jemrami9

Greetings. I just installed a new Viper Predator Pro MT sight on my bow. I looked through a bunch of information and read the forums to get an idea on whats out there. Rob gave this sight a stellar endorsement and I talked with him and decided to take the plunge. I am totally happy with this purchase. I will post a photo of how well I shot with it first time out. My question is what is the significance of the 3rd axis in regards to a bowsight. Obviously everyone is familiar with the standard 2 axis set-up with elevation and windage but what role does the forward/aft axis of the whole sight window play? I know that is something competitive shooters are very familiar with and I was just curious to know what advantages/disadvantages there are when it comes to hunting. If anyone cares to try to explain this in more detail, it would be greatly appreciated as always. Thanks!

Here is some visual proof of how well I can shoot using this sight, this happened on my 3rd group at 20 yds. I have never done this before so obviously it must be the sight right?? The funny thing is I was using some Easton Axis 400 arrows, I would have never thought you could robin hood those skinny things.

Greg / MO

Here's an explanation I've got saved in one of my "tuning" folders...

2ND AXIS

2nd axis on your sight is basically making sure the bubble level
on your sight reads level when the bow is vertical.

This presumes that your string is vertical when the bow is also vertical.
You essentially figure a way to hold your bow vertical (use a bow vise),
and then check to see that your bubble level in the sight is also reading vertical.

If not, then adjust the bubble level with the 2nd axis adjustment,
to make the bubble level on your sight read level, when the bow and bowstring are vertical.

3RD AXIS

Ok, so now we understand what 2nd axis is on your sight.

So, what is 3rd axis?

Remember your sight ring is on a threaded rod?

Well, what if the entire sight ring was mounted on a door hinge?

Yup. What if the entire sight ring could swing like a door?
You could swing the door towards you or away from you.

Well, let's say we swing the door towards you 45 degrees.
The bubble level still reads level, i.e., the threaded rod is still horizontal.

You know what will happen on a steep uphill shot?
Even if you aim uphill, and your bow is not tilted left or right,
the bubble level will lie to you and force you to tilt your bow.

Try this with a 24-inch level. Hold the level in your hand so that it is still horizontal, but the angle between the level and your arm is 45 degrees, as if you swung a door towards you. Raise your arm towards the ceiling.
The bubble level will not stay in the middle.

Adjust the third axis on your sight is the same as adjust the door swing so that it is 90 degrees.

HOW TO ADJUST 3RD AXIS



3rd axis will affect uphill shots (NFAA field rounds) or downhill shots (from a treestand).

Imagine that your sight ring is a door. If you bump your sight ring into a tree, the sight ring may bend towards you like swinging a door closer to your face. Let's say the sight ring "door" opened towards you 45-degrees. The bubble still reads level when you hold the riser straight up and down.

Now, hang a weighted string from the ceiling.
Kneel down on your knees, load an arrow in a safe spot, come to full draw and anchor.
Line up the weighted string with the left edge of the riser and your limbs.

Take a look at the bubble.
The riser and limbs are vertical because you are lined up with the weighted string.
If the sight ring threaded rod is bent towards you or away from you,
the bubble will not read level even though you are not canting the bow.

Adjusting the 3rd axis of a bow restores the sight ring door swing
back to 90 degrees, perpendicular to the sight frame.
The best way to check is kneeling down on your knees,
aiming up at a weighted string hanging from the ceiling.

If your sight has 3rd axis adjustment, then adjust away.

If you sight does not have 3rd axis adjustment,
you will need to use shims to adjust the entire sight or just the sight ring.

Cougar Mag

What Greg said. Following is an illustration.

gibblet

i don't put the sight on my bow when i make the 2nd and 3rd axis adjustments to it. it's easier for me to do it with it off the bow. not sure where having it on the bow would help.

Kanga

What do you know about these things now get back in your corner and make me my bloody stringand floating yoke cable

Actually I have a tool that allows me to set the 2nd and 3rd axis while the sight is off the bow and like gibby said it is a lot easier

Greg / MO

Here's another explanation that I found easier to understand from a VERY well-respected technician...


3rd axis adjustability on a sight,
just means that the scope housing has a door hinge on it.

It allows you to swing the door away from you,
or it allows you to swing the door towards you.

Here is an experiment.

Grab a 24-inch carpenter's level in your right hand.
Hold you right arm level (parallel to the floor).

Now, pretend the carpenter's level is like a door,
and while keeping the bubble level parallel to the floor,
swing the left end of the bubble level towards you
so the bubble level makes a 45 degree angle with your arm.

If you look at the bubble on the level, the bubble is still in the middle.
The bubble level frame is at 45 degrees to your arm, not even close to being 90 degrees.

Now, raise your right arm.

Look at the bubble.

The bubble is now all the way to one side.
If you tilt the bubble level,
and make one end of the frame lower, much much lower,
then you can make the bubble appear in the middle.


That's why, if you happen to BUMP your pin guard,
or your scope housing,
and you change the DOOR SWING ANGLE
to something more or less than 90 DEGREES,

then on a long range shot (80 yard field shot),
or a uphill shot (say a 3D target)
or a downhill shot (say a treestand),

the bubble will lie to you,
and force you to tilt your bow to one side,
to force the bubble into the middle

and you are going to miss a little to the left or a little to the right.

mobow

LOL....Greg, I've read both of those posts a couple of times, and I must say.......I have NO idea what you're talking about......I understand the concept of the "hinge" swinging to you or away from you, but I still fail to understand how it affects anything......

Man, I need a physics degree I think.....[&:]

gibblet

if your 3rd axis is off - as you point your bow downward - your level will lie to you - in a big way. if you can imagine that your level - instead of pointing at you like when you shoot - is pointing away from you (w/ you looking atit like the top of a pop can)- as you point the bow down the bubble will go up. so, if your level isn't facing you exactly - when you point your bow down or up - one end of the level will be closer to you than the other - and the bubble will move as you point the bow up or down due to the fact thatthe face of your level wasn't pointing squarely at you.

obviously your level could be arranged in a million ways in the horizontal plane and give you a good read, but there is only 1 way it can be arranged in that plane - and have your bow tilt - andit still give you a good read.

TFOX

If you adjust 3rd axis off the bow or adjust it to your sight bar.You will need to check the 4rth axis.This basiaclly is checking to see if your sight bar runs parralel with the arrow.If it doesn't,the bubble will still lie to youa little.


The sight should beperfectly perpendicular to the arrow,this iswhat we are trying to achieve.If you set the 3rd off the bow,this is impossible to do.In this case,go out and slide the bar forward all the way.Shoot a group into thetarget.Then move the sight bar out all the way and shoot another group.If thegroup is in the same relation left and right,you are fine but if they are not,you will need to shim the sight bar to where both groups hit the same.(This is where you may find that some risers are not square to centershot)Then it doesn't matter whereor how you set the 3rd axis.


This is splitting hairs when talking about a hunting bow that has an average shot of 17 yards.When you are talking about a target bow and want to hit a 1" dot at 40 yards and shooting at a 30 deg downhill angle,it will affect impact point.

Kanga

Here is a web site where you can get the tool I have plus a 4th axis that goes on the bow.

It also goes into get explaination of how the 3rd and 4th axis work.

http://www.archerytech.com/