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Pathos Laser Inverted Roller

Back2Narnia

Member
Jun 9, 2019
19
9
8
24
Germany
Hi Guys! I recently build a new speargun and i have some questions that i cant wrap my head around. I converted my Pathos Laser Roller 100 into an inverted roller. I changed the bands, the shaft and the trigger mech.
I "dry" fired it and shot a slowmotion video that showed the spear transforming into a spagetti and even turning sideways while still on the pipe of the speargun (alls parts worked as they should have). Sadly i do not have access to a pool.
So long story short: do you think the power will be fine in the water? And would an enclosed track fix this problem for good? Next logical step for me would be thicker shaft --> enclosed track.

20190609_133442.jpg
20190609_133740.jpg
20190609_133847.jpg

Bands:
2x17,5mm small ID Sigalsub 31cm long with 90cm band stretch (no pretention)
2x17,5mm small ID Sigalsub 21cm long with 72cm band stretch (no pretention)
2x 14,5mm small ID Sigalsub 34cm long with 90cm band stretch (1 cm pretention)
(kicker Band 14mm cut to 300% currently not installed)
--> Force should be halfed as i installed 2 Pulleys and the roller head.

Shaft:
7mm Sigalsub HRC (48-50) Shaft 130cm

Trigger:
Ermes Sub Double Roller


P.S. I know that most people like thier spearguns to follow KISS...but i wanted to try something differend with this build.
 

Kodama

Well-Known Member
Jun 20, 2016
343
138
58
Belgium - California
www.eastwind.be
Could you share the footage you shot? It would be beneficial in giving you solid advice.

I am not an expert on rollers but it certainly seems like you have overpowered this shaft. An enclosed track might help a little bit but is not going to solve your problem at all.

If you are looking for maximum range and accuracy the share needs to be propelled perfectly stable. Anything else is a compromise.

You probably need a thicker/stiffer shaft.

Testing out of the water is not going to tell you what you need to know. Can you take it to the sea to test it?

I am sure there are others who will be able to contribute more meaningful things than me.

Looks like a nice build I hope you get it to work properly. It is just a matter of trying different combinations until you find what works for this setup.
 
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Back2Narnia

Back2Narnia

Member
Jun 9, 2019
19
9
8
24
Germany
Thanks for your fast reply and your advice! Sadly the video file is to large to upload it directly to this post so i have to post a dropbox link. I hope thats fine.


I know that there is a huge difference between water / air physiks and im currently trying to get access to a pool and i would like to share my results with you guys!
(Also i would like to keep my dry fires as little as possible as it is a big strain for all the parts)
 

Kodama

Well-Known Member
Jun 20, 2016
343
138
58
Belgium - California
www.eastwind.be
The quality of the clip is really nice. If we would have footage of all the guns we are discussing here similar to this that would certainly help the conversation.
However I think that shooting your gun dry like that and holding it with your free hand is great way to get hurt eventually.
I hope you will have acces to a pool soon. If you can shoot similar footage like that in the pool both from a first person point of view and from the side I am sure the roller experts here could give you sound advice.
 
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Kodama

Well-Known Member
Jun 20, 2016
343
138
58
Belgium - California
www.eastwind.be
Looking at it again we can see that because you don’t control the recoil at all the muzzle shifts to the left. This among other things causes the shaft to take such a weird flight.

I am pretty sure that any worthwhile testing should happen in a submerged environment....
 

Broseidon

Lord of the Brocean
Aug 13, 2007
1,897
577
153
Somewhere
I'm doing the same conversion to my Pathos guns, albeit with the updated, enclosed invert roller head.

Firstly, I'd say that using 17.5mm bands seems like overkill. I'm using 14mm bands on mine. Pathos set up their factory guns with either 14mm or 16mm rubbers.

Obviously, we all know that dry firing a gun isn't the best idea. I wouldn't be in a rush to try that again..! Personally, given that you're firing it out of the water, I didn't think it look that bad. I'd just switch out the 17.5mm bands for 14mm ones.

Out of interest, why did you change the trigger mech? I know the standard Pathos line release looks a little odd but it works well enough - was that why you changed it or were you worried about the power?
 
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Back2Narnia

Back2Narnia

Member
Jun 9, 2019
19
9
8
24
Germany
@Kodama yes it is nearly impossible to control the recoil out of the water. Looking back at it i wont do it again any time soon. Today i ordered a 7.5mm and a 8mm shaft. I will update this thread with underwater footage if i get the change to visit the swimming pool of a friend of mine (latest will be July in the mediterranean sea).
I hope this will help us understand the physics of an inverted spearegun even better and clear up some myths.

@Broseidon I wanted a trigger mech that can support alot of weight and still have a crisp and smooth release of the shaft. Pathos mechs are great but can suffor from galvanic corrosion in the long run. The side line release was also a good point as i am convinced that this is the best design for a line release!
I am also going to follow your advice (also my own suspicion) and remove one pair of 17.5mm Bands as its simply to much power....atleast for the fish im going to shoot.
 

Kodama

Well-Known Member
Jun 20, 2016
343
138
58
Belgium - California
www.eastwind.be
Can you share your video setup with us? I am still impressed by the clear footage.
How super interesting would it be if we got to see footage like that of most guns around. It would really speed up the learning curve!
 
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Back2Narnia

Back2Narnia

Member
Jun 9, 2019
19
9
8
24
Germany
The setup i used is actually pretty simple. I used the ultra slow-motion (960 fps @ 720p if im not mistaken) video setting on my Samsung Galaxy S10. It is fully waterproof so if i get the chance to use my friends pool i will shoot the video with the same setup!
 

popgun pete

Well-Known Member
Jul 30, 2008
3,372
743
153
Australia
Water slows everything down as it is 784 times denser than air, hence shots in air tell you nothing and only stuff up your gear and are very dangerous. In many speargun instruction books firing the gun in air is strictly forbidden as spears have been known to travel great distances and penetrate objects such as car doors. Recoil and other aspects are so affected such tests are worthless as there is no hydrodynamic drag on anything.
Cable Rollergun.jpg
 

Lewy

Active Member
Nov 27, 2011
2
1
38
Brisbane
I think you could go with a much heavier shaft with the rubber on there, that's a similar set up to a mannysub inverted roller which would have an 8.5mm shaft.
 
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Back2Narnia

Back2Narnia

Member
Jun 9, 2019
19
9
8
24
Germany
I am currently optimizing the band setup and pre-stretch ratio. I think this setup has a massive potential to be accurate and powerfull (and cheap) at the same time. I will post an update to this thread including underwater footage with various shaft diameters. 7mm, 7.5mm and 8mm will arrive within this week!

*and no more dryfiring...i know dont worry*
 
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Back2Narnia

Back2Narnia

Member
Jun 9, 2019
19
9
8
24
Germany
Yesterday the new shafts arrived. I put on the 8mm for now and will see how it performs.
I optimized the band stretch ratio as pretension is the main advantage of inverted rollers and my config should offer a decent level of power.
The stretch ratios are as following:

Inverted Rubbers:
17,5mm Sigalsub Extreme Band @ 380% (21cm Band 80cm stretch) ; 21cm with 12cm pretension
16mm Pathos TNT Band @ 380% (21cm Band 80cm stretch) ; 21cm with 8cm pretension
14mm Sigalsub Extreme Band @ 340% (23cm Band with 80cm stretch) ; 23cm with 6cm pretension

Kicker Rubber:
14mm Pathos TNT Band @ 330% (30cm Band with 100cm Stretch)

Next up will be the unterwater test with video footage. This should be within 2 weeks from now.
How far will it shoot (effective range)? what do you guys think? ;) Im excited for the results.
 

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