Compound Bow Are these "beyond parallel" limbs?

jonUK76

Member
I have a Kinetic Trium X and would like to know if a Bowmaster bow press (with L adaptor) will be usable on it. I just thought it's a useful thing to have and I am considering changing my peep sight for a different one, and if I could do minor things like that without an 80 mile drive to the archery shop, that would be excellent. I'm aware these presses are said to be unsuitable for "beyond parallel" limbs.

I thought the bow had parallel split limbs at first, but I've seen something recently that had me questioning this, so would be very grateful for your opinions.

Stock pic ripped from user manual



Pic of actual bow (I know the angle is imperfect, but it's the best one I have at the moment)


Thanks
 


jonUK76

Member
Thanks Geoff. Hmm... It appears to work but looks a bit risky. I've got a 500 kg rated ratchet strap set, I'd imagine is strong enough? I'd perhaps go with Dyneema rope instead of paracord (much stronger)?

Anyway, I did what I should have done anyway and checked the angle of the limb at the tips against the string, and with the limb bolts wound out fully, it looks like it's a few degrees short of being parallel, definitely not past parallel. So I think the Bowmaster should work OK.
 


geoffretired

Supporter
Supporter
Heehee, we think alike it seems. I have a Bowmaster press that I converted and used bow string as part of the total press.
What I notice with near parallel limbs is that the adaptors tend to align so they are slightly inwards of the actual bow string, when in tension. For them to fall off the ends of the limbs( which is the real danger) they have to travel away from the riser. It should be an easy job to make a device that pulls the adaptor towards the riser, and therefore holding the adaptors on the limbs. Most of the work I do requires very little movement of the limb tips before the cables are all slack enough to work with.
I saw a clever device made from threaded rod with a toggle behind the adaptor through the gap between the split limbs and is fixed against the limb butts. A thumbscrew is used to tension things so the adaptor on the limb tip cannot move out from the end.
 


AndyW

Well-known member
If you are just going to be using it for peep etc. and not looking to swap string/cable then just draw the bow back a bit and get someone to put a dowel or pencil through the cam so as it fouls on the limbs and won't allow cam back rotation. Much safer than relying on a set of L brackets that you may knock. You will just need to draw again sightly to remove.
 


KidCurry

Well-known member
A genuine question; would a pencil hold the force being applied?...
Never tried a pencil before. I had doubts about its strength as well so I just tried it. Not a chance. Cams went through the pencil like a guillotine. I guess a drill bit would work if large enough but as they are hardened they won't take kindly to any lateral forces. I would probably use dowel of 15mm dia plus. My compound makes thing worse as the limbs are quite wide apart.
My only other concern would be that the cam design probably is not designed to take that kind of stress.
 


jerryRTD

Well-known member
If you are just going to be using it for peep etc. and not looking to swap string/cable then just draw the bow back a bit and get someone to put a dowel or pencil through the cam so as it fouls on the limbs and won't allow cam back rotation. Much safer than relying on a set of L brackets that you may knock. You will just need to draw again sightly to remove.
I am not sure that it's a good idea to put some thing through the cam. It could stress the cam in areas where it was not designed to be stressed possibly causing buckling and may be derailing.
 


AndyW

Well-known member
Oops. I went and put a well meaning comment on the interweb without thinking. You only draw it to slacken the string - not all the way back, it might be holding a pound or 2. You also rest the cam onto it avoiding just letting the string go.
Probably a misjudged post on reflection as someone is always going to do the ridiculous such as try it at full draw or with the wrong cam etc.. Don't.
Anyone who wants to come round my house to be shown how to do it without killing themselves pm me I might even use a wooden spoon to mix it up a bit - see what I did there.
Yes a drill bit will work but mark your cam / limbs as it's hard. Cams are not designed to be used in this way and neither are pencils or drill bits, a broom stale would be better.
If anyone is in any way unsure of what they are doing take it to a shop. An archery shop - not a butcher, grocer, florist.
 


geoffretired

Supporter
Supporter
Andy. I understood the very short amount of draw. We used that method to change strings when bows had steel cables and tear drops to fit a string to.
I know the string may have a light tension in it, but what about the cables? They have trapped the limbs to an extent that if the string broke, the limbs would open with a huge amount of energy in them.
If the pencil broke as it did for KidCurry, I am thinking it was a good job the string was just being eased back gradually. Imagine if the pencil broke after the string had been removed!!
 


jonUK76

Member
I've seen this done all the way to doing a string change. Frankly I don't like the look of it as I should think you have a real risk of damaging the cams. Might be OK with a very short draw for just relaxing the string enough to change a peep.

[video=youtube;gLkVuWwj2fA]https://www.youtube.com/watch?v=gLkVuWwj2fA[/video]

Actually I may need to change string/cable sooner than I imagined (just noticed something a bit concerning on my bus cable - I'll ask about it separately when I take some pictures).
 


KidCurry

Well-known member
... You only draw it to slacken the string - not all the way back, it might be holding a pound or 2. You also rest the cam onto it avoiding just letting the string go.
Okay... so I thought this does not sound right at all. Next experiment... :)
Limb gap width is 22mm. I put a pencil (StaedTler tradition 2B) across the limbs. Tied paracord to the point that the cam would apply the force to the pencil. Pencil broke at 72lb pull. It was at my limit of my ability to pull. I remembered the compound snapped the pencil like a cocktail stick.
Conclusion (1) ... force on pencil must be at least 70lb or 310N to be more correct. So next experiment...

Measure direct rotational force of the cam with my spring balance. How to do this? Well I need to measure from the point the cam rests against the pencil having only rotated about 10-12 degrees. So I tied some paracord around the cam web at the point where the pencil that touches the cam. This would measure the force applied to the pencil. The other end to a spring balance. It's a 90lb spring balance.
Started pulling. Well the spring balance topped out at 90lb and you could barely detect any movement of the cam. So not the 1lb to 2lb forecast. I'm not going to test my cam to destruction so I would have to guess the force that the cam can apply to an infinitely strong pencil would be around 150lb (670N) maybe even more. And that's for am initial cam rotation of no more than 10-12 degree. You got to love physics!

I've seen this done all the way to doing a string change. Frankly I don't like the look of it as I should think you have a real risk of damaging the cams. Might be OK with a very short draw for just relaxing the string enough to change a peep.

[video=youtube;gLkVuWwj2fA]https://www.youtube.com/watch?v=gLkVuWwj2fA[/video]
A screw driver will work fine :) if the cam holds out.
 


AndyW

Well-known member
Mmm. Got to say I'd never measured anything just did it without thinking about it. After what you've done I probably won't again. Proved wrong. Sorry All.
 


AndyW

Well-known member
geoffretired, Kid Curry put the work in to prove I was being a donkey, I'm thankful he did, better an embarrassed AndyW than someone getting hurt.
I've used a pencil in the past but I probably haven't been bit because I generally used an Allen key in preference and in latter years I've had a bow press - that'll teach me to be glib.
 


KidCurry

Well-known member
geoffretired, Kid Curry put the work in to prove I was being a donkey, I'm thankful he did, better an embarrassed AndyW than someone getting hurt.
I've used a pencil in the past but I probably haven't been bit because I generally used an Allen key in preference and in latter years I've had a bow press - that'll teach me to be glib.
To be clear, I was only talking about bows made today. In the past limbs were much closer together and softer. This has a massive effect on whether a pencil or dowel would work, and bows are much more efficient and have aggressive force draw curves now. I remember I used to press my old Hoyt with one cam on the floor and leaning on the top one. I definitely would not say a pencil would not have worked in the past :)
 


robert43

Member
I have owned a Bowmaster bow press . About 2 months ago I bought a Cartel ripoff off of the Synunm bow press & much better item than the bow master .If you were to buy 1 I wouldnt get the bow master again.
Best thing about the Synunm / Cartel with minor mods you can make a draw press with it
 


jonUK76

Member
I have owned a Bowmaster bow press . About 2 months ago I bought a Cartel ripoff off of the Synunm bow press & much better item than the bow master .If you were to buy 1 I wouldnt get the bow master again.
Best thing about the Synunm / Cartel with minor mods you can make a draw press with it
What does it do better than the Bowmaster? The number of ropes on the Synumn press scares me a little, in that it looks quite complicated!
 


KidCurry

Well-known member
What does it do better than the Bowmaster? The number of ropes on the Synumn press scares me a little, in that it looks quite complicated!
I used the Bowmaster for all my bows up 'till my PSE with over parallel limbs. I found the Bowmaster seemed like it was just hanging on by its fingernails on the PSE limbs. The Synunm, although way over priced in the UK as it can be found in the USA for $99.99, has a better profile for keeping contact with the limb tips. It's dead easy to use and extremely quick. Because it's a continual pulley it can let the bow right down. It's a shame it's so over priced in the UK.
 


robert43

Member
What does it do better than the Bowmaster? The number of ropes on the Synumn press scares me a little, in that it looks quite complicated!
Pain in the bum holding all parts together when you start . You have to know / mark which cable lug to use with your bow ( I have owned Hoyt bows with split limbs) also you have to use a ratchet spanner / socket due to the amount of turns to press the bow as the tommy bar is a joke.
The Synumn / Cartel press is fast & the ropes are easy as you dont break it down. Look up the Synumn how fast you can press the bow .
If you do buy the Bowmaster DONT buy the ripoff model Jinxx or what ever its called as there was a picture on the Australia archery forum , when the cable lugs stripped & then busted the limb
 


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