Moultrie Products
Center Shot, Center of Limbs ?
Equipment
Contributors to this thread:
Ambush 25-Mar-20
Ambush 25-Mar-20
CurveBow 25-Mar-20
x-man 25-Mar-20
GLP 25-Mar-20
Ambush 25-Mar-20
Buck Watcher 25-Mar-20
Ambush 25-Mar-20
x-man 25-Mar-20
WapitiBob 25-Mar-20
x-man 25-Mar-20
x-man 25-Mar-20
Ambush 25-Mar-20
x-man 25-Mar-20
Grey Ghost 25-Mar-20
Ambush 25-Mar-20
Grey Ghost 25-Mar-20
Ambush 25-Mar-20
Buck Watcher 26-Mar-20
x-man 26-Mar-20
Ambush 26-Mar-20
x-man 26-Mar-20
Ambush 26-Mar-20
x-man 27-Mar-20
x-man 27-Mar-20
Ambush 27-Mar-20
x-man 28-Mar-20
Grey Ghost 28-Mar-20
Rock 28-Mar-20
Ambush 28-Mar-20
Ambush 28-Mar-20
Ambush 28-Mar-20
x-man 28-Mar-20
GLP 28-Mar-20
Cornpone 29-Mar-20
Timex 29-Mar-20
Ambush 29-Mar-20
Ambush 29-Mar-20
x-man 30-Mar-20
Ambush 30-Mar-20
Ambush 30-Mar-20
From: Ambush
25-Mar-20

Ambush's embedded Photo
Ambush's embedded Photo
So last fall I put new limbs, strings and cables on my solo cam, tuned it up and used it. But I was not quite happy with the tune with large fixed broad heads.

I was putting a couple twists into the new string to bring everything back into spec, now that they have plenty of shots through them and doing a bit a yoke tuning. I had shifted my rest a bit to bring the broadheads closer to field points at thirty yards. I didn’t really like that as I’m pretty careful about keeping my rest “centered”, so I thought I’d verify that in as many ways as possible.

First was to eyeball the string, limb center and arrow from behind.

Then arrow shaft alignment with rod screwed into stab bushing.

I measured the distance between the shaft and riser, front and back.

Then something I’ve not done before. I ran a string around both limbs so I could center the shaft between the two limbs.

I did all this after setting the top cam to zero lean. If I lean the cam (yoke tune) then with the rest being the fulcrum, that will change the centring of the shaft between the bow limbs (string around limbs)

So can I just yoke tune? Or should I be tweaking the rest to maintain that perfect center alignment every time I lean the cam a bit? Will they come to an equilibrium at one point?

From: Ambush
25-Mar-20

Ambush's embedded Photo
Measuring shaft parallel to riser.
Ambush's embedded Photo
Measuring shaft parallel to riser.

From: CurveBow
25-Mar-20
It sounds & looks like you're quite familiar with necessary adjustments and have the equipment. But, I set the rest to centershot by looking down an arrow on the string while aligning the string with the center of the riser where the limbs meet it. Beyond that (assuming nocking point has been arbitrarily set), I shoot through paper at 6 feet and then make rest adjustments to chase the perfect bullet hole.

Once I get the bullet hole, I go back to 10-12 ft and check again. After that I shoot it out to longer ranger, then try broadheads. I'm usually having trouble from not too perfect form if I try this early in my pre-fall shooting. Once I'm in good shooting shape its easier and more reliable.

Good luck. I don't have a press so I don't mess with yoke tuning. If I think something there is out of whack, I go to a bow shop....

From: x-man
25-Mar-20
That's a slippery slope. If you try to center the shaft in the limbs (on some bows) you will end up chasing your tail tuning. The cable guard puts "some" input into the launch of the arrow, unless you're shooting an old Martin shoot-thru system. The centershot almost always "has to" be outside center of the limbs center.

From: GLP
25-Mar-20
How far is the center of the shaft out from the inside of the riser? On Mathews don’t they usually suggest starting at 13/16th ? Is this right x-man?

From: Ambush
25-Mar-20
Yes, 13/16” to 12/16” (3/4) I’m at 3/4” when all indicators say is good.

Right now some of the blame is form which could be suffering from shooting three different recurves quite a bit. And I blame that on a few trad guys that I respect ( and probably envy a bit) for making me want to shoot another bear or two with a single string this spring.

From: Buck Watcher
25-Mar-20

Buck Watcher's embedded Photo
Buck Watcher's embedded Photo
The above may help.

Once I used the following method, tuning my (& buddies) solo-cams was a breeze. This always got my FP & BH hitting the same at 50 yards. I only hunt to 30 yards so all good for me. >>>

Start with bow is spec and at max poundage. Set rest so center of arrow is 13/16" (at berger hole) from riser. I never move the rest left/right. Twist/untwist idler yokes to get perfect arrow flight. ie: If you have a right tear you need to move the nock left (using yokes). Someone told me think of it as getting the nock directly behind the BH.

Idler lean should NOT be straight at brace. It should be straight at full draw - have some stand behind you and look if you don't have a draw board. BUT if the bow shoots good, it might not be perfect.

From: Ambush
25-Mar-20

Ambush's embedded Photo
Elbow looks pretty good?
Ambush's embedded Photo
Elbow looks pretty good?
I’m pretty careful to keep my axle to axle, brace height and cam timing in spec.

From: x-man
25-Mar-20
If you have a draw board, set the idler/cam lean plumb when the draw force curve hits it's peak weight. You'll need to attach a scale to your winch between the cable strap/rope/cable and the string loop hook.

Mine aren't straight at brace, OR full draw. Somewhere in between.

From: WapitiBob
25-Mar-20
Too much bow hand in that pic for me. I’d rotate another 30 deg clockwise but those wood grips were the worst grips ever made.

From: x-man
25-Mar-20
Bow arm looks a little suspect...

From: x-man
25-Mar-20
Looks like Bob and I posted at the same time. I'd like to see that same picture with short sleeves.

From: Ambush
25-Mar-20
Short sleeves?!!? It’s friggin winter here!!

I changed my grip a bit last year to put a little more intentional pressure on the bottom of the “life line”. Also straight (locked elbow) bow arm.

From: x-man
25-Mar-20
Hey, I'm in Minnesota. I still have snow in my yard :)

Many folks confuse "locked" with hyper-extended. Not the same thing. When the arm bones are "in-line" with the least amount of muscle use, it will actually look bent from that over-head angle.

From: Grey Ghost
25-Mar-20
I always yoke tune to find the center between cam lean at rest and at at full draw. That minimizes the inherent nock travel caused by the the cable guard. Then bare shaft tune to find the correct rest position.

Matt

From: Ambush
25-Mar-20

Ambush's embedded Photo
The far right arrow I “yipped”.
Ambush's embedded Photo
The far right arrow I “yipped”.
Lots of snow here too, should be easy to spot those bears in about six weeks!

I’m a 74” wingspan. 29” bow, very short D-loop and release trigger is at the second knuckle. Shouldn’t be over DL.

I just retied my loop to make sure there is no pinch. Retimed the QAD rest. According to the group I just shot at fourteen yards, my bare shafts are a bit nock right and impact a bit left of fletched.

From: Grey Ghost
25-Mar-20
You're very close , Rod. Step out to 20 with your bare shafts, and tune accordingly. then try 30.

Matt

From: Ambush
25-Mar-20

Ambush's embedded Photo
Over corrected the sight a bit, but should be good when the shafts come together.
Ambush's embedded Photo
Over corrected the sight a bit, but should be good when the shafts come together.
Ok. I’m within about 2 1/2” of impact bare to fletched at twenty five yards. Going to quit for the day as it’s getting cold and I’m getting sloppy. Tomorrow I’ll turn the ribbon horizontal and finish the rest height before finishing the yoke tuning.

Then shoot some big fixed blades.

From: Buck Watcher
26-Mar-20
Another thing I thought of is try turning out the top limb bolt 1/4 or 1/2 turn. Theory is - since it is a solo-cam, the cam does all the work. The idler just goes for a ride, that limb doesn't use/lose as much energy as the cam one does. I have seen it work.

From: x-man
26-Mar-20
As a single cam rotates, the cable draws the two limbs together "similar" to how a trad bowstring does. They are slaved together. Adjusting one limb bolt at a time affects the vertical nock travel during the draw cycle and should only be done if one limb is weaker than the other.

If you have a draw board, you can experiment with that nock travel as you draw the bow. A sharpie in the string loop drawing a line on freezer paper as the bow is drawn. Play with the limb bolts until that line is as straight as possible.

From: Ambush
26-Mar-20
Some interesting ideas put forth. Adjusting limb bolts differently as suggested by buckwatcher to affect vertical nock travel is something I've never considered. Out of habit, I've always cranked my limb bolts all the way down, then back up one quarter turn. Thanks X-man for following up on that. And good point about checking cam lean at peak weight and not full draw after let-off. It does seem that I have to have my nock point quite low (level or even a bit negative) to get bare shafts to impact horizontally with fletched. Nock travel issue? Maybe my rest should stay up longer"

GG, setting your cam lean first on a draw board, then fine tuning with the rest is (I think) the opposite way around than must archers? But it must work for you.

Well it's a crappy, snowy day out today, so won't be shooting. I took my draw board apart two summers ago because I wanted the winch for another project. I did pick up another winch and cut up most of the parts for a more sophisticated model last winter but never got around to putting it all together. Great day to put it all together. Only item I can't find is the roller I had for the grip to sit in. Also, when I cut the mainframe tubes, I didn't allow to put a scale between the d-loop and the winch. I'll have to draw and hold just before break over and have my wife mark the arrow. Plotting the nock travel will be interesting too.

Hopefully by late afternoon I'll have the new draw board up and functional.

From: x-man
26-Mar-20
Once you get your nock travel plotted and fine tuned for the straightest line, you'll want to set you drop-away timing so the rest drops after one inch of travel past any noticeable "hump" in the nock travel. Usually right after peak draw weight.

From: Ambush
26-Mar-20
X-man, can you elaborate on the method to plot the nock travel? I'm assuming you mean horizontal travel? Just having a hard visualizing how to do that.

From: x-man
27-Mar-20
Well, it's plotting a horizontal line but,...it's tracking the vertical travel of your nocking point as the arrow moves in the draw cycle. With a sharpie in the string loop, it will look something like this _______--___ only not that pronounced obviously.

Horizontal travel is the amount of side to side travel of your nock as it moves in the draw cycle. If your sharpie is positioned to just touch the paper, then horizontal travel would make a thicker or thinner(maybe pull away from the paper) line as it moves.

Think of it this way.... standing behind the arrow and looking directly down the shaft... vertical nock travel goes up and down while horizontal nock travel goes left and right.

From: x-man
27-Mar-20
Horizontal nock travel is almost impossible to plot and track while drawing on a draw board. You would have to have a high speed camera and watch the release of the arrow back in super slow-mo.

In theory, the forward travel should be straight as far as horizontal travel is concerned through a shooting machine. Hand torque is what causes horizontal travel.

From: Ambush
27-Mar-20
Yes X-man, my mind was on cam lean and horizontal nock travel and I just could not envision applying that to a graph.

But: I set up a piece of cardboard under the nock loop and traced a line through the draw cycle, moving it over about an inch each time and graphed five lines. Each line made a slight consistent curve over about eighteen inches. The middle of the curve dropped about 3/16". I couldn't detect a "bump" in the line.

With yoke adjustments, I ended up setting the cam lean between brace and peak weight to the average of both. I shot one group of three fletched and three bare shafts at twenty five yards and the groups were within two inches of each other horizontally. Then I wiped out hard on the ice coming back from the target and figured that was enough till the rain, snow and nighttime freezing quits. It's been raining all morning, so I decided I might as well add a foot of length to the draw board (for a scale) and a winch rope guide too.

From: x-man
28-Mar-20
I think where we got ourselves confused is that my drawboard holds the bow in it's natural vertical state. It sounds like yours is on a bench with the bow sitting horizontal like a cross bow.

From: Grey Ghost
28-Mar-20
Rod,

You may never get the bare-shafts to group with the fletched arrows, if you're shooting a straight locked bow arm, because the only direction your follow-thru can go is left.

Also, per your earlier question, all of the top level competitive 3D archers, that I shot with back in the day, set cam lean first, then tuned the rest. I've never heard of trying to tune cam lean to a fixed rest position.

Matt

From: Rock
28-Mar-20
Good Luck Rod, but this sounds way to complicated and time consuming to me. Sure glad I shoot a Recurve as there is not as much to worry about :-)

From: Ambush
28-Mar-20
Haha, Ron! If you saw me shooting my recurves, you see plenty for me to worry about! And not to much for animals to be worried about.

GG, that’s basically what I’ve done now. A straight edge alongside my idler (top cam) comes to exactly the same place on my bottom cam, at brace and peak weight. All indicators say my rest is centred. I’m going to use form correction for the fine tuning.

X-man, my draw board is portable and can go horizontal or vertical. All my stuff is homemade and has no permanent home and so is designed for such. I did put it “crossbow like” for easier graphing, but it’s understood that vertical and horizontal are with the bow in shooting position.

I am going to graph again, paying special attention to the peak weight hump to valley portion of the draw. I’d like to find that bump you described.

Miserable weather again today and two days left of isolation, so it’s a nice diversion :)

From: Ambush
28-Mar-20

Ambush's embedded Photo
Ambush's embedded Photo
In the “crossbow” position. Can be clamped to a table top or bench for vertical.

From: Ambush
28-Mar-20

Ambush's embedded Photo
Ambush's embedded Photo
X-man, I think I found the “hump” and it seems to be in the last 1 1/4” of draw. Then goes goofy when pulled harder against the draw stop.

From: x-man
28-Mar-20
Yup, these new bows have come a long way since the first single cam bows that I did this with back in about 2001. I had a customer with a Mathews Ovation that had a hump almost a half-inch high and two inches long where the draw force curve hit the peak weight. It was the single biggest challenge with tuning single cam bows... flattening that curve(to borrow a current phrase).

From: GLP
28-Mar-20
Learned a lot from this thread ! Thanks Ambush and x-man. Keep us posted

From: Cornpone
29-Mar-20
I just bought a Bowtech Revolt and set it up per their online videos. For centershot I used my dial caliper as the OP. Then I shot several bare shafts...they were consistently nock left ~1" at 15 ft. Then I adjusted the cam lean. Cams were initially .980" measured from the limb edge to the cam bearing. They both ended up at .960" for a perfect bare shaft out to 10 yards (max I can shoot in basement).

From: Timex
29-Mar-20
Perhaps I'm wrong or just old school or both. But with any bow both trad & compound I eyeball everything then shoot some fletched & bare shafts together & make adjustments then shoot broadheads & make slight adjustments to bring broadhead & field point impact points together

From: Ambush
29-Mar-20

Ambush's embedded Photo
Ambush's embedded Photo
I’m getting there. This pic is sixteen yards, one each bare shaft, fletched field point and broadhead.

I was starting to wonder if I was overdrawn so I shot a few with my release on the string instead of the loop and that was definitely too short. I was 1/8" too long on my axle to axle measurement. so I put that back to spec and the bow became it's jumpy self again, waiting to take off if I relaxed even a bit. I asked X-man in a PM about twisting it up a bit to shorten the draw length and he recommended against that on the solo cam. So I took my spare, matching release and shortened it in 1/8" increments. I'm convinced I'm not to long in the draw length.

I did end up moving my rest 1/16" to the left to bring bare and fletched together.

I believe my grip on the grip may be partially to blame. Strongly considering buying a Shrewd grip.

From: Ambush
29-Mar-20

Ambush's embedded Photo
Ambush's embedded Photo
At twenty two yards though my broadheads are still a bit to the left of fletched and bare field points.

From: x-man
30-Mar-20
That could be hand torque. Most hand torque puts the BH's left of FP's for right handed shooters. Back in the day, I used to build my own shrewd grips out of wood. I was an engineer/custom guy at an architectural millwork company. Lots a cool tools and machinery for wood crafting... Now, I am working from home as an estimator for a similar company. I miss having access to that shop!

From: Ambush
30-Mar-20
X-man, yes I’m convinced it’s hand torque. I can see that the string comes off the idler as a right lean in the idler when I know it’s not on the draw board. With this factory grip, my hold on it to correct that feels unnatural. I have lots of time to play around with form and grips.

I can always grab my old Drenalin if I have to. I always say we are a perfect match; a little slow, a bit sloppy, a spongy back wall, but we’re good enough to get the job done :)

From: Ambush
30-Mar-20

Ambush's embedded Photo
Two 1 1/4” Slicktricks at twenty yards.
Ambush's embedded Photo
Two 1 1/4” Slicktricks at twenty yards.
So today is another snowy, freezing day, so I spent several hours in the shop shooting through paper, twisting, untwisting and tweaking. I wore a slippery thin glove on my bow hand. I was able to get rid of all horizontal tear, but still have a persistent nock high. I tried over and under rotating the cam. Timing the rest to drop immediately and having it stay up longer. Right now the nock is actually slightly below the rest. I haven’t tried it much more than 1/4” nock high. Maybe I should. Nock could be bouncing up off the rest?

But at five feet, fifteen feet and twenty yards, bare shafts , field points and broadheads are hitting the line :).

Can’t get farther out than that until some ice and snow are gone from my range. And that’s not looking like anytime soon :(

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