adjusting LetOff on a binary cam bow

[Ode1891]

BowTech Old Glory. My cables are timed and in synch with each other, the A2A is good, and the brace height is good. But the let off feels too stiff. Any suggestions?

[greywolf44]

Hi. I've spent about 6 hours in a pro-shop working on an '05 Constitution after I changed cams. On that bow, proper letoff is achieved by advancing the top cam a few degress relative to the lower. I believe the situation is similar on all binary cam bows. So, if your cams are in perfect time relative to each other, you will get 65% letoff and no valley. Yuk.

At full draw, you think the bow is trying to pull your arm off. Setting up one of these bows is not a do it yourself job. Unfortunately, Bowtech has not done a particularly good job of educating its dealers: a problem I just got finished dealing with. Fortunately, the information you need to get started is available on AT.

Before you go to work on this problem, here's a suggestion: forget everything you thought you knew about tuning a compound bow. The good news is that once you get the hang of it you will never shoot any other cam system. These bows are the best there is. Good luck.

Greywolf

[Ode1891]

Can you explain what you mean by advancing one cam?

The bow had what appeared to be a stretched cable in that both cams appeared to be rotated. The BT factory tech told me that I should set them evenly. He said to set the brace height and a2a as specified for the bow, and make the cables even and all should be correct. I put twists in one cable to even the cams, it sounds like I should have left them as they were? My Mathews is set 'intentionally' at the 65% stop. The BT just feels different at full draw.

[PA.JAY]

READ THIS :http://www.archerytalk.com/vb/showthread.php?t=218697

[harleyryder]

I thought it had a draw stop to adjust the let off?

[Ode1891]

There is a stop on the upper cam, but I thought it was foe draw length, not let off.

[Ode1891]

READ THIS :http://www.archerytalk.com/vb/showthread.php?t=218697

I read the thread and I'm more confused.

Which cable is the top cam cable? What does "retard the cable mean"?

Why didn't the bow tech factory rep tell me about these special adjustments for let off? The thread sounds like we're only talking about adding or reducing twists in one cable or the other after setting the other specs. It's not a complicated task, but the jargon used is VERY confusing. I only have one stop on the top cam on my Old Glory and that's how it came from the factory, so how do I tell that the stop is 1/16" different? I'll call the factory again today. Thanks

If anybody can explain the technique described in the thread linked above, with easy-to-understand language, please reply. If you say the top cam cable, tell me how to ID that cable vs the other. This aint rocket science. Thanks Again

[greywolf44]

It's the cable attached to the peg closest to the outer edge of the top cam. The draw stop peg affects draw length and letoff. Spend some time with Mr. Nowlin's thread. The information is relevant to all binary cam systems. Here are pictures of the bottom and top cams on a 2005 Constitution. Note the positions of the holes in the lobes near the string posts on the top and bottom cams. I have a 2006 Constitution that is timed the same way although it has timing marks on the cams and a much longer slot for the draw stop.

This is what we mean by the top cam position being advanced or the bottom cam position being retarded. Timing these cams is critical to getting proper letoff.

[Ode1891]

Thanks. I have a bow scale coming that allows you to read peak and hold weights which will help me set the letoff. The Bowtech guy and others say to add twists in that one cable only, while others say to do that and then untwist the other cable equally. I'd prefer to leave the other cable alone since my DA rest cord is attached. Can I get what I need by only twisting the one cable? What will that do to draw weight?

I did read that post again. Maybe it's me...but the terminology is too much for a novice like me. I understand exactly what you all are telling me on this post though and I thank you.

[greywolf44]

I think you've got the picture. Here's a summary of what we did to get my 2005 Connie timed:

1. Set the bow at its maximum draw weight with the draw stop peg at the factory spec 80% mark.

2 Adjust (twist or untwist) the control cables so that, on both cams, the distance between the bottom of the string posts is the same. On 2005 E cams this is 1/16th inch from limb face (you can use a 1/16" allen wrench for a feeler guage). 2006/2007 models have timing marks on the top cam that refer to a chart that is available on the Bowtech website.

3. Take 2 twists out of the lower cam control cable and test for letoff.

4. Repeat step 3 until you get close to 80% letoff. Then subtract half twists to get it exact.

5. If you use a pullcord dropaway rest install it and retest.

6. If the pullcord tension changes the letoff you can take out a twist or two to correct.

7. Set the bow to desired draw weight and move the draw stop to adjust the letoff.

I don't think it really matters whether you add twists to the top, subtract twists from the bottom or do it to both cams.

Let me know how this works for you.

Greywolf.

[Ode1891]

I'm pretty close to being confident about the process. But, if I do everything at the weight I want, I should be good without step 7. Correct?

7. Set the bow to the desired draw weight and move the draw stop to adjust the letoff.

I plan to wait for my Ultra press before I start. I have one of the cable presses, but that's a poor toll for this sort of process.

The bowtech guy said I should have 6 dots showing on each cam whenI start.

Thanks!

[greywolf44]

That makes perfect sense and may work. I don't think you can go wrong by trying that approach. All I know is what I did. I'll tell you what though: once you get that bow set up correctly, you won't want to touch it again and you'll never want to shoot another cam system.

I'm wondering if the first Bowtech guy you talked to was really a technician or just somebody who happened to answer the phone. If that was a technician he's due for some OJT.

Without regard to BT's lapses in customer service and dealer training, these bows are awesome. Happy shooting!

Greywolf.

[Ode1891]

Both Bowtech guys were great. I shot this bow when it was tuned for over a year and it is awesome.

I'll repost when I get'r done

[greywolf44]

I just had a thought. All that cable twisting is going to change your draw weight. When I set my cams equal on my connie the peak draw was 64 lbs on 60 lb limbs. After we got good letoff we backed the limb bolts off to get down to 50 lbs which is what I like to shoot for spots.

If I had started at 50 lbs and worked on both cables, I probably could have gotten the same result with no limb bolt adjustment. This goes to show that there is more than one path up the mountain.

Next time I change strings I'm going to try it this way. Meanwhile this honey shoots so good I don't dare touch it.

Greywolf

[Bellows1]

BowTech Old Glory. My cables are timed and in synch with each other, the A2A is good, and the brace height is good. But the let off feels too stiff. Any suggestions?

I think you may just need to twist up both cables one turn, then try the let off again. Go another if you need to.

[Ode1891]

I got the Easton scale and the press yesterday. I won't be able to assemble the press until maybe Monday. In the meantime, I did pull my bows with the new sacle. Expenisve but, a REALLY COOL TOOL! Old Glory is 58 pounds with a holding weight of 19.5 or 66% LOff. I have a half turn of tightening left on the limb bolts so I'm not concerned about the poundage.

Just to simplify this cable ID, I have a downward moving cable that pulls the drop away cord. It's the other cable, the one that moves upward, that I want to twist correct?

Thanks again for ALL the input.

[Bellows1]

I got the Easton scale and the press yesterday. I won't be able to assemble the press until maybe Monday. In the meantime, I did pull my bows with the new sacle. Expenisve but, a REALLY COOL TOOL! Old Glory is 58 pounds with a holding weight of 19.5 or 66% LOff. I have a half turn of tightening left on the limb bolts so I'm not concerned about the poundage.

Just to simplify this cable ID, I have a downward moving cable that pulls the drop away cord. It's the other cable, the one that moves upward, that I want to twist correct?

Thanks again for ALL the input.

Not correct. You will need to twist them both up the same amount. Twisting just one will throw your cams out of sync.

[Ode1891]

By twisting the upward cable 4 times , and moving the draw stop peg, I was able to get it to 78%. After hunting season , when I replace the string and cables, I'll tweak this cable/let off thing some more.

It's too close to the opener now. It paper tunes good so I'll shoot it in with broadheads this evening and tomorrow evening.

The Easton digital draw and holding weight scale is pretty cool. The ultrapress is outstanding! Thanks for all the help!

Bellows-I agree about wanting the cables in synch, 6 dots showing, but I'm not eager to cut off the peep and dloop and start from scratch. That's why I'm going with what I have.

Thanks again

[wrinkleydms]

Hi all, what's this about twisting cables on this bow?, what is involved, and can it be done without special rigs or tools?
cheers David

[oldglorynewbie]

You will need a bow press to relax the string and cables. 1 full twist is taking the cable off the peg on the cam and rotating the loop 360 degrees. 1/2 twist is of course just 180 degrees.

[BlueRidge]

If the top cam is advanced slightly more than the bottom cam, will the top cam hit the draw stops (not the peg but the cam flats) before the bottom cam? Or will they hit at the same time because the bow is not being drawn from the center of the string? TIA

[CaptPete]

READ THIS :http://www.archerytalk.com/vb/showthread.php?t=218697


OK Folks, I just stumbled onto this thread and read through the thread linked above. I bought an '08 Guardian last week and have a few questions.

I installed a drop away rest and have it tied into the down cable about 1" below the rest. I installed it the same way I did on my Hoyt...put the draw cord through the down cable, draw the bow and let the cable / rest set themselves.

Do I need to twist the cables and what happens if I don't?

If I need to twist the cable(s), which cable(s) do I twist & which way and how much?

Do I need to replace the draw cord and tie it in farther down the cable?

Do I need to worry about the cams "locking-up", like what is described in the other thread?

The cams don't draw stop pegs, how would I adjust the let -off?

I don't see any timing marks on the cams. How do I tell if they are in time / sync?


Kevin

[Dave Nowlin]

My thread titled Warning to Binary Cam Owners was directed at the 05 BowTechs. The 06,07 & 08 BowTech and Elite bows are not timed the same way they are much simpler to set up. If you go to the Elite Forum in the Tech section there is a thread titled Supertuned where I explain the setup for these bows. These instructions are correct for all of them except the center pivot BowTechs.

Dave Nowlin

[msfcarp]

Dave I sure would like to read that info you mentioned, but I can not find where that thread is?:eek:

[Dave Nowlin]

Elite Archery has a forum of their own. You can find it there. I gave Bellows permission this weekend to copy relevant portions of it over here. I guess he simply hasn't got around to it yet.

Dave Nowlin

[CaptPete]

Anybody have any info on tuning a '08 Guardian???

[wrinkleydms]

You will need a bow press to relax the string and cables. 1 full twist is taking the cable off the peg on the cam and rotating the loop 360 degrees. 1/2 twist is of course just 180 degrees.

Many thanks for the info, i'll have to wait for a bow press or have a dealer do it, although from the posts , i'm not sure if my dealer is that good!
cheer David