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Old 01-24-2018, 12:08 PM   #1
brandon cadalzo
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Another band calculator question ugggghh.....

Ok for the longest time if i wanted 380% stretch i would just divide by 3.8 and be done with it. I just went on spearitcos website to look at some stuff and saw they had a band length calculator. I thought it was cool except they donít give the relaxed length of the band as a value of 100% they count it as 0%. What is the right way of doing it??? Iím so freaking confused now. I want my bands stretched to 380%.


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Old 01-24-2018, 01:31 PM   #2
Tyson Brown
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Re: Another band calculator question ugggghh.....

I'm not a custom band maker, but I did engineering school...

If you want bands stretched TO 380%, I would say your relaxed length would be the stretched length divided by 3.8.

If you want bands stretched BY 380%, I would say your relaxed length would be the stretched length divided by 4.8.

My understanding as I've read about gun bands has always been that the 380% refers to the TOTAL length of the stretched band, and not just the INCREASE in length.

I'm with you - divide by 3.8. (Relaxed Length)*380% = (Stretched Length)

And now someone who knows can give a real opinion.
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Old 01-24-2018, 06:27 PM   #3
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Re: Another band calculator question ugggghh.....

There is a lot of info about 380%, which for any reason now seems to be the magic number...

I would cut them to 330% and then decide if I want to go to 380%. For me is excesive when bands are good quality and fresh. You can always cut a little more if you feel like doing it.
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Old 01-25-2018, 11:15 PM   #4
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Re: Another band calculator question ugggghh.....

You are way overthinking this unless you are planning on using heavy shafts. Measure the distance from band hole to loading tab ... multiply by 2 and then just divide by 3.6 (for 360%). That should be your starting cut as most people have no problems with 360% especially for small ID 14mm or 14.5mm bands. Bands tend to be difficult to load initially ... then they loosen up. If they feel uncomfortable then just make a slightly longer wishbone that you can later cut down and tighten as the bands loosen up. For 6.5mm to 7mm shafts ... you really don't gain much by going to more stretch as the shaft is way above Terminal Velocity using 360% on a good designed gun. Once you move to heavier shafts then you start to need more stretch and you will see an improvement in performance. For 8mm shafts you really are at the limit of the bands ability to push the shaft to Terminal Velocity even at 380% if you use only 2 bands ... but not worth putting a 3rd band as you don't gain that much more for the hassle. With 8.5mm shafts you should put on a 3rd band and maybe even go to 15mm small ID. Whatever extra band stretch you put on the 8.5mm shaft will be well used and will give you additional velocity as I think there is still room to grow to reach Terminal Velocity. 3 x 15mm small ID bands at 395% stretch is a really incredibly high performance setup and will crunch out some crazy velocities with incredibly flat shooting. The problem is not many people can load that and you really need to have a correctly designed gun and handle to be able to shoot that accurately.
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Old 01-26-2018, 03:12 PM   #5
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Re: Another band calculator question ugggghh.....

Spearq8: Haven't you found more difficult to load bands with longer wishbones? I did. Because when you pull, you tend to separate the bands and the wishbone becomes perpendicular to the shaft, making it more difficult to load in the sharkfin/notch. Besides, you loose band stretch.
This is with dyneema wishbones. With metal is the way you have described, but I think is not the case.

Now I use my wishbones as short as possible.
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Old 01-27-2018, 03:45 AM   #6
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Re: Another band calculator question ugggghh.....

Quote:
Originally Posted by Marco View Post
Spearq8: Haven't you found more difficult to load bands with longer wishbones? I did. Because when you pull, you tend to separate the bands and the wishbone becomes perpendicular to the shaft, making it more difficult to load in the sharkfin/notch. Besides, you loose band stretch.
This is with dyneema wishbones. With metal is the way you have described, but I think is not the case.

Now I use my wishbones as short as possible.
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Old 01-27-2018, 04:05 AM   #7
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Re: Another band calculator question ugggghh.....

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Originally Posted by spearq8 View Post
..........3 x 15mm small ID bands at 395% stretch is a really incredibly high performance setup and will crunch out some crazy velocities with incredibly flat shooting. The problem is not many people can load that and you really need to have a correctly designed gun and handle to be able to shoot that accurately.
370-380% comfortable max for me loading Benthic's grey/amber 14.9mm bands. Beyond that gets a bit too much like hard work [tho still a damn side easier than those hip-thrusting, ball-busting single short 3/4" bands of yore

looking forward to trying single 15.7mm Primeline @ 350% on 7mm x 140cm shaft dinner gun
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Old 01-27-2018, 09:56 PM   #8
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Re: Another band calculator question ugggghh.....

Quote:
Originally Posted by Marco View Post
Spearq8: Haven't you found more difficult to load bands with longer wishbones? I did. Because when you pull, you tend to separate the bands and the wishbone becomes perpendicular to the shaft, making it more difficult to load in the sharkfin/notch. Besides, you loose band stretch.
This is with dyneema wishbones. With metal is the way you have described, but I think is not the case.

Now I use my wishbones as short as possible.
Yes of course the shorter the better as you have no lost band stretch that is not working. But I sometimes make the wishbone about 2 or 3cm longer than my final size with new bands. Stiff spectra does pretty well in holding up and getting over a shark fin, but of course if you keep the wishbone too long it can get pretty difficult to get over a shark fin and you lose just way too much band stretch. I am always surprised when I see a gun from say Riffe that has the wishbones ridiculously long by default. That is just performance down the drain for no reason. You would be much better off having thinner and easier to load bands with shorter wishbones.

Metal wishbones are great and I always use them on a third band as it pulls the bands far to the sides and keeps your sight picture clean and neat. Being the last wishbone back ... even if it slips the shark fin it won't hurt your fingers. But of course that metal wishbone will smack into your front part of your gun and will nick it. Personally my guns are for hunting and I really don't mind a few nicks ... end of the season a little sanding and a coat of epoxy and it is good as new. But if you baby your gun and a scratch will break your heart, stick to the plastic inserts.
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Old 01-29-2018, 01:09 AM   #9
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Re: Another band calculator question ugggghh.....

spearq8 glad to see u back on the forum. I was inactive for a while but decided to come back and offer advice where I can/ learn from other more experienced spearos
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