Understanding Rock

[AdamTill]

Hi folks,

I'm new to the board (and to saddle design), but have really enjoyed reading everything so far.

I gather that there were previously a lot more threads that were lost in a server crash, so please excuse me if this topic has been discussed before, but I would really appreciate learning more about rock in saddle trees. I can understand flare and twist pretty easily, and the concept of rock itself is straightforward, but the details of rock are eluding me a bit. I also understand that every tree blends these concepts to a large degree, but for purposes of discussion, splitting rock out for now would benefit me immensely.

So, in no particular order:

1) If rock can be visualized as a curve, is the "low point of the bowl" under the low point of the riders seat (assuming jineta design)? In the middle of the bar? (assuming that point isn't one and the same)

2) If one were to micro-fit a tree to a particular horse, how does one determine the amount of rock? Is that designed for the case where the topline is fired, and the back dropped, or a worse case then that?

3) If looking at the horse from behind, is the "plane of rock" perpendicular to long muscles of the back, or parallel to the midline? So in the attached photo, if turquoise is the rough plane of the back, red would be perpendicular to that, and dark blue parallel to the midline. That may be overthinking things since the difference would seem to be small on most horses, but I'm curious.

Thanks tons...really appreciate any help anyone could offer.

Cheers,

Adam

[Rod and Denise Nikkel]

Adam,

Yes, there is information on this topic in the currently buried threads. But I believe they are getting closer to the surface all the time. Be prepared for a slug of reading when they do come back…

3) If looking at the horse from behind, is the "plane of rock" perpendicular to long muscles of the back, or parallel to the midline? So in the attached photo, if turquoise is the rough plane of the back, red would be perpendicular to that, and dark blue parallel to the midline.

One of the things that needs to be considered when getting a tree that fits a horse is the angle of the bars relative to each other. They need to match the horse’s back. A flatter backed horse needs a flatter angle to the bars. A more A shaped horse needs a steeper angle. This means that the bars will fit against the horse on the same “angle” as the horse is. So when you look at the bars, the curve from front to back (the rock) needs to be evaluated not compared to the ground, but compared to the horse. Thanks for the pictures. They help in explaining. The blue line would be cutting through the bar at an angle, and that angle would change with every difference in bar angles. Life is complicated enough without that, so red line on your drawing is how we evaluate rock. Does it make a difference? Actually, a little bit. Enough to worry about? Questionable. How the horse is standing and moving and using their body makes more of a difference, but at least this is one variable we can control.

1) If rock can be visualized as a curve, is the "low point of the bowl" under the low point of the riders seat (assuming jineta design)? In the middle of the bar? (assuming that point isn't one and the same)

The shape of the bottom of the bar is independent of the shape of the top of the bar. The bottom is shaped to fit the curves of the horse. It needs to fit with contact down its full length, yet with relief built into the bar edges and the tips of the bars front and back so that it doesn’t dig in and cause excess pressure anywhere. If there is too much rock, pressure is concentrated in the center of the bar, or else, depending on a number of factors, the tree tips forward and the whole front half has excess pressure while the back half isn’t doing its share of weight carrying. So rather than picturing a bowl, I guess I would see rock as more like a saucer. The curves are gradual and mild, and although I guess technically there has to be a “low point” somewhere, it is not an easily definable place. And when you put it on the horse, that spot would be in a different place than a bare tree sitting on a table, and may vary a bit from horse to horse as well. As to how rock relates to the low point for the seat, that isn’t necessarily correlated. Ultimately that part is determined by the saddle maker, though a tree maker can make it easier or harder for him to put in a good seat. (What a “good seat” is we will let the saddle makers fight about discuss.) Depending on the length of the seat and the conformation of the rider (e.g. how much “padding” they carry on their backside) where that low spot goes may vary a little along the bar while still forming a very good seat. The rock in the bars still needs to match the horse regardless of where the seat is placed.

2) If one were to micro-fit a tree to a particular horse, how does one determine the amount of rock? Is that designed for the case where the topline is fired, and the back dropped, or a worse case then that?

There are no specific terms or numbers to describe rock. The best thing we came up with on our own was making a pattern with a flexible curve along the horse’s back under where the bar runs and sending that to us. Dennis Lane’s system has the same idea, but he takes his 3 ½” from the midline, but with the card perpendicular to the horse, not the ground. We are still working out how we can use that information in the way we build trees, but it is a much more consistent way to measure than the flexible curves. However, you need to have the horse standing square with his head in “normal working position”, because as anyone who has ever taken back drawings knows, that head and body position affect what you get in terms of shape for the rock. Overall, unless you have a mule or a horse that is extreme on either end, the variations in rock are relatively small. You don’t want a saddle that consistently bridges, and you don’t want one that has so much rock it has constant high pressure in the center of the bar. Anything else will not hurt your horse.

There is a lot of variation in spinous processes and while there may be a correlation between topline and the shape of the side of the horse where the bar goes, I am not at all sure it is consistent. At least, we don’t have enough information to know what it is. So we have decided look at where the bar actually sits when figuring out amount of rock. We only use the topline for figuring out gullet and handhole height.

If the question is “What do you fit – a damaged horse or a healthy horse?”, that is a very difficult question. If you look at a horse with a “sway back” and say, “I can change that by working the horse differently”, and get a saddle to fit the not so swayed back you are hoping to achieve, you will be using a saddle that will bridge on that horse now. The pain in his loin will cause increased splinting of the back, etc. etc. etc. and perpetuate the problem. You can run into other problems if you make the opposite choice. If the difference is severe, it may take two saddles. This is why we don’t want to “micro-fit” for one horse. The horse moves under that tree constantly and if you could read the PSI as he moves it would be changing every microsecond under every part of the bar. And unless you have spots that have too much constant pressure or way too much intermittent pressure, you will not hurt the horse if you get the basics right. So we work to fit a type or style of horse rather than one particular horse at one particular point in time.

[AdamTill]

Adam,

Yes, there is information on this topic in the currently buried threads. But I believe they are getting closer to the surface all the time. Be prepared for a slug of reading when they do come back…

Hi Rod and Denise,

Thanks very much for the reply. I look forward to doing a bunch of reading - my workshop is packed up in preparation for putting the house on the market, and it's killing me to not be able to go down there and putter.

One of the things that needs to be considered when getting a tree that fits a horse is the angle of the bars relative to each other. <snip> The blue line would be cutting through the bar at an angle, and that angle would change with every difference in bar angles. Life is complicated enough without that, so red line on your drawing is how we evaluate rock.<snip>

Okay, I'm with you on all points there.

The shape of the bottom of the bar is independent of the shape of the top of the bar. The bottom is shaped to fit the curves of the horse. It needs to fit with contact down its full length, yet with relief built into the bar edges and the tips of the bars front and back so that it doesn't dig in and cause excess pressure anywhere. If there is too much rock, pressure is concentrated in the center of the bar, or else, depending on a number of factors, the tree tips forward and the whole front half has excess pressure while the back half isn't doing its share of weight carrying.

So rather than picturing a bowl, I guess I would see rock as more like a saucer. The curves are gradual and mild, and although I guess technically there has to be a "low point" somewhere, it is not an easily definable place.

By saying saucer rather then bowl, do you mean that it should be a more gentle curve, or do you mean that the rock curves at the bar tips are more upswept then the curves in the middle?

<snp> As to how rock relates to the low point for the seat, that isn't necessarily correlated. Ultimately that part is determined by the saddle maker, though a tree maker can make it easier or harder for him to put in a good seat. (What a "good seat" is we will let the saddle makers fight about discuss.) Depending on the length of the seat and the conformation of the rider (e.g. how much "padding" they carry on their backside) where that low spot goes may vary a little along the bar while still forming a very good seat. The rock in the bars still needs to match the horse regardless of where the seat is placed.

My thought process in saying that the low point was in the center of the seat was that the seat (in my mind) should ideally be centered in the middle of the span of the bar which contacts the horse in most cases (ie, the section that isn't flared to clear the shoulder). That way the center of pressure (from the rider's weight) is centered over the center of support (middle of that span of bar). Equally ideally, the support center of the rigging on the tree should designed to straddle the center of pressure, so the saddle doesn't rock or shift.

Not sure if that's true, but it makes sense from over here.

There are no specific terms or numbers to describe rock. The best thing we came up with on our own was making a pattern with a flexible curve along the horse's back under where the bar runs and sending that to us. Dennis Lane's system has the same idea, but he takes his 3 1⁄2" from the midline, but with the card perpendicular to the horse, not the ground. We are still working out how we can use that information in the way we build trees, but it is a much more consistent way to measure than the flexible curves.

I don't know Mr. Lane's system, but I think I can picture what he's doing. I'll attach a few files to this message with my interpretation of that, though I'll pull off a profile 4" from the midline instead (assuming the midpoint of a 5" wide bar positioned 1.5" off centerline). The dark blue line is the midline profile, and the light blue line is the profile at the offset distance.

Now, in the photographs I've overlaid the profile lines onto the actual horse (the profile was done two years ago, though it still seems close enough today). The angled red lines are just an attempt to get a feel for the boundaries of the saddle fit region (saddle might be a scotch forward in the photos), and the angled green line is the center of the seat (or close to). The taped bits on the horse are meant to show the scapular spine, the rear edge of the scapula, the shelf of the ribs, the (very defined) edge of the spinalis muscle, and the edge of the last rib.

So, taking all that, if you go to the attachment that shows only the line drawing with the two profiles and the saddle fitting range, I'm picturing the line of rock being something like the pink line in relation to the back profile underneath the bar (standing, at rest) as the light blue line. Thus the rock measurements I'm trying to get an appreciation for are the ones marked forward (considering rock ahead of the scapular seems pointless, as flare would dominate), and rear (at the end of the bar).

Does all that make any sort of sense? (tough concept to show in drawings I'm finding).

There is a lot of variation in spinous processes and while there may be a correlation between topline and the shape of the side of the horse where the bar goes, I am not at all sure it is consistent. At least, we don't have enough information to know what it is. So we have decided look at where the bar actually sits when figuring out amount of rock. We only use the topline for figuring out gullet and handhole height.

Absolutely…midline profile along the tops of the spinous processes would seem to be almost but not quite independent of the profile in the region where fit occurs. The files I've attached back that up (in this case, anyway).

If the question is "What do you fit – a damaged horse or a healthy horse?" <snip> This is why we don't want to "micro-fit" for one horse.

I guess I had taken micro-fitting to refer to customizing a tree for a specific horse (as opposed to using a "standard" tree from a given range that comes close enough), but I take it the term actually more specifically refers to fitting a horse "as-is" with no consideration for whether that's where you actually want them to be in the future. I'll remember that for the future, and I'll also heed your warnings against doing so.

Edited February 13, 2008 by AdamTill

[AdamTill]

Sorry, the last graphic had an error on it (rock was being measured past the end of where the bar ended)...should be as follows.

[David Genadek]

Adam,

It might be helpful to you if you think of it in terms of a board with two hinges in it. When you engage the hind quarter

you will be effecting the rear hinge when you raise the base of the neck you will be effecting the front hinge.

David Genadek

[daviD A Morris]

Adam,

You sure have done a heap of work on this. What CAD program are you using? Personly I use AutoCad but only because when I first went to work as an engineer thats what the company used and I don't have time to learn anything else.

Just a little something that "jumped out at me". Many years ago, back in the 1980's I went around making plaster casts of horse's backs and from them i made the fibreglass replica of the horses backs. This was to help me understand the true shape of horse's backs and one of the things I noticed which was different to what most people have stuck in their minds about what they think a horse's back is shaped like, is contour of that cyan colored line in this drawing or yours.

Notice where you have the numbers 7, 8, and 9 that the line is convexed almost like the horse has a bump there, It is only slight and I find is further down the side, where the ribs "spring out" than what appeas in your drawing, but that is the nature of 3d stuf. When i first noticed it i thought it was something to do with my casting method. interensting that you have the same thing. This begs the question, if you are "micro" fitting this horse are you going to make the tree-bar concaved in that area? personaly it did lead me to flattening the bar in that area. But when i say that, i had previously just copied the old factory made trees from the USA, which had a lot of "ball" to them. With a bar that is convexed placed against a convex shaped horse the preasure is increased. (Of course you know that, just adding for benefit of other readers) The benifit of bars with a lot of ball is that while they will not fit any horse extreemely well they not be extreemley "bad" on a greater range of horses. Unlike the flatter bars, which will fit some horses very well, but on a horse that they are not designed for, the edges, which ever edge it is that makes contact, will cause severe problems.

On another point - I am curious that you said ".... the seat should ideally be centered in the middle of the span of the bar..." It appears to me that the brown saddle on the horse in that photo has the lowest poiint of the seat way back towards the cantle, the bars appear to be quite short behind the cantle. Thus it appears, in the photo anyway, that your weight would be place a long way to the rear of middle.

Your post is very detailed, I'd like to have more time to discuss more with you. looking forward to yuor reply.

dam

Edited February 14, 2008 by daviD A Morris

[daviD A Morris]

I'm new to the board,.......

2) If one were to micro-fit a tree to a particular horse, how does one determine the amount of rock? Is that designed for the case where the topline is fired, and the back dropped, or a worse case then that?

Adam,

I only just noticed that you are new to the board. WELCOME, I'm looking forward to more of your posts.

Forgive me for asking such a dumb question - but what do you mean by "topline is fired" I have not heard the term before.

Acutaly the whole question "Is that designed for the case where the topline is fired, and the back dropped, or a worse case then that?" Lost me, but I am just a dumb saddlemaker

regards

dam

[AdamTill]

Adam,

It might be helpful to you if you think of it in terms of a board with two hinges in it. When you engage the hind quarter

you will be effecting the rear hinge when you raise the base of the neck you will be effecting the front hinge.

David Genadek

Hi David,

Okay, that helps, but I guess my next thoughts concern where the flex "points" of those hinges would be.

For example, from Dr. Deb's writings and the dissection course I attended, I don't really recall there being much flexibility to the spine along the ribcage. But that said, "much" is relative. Can the area from around T12 back to the last rib be fitted with a rock that roughly equals what the back would allow when dropped (spinous process gaps limiting that)? Then, when the horse rounds up and releases the muscles of the topline, do those relaxed long back muscles "absorb" and conform to the rock that isn't technically ideal for the rounded condition?

As a result, is the rock at the back of the bar mainly designed to keep the skirt of a "western" saddle off the horse's back? (and by extension, would an "english" saddle with bars like a western saddle need any rock at the back end of the bar, given no skirt). Is rock at the front of the bar in excess of what the dropped back requires designed to account for scapula movement?

Lots of questions, sorry, but any help would be appreciated.

Adam

[AdamTill]

Adam,

You sure have done a heap of work on this.

Hi David,

Less then it seems, actually...I did the back tracings for David G when I ordered a couple of saddles from him a couple of years ago.

What CAD program are you using? Personly I use AutoCad but only because when I first went to work as an engineer thats what the company used and I don't have time to learn anything else.

I'm an AutoCAD user myself, for the same reasons (I'm an engineer as well by day...used to do mechanical design, though I'm now in land development). I've had a copy of Rhino3D for about 3 years from when I vowed to get into 3D modelling for some personal CNC milling projects (molded model sailplane wings), but haven't had time to learn how to do much with that.

Just a little something that "jumped out at me". Many years ago, back in the 1980's I went around making plaster casts of horse's backs and from them i made the fibreglass replica of the horses backs. This was to help me understand the true shape of horse's backs and one of the things I noticed which was different to what most people have stuck in their minds about what they think a horse's back is shaped like, is contour of that cyan colored line in this drawing or yours.

Notice where you have the numbers 7, 8, and 9 that the line is convexed almost like the horse has a bump there, It is only slight and I find is further down the side, where the ribs "spring out" than what appeas in your drawing, but that is the nature of 3d stuf. When i first noticed it i thought it was something to do with my casting method. interensting that you have the same thing.

I noticed it myself, and didn't know if it was a true profile or just a legacy of transfering flexible rulers to paper, scanning those, and tracing them in CAD. I tried to be careful and did the tracings twice to verify, but who knows what creeps in. I'd need to go back out and check on Marshall's back to see what the actual case...coud be the spring of the ribs locally, could have been a stance thing...who knows...

I actually used a line of best fit on the other sketch, FYI.

This begs the question, if you are "micro" fitting this horse are you going to make the tree-bar concaved in that area?

Not sure...it would seem to depend on whether that bump is a result of a skeletal/structural shape or a muscle/stance shape.

personaly it did lead me to flattening the bar in that area. But when i say that, i had previously just copied the old factory made trees from the USA, which had a lot of "ball" to them. With a bar that is convexed placed against a convex shaped horse the preasure is increased. (Of course you know that, just adding for benefit of other readers) The benifit of bars with a lot of ball is that while they will not fit any horse extreemely well they not be extreemley "bad" on a greater range of horses. Unlike the flatter bars, which will fit some horses very well, but on a horse that they are not designed for, the edges, which ever edge it is that makes contact, will cause severe problems.

Not sure what "a bar with a lot of ball" is referring to, sorry...new to this area.

On another point - I am curious that you said ".... the seat should ideally be centered in the middle of the span of the bar..." It appears to me that the brown saddle on the horse in that photo has the lowest poiint of the seat way back towards the cantle, the bars appear to be quite short behind the cantle. Thus it appears, in the photo anyway, that your weight would be place a long way to the rear of middle.

I noticed that it seemed oddly rearward, but I think it's just a weird photo angle. That's one of David G's excellent endurance saddles, and he wouldn't design the low point of the seat to be back too far based on what I know of his design philosphy. This is a link to David's website of the same sort of saddle:

http://www.aboutthehorse.com/secure-web/html/ls2d.htm

I don't want to speak for something I didn't design, but it seems to me that the low point of the seat is about in the middle of the section of bar that contacts the horse most often. Happy to stand corrected if I'm misreading that, however.

Your post is very detailed, I'd like to have more time to discuss more with you. looking forward to yuor reply.

dam

These sorts of conversations are why I'm here - happy to participate.

Cheers,

Adam

[AdamTill]

Adam,

I only just noticed that you are new to the board. WELCOME, I'm looking forward to more of your posts.

Forgive me for asking such a dumb question - but what do you mean by "topline is fired" I have not heard the term before.

Acutaly the whole question "Is that designed for the case where the topline is fired, and the back dropped, or a worse case then that?" Lost me, but I am just a dumb saddlemaker

regards

dam

Hi again David,

Thanks much for the welcome - very nice board thus far.

No such thing as dumb questions...probably just a terminology thing. A "fired" muscle in my world is just slang for a contracting muscle. So a fired topline would be when the muscles of the back contact, and the spine drops. So my thinking is asking that was to say that when the back drops, there would be the greatest degree of downward curve to it, and thus the greatest need for rock in the bar.

Cheers,

Adam

[daviD A Morris]

Adam,

Thanks for clearing that up about "fired muscle". Terminology vs slang can be a stumbling block.

Not sure what "a bar with a lot of ball" is referring to, sorry...new to this area.

What I call "ball" is the side to side rock of the bar. I have heard other also use the term. But here is one of the great problems slowing down the advancement of saddle tree design - lack of some consistent terminology. It is making the communication very ineficient. however these forums are going to speed up the evolution of the terminology. The more we talk the quicker it will evolve.

To see a bar that has a lot of "ball" to it look at some of the older western saddle trees from back 1960 and earlier.

bye for now

dam

[David Genadek]

Adam,

I was trying to stay with in your bowl analogy when I said two hinges. You are correct to think in terms of many hinges as in each vertibrea being a hinge. There for the whole spine can be altered depending apon how it is acted apon. In this lies the rub. Does a saddle maker fit the horse as he is or should he fit tha actual back type the horse has. There is no right answer to this, it is a bussiness decision. If you make the choice to fit the actual back type you then have to have a team of people that can help the rider understand how they are effecting the conformation of thier horse. If you are more interested in the leather art portion of the saddlery world and you don't want all the hassle then you fit the horse as he is.

In your first post you prefaced your question from the Jineta perspective. From this perspective the rock will be closer to the base of the whither. In the Brida pholosphy the rock will be closer to the T14 postion as all these makers are talking about. The thing to understand is that if that portion of the back is the lowest point in the horses back It is highly likely that the rider is not getting engagement of the hind quarter or some other thing is causing the horse to operate his body upside down. Here is a link to Mustangs in the Pryor Mountains Here you can see a baseline for a given rib cage shape. Personally when I design a bar I design the rock for the baseline. At this point this is still largely a guess as no large amount of data has been collected and presented in a way that could be analized. Most of my business comes from people who are working with a skilled horseman who are addressing the horsemanship issues at the same time. We will often hold off on building a saddle until the horse has been taught to move right side up again at which time we can more accurately determine the ribcage and topline shape.

In regard to the Spinous process gaps limiting the downward movement of the back: I recently had a Client refered her from the U of Minnesota because her horse had Kissing spine. I can't remember the exact figure but she said the vet at the U had mentioned that over 70 percent of the horses out thier had some spinous process being fused together because of poor riding or poor care. To understand rock you need to understand collection then you need to get a handle on the ways that riding concepts can be distorted. Then you have to decide if you are in the Jineta or Brida camp. Clearly the popular thinking in the western tree design to day is in the Brida camp. So the age old argument goes on.

As for the rear of the bar I just flair the rear of it up a bit but I don't really consider it rock. I have found a correlation between rib cage shape and topline profile. In the end the twist rock and flair are all the same and they are just conceptual tools we use to understand the rates of change in the angles and thier directions as they pertain to a composite shape of a horse's back in movement.

David Genadek

Hi David,

Okay, that helps, but I guess my next thoughts concern where the flex "points" of those hinges would be.

For example, from Dr. Deb's writings and the dissection course I attended, I don't really recall there being much flexibility to the spine along the ribcage. But that said, "much" is relative. Can the area from around T12 back to the last rib be fitted with a rock that roughly equals what the back would allow when dropped (spinous process gaps limiting that)? Then, when the horse rounds up and releases the muscles of the topline, do those relaxed long back muscles "absorb" and conform to the rock that isn't technically ideal for the rounded condition?

As a result, is the rock at the back of the bar mainly designed to keep the skirt of a "western" saddle off the horse's back? (and by extension, would an "english" saddle with bars like a western saddle need any rock at the back end of the bar, given no skirt). Is rock at the front of the bar in excess of what the dropped back requires designed to account for scapula movement?

Lots of questions, sorry, but any help would be appreciated.

Adam

[AdamTill]

Does a saddle maker fit the horse as he is or should he fit tha actual back type the horse has. There is no right answer to this, it is a bussiness decision. If you make the choice to fit the actual back type you then have to have a team of people that can help the rider understand how they are effecting the conformation of thier horse. If you are more interested in the leather art portion of the saddlery world and you don't want all the hassle then you fit the horse as he is.

Well, that bit of the decision making process is easy - I make a decent enough living at the moment otherwise, and have no interest in the horse world from a business perspective. I worked in the hoofcare side of things part time for two years, and got a real eye opening lesson in how a lot of horse owners see their critters. The only thing that would prevent me from providing the best care for my horse that I can is the need to keep food on my own table and a roof over my head, but a lot of other horse owners seem to try to find the absolute cheapest way to do things (even while driving BMWs). I respect those willing to try to make a living from horsepeople, but have no interest in joining them So anything I make would be for my own use.

My first project will hopefully be an english-styled saddle with "western" style bars and seat like the one you made for the endurance saddle...possibly with the pommel, cantle, seat and bars molded from carbon fibre as a single unit. I'd like to learn what would be involved in making the flaps and seat using leather, but my first concern is shaping the underside of the bars.

I've been working with Alexandra Kurland (who studied with Bettina Drummond, Mr Oliviera's student) for a few years, and have also started clinicing with Josh Nichol on Dr. Deb's recommendation, so I'm happy that my horsemanship instructors are leading me in the right direction.

I'm also hoping that Dr. Deb's schedule allows for a skeleton assembly class up here this year, since the dissection class was so good last year. I've done a bunch of anatomy study via Equinology's courses (and am taking Dr. Ridgeway's saddle fit course this year), but being able to actually see and feel a psoas muscle vs learning "function, form and innervation" from a textbook, for example, was very helpful.

So, net result, I know enough anatomy to know how much anatomy I don't know. I'm just pretty new to thinking of it terms of saddle fit.

In your first post you prefaced your question from the Jineta perspective. From this perspective the rock will be closer to the base of the whither.

That would be because of a desire to get the rider's "center of motion" (or the average thereof) as close as possible to the horse's center of motion, correct? (and thus the sadde sits further forward)

In the Brida pholosphy the rock will be closer to the T14 postion as all these makers are talking about. The thing to understand is that if that portion of the back is the lowest point in the horses back It is highly likely that the rider is not getting engagement of the hind quarter or some other thing is causing the horse to operate his body upside down.

I didn't really read the other discussion regarding the low point of the back, but is placing the saddle on the horse's back so that the entire tree sits behind the scapula a brida concept? I had thought that the brida/jineta line was more to do with how the rider sits in the saddle (I have a copy of Conqueror's on order as well...just waiting for it to arrive).

Here is a link to Mustangs in the Pryor Mountains Here you can see a baseline for a given rib cage shape. Personally when I design a bar I design the rock for the baseline. At this point this is still largely a guess as no large amount of data has been collected and presented in a way that could be analized.

Most of my business comes from people who are working with a skilled horseman who are addressing the horsemanship issues at the same time. We will often hold off on building a saddle until the horse has been taught to move right side up again at which time we can more accurately determine the ribcage and topline shape.

I'll have to study those photos carefully...thanks for the link. Could you give a quick summary of a few of the points which you look at in seeing whether a back is healthy enough to accurately determine what it's proper shape might be?

In regard to the Spinous process gaps limiting the downward movement of the back: I recently had a Client refered her from the U of Minnesota because her horse had Kissing spine. I can't remember the exact figure but she said the vet at the U had mentioned that over 70 percent of the horses out thier had some spinous process being fused together because of poor riding or poor care.

I've heard statistics like that before...scary, but not overly surprising considering what's winning medals in just about every discpline (western or english) nowadays.

To understand rock you need to understand collection then you need to get a handle on the ways that riding concepts can be distorted. Then you have to decide if you are in the Jineta or Brida camp. Clearly the popular thinking in the western tree design to day is in the Brida camp. So the age old argument goes on.

I don't know all the differences between the two camps, but as a baseline I'd like to end up with a saddle that sits as close to the horse's "center of motion" as possible with without compromising shoulder movement but maintains sufficient support area under the bars, a rigging system that cradles the saddle evenly, and with a seating/stirrup arrangement that lets me sit in a balanced position (the "won't fall over backwards if the horse disappears" sort of balance).

As for the rear of the bar I just flair the rear of it up a bit but I don't really consider it rock. I have found a correlation between rib cage shape and topline profile. In the end the twist rock and flair are all the same and they are just conceptual tools we use to understand the rates of change in the angles and thier directions as they pertain to a composite shape of a horse's back in movement.

One of biggest concepts I'm struggling with the most is the degree of flexibility in the spin/rib cage that would factor into the bar design (ie the designing for movement part).

I understand the mechanics of collection, but horses don't always operate in a collected fashion if that describes a spinal shape with a "suppporting arch" (ie, highpoint in the middle, rather then lowpoint in the middle for a hollow back). I learned from Dr. Deb, for example, that in a true extended gait extension is actually defined by the spine oscillating between "arched" and "hollow" (to some degree), as opposed to standard gait which oscillates between arched and flat, or a collected gait which largely maintains the arched profile. That would still mean (in my mind) that some allowance has to be made for a "hollow" back...(ie) a bit more rock then a baseline, stationary back might otherwise show a need for. Is that how you think of things?

Thanks much!

Adam

[David Genadek]

Adam,

There are so many things that effect rock perhaps it would be best to begin with what effects it.

First let me say that everything I’m saying here is based on a horse in neutral position on level ground.

Let’s start with the concept of Orientation or how horizontal is the vertebral column. This is a very important concept in regard to saddle fit and it is largely ignored. We tell exactly where the spine is

Without an x-ray machine so what we will do is find easily identifiable points that give us a close idea. Dr Bennett came up with the whole x-ray vision concept a long time ago in regard to training horse judges and it has had a huge impact on the horse industry and can be of extreme value to the saddle maker. In this case we are trying to get a handle on where the actual vertebras are. You find the base of the neck which is pretty easy because it is where the neck gets really wide. Then you find the point of the hip and draw a line between them. This is what I call the line of Orientation (Photo spine 1). This is what tells you how downhill your horse might be, not the whither and croup as that can lie. Now we have a pretty good idea where the spine lies. Clearly this line is not always what we see on the top line however it is where the actual undulations in vertebral column that will be creating the range for the rock that you have been talking about in motion will occur.

In spine 2 I have changed the spines orientation by 5 degrees so you can get a handle on how it can affect the rock. You will also see a line drawing of a back in simplified form so you think about how the orientation will affect gullet width. To the side you will see side views of the simplified back in different orientations with a bar drawn in to show how this orientation line will affect the spread of the bars. If the seat is to be level then on a downhill horse (which most are today) then the saddle should be wider in the rear than the front. This concept will also affect how you view the rock of the saddle.

In spine 3 I have drawing the top line which is created by the lengths and angles of the spinal processes this is what is most often fit with no regard to the other influences. You can also see how the orientation affects this line. If the horse has been properly ridden so that the spine is still along the orientation line then this is not a problem but if you fit a horse whose spine has been pulled off that basic line for a multitude of reason then you will end up with a fit that will run into problem further down the road. I have not come up with an easy way to tell you if the spines basic line has been disrupted. Over the years and looking at thousands of horses you can tell by the muscles. Tightness in the top line and pockets behind the shoulders are good signs that the spines natural alignment has been effected by poor horsemanship. Here is the business decision for the saddle maker do you fit the horse as he is or as he should be?

Here is link to an article that Liz wrote that shows two horse’s with different conformations and how they need to be supported differently to achieve the same result. This is relevant to the topic of rock as it can help you understand how dependant the where and how the rock will be effected is on the overall conformation of the animal. The conformation will change which parts of the back will be affected the most in movement. When she refers to ventroflexed gaits she is talking about those gaits that require a hollowing of the spine as you mentioned from Debs perspecitve.

Here is a site with some good info on range of motion.

David Genadek

[Rod and Denise Nikkel]

On the whole, rock really isn’t that complicated. It is just a term (one of a number that are used) that means “the curve in the bar from the front to the back”. That is not an even curve by any means, but the term itself is a very general one and the concept is very straightforward.

As to the specifics of shape, again I come back to the basic fundamentals in building bars: #1) Don’t dig in anywhere, and #2) Have as much surface area on the horse as possible inside the bounds of #1. So you don’t want the saddle to consistently bridge, because that will cause soreness at the front and over the loin which can have severe ramifications. And you don’t want excess rock where the length of the bar, with the exception of the edges and ends where relief is built it, cannot contact the back. In that case the rider’s weight will only be carried in the center of the bar and over time that central area will get sore because of increased pressure over too small a surface area.

If you have a bare tree, put it on the horse, rig something to strap it down, and walk the horse around. You will find that as the horse moves there are times the tree is bridging slightly on one side as the center of the back falls. There are times of the rear of the tree on one side is lifted off and the front and center of the bar have all the weight. Turn him in a circle and you will see even more exaggeration in what is carrying the weight and what isn’t. Getting the shape to match exactly all the time just is not possible, not just because the bones move (and they do to a certain extent) but because the muscles are contracting and releasing all the time – which is what you want. So the amount of pressure under any particular area of the bar is always changing, which is a good thing. What you don’t want is constant high pressure, nor do you want intermittent very high pressure.

As the horse moves and his muscles contract, they will bulge a bit. This will lift the bar compared to when the muscle isn’t contracted. So you want to make sure that along the top and bottom edge there is enough rounding that the edges won’t dig in when the muscles are not contracted. Yet we want enough surface area to the bar so that when the muscles are contracted there is enough contact area that the PSI in that area isn’t too high.

On our bars, while the whole bar is rounded to varying degrees depending on which section of bar we are looking at, we build in the “relief” along the outside half inch or so of the top and the bottom edges. (Our bars are moderately thick which also increases relief.) We lift the back bar tip, say the last 2 inches, so that it won’t poke the horse in the loin no matter how he moves, though the underside of that area will contact the horse some of the time. We position the bar to start behind the shoulders with enough relief built into the front bar tip (again, the front couple of inches) to allow the back of the shoulder blade to slide under it when it is rotated farthest back. This happens when the leg is extended – which is an unweighted part of the stride – and thus does not cause high pressure. If the leg were weighted with the bar on the shoulder blade, that would be another story. But other than the edges and bar tips, we expect the full bar to be in contact with the horse most of the time as he moves, though the pressure changes from minimal to more under the different parts of the bar with every movement.

Overall, when building trees you are always looking for a balance. But it is not like you are walking a tightrope over Niagara Falls. The analogy is more like you are walking along a 6” wide line painted on the floor. Sometimes in trying to get too specific in one area, you can cause problems in others, so you always need to keep the big picture in mind.

[daviD A Morris]

I agree with Rod and Denise.

I also think that to keep things in perspective - I want to improve the "macro fitting" before I get to the "micro fitting"

From what I have read here over the last 6 months accross a number of topics on these forums - there is a spectrum of aproaches to this "fitting of saddles to horses backs". Starting at one end of the spectrum and working down I have seen:-

1. 
   The "one-size-fits-all" group who say " get a good saddle and it'll fit all good shaped horses. all you people that are into "fitting saddles" are just worrying yourselves for no good reason, are you goin to make a saddle specific for every single horse - where will it all end?"
   

1. 
   The 3 or 4 sizes fits all group - "full QH, semi QH, TB, Arab" thats all you need to know, nothing more nothing less.
   

1. 
   MACRO FITTING - This group is where I put myself - I just thought up this group now
   

1. 
   The "Micro fitting" group - who came up with this term? first I ever heard of micro fitting was on this forum. - I think their approach is to fit a tree specifically to a particular horse - and personaly I can't see why these trees won't fit other horses of similar shape. So whats wrong with that. Unless, that particular horse is very unusual.
   

1. 
   The "I'm so concerned about causing my horse the least discomfort that I realy should never even get on its back" group.
   

Tell me if you think I'm wrong

[jonwatsabaugh]

Rod, Denise, daviD A Morris,

Of all I've ever read or discussed on this subject, these last two posts are undoubtedly the most eloquent, and the most common sense approach to the philosophy of saddle trees I've ever heard! daviD, I love your analogies. Your subtle humor always makes me chuckle!

Jon

[ClayB]

I have to agree with Jon here. I try to read all the posts here on saddles and trees, and a lot of times I feel like I am just getting more confused. But, this last post by Rod and Denise explained "rock" in a way that makes sense to me. Thanks for keeping it going until even the slowest of us "get it".

Clay

[AdamTill]

Adam,

There are so many things that effect rock perhaps it would be best to begin with what effects it.

First let me say that everything I'm saying here is based on a horse in neutral position on level ground.

Let's start with the concept of Orientation or how horizontal is the vertebral column. This is a very important concept in regard to saddle fit and it is largely ignored. We tell exactly where the spine is

Without an x-ray machine so what we will do is find easily identifiable points that give us a close idea. Dr Bennett came up with the whole x-ray vision concept a long time ago in regard to training horse judges and it has had a huge impact on the horse industry and can be of extreme value to the saddle maker. In this case we are trying to get a handle on where the actual vertebras are. You find the base of the neck which is pretty easy because it is where the neck gets really wide. Then you find the point of the hip and draw a line between them. This is what I call the line of Orientation (Photo spine 1). This is what tells you how downhill your horse might be, not the whither and croup as that can lie. Now we have a pretty good idea where the spine lies. Clearly this line is not always what we see on the top line however it is where the actual undulations in vertebral column that will be creating the range for the rock that you have been talking about in motion will occur.

Okay, gotcha on the above. I did a few tracings a couple of years back as I was working through some conformation excercizes, and I'll add one to this post for the horse above. The dots in the cervical region were indicating joint spaces, and you seem to be going from the middle of C6, so I'll guesstimate that position. Then, ignoring all but the pink lines, I think this particular horse is built relatively level.

In spine 2 I have changed the spines orientation by 5 degrees so you can get a handle on how it can affect the rock. You will also see a line drawing of a back in simplified form so you think about how the orientation will affect gullet width. To the side you will see side views of the simplified back in different orientations with a bar drawn in to show how this orientation line will affect the spread of the bars. If the seat is to be level then on a downhill horse (which most are today) then the saddle should be wider in the rear than the front. This concept will also affect how you view the rock of the saddle.

Makes sense.

In spine 3 I have drawing the top line which is created by the lengths and angles of the spinal processes this is what is most often fit with no regard to the other influences. You can also see how the orientation affects this line. If the horse has been properly ridden so that the spine is still along the orientation line then this is not a problem but if you fit a horse whose spine has been pulled off that basic line for a multitude of reason then you will end up with a fit that will run into problem further down the road. I have not come up with an easy way to tell you if the spines basic line has been disrupted. Over the years and looking at thousands of horses you can tell by the muscles. Tightness in the top line and pockets behind the shoulders are good signs that the spines natural alignment has been effected by poor horsemanship. Here is the business decision for the saddle maker do you fit the horse as he is or as he should be?

Well, before I bought him this particular horse was used hard and unappologetically as a lesson horse even after foundering, so he has his fair share of issues (which we're working on). Taking your example and translating it onto the topline, it's interesting to see that the topline and "balance lines" are offset and showing those "issues". I guess in essence this is a continuous state of ventroflexion, for all intents and purposes. Very interesting - thanks for this.

Here is link to an article that Liz wrote that shows two horse's with different conformations and how they need to be supported differently to achieve the same result. This is relevant to the topic of rock as it can help you understand how dependant the where and how the rock will be effected is on the overall conformation of the animal. The conformation will change which parts of the back will be affected the most in movement. When she refers to ventroflexed gaits she is talking about those gaits that require a hollowing of the spine as you mentioned from Debs perspecitve.

Thanks for the article...I'll study that one to see what you mean.

Here is a site with some good info on range of motion.

Wow, that's exactly what I needed to get started...thanks tons. I'll play around with that ROM data and see if I can't come up with something interesting.

Cheers, and thanks again.

Adam

[Blake]

Rod, Denise, daviD A Morris,

Of all I've ever read or discussed on this subject, these last two posts are undoubtedly the most eloquent, and the most common sense approach to the philosophy of saddle trees I've ever heard! daviD, I love your analogies. Your subtle humor always makes me chuckle!

Jon

"Common Sense" being the Key phrase here.

I agree with Jon. Good Job Denise.

Blake