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Old 09-13-2017, 09:51 PM   #1
fr0sty
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Shaft for short roller

I have an 80cm mako that I'm converting into a roller. I already have a 90 roller so was thinking about cutting the mako down to 70cm. I'm planning on using 14mm small ID bands that would utilize the full barrel length to ultimately be stretched to 350%.

Question I have is whether I should use just use the old 6.5mm 120cm shaft or if I should get a 7mm 110cm shaft? Or even a 6.5mm 110cm shaft?

I was reading some stuff that for rollers, it'd be better to have a shaft with higher mass to counteract the shorter spear. Other things I read were it's better to have a thinner shaft. Any new ideas or experience from your guns?
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Old 09-14-2017, 03:21 AM   #2
TVA
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Re: Shaft for short roller

What has been generally noted on standard roller guns is that the rubber contraction speed is highest right when the shaft is released and that as the shaft accelerates and the rubber slows down as it gets to the muzzle, the wishbone is actually no longer in contact with the shaft even though the rubber is still contracting and the shaft hasn't fully left the gun yet. That's wasted energy. A way to somewhat counteract this is to use a heavier shaft that requires more energy to accelerate, meaning it will stay in contact with the wishbone longer and absorb more of the energy that the bands have to give. It's a balancing act as you want the shaft heavy enough to absorb what it can, but not so heavy that it's too slow. It your case I'd run the 7mil and up your stretch ratio to 380% - 400%. Also, make sure that shaft has a loading tab or dog house closer to the middle to attach the mono to. That makes a difference as well.
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Old 09-14-2017, 07:48 AM   #3
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Re: Shaft for short roller

Interesting. Any reason as to why to 380-400%? Also, what kind of difference would attaching the mono to the middle versus the end have?
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Old 09-14-2017, 08:44 AM   #4
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Re: Shaft for short roller

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Originally Posted by fr0sty View Post
Interesting. Any reason as to why to 380-400%? Also, what kind of difference would attaching the mono to the middle versus the end have?
With these small ID 14mm rubbers the optimal performance seems to be around 380-400%. The mid point connection on the shaft will both help prevent the mono from getting pinched by the wishbone and affect the flight of the shaft less.
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Old 09-14-2017, 08:51 AM   #5
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Re: Shaft for short roller

380-400%? really? I thought it was 350-360%, that's what I've been using/tying. I thought it was already more than the 300% for normal ID bands.
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Old 09-14-2017, 09:05 AM   #6
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Re: Shaft for short roller

I tied my 16mm small id band on my roller at 350% and the 14mm small id bands on my other roller at 370% and I have noodle arms. It isn't as hard as you think.

I tried a 20mm on my hole gun at 350% once. That gun went back to the dual reg id 16mm's at 350% after that dive.
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Old 09-15-2017, 04:44 AM   #7
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Re: Shaft for short roller

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380-400%? really? I thought it was 350-360%, that's what I've been using/tying. I thought it was already more than the 300% for normal ID bands.
For the past couple years I've been using Primeline small ID exclusively. Batches have varied from 14mm to nearly 15mm, but I've always run it between 380 and 400%. Still easy to load and the smoothness with power can't be beat. On a small roller like you're describing even with the bands at 400% they'll be easy to reach/load so there's no reason not to get all the performance you can out of it. How are you going to be securing the bands on the bottom of the gun?
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Old 09-15-2017, 07:44 AM   #8
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Re: Shaft for short roller

Quote:
Originally Posted by fr0sty View Post
I have an 80cm mako that I'm converting into a roller. I already have a 90 roller so was thinking about cutting the mako down to 70cm. I'm planning on using 14mm small ID bands that would utilize the full barrel length to ultimately be stretched to 350%.



Question I have is whether I should use just use the old 6.5mm 120cm shaft or if I should get a 7mm 110cm shaft? Or even a 6.5mm 110cm shaft?



I was reading some stuff that for rollers, it'd be better to have a shaft with higher mass to counteract the shorter spear. Other things I read were it's better to have a thinner shaft. Any new ideas or experience from your guns?


Your not going to get shaft whip with that short of shaft 6.5 in 110cm will be perfect


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Old 09-15-2017, 10:38 AM   #9
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Re: Shaft for short roller

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How are you going to be securing the bands on the bottom of the gun?
I'm going to install two pegs (https://www.mvd-retail.gr/index.php/...ks-pair-detail) on the sides by the handle and then when I head out, will pull the bands to it to get pretension before actually loading the gun.
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Old 09-15-2017, 05:40 PM   #10
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Re: Shaft for short roller

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Originally Posted by fr0sty View Post
I'm going to install two pegs (https://www.mvd-retail.gr/index.php/...ks-pair-detail) on the sides by the handle and then when I head out, will pull the bands to it to get pretension before actually loading the gun.
Sounds good. You want to anchor the bands as far back as is practical. A big part of the reason that rollers have more power per band than a traditional setup is that the pair of bands that make up a single roller band (sides if you will) are generally longer than the looped band of a traditional setup. More rubber stretched to the same percentage means more stored potential energy. Anchoring them as far back as possible will allow you to make them as long as possible while still hitting your target stretch percentage.
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Old 09-16-2017, 04:11 AM   #11
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Re: Shaft for short roller

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Your not going to get shaft whip with that short of shaft 6.5 in 110cm will be perfect


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+1 ... even up to 135cm length shaft, you will not get shaft whip on a 6.5mm shaft unless it is a slotted shaft or made of very soft metal. Lack of shaft stability on exit does not necessarily have to mean shaft whip.
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Old 09-19-2017, 08:36 AM   #12
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Re: Shaft for short roller

Good to know. What's the harm is using a shaft with a longer overhang (i.e., the 120 vs buying a 110)? Just the aiming is a bit different? Or is it because it basically defeats the purpose of cutting the gun shorter but still having a long shaft?
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Old 09-19-2017, 12:29 PM   #13
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Re: Shaft for short roller

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Or is it because it basically defeats the purpose of cutting the gun shorter but still having a long shaft?
That, plus the possibility of ballasting issues (i.e. making the gun too nose heavy), and if you go way too long in a thin shaft it becomes much too noodley. It's best to build/select your gun around the shaft you want to use, not the other way around.
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