Roller spearguns

I have almost two years without fishing ..... and I think I am not qualified to talk about fishing equipment .....

I would test a roller to have a certain impression, try a kit my marlin 85.

I read many opinions of advantages of roller (size, maneuverability and power) These comments remind me just how excellent are the pneumatic spearguns and now much more with new models.

I think Dan makes an interesting challenge, I would pay just to prove the theory and pratctica.

Tengo casi 2 años sin pescar..... creo ya no estoy calificado para hablar de material de pesca.....

Me gustaría probar un roller para tener una impresión cierta, probar con un kit mi marlin 85.

Leo muchas opiniones de ventajas del roller ( tamaño, maniobrabilidad y potencia), Estos comentarios solo me recuerdan lo excelentes que son los spearguns neumáticos y ahora mucho mas con los modelos nuevos.

Creo que Dan hace un reto interesante, yo pagaría solo para demostrar la teoría y la práctica.

José

Quote from Wishihadgills

From my understanding of the physics, all of the advantages of a roller gun come from where the top band stops applying force.

On a classic configuration the bands no longer produce force once they have reached their relaxed size. On a gun with 100 cm from band hole to mech this is somewhere between 20 and 30 cm from the band holes. From this point forward the spear is no longer accelerating.

On a roller gun the band pulls all the way to the tip of the gun. This provides two advantages. First, if comparable bands are used in both guns then the shaft from the roller gun will leave the speargun at a higher velocity. Assuming the mass of the spears is the same this will give it more kinetic energy/momentum and will lead to better penetration (also assuming the tips of the spears are identical).

The second advantage of the longer band stretch is the recoil. One way to look at recoil is wight the impulse momentum theorem. F = (Change in Momentum/Change in time). Because the spear is accelerated over a larger period of time the felt force is smaller. This is why guns rigged with 3/4" bands are described as "punchy" or "snappy" The band produces a large amount of force in a very short time. Guns with short thinner bands are often described as having a much smoother recoil.

Personally I think rollers have their purpose but are not necessarily for everything/everyone. They make sense for blue water where you aren't taking a lot of shots and reloading a bunch and the shorter length is helpful for maneuverability. They are also good for holes as mentioned. Perhaps their best use is in really dirty water shooting big fish. When you can't see more than a few feet having a 120 just isn't practical but you still need the power to penetrate a large fish like a striped bass. For SFL with clear water and constantly hoping in and out of boats I don't want to deal with the reloading process so I don't use them.

Just my .02

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Pneumatic guns have all the features mentioned and then some more.........

Quote from Dan

For grossetti and others who may be having difficulty visualizing why a "single" band roller is the same as a two band conventional speargun, I made this animation highlighting the bands with a red line. Clearer than this I really can't make it so I'll just sit back at this point.

Thanks Dan, I think we may not have the definition of what makes makes up a single or double banded speargun. From your image I take it that for you the fact that the roller has one rubber on one side and another on the other side that makes it equivalent to a double. If that case, a single band euro gun is also a double, as it has one rubber on one side and another on the other side. If you look at a roller gun, it is just a standard single euro with longer rubbers. Since they are longer but the body of the gun is not, they are wrapped around using a pulley (to reduce friction). If you were to elongate the body of the speargun, your roller gun would effectively be a simple (albeit long) euro gun.

For me a double sling refers to the number attache points (wishbones) on the spear (e.g. in parallel).

I would also like to point out that a dual band or even single band (using my definition) speargun has each of it's pairs of rubbers supply 100% of their energy, in a roller gun this is not the case, the band still has stored energy after the shot (i.e. it is still stretched). So you cannot even say since it is 2x longer it is like having two bands.

That is why I believe the comparison is wrong. In your setup the dual band will be more powerful, I believe, simply because you are comparing different things.

The only way to be sure is to calculate the physics of it anyways, I will try to find some time to do it.

Would it not be correct to say that a single band roller gun has the equivalent power of equal length standard single band gun plus the extra cm band stretch your achieving with the roller set up? I only have the most basic understanding of roller guns but it seems that simple. More powerful than a single band gun of the same size but not as powerful as a same sized double band gun.

Wasn't there was a massive thread on the forum about rollers which was full of graphs and maths and tests? I can't find it unfortunately, but I remember seeing it and thinking I should spend some time trying to understand it at some point. It was about 12 months ago from memory.

Quote from grossetti

From your image I take it that for you the fact that the roller has one rubber on one side and another on the other side that makes it equivalent to a double. If that case, a single band euro gun is also a double, as it has one rubber on one side and another on the other side. If you look at a roller gun, it is just a standard single euro with longer rubbers.

I think he is referring to the fact that the roller has the rubber running under the gun and then again on top of the gun as well. That would be the logic in comparing it to a double banded gun. I don't see a fair comparison in regards to a single banded euro and a single banded roller. MJK used a rob allen roller, single banded, and the shaft passed all of the way through the YF Tuna, which weighed over a hundred pounds. Just the mass of that fish would eliminate the comparison to a single banded euro because I do not think that would have been possible had he used one. It would've stuck the fish no doubt, but certainly wouldn't have passed completely through the fish putting the fish on the shooting line.

Just my .02,

Chase

Live action

http://www.youtube.com/watch?v=Suykab-3o-g

A single pulley merely changes the direction of the force, nothing more, 50 lbs force on one side transfers 50 lbs on the other side.

I agree the anchorage is in a different place on a roller, but if you make the barrel longer, keep the roller head, tie two strong lines (one for each side) to the bottom anchorage system and the other side of the lines to the ends of the rubbers, in such a way that the line wraps around the pulley and the rubber's en sits just after it. You still have the same power transferred to the spear as before, nothing has changed in that perspective.

I over simplified it in reality because as mentioned in my previous post on a roller not all of the rubber's force is transferred to the spear, but you should get the idea.

I'm always answering from my mobile so I can't draw it for you.

I would like to remind you that to make a speargun more powerful (I'm simplifying it a bit) you must either tweak the rubber (get a thicker one or shorten it, use a smaller ID, etc), use a longer tube or add rubbers in parallel. The roller is a variant of the longer tube with a tweak (wrap the rubber around so you don't have to have a longer tube). I don't see why this is so difficult to understand, it is not magic.

There is some diferent roller sistems around, not just "the roller" I had tried some of them, single, double, triple, inverse, multi. A good wooden design is far better than a kit convertion. And with an eclosed track even better.

Other thing in a good design you can set several power configurations with the same band with the anchorings on the bottom.

Example of :

http://i59.tinypic.com/2a9zgnk.jpg

http://i60.tinypic.com/2rr1noj.jpg

Dan I think grossetti and I have both described how a roller gun has potential to be more powerful in a shorter package. Whether they are or not is going to be a function of the band combination used. This is true of any band gun. I can make a my riffe more powerful than yours if I put heavier(more) bands on it. If we take that to the limit, and put the heaviest bands that can be loaded by the user the roller gun will have more power because it can apply the force for longer. That is physics plain and simple. But I also agree that they are not always (maybe not even usually) the best option but they do have their advantages.

Like someone mentioned their advantages are similar to this of pneumatics which are also more powerful than an equivalent length band gun. Pneumatics also have their own problems but thats another discussion.

Chase I think you are misunderstanding the term "shoot slower." Because they accelerate the shaft with a smaller force for a longer distance it takes longer from the time the trigger is pulled until the shaft is no longer in contact with the bands. It feels slow but this does not reflect on the final velocity of the shaft when it leaves the gun. The addition of the single band speeds up this process but still allows the roller band to apply force over the last tip of the gun.

Ok. This may take awhile but I'm onboard with this experiment...and I'll keep an open mind. Even though I have now hunted with my shortened roller and am convinced of the desired performance characteristics of a shorter gun (140 cut to 110), and have noticed the reduced recoil and muzzle lift that would be comparable to smaller diameter bands, I will convert and re-rig two of my guns. I will convert my former go-to Hawaiian teak gun with enclosed track to a roller after taking a series of shots in its current configuration. I'll post the dimensions and set up with the results. I've ordered a Meandros Roller DIY for wood guns and will install on the same gun then put it through another series of shots. I'll film both. Then I will do the same with my Aimrite 110 roller. I'll reinstall the original muzzle and stock band configuration.

Like I said this will take me awhile so if you don't hear from me for a while, just be patient. My life is rather busy but I'm up to the challenge and I also would like to know the comparisons. Oh yeah, if anyone wants to contribute that amazing small ID Speardiver rubber for bands feel free to send em my way. Perhaps this can be a sponsored event? :laughing:

Aloha,
Makoa

I'll post the length on Thursday. I'm traveling right now...Fort Meyers tonight, LA tomorrow.

The basic difference is the same as applying two springs in series (roller) instead of two springs in parallel (two band gun).
Series and parallel springs - Wikipedia, the free encyclopedia


What Dan is basically saying is that the potential energy captured by the two bands is the same for two bands in series or parallel if the strain is the same, which checks out with physics if we assume rubber is a linear spring. If we convert potential energy into kinetic energy don't we then get the same speed?
As the rubbers on a roller are in series you need less force to get the same strain than the same two rubbers in parallel. If the limiting factor on loading is arm strength you could theoretically apply more strain to the rubbers, have more stored energy and get a higher speed on firing. But that assumes that you load the two rubbers in parallel together. Because we load the two bands one at a time I would have to do the maths which is all getting to hard so I'm going back to my single rubber pipe gun.