Expert: Chip Aki - 9/2/2004

Question
I would like to know the best way to cal. ball speed and rev rate.

I have some formula to cal speed by taking the time in seconds and dividing into 40.9.  I think this is accurate but not sure about what speed this is.  Average ball speed? Initial ball speed? or what.  What is the relationship between those.  Is there a factor to use with this calc to reconcile with ball speed off the hand?

Next rev rate.  I put a piece of tape on the ball from the pap to above the fingers. I located via video the point of release relative to a clock face.  I then advance the film 10 frams and noted the change I took the amount of change and multiplied by 15 to get rmp's.  My video is shot at 30 frames per second.

Are you familiar with these formulas and are they accurate.  Since I film 30 frames per second, there are some lost time that is not recorded on film between frames like .04 of a second.  Is this relavant?

Please send me your thoughts or confirmation.

Thanks
Mike Johnston

Answer
I am sorry I have not replied to this in a timely manner.  My Mother has been in the hospital and I have been a bit preoccupied.

You seem to have everything figured out.  The .o4 really wont matter much.  

The ball speed you are able to figure is average ball speed.  This type of measurement really depends on the lane condition.  The more friction, the slower your ball speed will be due to the greater loss of momentum.

I have the Bowlersmap program that I use for instruction here.  Ball speed and revs are the info that most people get the biggest kick out of knowing.  It is not the end all though.  You just want the numbers to be consistent.  ALso, you want your ball speed and rev rate to match up well.  Too much speed and not enough revs, or too many revs and not enough speed or things to look for as well.

Good luck and sorry for the delay.

Chip