# Higher Draw Weight Does Not Always Result In Higher Speed



## Charles (Aug 26, 2010)

This is in partial response to a discussion that took place in the following thread:

http://slingshotforu...mm-steel-video/

I just wanted to make the point that higher draw weight does not result in greater velocities. And in fact, doubling straight cut bands was not a significant improvement over simple tapered bands. The test results which I quoted there were done with 3/8 inch steel ammo. Some wondered whether the results would hold for heavier ammo. So I did some more tests using .46 and .56 caliber lead. I doubt that many people ordinarily shoot ammo as heavy as .56 lead balls, so I regarded those as an extreme case.

Before presenting the data, I should say a word about the rig with chained Alliance 64s. Think of a rubber band as pressed flat, so it has a loop at either end, call them loop A and loop B. I always made chains by putting the loop A1 of one band through the loop A2 of a second band, and then feeding the loop A1 of the first band back through the loop at its opposite end, B1. Then when you stretched the two bands, you got a sort of figure 8 arrangement in the middle. As the bands were stretched, this knot would continue to tighten. Of course you could make chains by clumping together 2 or more bands and joining them to other bands in the same way. But someone on the forum (can't find it now, sorry) showed a photo in which the bands were just doubled and the loops never tied together. Here is a photo:










The nice thing about doing things this way is that there is no knot. Hence the bands do not seem to wear as quickly. And it is easier to take a chain apart and replace a failing band. The downside is that no section of the chain can have less than four strands of rubber ... a single rubber band folded onto itself. In the photo above, starting from the pouch, I have used 1, 1, 1, 3, 3. That is the chain that I used in my tests. After I assembled it, I realized that I should have tried 1,1,2,3 for a smoother taper, but I was too lazy to undo it.

With all of that said, here is the table with my chrony results:









I have listed the rigs in order of draw weight. Each Tapered Alliance 105 was made by cutting a 105 band to give one 10.5 inch strip; then measuring down 1.5 inches from one end; and finally cutting from the 1.5 inch mark down the length of the band to a point at the half width at the opposite end of the band. The Straight 105 bands were each made from one 10.5 inch strip. The half double bands were made from three 105 bands; each band was made by affixing half of a 10.5 inch strip to the middle of a full 10.5 inch strip. For the Double in this test, each band was made by placing two 10.5 inch strips back to back. Rubber band ties were used at the forks. Except for the chains, the pouches were attached with short sections of Chinese tubes.

On the table, note that the Double bands had the highest draw weight, but consistently under performed both the 64 Chain and the Half Double bands ... no matter what the weight of the projectile. So draw weight is clearly NOT a good indicator of performance.

Note also that the Double band rig was only marginally better than the single Tapered band rig until the heaviest projectile. With a projectile that heavy, the Tapered band just did not have the umph to move it, and the performance of the Tapered band dropped to that of the Straight band.

I did not make up a rig in which I doubled the cut tapered bands ... just ran out of time. Their draw weight would be less than the straight Double band rig, and I would be willing the bet the performance would be comparable or better.

Cheers ....... Charles


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## NightKnight (Dec 16, 2009)

Great thread Charles! I appreciate all the research you do, and I am sure others feel the same.


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## NaturalFork (Jan 21, 2010)

Nice speed from chains!

I think most people think higher poundage = faster because of bows. However in the bow world with the newer limb technology etc ... that isnt always the case these days either.


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## bullseyeben! (Apr 24, 2011)

Yes great post as always, Charles... I'm at work so gotta be brief.. I did some tests last night too, will post vid later... you may remember the other day I shot the ply board with .44 and 9mm, with 2layers tb blue, with only the .44 going clean through. Well last night I tried 1 layer tb gold cut only 10mm wide, at about 8".. and shot butterfly popped the 9mm clean through! .44 not a chance because it doesn't have the torque to accelerate heavier shots... so long draw does produce speed indeed, but is affected more dramaticly as the ammo weight increases...


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## notchent (Aug 4, 2011)

Thanks for all your work Charles







I'm really happy to see the chained 64s doing well, since I've been using a tiny version of chains on my mini BB shooter. If you get a moment to check out that setup with a BB, I'm really curious to know speed it generates. It's definitely time for me to get a Chrony...


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## Charles (Aug 26, 2010)

bullseyeben! said:


> Yes great post as always, Charles... I'm at work so gotta be brief.. I did some tests last night too, will post vid later... you may remember the other day I shot the ply board with .44 and 9mm, with 2layers tb blue, with only the .44 going clean through. Well last night I tried 1 layer tb gold cut only 10mm wide, at about 8".. and shot butterfly popped the 9mm clean through! .44 not a chance because it doesn't have the torque to accelerate heavier shots... so long draw does produce speed indeed, but is affected more dramaticly as the ammo weight increases...


Interesting ... I am sure the long draw would accelerate the .44 faster than the short draw would accelerate the .44. The moral of this story is that each given band configuration has a maximum mass of projectile which it can propel effectively. If you use a projectile that is too heavy for your bands, then the total energy and momentum will drop, relative to that of a lighter projectile. From my table above, you can see the same effect with the Tapered bands, going from .46 to .56 caliber. At .46, the Tapered band is doing a better job that a Straight band; but at .56, they are about equal, with the Straight band being marginally better. And you can really feel the difference when you shoot something too heavy for the bands ... everything is slow to get started, you feel like you want to sort of push it along somehow.

Cheers ...... Charles


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## Charles (Aug 26, 2010)

notchent said:


> Thanks for all your work Charles
> 
> 
> 
> ...


I really have had no interest in shooting BBs, but I thought I would give it a try since you asked.

I reduced my 64 chain to 1,1,1,2,2 from the pouch to the fork. Remember, each of those 64s is doubled over. The draw weight was 10 pounds. Here are the velocity results for steel:

3/8 ----- 186 fps
1/4 ----- 204 fps

I also tried .177, the traditional BB. But the results were very erratic. One problem is that I am using large pouches, suitable for stones. I think the BBs just bounced around too much during transit by the bands. Also, I think I was reaching the maximum velocity of those bands/pouch. The .177 BB just did not have enough resistance to the pouch, and the result was like dry firing. Hope this helps.

Cheers ....... Charles


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## bullseyeben! (Apr 24, 2011)

I reckon you said it there Charles my man....I could put a vid up now that's just baffled me again.. im testing ply against 9mm and ..... I don't think ill even go there lol,


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## bullseyeben! (Apr 24, 2011)

Ok well this sorta proves the point about weight and needing power to accelerate it... not shooting heavy stuff this time, just 9mm lead, the short double set up ****s all over the butterfly... reason being I think more width is needed on the long draw to accelerate... whilst the double bands although much shorter have the torque..


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## Ted (May 27, 2011)

Charles said:


> The half double bands were made from three 105 bands; each band was made by affixing half of a 10.5 inch strip to the middle of a full 10.5 inch strip.


Charles, in the half double bands, did you glue the half strip to the full strip? If so, what do you use as glue? Thanks.


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## notchent (Aug 4, 2011)

Charles said:


> Thanks for all your work Charles
> 
> 
> 
> ...


I really have had no interest in shooting BBs, but I thought I would give it a try since you asked.

I reduced my 64 chain to 1,1,1,2,2 from the pouch to the fork. Remember, each of those 64s is doubled over. The draw weight was 10 pounds. Here are the velocity results for steel:

3/8 ----- 186 fps
1/4 ----- 204 fps

I also tried .177, the traditional BB. But the results were very erratic. One problem is that I am using large pouches, suitable for stones. I think the BBs just bounced around too much during transit by the bands. Also, I think I was reaching the maximum velocity of those bands/pouch. The .177 BB just did not have enough resistance to the pouch, and the result was like dry firing. Hope this helps.

Cheers ....... Charles
[/quote]

Thank you so much Charles! My initial guess was that the BB setup got somewhere around 230 fps, with ~4.5 lb pull. Based on your results, I think that may be in the right ball park.


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## whipcrackdeadbunny (May 22, 2010)

Great stuff Chuck, thanks.


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## Charles (Aug 26, 2010)

Ted said:


> The half double bands were made from three 105 bands; each band was made by affixing half of a 10.5 inch strip to the middle of a full 10.5 inch strip.


Charles, in the half double bands, did you glue the half strip to the full strip? If so, what do you use as glue? Thanks.
[/quote]

No, I did not use any glue, just short lengths cut from small diameter Chinese tubes. I discussed the method in the following thread:

http://slingshotforum.com/topic/10994-taper-by-partial-doubling/

And here is the photo. The half doubled rig is in the middle.










By the way, the doubled bands I used for the tests in this thread were doubled in the usual way, not chained together as in the photo above ... but the performance seemed to be virtually the same.

Cheers ........ Charles


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## Jacktrevally (Feb 14, 2011)

Charles, the zen pfs, is tat cut from a wooden spoon\ spatula? Looks cool, like it


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## Charles (Aug 26, 2010)

Jacktrevally said:


> Charles, the zen pfs, is tat cut from a wooden spoon\ spatula? Looks cool, like it


Thanks for the kind words. Yep, the Zen PFS was cut from a laminated bamboo spatula that I found in a second hand store ... I seem to remember it was less than $1. It just looked too cool to pass up. It is a bit thicker than many I have found, so it sits well in my hand.

Cheers ....... Charles


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## Charles (Aug 26, 2010)

Well, I cut four tapered 105s today and made up a rig with doubled tapered bands. I have updated my table from above with the new data on the double tapered.









The Tapered Doubled had a draw weight of 9 pounds, which was not too bad. You can see that its performance was almost the same as the Half Double bands, but at significantly less draw weight. The Tapered Doubled will probably be safer in case of band failure, as it is unlikely that both members of a given side would fail at once. It is interesting to note that the Tapered Doubled maintained performance, even with the heaviest ammo. Unless band life is singnificantly shorter for the Tapered Doubled, it looks to me like a clear preference of all these arrangements. I suppose that if one were going to stick to target shooting with 3/8 inch steel or lighter, then the single Tapered band might be preferred because of its very light draw weight.

Cheers ........ Charles


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## Jacktrevally (Feb 14, 2011)

That you very much. Cleared my doubts.


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