Wow - it is like being back in math class!
Should we pass on this info to Marv?
I've sent Marv an email with the same information as in the thread. We'll wait and see where my thinking has gone astray.
Thank you Arvid! After reading the article yesterday, I stared at Marv's code and knew there was something wrong with it but could not put my finger on it. No wonder I keep getting a negative number for the mandrel diameter when I select phosphorus bronze with my program. It's curious that it's not the case when I run Marv's version of the program. I get the same results whether I select music or bronze wire.
Excellent analysis!
With your information I can now finish up the program.
Ed
"k = mx + b
where m = -0.0124727272727273 and b = 0.980818181818182 for music and stainless steel wire
and m = -0.0109727272727273 and b = 0.984909090909091 for phosphor bronze wire.
and x is the Spring Index."
Arvidj, are thes values for m and b constants? Or are they just for the example in the article?
Chuck
(07-03-2013, 09:33 AM)chucketn Wrote: [ -> ]"k = mx + b
where m = -0.0124727272727273 and b = 0.980818181818182 for music and stainless steel wire
and m = -0.0109727272727273 and b = 0.984909090909091 for phosphor bronze wire.
and x is the Spring Index."
Arvidj, are thes values for m and b constants? Or are they just for the example in the article?
Chuck
They are constants derived from the graph, not from the example.
I looked at the graph on page 20 and entered the data points into Excel ...
Music or Stainless Steel Wire
Code:
5 0.922
6 0.907
7 0.893
8 0.880
9 0.867
10 0.854
11 0.842
12 0.829
13 0.818
14 0.807
15 0.798
Phosphor Bronze Wire
Code:
5 0.933
6 0.920
7 0.908
8 0.896
9 0.884
10 0.874
11 0.863
12 0.851
13 0.842
14 0.833
15 0.823
I then ran a linest function on the data to determine the "best fit" straight line that fit the data ... i.e. a line that is defined by y = mx + b. The results are:
Music or Stainless Steel Wire
Code:
-0.0124727273 0.9808181818
0.0002209421 0.0023172607
0.9971838746 0.0023172607
3186.8803611737 9.0000000000
0.0171125818 0.0000483273
Phosphor Bronze Wire
Code:
-0.0109727273 0.9849090909
0.0001841018 0.0019308762
0.9974728525 0.0019308762
3552.3275535085 9.0000000000
0.0132440818 0.0000335545
The first row, first column is m and first row, second column is b.
The third row, first column the coefficient of determination ... a value between 0 and 1 that indicates how accurately the mx + b formula predicts the given y values for the data that was provided. A value of 1 means 'perfect fit' and 0 means 'not even close'.
In this case the values are so close to 1 that we are safe in assuming that "for any value of x [the spring index], the value of y [the elusive k] is ((-0.0124727273 * [spring index]) + 0.9808181818) for music and stainless wire and ((-0.0109727273 * [spring index]) + 0.9849090909) for phosphor bronze wire.
(07-03-2013, 09:15 AM)EdK Wrote: [ -> ]...
It's curious that it's not the case when I run Marv's version of the program. I get the same results whether I select music or bronze wire. ...
Ed
Very possibly a case where the code and the exe do not match. Developers love those types of challenges ...
(07-03-2013, 08:54 AM)arvidj Wrote: [ -> ]I've sent Marv an email with the same information as in the thread. We'll wait and see where my thinking has gone astray.
I just got this from Marv ...
From: Marvin W. Klotz
Sent: Wednesday, July 03, 2013 11:04 AM
To: Arvid Jedlicka
Subject: Re: Possibly a bug in the mandrel application ...
Arvid,
Good catch. I don't think I've ever seen such a thorough analysis of a
suspected error. I'm convinced. I've incorporated all your constants
into the program and prepared a new version to go up on the website soon.
Thank you so much for taking the time to work through this and advise me
of the problem. I really appreciate your efforts.
Regards, Marv
Home Shop Freeware
http://www.myvirtualnetwork.com/mklotz
I got the Windose program running now with Arvid's new numbers. I'll upload it once I've done some more testing.
Ed
[
attachment=5590]
Ed,
When you get all the details worked out, I'll give it a real world test drive.
Tom
(07-03-2013, 02:12 PM)TomG Wrote: [ -> ]Ed,
When you get all the details worked out, I'll give it a real world test drive.
Tom
That would be wonderful Tom! I'll have it uploaded this evening.
Thanks,
Ed