Roller spearguns

    Quote

    George, are you insinuating that I have an ulterior motive with this thread? Do you seriously think I can't sell roller guns and muzzles if I chose to? Do you have a problem with the business of sale and manufacturing of diving/spearfishing gear in general?


    Lets make this painfully clear. The idea that just because of a pulley a speargun becomes more powerful is STUPID. It will not be the first nor last time people accept something without seriously questioning it. But if after being explained in detail they still stick to their erroneous belief, that makes them stupid. Chuckd prefers to use a roller, he enjoys it and I celebrate that, I would not down talk his choice of a fish taking tool. But he knows it's not more powerful than a conventional speargun of the same length and would not promote that idea. What I do have a problem with is stupidity.


    Dan that's crazy talk, and pretty confused as to you saying that. .. a shit load of my gear is gear I happily bought from you as you well know. But if I have a problem with a piece of equipment from you I will without hesitation bring it up here, and I trust that the conversation would not be censored like on spear board. I am only active on this site out of the many available, the reason being the lack of a draconian overlord and great members. I did not like the way you spoke to Seal as the owner of this site, it smacked of censorship of another members valid opinion. Let me be clear that I respect your experience and opinions, don't agree with some of them but that's okay with you right? I am no nodding fool, may be wrong about my stance on certain things but I am willing to learn [emoji4]

    A bad day at sea is better than a good day in the boatyard
    George Steele

    Censorship is not permitting someone to speak. I've done nothing of the sort here because there's no content that needs to be censored. It would've been easy for you to leave it at: I don't like what you said Dan. But to be "disturbed" because I said someone is confused and adding the spiel about politics and motives seemed to imply more. While running this forum does put me in a position of greater responsibility/accountability about what I say, I'm still just a person who likes spearfishing and gear, and I'm not going to kill myself holding my tongue.

    I have been following this thread and I see a lot of theory being suggested. There is one sure way to answer this question. Shoot comparable guns over a chronograph. If a roller gun will propel a shaft of the same mass with a faster muzzle velocity than a non-roller gun then it is more effective. If it does not, then it is not. There has been a lot of research done in archery regarding power curves in compound bows. The actual science gets pretty complicated. Still, the only way to increase the power of a bow is to propel an arrow of the same mass faster. I would have to see the chronograph numbers to believe that adding rollers and increasing the power stroke by a few inches without also increasing the pull weight of the bands would make any difference.


    Whether they are more accurate/easier to be accurate with is a completely different question and mostly times comes down to personal preference.


    Just my 2 cents.


    Dennis


    Do you have a chronograph we can use? Not trying to be rude, I really would like to use one. That would give you a definitive answer as to velocity differences but you would still need to know the forces applied to the shaft to know which was more efficient/powerful.


    It would be possible to build a scale and us a go pro with a very high frame rate to calculate the velocities more precisely than Chucks video. Not as good as a chrono but it works.

    You don't need a chronograph. You can use a Gopro or any waterproof digital microphone. Edit the resulting sound file in any free sound editor, and you will see the precise time between the two peaks of the trigger releasing and the spear hitting the target.

    At the risk of stating the obvious this is all a rollergun is, a shortened version of the same gun with the front end lopped off and the slack band wound under the barrel. The conventional gun has one band, the diagram just shows it before and after cocking. A rollergun of the same length as the conventional gun is using longer bands than would fit on the conventional gun when cocked and any comparisons need to take this aspect into account.

    I dont think the sound from videos is verry precise method to measure the speed,but please somebody who is good with editors mesure this.I can try do it but obviously my conclusions have no big value.
    These are four serial shots folowing each other.The target is same building foam from the test that was posted priviously.Just to say that my smallest double roller 80 has the same penetration=power like the 120 Denton.I have a video wich prooves that but obviously the video evidences are not good enough for some people to belive.
    May be some people have allready seen these videos with the 130:
    https://www.youtube.com/watch?v=9LtktOdlMCY
    https://www.youtube.com/watch?v=dYEutW2bm-4
    https://www.youtube.com/watch?v=Iiquq06jJJs
    https://www.youtube.com/watch?v=9iMZmf4z0gQ

    Edited once, last by seal ().

    Roller
    2x22" bands plus 2x2" wishbones
    42" top from notch to roller
    30" bottom hook to roller
    So 22" elongated to 70" = 318%
    Force x 2 pulled over 42" length
    Therefore, 84" of pull.


    MGS
    2x26" bands with 3" wishbones
    40" and 43"
    So 13" elongated to 39" and 42" = 300% and 320%
    14" relaxed
    Force pulled over 26"(band 1) x 2, and 29"(band 2) x 2.
    Therefore, 110" of pull.


    caveat: the second band on a double banded gun doesn't double the power

    [VIMEO]39516657[/VIMEO]



    Here's my roller gun in action. Some shots are with a partial bottom load for less power.


    Sorry I guess I'm missing some thing. Where did 2 pulled over 42" come from? 70-22 is 48 so wouldn't it be 96" of pull? Just trying to follow thanks.

    Quote from Treebilly3

    Sorry I guess I'm missing some thing. Where did 2 pulled over 42" come from? 70-22 is 48 so wouldn't it be 96" of pull? Just trying to follow thanks.


    The bands only pull the shaft from the shark fin tab while loaded to the Roller, or to the relaxed length of the bands in a normal gun.


    The roller allows the bands to pull all the way to the roller with good force due to the preload.


    C

    Why does everyone keep saying that penetration doesn't prove anything? Let's get some video of a properly balanced and powered up conventional gun side by side with a comparable roller in regards to length, bands, etc. And have them both shoot through a nice foam target from 5 & 6 meters away. Screw the chronograph, we're not clocking baseballs here. Out in the field on the hunt penetration with a flat trajectory is KING, period. And best of all, this would be a simple test to do.


    This guy seemed to nail it here:


    http://www.youtube.com/watch?v=dSxIDUdjv8Q


    http://www.youtube.com/watch?v=L6AfkBMwRIg



    And then we can all get back to shooting fish :thumbsup2: Keep the peace :D

    Relax & Go Spearfishing

    I am in Orange Beach AL. If there is someone close by with a roller gun we can shoot it over a chronograph. And the chrono is conclusive. If you have two projectiles of the same mass and form (spears), the one that has the fastest muzzle velocity will have the most energy. This equals flatter trajectory and more penetration. Penetration comes from momentum, or the remaining energy when it reaches the target. If you want to prove it to yourself, go to any ballistics program, select a bullet, then run the program with two different muzzle velocities using the same projectile. The one with the higher muzzle velocity will shoot flatter and retain more energy downrange. Whether you are shooting bullets, arrows or spears the science that predicts performance is called ballistics and is a function of the mass and form of the projectile and the amount of energy that is used to launch the projectile.


    No matter which method you use to test the theory, (chronograph, Go-Pro, or penetration test) you need to make sure the butt end of the guns are supported in a manner (such as against the pool wall, perhaps with a foam cushion between the gun and wall) so that differences in recoil due to differences in the mass of the guns will not affect the results.


    If the roller guns provide a smoother power curve and deliver less recoil, they may seem more accurate to some users for that reason. I think this is one of those - "If it floats your boat, then use it!" scenarios. Personally, I like to keep it simple so I will continue using a conventional style. If you like the roller guns, then that is good.


    Dennis


    Congrats for being the most level headed person in this discussion. We have a member MIGHTYKC in your area, but I'm not sure if he has any rollerguns. He may though, if I recall correctly he has a lot of different spearguns.

    Scupper Pro Gives You Wings!


    Honestly not quite what I was expecting. Im still curious as to the force being produced by the bands. It would seem that as Pete stated the double banded conventional gun is producing much more force than the single banded roller. I don't think it is quite double but it may in fact be pretty close. Chuck, just from feel how would you compare loading the one roller band to loading one of the conventional bands?


    Chase. It's not that penetration tests aren't useful. The problem is there are a lot of variables that influence penetration. Tip shape, sharpness, mass, roughness, variations in density of the target material, angle of penetration and others. If you could control enough of these or take enough test shots that the error is minimized you could get useful information from penetration. It's just a lot more work than simply measuring the velocity.

    Dennis
    are you talking about a Shooting Chrony type chronograph?
    I ask because these choreographs run under $100 and if some one was willing to shoot there guns(with out line) above water it will still show what we need.

    My conclusions:


    A single banded roller gun will generate a force on the shaft slightly less than an identical 2 banded gun. And it's very close. (You can't increase the length of pull without lengthening the gun or adding bands in parallel. You can thicken or shorten bands to gain more power, but that goes for either configuration)


    A roller gun has slightly less recoil and significantly less muzzle flip than a 2 banded gun. Therefore it is more accurate. (And obviously some guns have less muzzle flip than others)


    Roller guns should have enclosed tracks and thicker shafts to take advantage of the higher forces without getting shaft whip.


    Loading time of a double action roller is the same as a double banded gun.


    Roller guns are not good for scuba freeshafting. Too long to reload compared to a single banded scuba gun.


    Charlie

    Quote from dsculley

    And the chrono is conclusive. If you have two projectiles of the same mass and form (spears), the one that has the fastest muzzle velocity will have the most energy. This equals flatter trajectory and more penetration. Penetration comes from momentum, or the remaining energy when it reaches the target. If you want to prove it to yourself, go to any ballistics program, select a bullet, then run the program with two different muzzle velocities using the same projectile. The one with the higher muzzle velocity will shoot flatter and retain more energy downrange. Whether you are shooting bullets, arrows or spears the science that predicts performance is called ballistics and is a function of the mass and form of the projectile and the amount of energy that is used to launch the projectile.


    No matter which method you use to test the theory, (chronograph, Go-Pro, or penetration test) you need to make sure the butt end of the guns are supported in a manner (such as against the pool wall, perhaps with a foam cushion between the gun and wall) so that differences in recoil due to differences in the mass of the guns will not affect the results.


    Dennis


    It is THIS ^^^ simple. I've been saying THIS ^^^ for YEARS.
    No magic, no opinions, no bs
    FINALLY someone else got it right :fanwave:
    Thanks dsculley for making this solution so clear that even a seal :laughing: could understand.

    SPEARFISHING and RECREATIONAL FISHING NEEDS THE NRA
    Spearfishing Store

    Edited 4 times, last by hau ().

    Quote from hau

    It is THIS ^^^ simple. I've been saying THIS ^^^ for YEARS.
    No magic, no opinions, no bs
    FINALLY someone else got it right :fanwave:
    Thanks dsculley for making this solution so clear that even a seal :laughing: could understand.


    It's not entirely true. A long thin flexible spear with a flopper is slightly more complex than a bullet.


    And I've seen guns so overpowered that the shaft comes out oscillating severely which significantly affected it's rate of decrease in velocity.


    You can simply set up a grid and do a frame by frame on a video as the shaft leaves to gun to calculate velocity at that point. That's the number we are all looking for. And looking at my video in slow motion, it's very close between my two guns. And that's comparing apples to apples. Same length gun, identical shafts, same band thickness.


    C

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