My rollergun setup!

[lawstraljan16]

Hey guys. I just got myself a Alemanni rollerhead kit for my 95cm Beuchat Marlin Elite and am about to set it up.

I was talking to argueably the best spearo in my country (said by locals) and he offered to help me achieve the best performance out of the rollergun.
I am about to meet him tonight and see how it goes.

So far what I do know is he said that a 7mm spear is needed, and 14mm bands (not sure about stretch %).

He will be showing me how to tie the best knots, and types of dyneema's, monoline etc that creates the least drag.

He said with a 85cm gun using this setup he was able to hit constant bullseye shots from a 4m distance.

Obviously a lot of tinkering is needed to achieve the best performance (trial snd error); but

My main concern is that I kind of see 14mm bands to be weak for a 7mm spear, but I guess I'll have to check it out.

Also the bands he has is of a certain quality which he gets from sponsors overseas, so maybe that'll be the big difference in performance.

What do you guys think?

I will be trying his setup no doubt, because I am more than certain he has far more experience than me in everyway possible, as I said he is known about by almost all pro and rookie spearos in the country.

Just trying to make a discussion, so discuss playing around with setups is one of the reasons why I love spearing, people think it's easy but it's not, that is if you want perfection ofcourse!

 

[Scoobaru]

Sounds very interesting and I will be following this post closely, as I love the concept of roller guns. From what I've read 14mm bands are An ideal size to use. The conventional spearguns only use about 70-80% stretch rates in the rubbers because they are slack before being pulled down the length of the gun. Whereas a rollergun the bands are already pre-tensioned, or rigged in such a way they are under tension for most of the length of the barrel. so then you are utilising the full length of the gun

Eg for an 85cm conventional gun (using a stretch ratio of 70%)
75% x 85cm= 59.5cm so the rubbers will only be under tension for 59.5cm of an 85cm barrel

But if for example a rollergun uses a 95% stretch rate
95% x 85cm= 80.75cm.

This is where the extra power comes from, resulting in a greater shooting distance. But because you are using more power than a conventional setup you require a thicker spear to stop it bowing when the gun is loaded. Rollerguns are more accurate because the momentum of the rubbers heading along the barrel, and then in a downward motion under the muzzle counteracts the recoil of the gun.

The above figures are just guesses, to try and explain the principle of rollerguns from what I've read. I have never owned a roller gun and am not an expert. So if anyone has accurate stretch percentages based on credible scientific experiments I would be interested in seeing the figures. I hope this helps you a bit with your questions regarding rollerguns

 

[lawstraljan16]

I've finished my first setup which I'm using 16mm bands set at 300% stretch, a 7mm spear and pre-load tension of about 20%. So far it's looking good, but I need to test it. I'll be trying the 14mm setup when i get ahold of these special but rare bands arrive (dont ask me what they are, I dont know yet).

I'm aiming for at least an accurate shot at the 5m range. So I'll be making some targets and will test it out ASAP and post my results here (including videos).

I'll also post a couple of pics of the gun soon

 

[lawstraljan16]

Trial and error is part of getting the maximum performance out of a roller. A lot of calculations and work to be done on it.

No use in having a rollergun if there are only minimal changes from a standard gun!

 

[lawstraljan16]

Rollerhead setup pic 1

 

[lawstraljan16]

Rollerhead setup pic 2

Videos of results will be posted next dive, which is hopefully tomorrow.