CANT , and it's effect ?

[lbc_PSI]

@Cornpone
There is a reason the KISS principle is not the KIS principle. "Duh" right back at ya.

Uh - interj. - Used to express hesitation or uncertainty.
Duh - interj. - Used to express disdain for something deemed stupid or obvious, especially a self-evident remark.

I believe if you re-read my previous post, you'll find I used the former, not the later.

Uh huh, the drawings you are posting are Copyright "Pinwheel Software". So I guess the first question is do you own them? They aren't very good, are they? Can you link the document you are pulling them from because a visit to the site simply shows me they do software for archery "ballistics". I'd like to see what other misinformation the company is putting out.

As for the documents, yes, they're mine. My opinion. Created for this discussion. Yes, I own Pinwheel Software..wrote the software, made the website, one-person shop. It's been a going concern for 21 years. Just to be clear, that was "years", not "ears". ;-) That said, I probably don't know enough about ballistics, drag, wind drift, calculating proper arrow spine, making sight tapes from drop tables to match a shooter's "clickable" target sight..but I am still learning..sigh.

It seems to me the surest way to simplify this problem is to introduce another two or three optical systems before we start to simply DO THE MATH? Because there is NOTHING like half a dozen extraneous variables to simplify the problem, right?

Before the math can or needs to be resolved, we need to start with "why". There's really more than one..but they're connected. Why do scope height and LOB matter?. The picture I think you're referring to is actually one image at different perspectives. The top one represents LOB and two LOS at different heights as viewed from the side..as if there is 0 cant. The bottom two pictures show the original image normalized around each LOS..Scope1 LOS and Scope2 LOS..so laying flat viewed from above..as if canted 90 degrees. The dotted red lines of different lengths are to show that when canted 90 degrees, LOB will not be pointing in the same direction. I could have shown the same thing knowing the angles created from scope1&2 heights and LOB. The inference is..and this answers the "why"..when canting occurs, LOB will not point in the same direction as when no cant exists. The greater the angle between scope and LOB, the more divergence there is. The logical conclusion would be, both degree of cant and scope height effect shot outcome.

As for how good the drawings are? IDK. I think they disprove the main premise of the Szottesfold paper..so I suppose they're good enough. No math required. ;-)



@everyone-else

Does it matter for FT events? IDK. Probably not. FT seems very specialized to me. Shoot the fastest pellet allowed by the event energy constraints..minimizing hold-over, cant, and distance estimation errors. FT limits the shot distances from 9M to 50M. FT increases target size with distance shot. So as cant error increases with distance, target size increases and masks the issue..for FT. Having never shot FT, I'll guess average shot distance is in the 30 to 40 range. If all FT targets were the same small size..say 1/2"..then cant error would be more of a concern. But they aren't..so it isn't.

Shooting live targets makes cant more important. Squirrel brains don't grow in size as their distance from you increases. Misses on live targets have consequences.

 

[Scotchmo]

Cornpone,

In your spreadsheet, the thing that I corrected was the Drop values. The only major formula error I saw was in cell G9, and you did not use it anyway. The G9 formula was not usable as-is

=TAN(G8*(3.1415926/180))

it should have said:

=SIN(G7*3.1415926/180)

But remember from my earlier post about your spreadsheet:

I said - "You used tan instead of sin, and that is fine, as in this case they are almost the same, but only for relatively small gun cant angles like 5 degrees."

The cell G8 formula that you called instead, gave values that were close enough (tan vs sin). So all the vert and horiz values as well as the two graphs are good. If you plan on testing greater cant angles, you will need to correct cell G9 and column H so as to use the preferred sin function.

"...ccw as the direction of positive rotation..."

Direction does not matter when calculating just the magnitude of a gun cant error. Positive for ccw is the direction I would use when it matters, though a layman might think the opposite. If you want to combine scope cant with gun cant, then direction will matter.

A good check of the final spreadsheet will be to plot the horiz vs vertical shifts for a full range of cant angles. It will form a perfect circle if you are looking at just the gun can angle or just the scope cant angle.

 

[Scotchmo]

...
As for how good the drawings are? IDK. I think they disprove the main premise of the Szottesfold paper..so I suppose they're good enough. No math required. ;-)



@everyone-else

Does it matter for FT events? IDK. Probably not. FT seems very specialized to me. Shoot the fastest pellet allowed by the event energy constraints..minimizing hold-over, cant, and distance estimation errors. FT limits the shot distances from 9M to 50M. FT increases target size with distance shot. So as cant error increases with distance, target size increases and masks the issue..for FT. Having never shot FT, I'll guess average shot distance is in the 30 to 40 range. If all FT targets were the same small size..say 1/2"..then cant error would be more of a concern. But they aren't..so it isn't.

Shooting live targets makes cant more important. Squirrel brains don't grow in size as their distance from you increases. Misses on live targets have consequences.

'... I think they disprove the main premise of the Szottesfold paper...."

Everything I've read here proves Szottesfold. For every scenario that "disproved" it, they started with a POA vs POI error and then induced gun cant. Instead, start out with a coincident POA and POI.

Different scenarios:

"...If all FT targets were the same small size..say 1/2"..then cant error would be more of a concern. But they aren't..so it isn't...."

You might want to rethink that. Even with an otherwise perfect shot, a 5 degree gun cant will put you completely outside the killzone of a 50+ yard target (40mm or 1.5" diameter).

 

[Guest]

Uh huh, the drawings you are posting are Copyright "Pinwheel Software". So I guess the first question is do you own them? They aren't very good, are they? Can you link the document you are pulling them from because a visit to the site simply shows me they do software for archery "ballistics". I'd like to see what other misinformation the company is putting out.

As for the documents, yes, they're mine. My opinion. Created for this discussion. Yes, I own Pinwheel Software..wrote the software, made the website, one-person shop. It's been a going concern for 21 years. Just to be clear, that was "years", not "ears". ;-) That said, I probably don't know enough about ballistics, drag, wind drift, calculating proper arrow spine, making sight tapes from drop tables to match a shooter's "clickable" target sight..but I am still learning..sigh.

I feel your pain. The first ballistics software I wrote was in 1992 when I was trying to calculate the BC of various pellets. I had just bought my D48 and wanted to discover the flattest shooting pellet on the market because the Jack Rabbits in El Paso weren't letting me get very close to them. I also wanted to compute the trajectory for that pellet in my Diana. It turned out the Crossman Premiers in the brown box were the flattest shooting pellet I could obtain at the time. I used the data in the back of a Speer handloading manual as the basis for the software I wrote at that time. I think I uploaded it to a couple of BBS systems (nobody other than academia and the government were doing much with teh Interwebz).

From there I went to the Naval Surface Warfare Center in Dahlgren, VA and wrote R&D software for the Automated Ship Self-Defense System. It was an expert system which automated the combat functions normally performed on a ship which was under attack. The reason for the project was a shoot down of an Iranian passenger jet by a US Destroyer LINK We wanted to see if we could prevent that sort of "error" in the future. I was writing system libraries that did things like fuse multiple sensor tracking data into what we called "ground truth". The math was kinda hard and I occasionally had to go for "tutorials" from the PhDs who were doing the hard math... I could write the code because that's what Computer Scientists do. They could do the math because that was physicists do. Teamwork, wins every time.

Still learning how to be humble here ...

As of right this moment, I am going to put my trust in the architect over the IT guy who does not feel a need to explain his math...

 

[Guest]

Sure, but the DROP does not change. This is drop from LINE OF DEPARTURE. Line of Bore is the same thing. The projectile NEVER rises above LOB, not ever. At T=0, when the projectile exits the bore it instantly drops below LOB and that drop is a simple Newtonian equation.

I did not say the trajectory rises above LOB.  Duh! Watch the video link and try to understand what the guy is saying.

So yeah ...

Like I said, I am not competent to argue with you two and didn't want to in the first place. I got Scotchmo to talk to me and to explain his thinking with the math. Couldn't get you to do that. Time for me to bow out and leave the arena before one of the elephants stomps on me. I'll just scurry back to my corner and figure this out, then I'll get back to you. Meanwhile I am finding ZERO errors in Szottesfolds work. But then he is an architect ... they tend to do a TON of trig in their work ... you know load bearing surfaces, high tension cables, trivial problems like wind drag and parasitic harmonics on suspension bridges ...

 

[Guest]

Cornpone,

In your spreadsheet, the thing that I corrected was the Drop values. The only major formula error I saw was in cell G9, and you did not use it anyway. The G9 formula was not usable as-is

=TAN(G8*(3.1415926/180))

it should have said:

=SIN(G7*3.1415926/180)

But remember from my earlier post about your spreadsheet:

I said - "You used tan instead of sin, and that is fine, as in this case they are almost the same, but only for relatively small gun cant angles like 5 degrees."

The cell G8 formula that you called instead, gave values that were close enough (tan vs sin). So all the vert and horiz values as well as the two graphs are good. If you plan on testing greater cant angles, you will need to correct cell G9 and column H so as to use the preferred sin function.

"...ccw as the direction of positive rotation..."

Direction does not matter when calculating just the magnitude of a gun cant error. Positive for ccw is the direction I would use when it matters, though a layman might think the opposite. If you want to combine scope cant with gun cant, then direction will matter.

A good check of the final spreadsheet will be to plot the horiz vs vertical shifts for a full range of cant angles. It will form a perfect circle if you are looking at just the gun can angle or just the scope cant angle.

Thanks you, sir. Copy all and rgr on that formula in G9, caught it yesterday evening. Agree on the preferred use of sin and cos for solving the triangle you are solving and in particular for large cant angles. Playing with them is what threw me off the whole spread sheet and put me back into research mode. I am reading the Szottesfold documents right now, so far, so good. After I have that down, maybe I'll write a little code.

 

[lbc_PSI]

Sure, but the DROP does not change. This is drop from LINE OF DEPARTURE. Line of Bore is the same thing. The projectile NEVER rises above LOB, not ever. At T=0, when the projectile exits the bore it instantly drops below LOB and that drop is a simple Newtonian equation.

I did not say the trajectory rises above LOB.  Duh! Watch the video link and try to understand what the guy is saying.

So yeah ...

Like I said, I am not competent to argue with you two and didn't want to in the first place. I got Scotchmo to talk to me and to explain his thinking with the math. Couldn't get you to do that. Time for me to bow out and leave the arena before one of the elephants stomps on me. I'll just scurry back to my corner and figure this out, then I'll get back to you. Meanwhile I am finding ZERO errors in Szottesfolds work. But then he is an architect ... they tend to do a TON of trig in their work ... you know load bearing surfaces, high tension cables, trivial problems like wind drag and parasitic harmonics on suspension bridges ...

I really hate trying to communicate on the internet. When you read #6 you probably assumed I was referring to #4 when I was actually referring to #2. What I meant when I used "Duh!" in #4 was that "it goes without saying that "when the projectile exits the bore it instantly drops below LOB"". "Duh" was intended to mean "obviously", not "stupid".

So I apologize if what I said was unclear. No disrespect was meant.

Oh, and just for the record, being called an "IT guy" was probably the worst thing you could call a programmer or software engineer. Just sayin'. ;-)


1 - Cornpone said
If it does not depend upon drop then feel free to SHOW YOUR MATH. If I don't understand it, I am sure you will explain it to me like Scotchmo has. If you have another way to calculate it then show me the calculation. Once you have done that you can explain to me what you call the situation shown below.. Surely it is some form of "cant".
<image of scope cant..not system cant>

2 - lbc_PSI said
Uh…someone that doesn't know how to set up their shooting system.

3 - Cornpone said
Sure, but the DROP does not change. This is drop from LINE OF DEPARTURE. Line of Bore is the same thing. The projectile NEVER rises above LOB, not ever. At T=0, when the projectile exits the bore it instantly drops below LOB and that drop is a simple Newtonian equation.

4 - lbc_PSI said
I did not say the trajectory rises above LOB. Duh! Watch the video link and try to understand what the guy is saying.

5 - Cornpone said
Uh huh, the drawings you are posting are Copyright "Pinwheel Software". So I guess the first question is do you own them? They aren't very good, are they? Can you link the document you are pulling them from because a visit to the site simply shows me they do software for archery "ballistics". I'd like to see what other misinformation the company is putting out.

It seems to me the surest way to simplify this problem is to introduce another two or three optical systems before we start to simply DO THE MATH? Because there is NOTHING like half a dozen extraneous variables to simplify the problem, right?
There is a reason the KISS principle is not the KIS principle. "Duh" right back at ya.

6 - lbc_PSI said
Uh – interj. – Used to express hesitation or uncertainty.
Duh – interj. – Used to express disdain for something deemed stupid or obvious, especially a self-evident remark.

I believe if you re-read my previous post, you'll find I used the former, not the later.

 

[Airgun-hobbyist]

Uh huh, the drawings you are posting are Copyright "Pinwheel Software". So I guess the first question is do you own them? They aren't very good, are they? Can you link the document you are pulling them from because a visit to the site simply shows me they do software for archery "ballistics". I'd like to see what other misinformation the company is putting out.

As for the documents, yes, they're mine. My opinion. Created for this discussion. Yes, I own Pinwheel Software..wrote the software, made the website, one-person shop. It's been a going concern for 21 years. Just to be clear, that was "years", not "ears". ;-) That said, I probably don't know enough about ballistics, drag, wind drift, calculating proper arrow spine, making sight tapes from drop tables to match a shooter's "clickable" target sight..but I am still learning..sigh.

It is nice to see that Pinwheel Software is here and writing a ballistics program for us airgunners. I have used the Pinwheel Software archery spine calculation program for years to build my custom arrows and it is very easy and accurate to use. Thank you for your contributions to both sports Ibc_PSI.