John,
Back in 1989 a club member named Al Chute came to our Indoor contest and
brought us some hand plotted graphs with what he called the "K" factor
method of calculating turns. His graphs were turns per inch on the Y
axis and ounces per motor inch on the X axis. The "K" factor was used in
the formula to plot the curves then you tested your rubber and found
what "K" value it broke at. Where and how he came up with the formula I
am not sure. So all I have done is convert units and by winding tests
determined the 44.2 value. It was only about a year ago when I tested a
bunch of my rubber batches did I realize the "stretch ratio" in the test
I do correlated right to the K value in the formula. So I no longer wind
and break motors to get the K value on a batch of rubber, I use the
stretch ratio from my rubber pull tests when I initially evaluate the
batch, then use that value in the formula, so each batch has its own "K"
value.
Don S
On 4/28/2018 8:25 AM, 'John Barker' john.barker783_at_ntlworld.com
[Indoor_Construction] wrote:
>
> Don,
>
> Can you tell me where your turns formula came from? I am interested
> because in 1995 I worked out a formula by theory (no actual rubber
> winding tests) but it gave good results. It took into account things
> like rubber density and maximum stretch. A year or so later I took
> some of the variables that were near enough constants and assumed that
> lengths would be in inches and weights in grams and used just one
> constant (which was near enough 44) for general use. This made my
> formula: 44 sq.root( L^3/w), where L is the length of the motor and w
> is the weight of the rubber. As you can see, my formula is the same
> as yours so I am puzzled that someone else would have used the same
> sort of reasoning that I did.
>
> John Barker – England
>
>
> Don Slusarczyk
Received on Tue May 01 2018 - 02:58:18 CEST
This archive was generated by Yannick on Sat Dec 14 2019 - 19:13:49 CET