Re-aligning ILF limbs

Gee Emm Bee

New member
Have never touched the alignment screws on my ILF riser -- have only ever adjusted the tiller and draw weight using the limb bolts.
But last night the bow looked like this -


It may not be very obvious from that pic above so the 2 following pics are 'zoomed-in' shots of the bottom and top of the riser taken from the same photo -


and the upper part -


When the string is aligned over the middle of the rear of the lower limb bolt it is visibly off to the right of the top limb bolt.
This tells me that at least one of the limbs is out of alignment -- if the string is aligned over the middle of the upper limb bolt then it would be out in relation to the lower bolt, so how do I determine which limb is out, or indeed how do I determine if both are out of alignment?
From that photo, assuming that the lower limb is OK I would imagine that the top limb would have to be moved to the left as viewed from the 'string side' of the bow in order to align the string with the upper limb bolt?
 

geoffretired

Supporter
Supporter
There is a very good sticky in the Methodology Tuning ,Coaching section that goes through the whole process of getting the bow aligned.
Your idea about moving top limb to the left, should make things better, but remember that as you do that the string will be moving left by a smaller amount at the bottom limb bolt, so it will move very slightly left of centre.
When you read the sticky you will find that other things can play a part, such as the limbs being twisted so they aren't pointing straight ahead at the recurve section. Any twist there will push the string groove off centre, even if the limb is, otherwise, perfectly in line.
Read the sticky and get the bow set up in the most efficient order, otherwise you could end up going round the whole cycle time and time again.
 

Rik

Supporter
Supporter
I agree with Geoff... All you can tell from an image like that is "something is slightly out". Tracking down the cause is a little more complex.
That said; it is only very slightly out and it may not be worth spending a lot of time on it...
 

Timid Toad

Moderator
Staff member
Supporter
Fonz Awardee
Ironman
That said, it's a very good learning process and you'll have a much better understanding of how your bow works at the end of it.
 

Gee Emm Bee

New member
Thanks for your comments.

I tried tweaking the adjustment screws a little and the improvement was minimal.
After having a look at the sticky thread suggested by Geoff, the kitchen table came into use -


Here's the view I saw down at arrow level -


From that view I have to guess that my riser has a twist. Never having dealt with that problem before, apart from buying a new riser, what's my best course of action - try shimming one side of one of the limb pockets?
 

Timid Toad

Moderator
Staff member
Supporter
Fonz Awardee
Ironman
Or perhaps leave it alone. I've seen a lot worse on very expensive risers, and it shoots just nicely. It just makes it a bit trickier to tune, that's all.
 

geoffretired

Supporter
Supporter
Shimming one side of one pocket is not that difficult. If it gives you the peace of mind that you want, go for it.
If you are going to try that, it would probably be a good idea, to first check the notches for the string loops on both limb tips.
Some folks on here have found( not with any particular brand) that they have had notches that were not symmetrical, which caused the string to be off centre at the loop ends and therefore not sitting centrally in the groove down the limb at the recurve.
They should be level with one another and equally deep,.. or equally spaced from the limb centre line.
 

ben tarrow

Well-known member
Is this something that has "just" happened or is this the first time you've ever checked it?

After all, inaccuracies in riser machining was why ILF and the dovetails and limb adjustments were invented in the first place.
 

Gee Emm Bee

New member
Is this something that has "just" happened or is this the first time you've ever checked it?
The string alignment has been checked a couple of times since I got the bow and then just got on with the shooting. Last week I felt I had to re-adjust the pressure button and it was when I had an arrow on the string and sighting it across the rest that I noticed the two limbs bolts were arguing over which one would claim the string over its centre.
 

geoffretired

Supporter
Supporter
When you are shooting, the eye will focus on the target and you will see a string blur. It would be distracting to look up at the top bolt or down to the bottom one. Better to see how that blur lines up with the sight aperture, if you use a sight.
Having said that, some people, me included, would feel better( not shoot better) if things were as they " should be".
If the bow was looking out of line in a different way each time you strung it, that would be a greater cause for concern.
 

f_thomas

New member
I would recommend getting a couple of sets of Beiter Limb Line Gauges. It would seem really difficult to determine if the riser is twisted vs. the limbs. Using the Beiter Limb Line Gauges makes the task so much easier. I have also placed 1 inch wide masking tape across the limbs and measured at the top and bottom with a caliper then mark the center and connect the marks for a center line. Use something wide enough to mark it so it is not visible below the string. Kind of a DIY limb gauge. Follow the riser manufacturer instructions for their alignment system. Jake Kaminski has a lengthy video on YouTube setting up his new Win&Win TFT riser, which also provides a means to shim a slightly twisted limb in addition to moving the tip left or right and also moving the whole limb to align top and bottom limbs. I read somewhere that you can use feeler gauges cut and glued under the limb bolt to correct a slightly twisted limb.
 

turtle

Member
Some very, very strange things happen with bows. I have a (wooden ILF) riser that I know is straight (that shows dead straight with two of my sets of limbs) and a set of Hoyt Satori Traditional limbs that are straight on two of three risers, however, put the Hoyt Trad limbs on the wooden riser and they're a mile out. So much so that they cannot be brought straight. I have not yet figured out what is happening - there is no sense to it.... but there must be a reason why the two aren't jiving.

In your case, could you let us know what kind of riser it is and what draw weight you have on the fingers. If it is a cheap case riser and you are drawing a lot of weight, that may be a factor.
 
Top