Mr. Donald asked me a difficult question - Page 4

Just to demonstrate the above here's  a demo of what happens when line WA (sum of all fore assembly bones and positions they stop at in full trot).

Fig 1. : Longer line WA effect on the trot, due to longer sum of bones at same stop position of bones at full flight. This comes from longer Shoulder blade, longer pastern & longer fore leg mainly.


Fig 2. : Longer line WA effect on the trot, due to bigger angle of start at point W (bigger angle of shoulder blade) accompanied with longer sum of bone lengths in the shoulder blade itself. Fore leg and pastern are playing minute effect here as line WB is constant here.

Fig 3. : Directly increasing line BA, this comes from longer pastern, longer fore leg, longer shoulder, & better opening of joints. I made it seperate so it is not confused with bigger shoulder blade angle in above figure.

I am seperating them for ease of understanding, in a certain dog it can be one, two or all combinations. A note here we can increase the fore leg and pastern bones to a certain limit which is the 65 cms height at withers when we add to them the chest depth.
It will be easier in a few minutes when we illustrate the bones and connect their effect to each of the above diagrams.


This is a tracing of the bones in the fore assembly of a well structured GSD with pronounced trot done by Mr. Fred Lanting. Please note the line AW, in a well angulated GSD strarts at the top mid point of the shoulder blade, passes through its center line upto to tip of toes after a full trot when the toes touch the ground.
Let us start with bone number 1, the longer it is it adds to line WA directly and as it is with positive inclination to the line BA it adds to it with an amount relative to how small its imaginary extention makes with line BA. 
Demo

So bone number 1 effect is represented is in fig 1, 3 and when its angle is bigger it is also represented in fig 2, but a note here, for a bigger angle of shoulder blade in order it complete its positive effect on front reach it should be associated with longer bones of shoulder blade itself, fore leg, pastern, one or two or all of them, or theretically more opening of joints but assuming Mr. Lanting's dog is in best open of joints we eliminate the more opening of joints.
A theoretical reason for lifting up of fore leg in trotting is bigger shoulder angle but not enough length in the said bones.
Another theoretical explanation for lifting up is weakness in muscles controlling the shoulder blade movement and thus more opening of the angle in full flight.
Another theoretical reason is no enough muscles at the withers due to shorter withers or narrow distance in between blades.
Think of it as if line WA is opening more and tries to connect with line BA at further point but fails and redirects itself to a lesser open to connect with line BA. This can be seen in a video of gaiting when the dog shakes a bit and pushes its neck to redirect its WA line shorter. Some handlers gaiting their dogs on leash pull back raising up the WA line more and then fore leg stops in the air momentarily waiting for WA to redirect itself shorter so they can meet.

We go now to bone number 3, just look at it, it tends to push line WA to the out (further opening) and it tends to push line BA forward (smaller angle with line BA than that of bone number 1 and thus bigger effect), its effect is represented in all the figures above, more effect than bone number 1 in regards to increse of bone length alone.
Also same context applies to bone number 4, its effect on BA length is more than number 3, thus also more than than that of number 1. 
Therefore if we place importance of length of individual bones discussed so far in sequence from higher to lower

1. Bone number 4, the pastern
2. Bone number 3, the fore leg
3. Then bone number 1 the shoulder.

But bearing in mind the tremendous effect of the shoulder blade angle whether positive or negative on the whole fore system.

Remains bone number 2, the fore arm, after some rest.

Now to understand bone's number 2 role and effect, we split the fore assembly system in two:
1. The shoulder, shoulder blade and fore arm.
2. Fore leg including pastern and foot

The fore upper arm being the connecting bone in between both of them.

When looking at bone number 2 effect in full open on the  lower system, what matters is only the degree it opens to, the closer it gets to 90 degrees the better, because the more it opens the more it pushes the fore leg forward and then the pastern and thus more effect like what bone 3 & 4 do.
Why did we split in two systems ? because the length of upper arm is adjusted for in the shoulder itself, and therefore increase or decrease in its length is adjusted for in the shoulder and does not affect the lower parts in any way in a well balanced dog in the fore assembly.

When we look at the full fore assembly we should keep in mind the line of ideal balance.



In standing position this line when vertical, starts from the top mid point of the shoulder blade and goes through the joint between fore leg and front upper arm then through pastern joint, it tells you this dog is correctly balanced in the fore assembly system.
Now let us look at the shoulder itself.

The red line is in proportion with the line continuing to the ground, in other words to the fore leg. So consider it constant in length and consider shoulder blade at the best angle of 45 which is the ideal in standing position with some increase when in full stride, and for ease of understanding think of the shoulder blade as a non-moving bone, though it does move to a certain extent. Now we have the red line as constant, shoulder angle is ideal at 45 degrees then what combination can take place in between the two bones number 1 and 2 from previous diagram?
Note that the best scenario is when the joint in between the two bones is placed forward/down in line with shoulder blade axis, why? refer to the effect of bone number 2 explained above, and add to it that this way it takes all lower bones in forward/down effect furthering the effect of open in each two adjacent bones and thus increases the distance BA as desired and discussed above.

In a correctly angled shoulder blade, the longer it is the better the front upper arm angle gets. The controlling factor is the length of the shoulder blade, breed for correct lay of shoulder blade 1st, then longer shoulder blade and upper arm will follow. Watch the line of balance it should always be correct.

Now that is mathematics and physics, join it with genetics and actual knowledge from examining big number of dogs to have practical knowledge of realistic various proportions, and watch at what limits up or down a certain negative tendency appears to determine proportion ranges between all bones,  best for big effective trot. Length and angle of upper arm themselves are not the goal, the aim is correctly laid and longer shoulder, front upper arm will follow, balance line is a must, without it you get nowhere.
Now to test other lengths or bones etc, you can assume a constant length and test two variables. Like keep shoulder blade constant and test front upper arm with the red line (in previous post fig) and do remember it is in proportion with total height/and fore leg), I guess that who put it at 45% ideal did something of this sort.

I am done Mr. Donald, Sirs and Ladies all comments are welcome.

Don´t kill me, this doesn´t belong to the topic ( you did an amazing research - great ! )...

I met Dingo several times, his gait was amazing, but the dog itself didn´t impress me at all. Dingo standing in front of me was a " normal" dog, and most of his progeny didn´t impress either.

Am I the only one who felt like this ???

I see this note is very important, any piece of info about Dingo is very important and dear, if you can still remember any more details about him, please do share them, no matter what they might look minute, someone may find a helpful connection somewhere, thanks Susie.

Ibrahim

That´s difficult to explain-if this dog would be your neighbours dog, you wouldn´t look twice. For me his front was too high, I didn´t like the shoulder/forecheast, people whispered about problems with the hips in his offspring. While running his ears often were down. Some of his sons were in my neighbourhood, good dogs, but nothing "special". Mostly the smaller breeders used him as stud.
But all of this is long ago, at least a high percentage of his offspring was titled...and that´s an imortant point.
You are good in maths, maybe you are able to determine the percentage of the possibility, that you still can find some Dingo gens in a dog bred today out of Dingo.
I really don´t want to blame this dog, all of this is MY subjective opinion, nothing else.