Home Tournaments Calendar Weather Merchandise Sponsors

Go Back   Spearboard.com - The World's Largest Spearfishing Diving Boating Social Media Forum > Spearfishing Gear > All About Guns

All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here!

Reply
 
Thread Tools Rate Thread Display Modes
Old 12-04-2016, 06:07 PM   #61
popgun pete
Registered User
 
popgun pete's Avatar
 
Join Date: Mar 2006
Posts: 1,564
Re: Alemanni Demultiplied Rollerguns

Bottom line is the band rollergun was originally designed for two reasons. A lever cocked over-the-center toggle action gun for those who could not easily load a long (but not very long) band speargun and a very short band gun to shoot catfish in murky water that had enough power for the job without using ridiculously short bands. Otherwise a multi-band gun will do what you want, but you need to shoot with two hands on the gun. If you want to shoot with one hand then you get a rollergun and "pay" the extra, including any repair time out on the boat. Although the band energy storage graphs have wishbone travel distance shown on the x axis, if you replace it by time then you can see the difference in the jerk as jerk is the gradient or dF/dt, whereas on the graphs the gradient shown is dF/dx. However the difference in jerk is pretty obvious just by looking at these present graphs.
Attached Thumbnails
Click image for larger version

Name:	Norbert Ebeling catfish gun.jpg
Views:	103
Size:	133.4 KB
ID:	230310   Click image for larger version

Name:	Hurricane rollergun (Inv. Martineau) A.jpg
Views:	100
Size:	138.2 KB
ID:	230311  

Last edited by popgun pete; 12-05-2016 at 02:37 PM. Reason: adding patent diagrams
popgun pete is offline   Reply With Quote
Old 12-04-2016, 06:31 PM   #62
Satdiver
Registered User
 
Join Date: Dec 2012
Location: Bali
Posts: 32
Re: Alemanni Demultiplied Rollerguns

Hi Majd, I will be back in Bali in the next few weeks and will do a pool test as you suggested with the 135 Vela. Whats the best position to video the test?
8 meters is a long shoot, just wondering if you have made some sort of gun rest before? I think there will be a lot of human error shooting such a long shot if trying to achieve a precise accurate test. Im thinking its possible to make something for the Vela as it has almost no recoil.
Satdiver is offline   Reply With Quote
Old 12-04-2016, 06:45 PM   #63
jstiver09
Registered User
 
jstiver09's Avatar
 
Join Date: Feb 2013
Location: Venice, FL
Posts: 1,682
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by Satdiver View Post
Hi Majd, I will be back in Bali in the next few weeks and will do a pool test as you suggested with the 135 Vela. Whats the best position to video the test?
8 meters is a long shoot, just wondering if you have made some sort of gun rest before? I think there will be a lot of human error shooting such a long shot if trying to achieve a precise accurate test. Im thinking its possible to make something for the Vela as it has almost no recoil.


You don't need a rest. Just make sure the camera angle has a clear view of the shaft the entire flight. Measure 8' from the tip of the spear and aim for the middle of the target. See Peterislame's posts, he has good camera angles on his videos.


Sent from my iPhone using Tapatalk
jstiver09 is offline   Reply With Quote
Old 12-04-2016, 08:30 PM   #64
Behslayer
Senior Member
 
Behslayer's Avatar
 
Join Date: Aug 2008
Location: Rhode Island
Posts: 4,764
Re: Alemanni Demultiplied Rollerguns

Pete, on another forum we discussed the possibility of using a single set of heavy bands or possibly a set of weighted bands and a cable on an otherwise standard 3 band gun not to utilize the force of the 4th band pushing the spear, rather to cancel the recoil. Recoil is the great robber of range and accuracy on a classic band gun. Do you think this could be viable.
Behslayer is offline   Reply With Quote
Old 12-04-2016, 08:32 PM   #65
Behslayer
Senior Member
 
Behslayer's Avatar
 
Join Date: Aug 2008
Location: Rhode Island
Posts: 4,764
Re: Alemanni Demultiplied Rollerguns

SAT where do you live in Bali? Who you diving with and where? Subuh bidit biso omong omong Bahasa?
Behslayer is offline   Reply With Quote
Old 12-04-2016, 09:17 PM   #66
popgun pete
Registered User
 
popgun pete's Avatar
 
Join Date: Mar 2006
Posts: 1,564
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by Behslayer View Post
Pete, on another forum we discussed the possibility of using a single set of heavy bands or possibly a set of weighted bands and a cable on an otherwise standard 3 band gun not to utilize the force of the 4th band pushing the spear, rather to cancel the recoil. Recoil is the great robber of range and accuracy on a classic band gun. Do you think this could be viable.
It would be unlikely if you look at the physics. The spear is ejected from the gun at a certain velocity as it leaves the muzzle, as well as getting up to that velocity on the gun's guide track. For that effect to cancel something of equal momentum has to go backwards. You might think that something more massive, but moving slower, would balance out if it traveled rearwards, but its center of mass cannot leave the gun. Whereas the spear's center of mass leaves the gun completely.

During WWII the Germans tried mounting a tank busting cannon on a Me 210/410 Hornisse Zerstorer, it could knock anything out with a single shot. The canon's firepower and tremendous recoil could not be absorbed by the airframe, so they mounted a rocket cartridge on the ventral canon installation that fired rearwards. The high velocity gases from the rocket cancelled out the canon's recoil as it sent the armor piercing projectile forwards. However after a few successful test shots the synchronization between the canon firing and the rocket cartridge detonating got slightly out of whack, tearing the entire canon and rocket installation out of the test aircraft instantly destroying both it and the flight crew. Bazooka or rocket propelled missiles might be recoil-less, but I don't see it as very practical in a speargun. Rather better to ballast the gun and let it absorb the recoil by its sheer mass moving, which we already do. I helped design a heavy trigger mech for this very job to add to that ballast.

One remaining possibility is a hydraulic shock absorbing, telescopic stock, but if it fails then you get the gun travelling back into your face. Better to hang on with two hands and brace your arms I think, plus guns need to be simple, as in the KISS principle, to keep them going when conditions are adverse.

Last edited by popgun pete; 12-05-2016 at 12:41 PM. Reason: Hornisse has double s, nor one
popgun pete is offline   Reply With Quote
Old 12-05-2016, 12:16 AM   #67
popgun pete
Registered User
 
popgun pete's Avatar
 
Join Date: Mar 2006
Posts: 1,564
Re: Alemanni Demultiplied Rollerguns

The "Vela 135 Special" could increase grunt by using 2 x "band group 2" wrap around bands instead of one set as it does now. Would it fit and would the stock take it in terms of the inherent strength given that larger windows are required for tandem rear pulleys?
Attached Thumbnails
Click image for larger version

Name:	vela 135 top XKD.jpg
Views:	92
Size:	37.2 KB
ID:	230303  
popgun pete is offline   Reply With Quote
Old 12-05-2016, 01:44 AM   #68
spearq8
Registered User
 
spearq8's Avatar
 
Join Date: May 2009
Posts: 2,955
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by Satdiver View Post
Hi Majd, I will be back in Bali in the next few weeks and will do a pool test as you suggested with the 135 Vela. Whats the best position to video the test?
8 meters is a long shoot, just wondering if you have made some sort of gun rest before? I think there will be a lot of human error shooting such a long shot if trying to achieve a precise accurate test. Im thinking its possible to make something for the Vela as it has almost no recoil.

Using a rest is not practical as it gives wrong data. You want to shoot in a way that is similar to how you hunt. I agree 8 meters is a long way but you are not trying for 1 inch groups at that distance ... if you can get 3 shots inside a palm sized group that is already fantastic accuracy. I think more important to look for is shaft drop. Choose one aim point and move back 1 meter at a time ... 5m to 6m to 7m to 8m ... and observe shaft drop. If you want to compare with a good classic setup ... up to 6 meters there should be less than an inch of shaft drop with an 8mm shaft and zero shaft drop with an 8.5mm shaft. I haven't really tested in depth the heavier shafts ... but I will test a 9mm shaft soon. I can't imagine shooting anything with a heavier shaft than that as it just seems to be counter intuitive. Once you get to 8.5mm shaft or heavier ... a slip tip seems like the way to go ... and with a slip tip you don't have to go all the way through a fish (as you do with a flopper) ... you just need enough penetration for the slip tip to work.

Of course being able to do penetration testing is also good as we can cross compare results. But not sure you are able to get the same styroboard that I use in your area. If you can, try getting 3 x 5cm of XPS foam @ 35cfm ... this is what I use for the Tuna Penetration Test. Anyway ... if you are getting good accuracy with flat shaft flight ... penetration is bound to be very good. I tend to find that if your gun is shooting flat and straight up to 8 meters, high penetration is a guaranteed by product.

Rollers can be tricky. You can get them to shoot flat ... but the only way I was able to do that is to reduce power. I think even Alemmani recommend that for best results you should load your wishbones on the rest tab rather than the back shaft notches. My guess is that they found out that this prevented shaft diving. But this dramatically reduces the power of your setup ... and the gun will not shoot well at longer ranges as it simply doesn't have the shaft velocity required. It is a tough nut to crack and eventually I think someone will. As of today I haven't seen that happen yet.
spearq8 is offline   Reply With Quote
Old 12-05-2016, 01:02 PM   #69
popgun pete
Registered User
 
popgun pete's Avatar
 
Join Date: Mar 2006
Posts: 1,564
Re: Alemanni Demultiplied Rollerguns

If you light up the shaft tail then you can track the flight of the spear looking from the rear with a camera. Some years ago I was talking to the Navy gun crew on a dual purpose anti-ship, anti-aircraft battery and they said the departing shells were tracked by radar using a unit situated between the twin barrels (4.5 inch guns) and that a flare lit up on the rear of the shells so that their trajectory could be followed after they had cleared the barrel bores and the cordite gunsmoke had blown away. Later on I watched on as the barrels swung and pivoted rapidly to get rid of any stiction and then they opened up with an impressive rate of fire blasting away at a tow target trailing a very long way behind a twin engine prop-driven aircraft. Shooting was on target that day as one shell blew the tow cable in two and the tow target (a long sock type tube) slowly tumbled down into the sea to the rousing cheers of the onlooking crowd at the Navy's "Gunnery Open Day".

Those twin turret mounted 4.5 inch naval guns are now out of service according to this issue of the "Navy Daily".
http://news.navy.gov.au/en/Feb2014/F...m#.WEXU79V97IU
Attached Thumbnails
Click image for larger version

Name:	The-Gunnery-Flinders-Victoria.jpg
Views:	78
Size:	48.6 KB
ID:	230313  

Last edited by popgun pete; 12-05-2016 at 03:19 PM. Reason: adding a reference
popgun pete is offline   Reply With Quote
Old 12-05-2016, 05:34 PM   #70
Satdiver
Registered User
 
Join Date: Dec 2012
Location: Bali
Posts: 32
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by Behslayer View Post
SAT where do you live in Bali? Who you diving with and where? Subuh bidit biso omong omong Bahasa?
I have a villa at Canggu. I dive with Andre quite a bit, who Im sure you know. Places I go are Ambon, Flores, Raj Ampat. Lombok and around Bali.
My Bahasa is rubbish, I should be able to speak Bahasa as my wife is Indonesian and have twins that can speak both english and bahasa.
Satdiver is offline   Reply With Quote
Old 12-05-2016, 11:37 PM   #71
Diving Gecko
Shooter & Shooter
 
Join Date: Nov 2014
Posts: 646
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by spearq8 View Post
[...]Of course being able to do penetration testing is also good as we can cross compare results. But not sure you are able to get the same styroboard that I use in your area. If you can, try getting 3 x 5cm of XPS foam @ 35cfm ... this is what I use for the Tuna Penetration Test. Anyway ... if you are getting good accuracy with flat shaft flight ... penetration is bound to be very good. I tend to find that if your gun is shooting flat and straight up to 8 meters, high penetration is a guaranteed by product.[...]
Quote:
Originally Posted by Satdiver View Post
I have a villa at Canggu. I dive with Andre quite a bit, who Im sure you know. Places I go are Ambon, Flores, Raj Ampat. Lombok and around Bali.
[...]
Hi Satdiver,
There's a chance I might be in Bali in late Jan or early Feb. If so, I could possibly bring you some blue no-name foam from China so you can test and compare to Majd;-). The stuff I can get is about 37 kg/m3, so should be close enough to make valid findings.

Last edited by Diving Gecko; 12-05-2016 at 11:46 PM.
Diving Gecko is offline   Reply With Quote
Old 12-06-2016, 04:26 AM   #72
popgun pete
Registered User
 
popgun pete's Avatar
 
Join Date: Mar 2006
Posts: 1,564
Re: Alemanni Demultiplied Rollerguns

When stripped of its cable pulley system you can see the "Vela 135 special" for what it really is, hence although a beautifully made gun it is not really a miracle gun at all, but a slightly under-powered one compared to something that costs maybe half as much. The recoil will be less because it has less power, as well as the weakening effect of the "demultiplier" system.

Things could be improved by pre-tensioning more bands, or shortening them to use more stretch.
Attached Thumbnails
Click image for larger version

Name:	vela 135 vs 4 band gunRR.jpg
Views:	130
Size:	83.2 KB
ID:	230322  

Last edited by popgun pete; 12-06-2016 at 12:49 PM. Reason: extra comment
popgun pete is offline   Reply With Quote
Old 12-06-2016, 05:50 AM   #73
Satdiver
Registered User
 
Join Date: Dec 2012
Location: Bali
Posts: 32
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by spearq8 View Post
Using a rest is not practical as it gives wrong data. You want to shoot in a way that is similar to how you hunt. I agree 8 meters is a long way but you are not trying for 1 inch groups at that distance ... if you can get 3 shots inside a palm sized group that is already fantastic accuracy. I think more important to look for is shaft drop. Choose one aim point and move back 1 meter at a time ... 5m to 6m to 7m to 8m ... and observe shaft drop. If you want to compare with a good classic setup ... up to 6 meters there should be less than an inch of shaft drop with an 8mm shaft and zero shaft drop with an 8.5mm shaft. I haven't really tested in depth the heavier shafts ... but I will test a 9mm shaft soon. I can't imagine shooting anything with a heavier shaft than that as it just seems to be counter intuitive. Once you get to 8.5mm shaft or heavier ... a slip tip seems like the way to go ... and with a slip tip you don't have to go all the way through a fish (as you do with a flopper) ... you just need enough penetration for the slip tip to work.

Of course being able to do penetration testing is also good as we can cross compare results. But not sure you are able to get the same styroboard that I use in your area. If you can, try getting 3 x 5cm of XPS foam @ 35cfm ... this is what I use for the Tuna Penetration Test. Anyway ... if you are getting good accuracy with flat shaft flight ... penetration is bound to be very good. I tend to find that if your gun is shooting flat and straight up to 8 meters, high penetration is a guaranteed by product.

Rollers can be tricky. You can get them to shoot flat ... but the only way I was able to do that is to reduce power. I think even Alemmani recommend that for best results you should load your wishbones on the rest tab rather than the back shaft notches. My guess is that they found out that this prevented shaft diving. But this dramatically reduces the power of your setup ... and the gun will not shoot well at longer ranges as it simply doesn't have the shaft velocity required. It is a tough nut to crack and eventually I think someone will. As of today I haven't seen that happen yet.
Quote:
Originally Posted by Diving Gecko View Post
Hi Satdiver,
There's a chance I might be in Bali in late Jan or early Feb. If so, I could possibly bring you some blue no-name foam from China so you can test and compare to Majd;-). The stuff I can get is about 37 kg/m3, so should be close enough to make valid findings.
Hi Diving Gecko, I was able to buy some XPS foam, Thanks. Contact me when you are in Bali. If I'm not away at work, I can organise some spearfishing.
Satdiver is offline   Reply With Quote
Old 12-06-2016, 05:56 AM   #74
Satdiver
Registered User
 
Join Date: Dec 2012
Location: Bali
Posts: 32
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by spearq8 View Post
Using a rest is not practical as it gives wrong data. You want to shoot in a way that is similar to how you hunt. I agree 8 meters is a long way but you are not trying for 1 inch groups at that distance ... if you can get 3 shots inside a palm sized group that is already fantastic accuracy. I think more important to look for is shaft drop. Choose one aim point and move back 1 meter at a time ... 5m to 6m to 7m to 8m ... and observe shaft drop. If you want to compare with a good classic setup ... up to 6 meters there should be less than an inch of shaft drop with an 8mm shaft and zero shaft drop with an 8.5mm shaft. I haven't really tested in depth the heavier shafts ... but I will test a 9mm shaft soon. I can't imagine shooting anything with a heavier shaft than that as it just seems to be counter intuitive. Once you get to 8.5mm shaft or heavier ... a slip tip seems like the way to go ... and with a slip tip you don't have to go all the way through a fish (as you do with a flopper) ... you just need enough penetration for the slip tip to work.

Of course being able to do penetration testing is also good as we can cross compare results. But not sure you are able to get the same styroboard that I use in your area. If you can, try getting 3 x 5cm of XPS foam @ 35cfm ... this is what I use for the Tuna Penetration Test. Anyway ... if you are getting good accuracy with flat shaft flight ... penetration is bound to be very good. I tend to find that if your gun is shooting flat and straight up to 8 meters, high penetration is a guaranteed by product.

Rollers can be tricky. You can get them to shoot flat ... but the only way I was able to do that is to reduce power. I think even Alemmani recommend that for best results you should load your wishbones on the rest tab rather than the back shaft notches. My guess is that they found out that this prevented shaft diving. But this dramatically reduces the power of your setup ... and the gun will not shoot well at longer ranges as it simply doesn't have the shaft velocity required. It is a tough nut to crack and eventually I think someone will. As of today I haven't seen that happen yet.
Hi Majd, I was able to find some XPS foam. I will do the test as you recommend. The lightest shaft I have for the test is 9.75mm x 170cm. Should be interesting to see the results.
Satdiver is offline   Reply With Quote
Old 12-06-2016, 07:00 AM   #75
Diving Gecko
Shooter & Shooter
 
Join Date: Nov 2014
Posts: 646
Re: Alemanni Demultiplied Rollerguns

Quote:
Originally Posted by Satdiver View Post
Hi Diving Gecko, I was able to buy some XPS foam, Thanks. Contact me when you are in Bali. If I'm not away at work, I can organise some spearfishing.
Thanks so much for the offer, much appreciated:-). If nothing else, I might just pick your brain a bit. Hope to have enough time to head a bit east, too.
Diving Gecko is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 02:41 AM.


The World's Largest Spearfishing Diving Social Media Forum Powered by vBulletin® Version 3.8.1
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
Copyright ©2002 - 2014 Spearboard.com