the barrel is longer and the gun has recoiled higher before the bullet exits the barrel.

I would think that a slow moving cannon ball in a heavy recoiling cannon would still be in the barrel as the barrel climbs during recoil.

[Double D]

The ball will never rise above the the bore line.  If the barrel is elevated the bore line is elevated.  If bore line is elevated the ball will start falling below the bore line as soon as it leave the barrel.

The reaon isd gravity and as soon as the ball leaves the barrel gravity pulls the ball towards the earth.  Velocity gives the ball forward momentum and  causes the ball to fall in an arc away from the bore line. 

Simple 6th grade physics, even Mythbusters got that one right.

[subdjoe]

Simple 6th grade physics, even Mythbusters got that one right.

Well, that's one.