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Double rollers: are they good? Red Tide double roller. can you shoot by loading half of the shaft? is double roller more range then single roller?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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I'm sure other people will chime in, but I'll give my opinion to help bump this.
First off, that's a nice looking gun! I like the integration of the rollers.
As far as if they're any good or not, as long as the bands are powered appropriately (assuming gun components give no issues) to the shaft size, it should shoot fine. My main concern would be making sure you're not over powering the shaft.

By shooting half the shaft, do you mean loading on the rest tab only, or shooting only one band? Regardless, the answer would be yes, with the exception of trying to load two wishbones on the rest tab. I wouldn't do that. But loading one band on the rest tab only wouldn't really shoot well. And if you're loading only one band, completely, it may not be very effective, unless you're just trying to shoot something point blank.

As far as range, I think a properly setup single roller can have just as much range as a double roller.
 
Guns with multiple bands are about splitting the loading effort, not bumping up the shooting range. Ideally the completely banded up gun shoots the spear at the maximum stable velocity out of the gun. Too much power into the shaft and it will flex in the gun and bounce off part of the gun structure sending the shaft off course. The downside of splitting the loading effort is the gun takes longer to load. Shooting the gun with it only partially loaded will reduce the speed out of the gun and the range of the shot, with the shaft falling earlier in its flight.
 
Reactions: Mr. X
With original guns to lesson power you crimped the rubber mid way with your hand. Haven’t tried that with rollers and don’t think it would work And I wouldn’t try it with a tabbed shaft. Instead I run a slightly longer line that connects the two rubbers near the handle. If you spot a cray or need to de power, slacken off the line. I use a quick release half hitch. It never comes undone unless you pull the tag end. Works a treat.
 
Andrew the fish said:
aha, “properly setup”, what if we have properly set up double roller then?
Click to expand...
My statement was assuming a properly setup double roller. As Pete mentioned above, it's about splitting the load, not increasing the range. If someone wants a thicker shaft for bigger game, then a double roller might be a better option as loading a single band to make the thicker shaft shoot at max stable velocity might be quite a task.
 
musubi said:
As far as range, I think a properly setup single roller can have just as much range as a double roller.
Click to expand...

I don’t understand what you are talking about. Define your version of “properly setup” then. I am imagining a roller with single band, with band stretch at max, and thickness just about manageable to load. This is what I would call a “properly setup single roller”.

Now, assume the barrel is sturdy, and shaft is thick, and trigger mech is plenty strong. Adding one more band will increase the shaft energy.

What Pete has mentioned, is the situation when increasing the band thickness is not possible. Refer to my version of “properly setup” roller with maxed-out band thickness, say, 16mm. We split the load into two 16mm bands rather than upping the thickness to some monster 22mm, and this is how we split the load. We might go with two14mm bands, which would be even more comfortable to load, and still get an increase in range, over our original single roller.
 
Properly setup would be where a gun is equipped with a shaft and appropriate band(s) for the shaft as to not over power the shaft nor cause excessive recoil such that the gun or the user can't handle, but provides adequate power for the fish being hunted.

Pete can speak for himself, but I believe he was referring to any multiple banded gun, regardless if the person used a band thicknesses that were possible or not.
 
Yes, that is right,

A given spear can only be driven so fast on an open track gun before it buckles on the way out, so there is an upper limit to how much energy can be applied to it by the gun and still be shooting straight. That energy can be provided by one band or multiple bands, the latter splitting the loading effort. Practically bands only get so large in diameter, so then you need at least two as few could load a single band with a 200 pound plus pull. Efficiency falls off with extra wishbones and band mass dragging through the water, but this can be offset by slightly stronger bands making up for it, however the same energy ends up in the shaft. To drive the shaft past this limit you can use a closed track gun, but this in turn gobbles up energy through extra friction in the closed track, so more band power is needed as you are throwing some away, but the spear energy goes up. Guns operating like this are often in an area of diminishing returns, more and more band energy is needed to gain just a little bit more at the shaft and the gun takes a long time to reload.

Spears can be driven at greater velocity out of tail end drive, closed track guns like hydropneumatics because a loading pump splits the loading effort, but these guns are nowhere as versatile to use as a band gun and take a long time to load. Pneumatics are similar, but limited by the loading effort, plus there is a danger you can bend the spear if you don’t push straight during muzzle loading. Usually this is done with one arm, you can use two, but you will be standing on something to do it and using a double-handed loader. If the spear gets away from you before latching then you are in big trouble.

All spearguns are limited by the drive length onto the shaft, a longer stock gun can drive the shaft for that much longer and a rollergun, like a pneumatic or hydropneumatic, can drive the shaft the full length of the gun stock, something a standard band gun cannot do. However the latter are the fastest guns to load and shoot, plus they enable a rapid change of busted bands, something that takes much longer on a rollergun. If you can toss one gun in the boat and grab another then that is not such a problem because you can always repair the first gun later after the dive.
 
Reactions: Mr. X
FYI somebody called something like coatesman has posted quite a good series on rollerguns on YouTube.

I think he sells muzzles for and/or with Rob Allen railguns. Pretty sure he featured double rollers on some/all his videos (perhaps as RA sell their own single rollers?).

He seemed to use mainly rollers these days. At least that's what he seems to recommend.

I think you can possibly load just one band or/and just load to the easier shark fin if you want less power. But I think double rollers are a bit extreme, perhaps best reserved for " Blue water" hunting?
And better to use something shorter and simpler for reef hunting.
 
Thanks everyone ofr the reply.
i think a 16mm band on a roller is a bit hard to load, which is why i was debating to use a double roller with 14mm bands.
In the end im going after pathos roller laser carbon 110 . its better for reef hunting
 
Reactions: Mr. X
two 14mm bands is what I am thinking too. Ease of loading makes hunting so much more pleasant.

About speed of re-loading, since we touched this subject, I have to say that for me, untangling the shaft line and locking the shaft in and wrapping the line takes the most time. Also taking care of fish, this could be a long minute. Single band or double makes hardly much difference, 10 seconds at most.
 
Reactions: Mr. X
I would think a 110cm single roller speargun would be powerful, even with 14mm bands.

Or try using a long (40cm?) loading aid (elastic loop, with hook and wishbone) with thicker bands?

I think my 95cm rollergun uses 16mm bands. I have a thicker loading grip loop built into the wishbone, which helps. I bought some spare bands specifically for it in a closing down sale but they are even thicker (19mm?); I would have much preferred 14mm bands . I was able to load it ok with 16mm bands but 14mm would have been easier and more pleasant. And probably still plenty powerful (?).
 
i just bought the pathos roller 110 speargun. the loading tabs it has in the bottom will help me a lot.
main reason is that in taiwan no one sells the loading assist, and i bought 2 from dive inn websit before. one came with really bad rubbers which seems that it was in the storeroom for a long time, first time use and it broke fell down to deep sea. I generally dont want to be dependent on load assist when i cant get them easily.
 
Reactions: Mr. X
Before I forget it is the jerk or rate of acceleration change that can buckle the shaft. A conventional gun with say four bands gives a big impulsive jerk to the shaft , and similarly to you holding the back end of it. What a rollergun does, and there are many different types so this is not universal, is that it applies the force for longer and lessens the jerk. All guns recoil, it is a fact of physics, it is how that recoil is felt that counts. The decrease in jerk or rate of acceleration is due to an energy absorber in a rollergun, i.e. the band going in a 180 degrees turn around the muzzle roller that sucks some energy out of the system. Cable rollerguns don't wrap their rubber bands, some do but we won't mention them here, but have to drag side pulleys through the water which act as brakes on the drive system. You can get a more manageable transfer of power to the shaft with a rollergun that has been carefully set up to optimise the band power to the shaft.

If you're shooting a ballasted tree trunk the sheer mass of the gun reduces recoil and you can just pile on the bands on what is a souped up standard gun with an enclosed track, but be prepared to take few shots, so make sure they count. The power is needed to slam shafts deep into the area behind the head, rather than long distance shooting. Gill plates are protection for the fish's means of obtaining oxygen and very hard to poke a hole in, the reason for their design.
 
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This is a diagram that I made for the basic rollergun energy diagrams thread, but it will serve here for the sake of explanation, If we ignore band soak, that is stretch a band, leave it and then the force falls slightly, or dangle a weight on it and it gets slightly longer. These graphs show the energy going into the bands. It will also be an indication of the energy on the way out, but does not take into account energy losses as the bands bend around rollers, dynamic effects in the rubber, etc.

Although not to push the analogy too far you can think of a multl-band standard gun as an artillery piece, a mighty bang and the projectile gets blasted out. A rollergun is more like a rocket, the thrust is developed over a time interval and not a split second, but of course it is all relative, we cannot see it visually. You can actually see this on the graphs for a standard gun versus a rollergun. The key is the slope of the energy graph, when it is steep you have to cope with a bigger jerk, when it is shallower the jerk is less. That is all there is to it. If you want to get technical we all know F = m x a, there is a constant in there but in the units used that constant is 1.0. If we take a differential with respect to time we get dF/dt = dm/dt x da/dt. The mass m does not change with time so that then becomes dF/dt = m x da/dt. Jerk is defined as da/dt and dF/dt is the slope on those green graphs, the final ones that is. Strictly speaking the x axis on these graphs is distance not time, but the time graphs will not be too different, governed by the contraction rates. For these comparisons we assume all guns use the same bands, they are just longer or shorter to fit the gun layout. Stretch characteristics are identical.

The key take away here is short of the seven band gun ballasted to be the mass of a blacksmith's anvil no one could shoot it, but pretty well anyone could shoot the Vela, if they could afford to buy it.

The diagram first appeared here: https://forums.deeperblue.com/threa...gy-storage-diagrams.107171/page-3#post-985014
 
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As a quick primer for those who are not familiar with such things in physics these are the definitions. For distance x and time t we have the following.

Velocity v is the first differential with respect to time t or dx/dt.

Acceleration a is the second differential of x and also dv/dt.

Jerk J is likewise the time differential of acceleration and is da/dt

Spearfishermen when they shoot their guns which are firing a projectile far heavier than any bullet will always experience recoil, but what they pick up most on is the Jerk delivered by the gun. Rollerguns are way less jerky weapons than multiple band guns, The Jerk can be minimized by dropping the acceleration due to the mass of the gun being greatly increased relative to the spear, that is what ballasted guns represent, but such guns are heavy to lug around even though they float. If we're stuck with a lower mass m then we can only try and reduce the acceleration change as we can brace against a certain level of acceleration, but not if it changes as in going up rapidly. All this happens very quickly, in the blink of an eye, but if we used a high frame rate camera we could see what was going on.

To check if your gun really has recoil, turn your wrist to shoot the gun at a right angle to your body and see what happens. I recommend that you don't do this as the gun will deliver you a big surprise and the shot could end up anywhere.
 
When I built my inverted roller, I calculated the Work my 2 banded gun did and tried to power my invert gun similarly as a start. I then started tinkering with increasing the power bit by bit. The main benefit of rollers is reduced recoil, period. The idea that a shorter roller gun = a longer standard banded gun has been passed around so much that lots of people in Hawaii just automatically think rollers are more powerful or can shoot farther. There are pros and cons for each setup and it's just a matter of what you're willing to accommodate. I'm just picky with things in general so I'm willing to deal with the complexity of the invert for the benefit of the most reduced recoil.
 
The explanation that I offered is the reason why, it is all about flattening the energy release curve out. However if you have a gun of reasonable mass and use the bands that don't overdo the propulsion then you don't need a rollergun. Virtually all my fish have been shot with standard guns, some rather big, and pneumatic guns, but then I am a two hand shooter and always have been.
 
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