# Twisting cables question



## SonnyThomas (Sep 10, 2006)

Yes, there is a point of diminishing returns. No, cable and bow string are not working against each other. And have you checked brace height? More than likely it's increased....

You'd be best off checking with the bow manufacturer, if of the bow manufacturer's. Or you could talk with a string maker to see if it's viable to achieve draw weight and keep bow within reasonable specs.


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## b0w_bender (Apr 30, 2006)

Agree with the above. 
I'm assuming that since you changed out your cam you were looking for a shorter draw length?

If that assumption is correct then what you need to understand is that a shorter draw takes up less cabling on the cam. this causes the limbs not to compress as much and you get a lighter draw weight. By reducing the ATA you are compressing the limbs more prior to the draw Cycle so when you draw the bow the limbs are getting closer to the compression they had prior to the swap. But as mentioned above this will often cause changes in the brace height (depending on the limb angle) If you want the bow to stay within the manufacturers specifications both ATA and Brace height you'll need a heavier set of limbs that are designed to get the weight you want with the shorter power stroke. So less draw length less limb compression. I would think you could get the weight up there if you were to drastically reduce cable and string length but if your limbs aren't of the beyond parallel type then that technique will give you a larger brace height which will increase your draw length again. 

I hope that makes sense.


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## Darkvador (Oct 15, 2013)

Thanks for the replies. I actually swapped them for a longer draw and more speed. What doesn't make any sense is I measured my bow at full draw with stock cams. Then I swapped the donor cams onto the bow and twisted the cables and string to get the same ATA at full draw that I had with the stock cams. My new ATA at rest is only 1/4" shorter than with stock cams. At full draw the same. Lost a little more than 10lbs. Still mystified. Oh, to keep the bow in time, my new bow string had to be 1 3/4" shorter than the stock cams string. Could that have something to do with it?


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## b0w_bender (Apr 30, 2006)

Hmmm, you may have stumped me, I'm guessing the longer draw may be using a smaller cam? or have greater let-off?


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## nuts&bolts (Mar 25, 2005)

Darkvador said:


> Thanks for the replies. I actually swapped them for a longer draw and more speed. What doesn't make any sense is I measured my bow at full draw with stock cams. Then I swapped the donor cams onto the bow and twisted the cables and string to get the same ATA at full draw that I had with the stock cams. My new ATA at rest is only 1/4" shorter than with stock cams. At full draw the same. Lost a little more than 10lbs. Still mystified. Oh, to keep the bow in time, my new bow string had to be 1 3/4" shorter than the stock cams string. Could that have something to do with it?


STOP.

YOu are short stringing your bow, and THAT is why you are losing poundage.

STEP 1. MEASURE the current draw weight.

STEP 2. MEASURE the current holding weight.

So,
let's say you have a 70 lb bow,
and you swapped cams for a LONGER cam.

You get 65 lbs.

Let's assume you have 80% letoff cams,
so your HOLDING WEIGHT, SHOULD be 20%.

So,
at 65 lbs of draw weight,
IF you have the string length CORRECT,
you SHOULD be getting 13 pounds of holding weight.

BUT
BUT
BUT
you are getting 18 POUNDS of holding weight...HOLDING weight is TOO HIGH.
WHEN holding weight is TOO HIGH,
your DRAW WEIGHT GOES DOWN.

So,
the FIX is to make the bowstring LONGER....not MORE SHORT.

When you make the bowstring LONGER and LONGER and LONGER and LONGER....

TWO things happen

a) the holding weight starts to DROP
b) the DRAW WEIGHT GOES UP...

that's right,
when you make a bowstring STRETCH LONGER
when you make a bowstring UNTWIST LONGER...

the draw weight goes UP...not down.

So,
keep measuring the DRAW weight
keep measuring the HOLDING WEIGHT...

and make the bowstring LONGER and LONGER and LONGER and LONGER

until your HOLDING WEIGHT is 20% of the NEW draw weight.

You twisted your STRING too short,
is the problem.


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## Darkvador (Oct 15, 2013)

I failed to mention this is a frankenbow. The only thing I swapped from the donor bow was cam and idler wheel. I will invest in a better scale an pay attention to my holding weight. Things went so smooth at first and I was pumped. Then I got a little frustrated. Thanks to all the input I get on AT, I am motivated again. I think we all have an idea of what the ultimate bow would be for us personally. But we shoot what the manufacturers produce and live with it. I just decided to dive in and go for it. I think I am so close. I also have a dual cam setup to try but I thought the single cam would be easier. Thanks Nuts&bolts, let me know if a house in your neighborhood comes up for sale. Maybe not, I would probably drive you crazy.


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## Darkvador (Oct 15, 2013)

b0w_bender said:


> Hmmm, you may have stumped me, I'm guessing the longer draw may be using a smaller cam? or have greater let-off?



The donor cam is a little smaller but the idler wheel is a little bigger than the ones that were on the bow. Original cam was 80%. Donor cam is 75%. Brace height on donor bow was 7 1/4. Brace height on my bow was 8 1/4. My bow now has the donor cams on it and I retained the 8 1/4 brace height. I initially tried for a 8" BH but the bow barely pulled 60lbs.


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## nuts&bolts (Mar 25, 2005)

Darkvador said:


> I failed to mention this is a frankenbow. The only thing I swapped from the donor bow was cam and idler wheel. I will invest in a better scale an pay attention to my holding weight. Things went so smooth at first and I was pumped. Then I got a little frustrated. Thanks to all the input I get on AT, I am motivated again. I think we all have an idea of what the ultimate bow would be for us personally. But we shoot what the manufacturers produce and live with it. I just decided to dive in and go for it. I think I am so close. I also have a dual cam setup to try but I thought the single cam would be easier. Thanks Nuts&bolts, let me know if a house in your neighborhood comes up for sale. Maybe not, I would probably drive you crazy.


Since this a frankenbow,
forget the DONOR bow specs
forget the 'ORIGINAL' bow specs...

you gotta SHOOT the bow to figure out the brace height that works.

For a single cam,
there is only ONE cam rotation position that will deliver LEVEL nock travel.

So,
LEVEL nock travel
means a FLETCHED arrow and the BARESHAFT arrow BOTH hit at the same height.

So,
for a SINGLE cam,
you twist the bottom end loop for the buss cable...EITHER ADD more and more twists or REMOVE more and more twists...

until you get THIS result at 20 yards.



WHen you have the buss cable length MATCHED to work with the bowstring length...

you will get the bareshaft and fletched arrow to have the SAME height,
for point of impact.

YOU HAVE TO LIVE with whatever draw weight you get.


So,
check the draw length.

*IF the draw length is TOO SHORT on a single cam....*

you SHORTEN the buss cable AND the bowstring...

to GROW the brace height,
which will GROW the draw length.

THEN,
you leave the string alone
and repeat the masking tape exercise at 20 yards, and play ONLY with the buss cable (add or remove twists).


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## nuts&bolts (Mar 25, 2005)

WHen you have the buss cable length MATCHED to work with the bowstring length...

you will get the bareshaft and fletched arrow to have the SAME height,
for point of impact.

YOU HAVE TO LIVE with whatever draw weight you get.


So,
check the draw length.

*IF the draw length is TOO LONG on a single cam....*

you LENGTHEN the buss cable AND LENGTHEN the bowstring...

to SHRINK the brace height,
which will SHRINK the draw length.

THEN,
you leave the string alone
and repeat the masking tape exercise at 20 yards, and play ONLY with the buss cable (add or remove twists).


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## nuts&bolts (Mar 25, 2005)

Darkvador said:


> The donor cam is a little smaller but the idler wheel is a little bigger than the ones that were on the bow. Original cam was 80%. Donor cam is 75%. Brace height on donor bow was 7 1/4. Brace height on my bow was 8 1/4. My bow now has the donor cams on it and I retained the 8 1/4 brace height. I initially tried for a 8" BH but the bow barely pulled 60lbs.


SMALL diameter cam
and LARGE diameter idler wheel....

you are going to have some WEIRD effects,
and most likely will need ONE limb bolt out of balance with the OTHER limb bolt
to get THIS result...at 20 yards.


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## Darkvador (Oct 15, 2013)

YOU HAVE TO LIVE with whatever draw weight you get. That is the key phrase I was looking for. I have followed all the tuning tips I have learned and read over the years. I just couldn't grasp how I lost so many pounds when the donor cams compress the bow to within 1/8" of what the original cams did. At least now I know this can happen and I have to live with the poundage or try a dual cam swap and see what happens then. Its all a good learning experience and thanks to all for taking the time to help me.


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## markdenis (Sep 7, 2010)

nuts&bolts said:


> WHen you have the buss cable length MATCHED to work with the bowstring length...
> 
> you will get the bareshaft and fletched arrow to have the SAME height,
> for point of impact.
> ...



To shoot a bare shaft on the same level as a fletched shaft, isn't moving the nock up or down doing the same thing as twisting cables?


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## nuts&bolts (Mar 25, 2005)

markdenis said:


> To shoot a bare shaft on the same level as a fletched shaft, isn't moving the nock up or down doing the same thing as twisting cables?


ADD Half twist on the buss cable is VERY repeatable.
ADD 1 full twist on the buss cable is also REPEATABLE and un-do-able.

REMOVE 1.5 twists on the bottom end loop of the buss cable is very repeatable.
You change your mind,
and decide to add back in 1 full twist.


MOVE the d-loop 3/64ths of an inch.
NOT very repeatable.

MOVE the d-loop up 3/32nds of an inch.
Change your mind
and move the d-loop down 1/64th.

Not going to happen.

Work the cables,
add or remove twists.

Install the d-loop, PULL TIGHT with needlenose pliers
and NEVER EVER touch the d-loop again.

Work the buss cable (single cam)
work the control cable (hybrid cam)
and change the cam rotation position,
to fine tune for LEVEL nock travel.

A half twist
or a full twist
or maybe 1.5 twists in the correct direction
SHOULD fix you right up...

IF the cables were installed at the correct length
IF the bowstring was installed at the correct length.

IF one cable is installed at the wrong length,
then,
you will need to get the cable to the CORRECT length

and remove the d-loop
and re-install the d-loop
AFTER you get the cable to the correct length.

Then,
LOCK down the d-loop knots TIGHT
and never ever touch the d-loop again.

MUCH more control
working the cable end loops.


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## markdenis (Sep 7, 2010)

nutsandbolts:
OK, thanks...I understand. 

There is another question that interests me about one cam bows. Lets say there is no d-loop on the bow at all and the limbs are bottomed out and the tiller is even. Then back the bottom limb out two complete turns and leave the top limb alone. Now put the d-loop on a place that shoots the arrow level, bullet hole, straight out of the bow... what have you done, what does it do to the performance of the bow? Does it even matter?


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## nuts&bolts (Mar 25, 2005)

markdenis said:


> nutsandbolts:
> OK, thanks...I understand.
> 
> There is another question that interests me about one cam bows. Lets say there is no d-loop on the bow at all and the limbs are bottomed out and the tiller is even. Then back the bottom limb out two complete turns and leave the top limb alone. Now put the d-loop on a place that shoots the arrow level, bullet hole, straight out of the bow... what have you done, what does it do to the performance of the bow? Does it even matter?


two turns less on the bottom bolt
obviously,
the bottom limb is working LESS hard.

So,
the top limb is working HARDER....

cuz,
with the d-loop NOW installed MUCH CLOSER to the top axle, than normal

you are pulling the TOP axle down to your anchor
the TOP axle moves down MUCH more than normal,
cuz,
the d-loop to the top axle distance is SOOOOO MUCH closer now.

With the bottom limb bolt 2 turns out from maximum,
the bottom limb is UNBENT noticeably
and
so the bottom axle has now moved AWAY from the d-loop
so the bottom limb works LESS HARD
the bottom axle moves LESS when you pull the bow to full draw.

SINGLE cams are notorious for NON-level nock travel...

meaning,
MOST cases,
the d-loop has to be installed NOTICEABLY above LEVEL

the d-loop may need to be installed 1/8th above LEVEL
the d-loop may need to be installed 1/4-inch above LEVEL
the d-loop may need to be installed 3/8ths ABOVE LEVEL

to get LEVEL nock travel.

THIS has to do with the SIZE of the idler wheel
versus the SIZE of the cam, the METAL THINGY on the bottom axle.

IF you have ONE idler wheel size for ALL fixed draw length cams..

there is ONLY ONE combo
idler wheel and FIXED draw length cam that WORKS best...

and
ALL OTHER fixed draw length cams that are SHORTER than the ONE perfect matched combo
ALL OTHER fixed draw length cams that are LONGER than the ONE perfect matched combo....

you have to TWEAK the bow balance
UPPER versus LOWER limb balance...

by MOVING the d-loop HIGHER and HIGHER to make the UPPER LIMB work HARDER...to get LEVEL nock travel
or
by WEAKENING the bottom limb bolt, which makes the UPPER LIMB work HARDER and HARDER...to get LEVEL nock travel.

So,
two ways, to do the same thing,
which is to make the UPPER LIMB work HARDER
which CAN work for a single cam bow.

BUT...

depending on the shooter,
specifically the bow hand wrist...

the shooter might need the OTHER way around (kinda rare)
the shooter might need the BOTTOM limb to work HARDER...
so

you COULD move the d-loop LOWER and LOWER down the bowstring
or
you COULD weaken the TOP limb bolt, which makes the BOTTOM LIMB work HARDER.

Whatever it takes to get LEVEL nock travel
which is a fancy way of saying,
FLATTEN your arrow groups.


BACKING out the bottom limb bolt 2 turns
AND
setting the d-loop for a LEVEL nock

makes the TOP LIMB work EXTRA HARD...

which is not surprising for a single cam bow....

smells like a cam size that is TOO LARGE for the idler wheel diameter (cam design)
or
another way to put this,
the idler wheel diameter is NOT LARGE enough to work with THAT size of FIXED draw length CAM or DL module.

IDEALLY,
EACH draw length module
would have a CORRESPONDING IDLER wheel size...but, this would be cost-prohibitive

IDEALLY
each FIXED DRAW length cam
would have a CORRESPONDING IDLER wheel size...

but,
usually,
you get ONE idler wheel size
and you have that ONE idler wheel
for ALL fixed draw length cam sizes
for ALL draw length module sizes...
so

the FIX
is to move the d-loop higher or LOWER
to COMPENSATE for this design...compromise.


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## dwagoner (Sep 27, 2007)

*what bow? what cams did it have? and what were the new cams you installed????*

hard to get a good read on whats going on without even knowing what the equipment is???


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## b0w_bender (Apr 30, 2006)

dwagoner said:


> *what bow? what cams did it have? and what were the new cams you installed????*
> 
> hard to get a good read on whats going on without even knowing what the equipment is???


Ya not knowing this was a franken bow in the first place was a bit of a handicap.

I'm going back to my original premise that the new Cams are not compressing the limbs as much as the older cams did.
I'm going to make another assumption that the cams you used were for a bow that had similar limb angles. Now look at the rotation of the cams and make sure you have them in the proper rotation. You may need to look at the manual of the bow they were robbed from. Most cams have some sort of registration reference markings. Once you have them in the proper rotation. Shorten both the strings and the cables to compress the limbs more before you start the draw. Yes of course this will likely change ATA and brace height. That would be the trade off to get the poundage back. You may also have to adjust string length and or cable length the tweak the draw length. 

Now if the bow you stole them from has a drastically different limb angle well then as N&B said above you just have to fiddle with it until you get the optimal performance.


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## Darkvador (Oct 15, 2013)

Sorry about that. I should have been more specific. My bow is a TNT Defiance single cam. Donor bow is a PSE Sinister single cam. I chose the sinister because it compressed the limbs 1/4" less than my Defiance at full draw. I figured it would be a safe swap and I could get that 1/4" back by twisting the cable. Since I took the 1/4" off the TNT's ATA, it now has the same full draw ATA that it did with the stock cams. PSE has a timing mark and I kept the bow in time. The bow draws great, is 20fps faster and the draw length is better than the stock cam. Just lost more than 10lbs. If I could get 5 of those back, it would put me close to the fps that I am looking for. Might be like Nuts&Bolts says. It is what it is. I have a dual cam PSE DNA set up to try also. With those nasty cams, I should hit my target velocity even if I loose pounds with them also. Thanks again guys.


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