Mr. Donald asked me a difficult question - Page 9

Let us pay a closer look at the shoulder itself



General

Any triangle has a sum of 180 degree, this is a mathmetical rule.
The line you see seperating the big shoulder triangle into 2 smaller triangles is the horizontal. Where it meets the imaginary vertical (the 27.25 cm line) it makes an angle of 90 degrees up and 90 degreed down, this is also a mathematical rule ( angle between the horizontal and the vertical is 90 degrees.

Looking at top small triangle and since we're assuming the shoulder angle to be 45 degrees then the remaining third angle (top one) is = 180 - (90 + 45) = 45 degrees.

Looking at bottom triangle and since we're assuming the front upper arm is 45 degrees then the remaining third angle (the bottom one) is= 180 - (90 + 45) = 45 degrees.

After drawing the two 45 degree angles the software (autocad) gives us the shoulder length and front upper arm length to be equal and each 19.2687 cms in this dog's case (65 cms high and chest depth 45% from total height at withers, imaginary vertical line connection the mid point of top of shoulder blade and elbow joint where front upper arm rests in the cavity at top of front leg.)

This (the two lengths being equal is correct and a rule in a triangle of two 45 degree angles and third one 90 degrees.

For more details of properties of this angle see herehttp://www.mathopenref.com/triangle454590.html

The sum of shoulder bones in this case is 38.5374 cms and the sum of shoulder angles is 90 degrees and  its corresponding reach is 44.37 cms

Let us look at the more real ideal shoulder of 45 degree shoulder and 53 degree front upper arm angle

Let us have a closer look at the shoulder itself



As we did before and after setting the sfront upper arm angle at 53 degrees the thirs (bottom) angle is calculated too be 37 degrees, actually the software (autocad gives it or makes it automatically). Please note as the front upper arm angle becomes bigger this third angle (in this case 37 degrees) becomes smaller causing the direction that front upper arm goes from elbow joint towards the shoulder joint steeper. Just to give you a smile in the beginnings when a member said a dog had a steeper front upper arm I was confused what that exactly meant, well to those who are still confused at this term that is what it actually means, bottom angle lesser more steep the front upper arm is, lol.

The sum of shoulder bones in this case is 36 cms, a decrease of 1.5 cms or 3.9%,  
And here is the corresponding reach 43.2 cms, with a decrease of 1.17 or 2.8%. Maybe that is why some are still longing for the 90 degree shoulder!!!!!!!!

What do we learn from the above, ( but not final till we see more examples and more shoulder angles and lengths combinations):

The bigger the front upper arm angle

1. The shorter is the shoulder blade
2. The bigger is the sum of total shoulder angle
2. The shorter is the front reach
3. The steeper is the front upper arm
4. The less is the sum of shoulder bones, and therefore the less is the sum of front assembly bones

Also we learn as long as the shoulder blade remains at good angle of 45 degrees, the longer the shoulder blade is the better (less angle) angle we get in the front upper arm, but let us wait till all possible combinations in the shoulder are demonstrated to see if this hold correct and upto which point.

Also we learn from these two cases that the increase of front reach is due to the increase in the length of the shoulder blade (in the first case of 45 degrees of shoulder blade and front upper arm) because when the front upper arm angle got bigger, 53 degrees, the front upper arm length got slightly bigger. So what really matterred is the increase of shoulder blade length.

But again let's wait and see the other combinations and what holds true for all demos.

Also we learn that the longer the sum of shoulder bones the better the front reach,
Also we learn the less the sum of shoulder angles the better the reach is,
again we'll see other combinations and decide.

Ah, one more point we learn here, you see in case of 45 degrees both the shoulder and front upper arm angles the shoulder blade and front upper length lengths are equal and the proportion is 1:1, so we learn that the less the proportion the better is the front reach, but again let us wait and see if this hold true in other shoulder combinations.