Home | Tournaments | Calendar | Weather | Merchandise | Sponsors |
|
All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here! |
|
Thread Tools | Rate Thread | Display Modes |
12-03-2016, 11:07 PM | #46 | |
Registered User
Join Date: Mar 2006
Posts: 4,245
|
Re: Alemanni Demultiplied Rollerguns
Quote:
https://forums.deeperblue.com/thread...agrams.107171/ and the apparent low recoil explained here: http://www.spearboard.com/showthread.php?t=191777 A longer spear transit time on the gun's guide track, then less jerk, but muzzle exit velocity can still be high. Conventional band guns are short impulse weapons (high jerk), rollerguns are less so as the impulse drive takes place for much longer in the gun (low jerk). A canon versus a rocket, with the rocket at times getting a two stage push as the roller drive changes modes when the roller starts turning. I wrote about these modes of propulsion some time back, but only high speed photography looking at the guns will prove it. The bands will need to be marked in segments, like a banded sea snake, and the roller face, seen end on as a circle, marked in angular sectors in order to distinguish relative movements during the power stroke of the gun. Last edited by popgun pete; 12-04-2016 at 02:44 PM. Reason: explanation of video test |
|
12-03-2016, 11:18 PM | #47 | |
Registered User
Join Date: Dec 2012
Location: Bali
Posts: 80
|
Re: Alemanni Demultiplied Rollerguns
Quote:
|
|
12-04-2016, 12:07 AM | #48 | |
Registered User
Join Date: Aug 2012
Posts: 140
|
Re: Alemanni Demultiplied Rollerguns
Quote:
hmmmmmmm The clip of him shooting the doggie is almost comically bad in slow mo. go to 2:59 and set the playback speed to .25 https://www.youtube.com/watch?v=O17stsVSJF0 Last edited by peterislame; 12-04-2016 at 12:17 AM. |
|
12-04-2016, 01:28 AM | #49 |
Registered User
Join Date: May 2009
Posts: 3,292
|
Re: Alemanni Demultiplied Rollerguns
The Alemanni Vela 135 looks impressive and it is a huge improvement over the Vela 130 ... but someone independent needs to get one in a pool and test accuracy and penetration. All other rollers so far have not been impressive IMHO. Sure they might be impressive when compared to some of the older designed classic guns ... but things have improved quite a bit with classical setups, and the bar is much much higher now. I actually don't believe that even the Vela 135 can outperform a good 3 banded classic gun with 135 cm band stretch. Of course I could be wrong and I have been wrong many times before. In the end it is all about getting a shaft to come out of the gun stable ... if you can do that then you are on the right track. So far, roller guns have a problem with shaft diving when you start to push the loading high. Maybe with a 10mm shaft things are solved simply due to the slower shaft speed of the heavier shaft ... but this needs to be tested. I do think there must be a design solution to the problem ... but this solution needs to work without reducing power. Then of course you have the complications and loading time of a roller ... I agree that the performance has to be really a big improvement to accept that.
In the end ... you are trying to push a shaft to its terminal velocity. How you do that is not important. The shaft has to come out super stable and super flat ... this way it can retain velocity and accuracy throughout its flight. A diving shaft might look impressive at shorter ranges ... but at longer shooting distances it fails miserably. I really think very few people realize what is possible with a properly setup speargun that can shoot flat, hard and accurate. It is a completely different type of spearfishing ... your speargun becomes a long range sniper rifle ... I haven't seen a single spearfishing video on youtube that shows that. Any fish that is 8 meters or closer to the tip of your gun is as good as on your stringer! |
12-04-2016, 02:34 AM | #50 | |
Registered User
Join Date: Dec 2012
Location: Bali
Posts: 80
|
Re: Alemanni Demultiplied Rollerguns
Quote:
The photo of MJK shooting the Dogtooth tuna is the older 130 design Alemanni roller I believe, not the new design with the rollers at the mechanism. http://m.youtube.com/watch?v=OX2cNb-bm0A Last edited by Satdiver; 12-04-2016 at 02:53 AM. |
|
12-04-2016, 02:56 AM | #51 |
Registered User
Join Date: Mar 2006
Posts: 4,245
|
Re: Alemanni Demultiplied Rollerguns
We can check out the "Vela 130" because I had a close look at it yesterday. The most obvious difference, bar it being shorter than the "Vela 135 Special", is that it lacks band group 2 and the associated rear pulleys that sit in the window cut-outs in the latter gun. Hence no rather long pre-stretched band that has to be accommodated on the upper and lower gun decks. The "Vela 130" has that extra band on the top deck which looks longer than the one on the "Vela 135 Special". With enough rubber in the "band battery" this band can be eliminated, especially if it gets swept up by the main wishbone travelling behind it, it being anchored well back from the muzzle (band group 5 on the "Vela 135 Special").
|
12-04-2016, 02:59 AM | #52 | |
Registered User
Join Date: Aug 2012
Posts: 140
|
Re: Alemanni Demultiplied Rollerguns
Quote:
|
|
12-04-2016, 03:48 AM | #53 |
Registered User
Join Date: Mar 2006
Posts: 4,245
|
Re: Alemanni Demultiplied Rollerguns
My thoughts are the halving of the tension from the "Vela 130" band battery of 3 bands (note that they each have slightly different slack lengths in order to match their anchor position and what they wrap around, or tie to) made that gun a bit short on horsepower, even though it shoots a shorter spear compared to a standard speargun. The extra top deck conventional band was added to make up for the shortfall, but it cannot add a full power stroke as the main wishbone does. In the later "Vela 135 Special" this situation was redressed by adding another band to the band battery, this band being pre-loaded to harvest more energy by moving further up the band energy graph, hence in a way it represents more than just one extra band. The top deck band was retained in case the augmented "band battery" was not up to the job, especially with an even longer spear to propel.
|
12-04-2016, 07:09 AM | #54 |
Registered User
Join Date: Feb 2013
Location: Venice, FL
Posts: 1,684
|
Re: Alemanni Demultiplied Rollerguns
Why make a video of the pool test if you are not going to show the shaft flight?? IMO the fact that the gun shoots that inaccurately at 8m (which is looks like the shooter be reaching and making it more like 7.5m) makes it very unimpressive. A $2600 gun that shoots worse than other 3 banded classic guns of the same length.
Sent from my iPhone using Tapatalk |
12-04-2016, 11:22 AM | #55 |
Registered User
Join Date: Aug 2008
Location: Big Island
Posts: 5,098
|
Re: Alemanni Demultiplied Rollerguns
It's amazing that you can watch these videos at such High Rez and slow speed and see things frame by frame. The power is unquestionable. 10mm shaft. But, unfortunately, he missed the fish, or at best hit it in the bottom of the belly and then that 10mm shaft tore out. My intuition is that the gun is overpowered. Take off a band or two, tighten them up a little and drop to an 8.5mm shaft. Maybe you'll lose your recoil shift? To me this is overpowering. wasted energy. Start from your goal. Bullseye accuracy with kill shot power (does not need to go through a truck) at 8mtr from the tip. Then scale back your power and your shaft diameters so that you are not reaching the goal, and then move up your power and your shaft diameters until you do. Then you are optimized. An 8.5mm Shaft can carry energy 8mtrs too.. I know so, because we've tested our mid classic midhandles with 3 bands shooting 11/32" shafts with kill power and accuracy at 8mtrs. I disqualified our 62" 3 band rear handle shooting 11/32" shafts with kill power at 8mtrs because we had less recoil shift than they experience in this video, but that could easily be remedied by adding some belly and making a gun specifically for that purpose.
In High rez, at 0.25 speed, you can slow this down to frame by frame by pressing pause/play over and over and over. you can see the shaft arcing downward a little just as it is released within 17 seconds mark? Back to the positives. He's shooting a 10mm shaft with incredible power with one hand with very little recoil. That is what is interesting to me here.
__________________
https://www.facebook.com/Ulusub/ Last edited by Behslayer; 12-04-2016 at 01:15 PM. |
12-04-2016, 01:14 PM | #56 |
Registered User
Join Date: Aug 2008
Location: Big Island
Posts: 5,098
|
Re: Alemanni Demultiplied Rollerguns
Agreed. Nobody here can point to a video of a definitive static test showing both great power and stable shaft flight/accuracy. But, I know of many reallllly good divers who swear by these things, and there are plenty of videos showing great power with low recoil in static tests, as well as heaps of videos of guys nailing fish at seemingly far distances with almost no recoil. The conundrum.
__________________
https://www.facebook.com/Ulusub/ |
12-04-2016, 02:29 PM | #57 |
Registered User
Join Date: Mar 2006
Posts: 4,245
|
Re: Alemanni Demultiplied Rollerguns
Energy Storage Diagram for "Vela 135 Special" Band Battery.
Rollerguns and Cable guns both use rollers, but unless they are identified as one or the other confusion will reign. A band roller gun is a very different animal to a cable roller gun. A cable gun does not necessarily use bands as the energy storage, such as this pneumatic gun based version from the Mares speargun designer, but it still has rollers. Last edited by popgun pete; 12-04-2016 at 03:55 PM. Reason: more info |
12-04-2016, 02:49 PM | #58 | |
Registered User
Join Date: Mar 2006
Posts: 4,245
|
Re: Alemanni Demultiplied Rollerguns
Quote:
The "Dreamair" cable gun has no bands and has no rollers, its cable wishbone draw is not dictated by the power stroke of its compressed air power battery, but by the spiral track lengths of its outer and inner winding drums. I hope that it works well enough to justify the big investment as it enters completely new territory for cable guns. Last edited by popgun pete; 12-04-2016 at 03:56 PM. |
|
12-04-2016, 03:58 PM | #59 |
Registered User
Join Date: May 2009
Posts: 3,292
|
Re: Alemanni Demultiplied Rollerguns
I think you guys are way over thinking this. Shaft has to go out super stable (without diving), if it dives it loses velocity very quickly and all the band power will dissipate. I have verified this many times ... 10 bands with 380% band stretch will actually shoot a shaft slower than if you removed 8 bands and kept only 2 ... reason being that with 10 bands the shaft is not coming out stable. Just like a 1000 lb gorilla can't throw a paper airplane a longer distance than a 7 year old kid.
Get the gun ... have the builder set it up to what his experimentation has shown to be the absolute best ... choose one aim point and shoot 3 shots at 6 meters and 3 shots at 7 meters and another 3 shots at 8 meters ... this will give you how flat and accurate the gun is shooting ... then do a penetration test at 8 meters ... mystery solved. From my experience though, if the shaft is not coming out flat and straight ... results will be miserable once you pass 5 meters ... let alone 6, 7, or 8m. The pool test just shows 2 shots ... one with a Vela 130 and the other with a Vela 135. Penetration wise the 135 seems much better. But accuracy wise ... I don't know ... 8 meters if pretty far away and even in a pool there is a lot of movement happening and a human is only human ... I can tell you that the target looks mighty small at 8 meters !!! ... you need more than 1 shot to verify accuracy. Accuracy should be a group of at least 3 shots that are done one after the other with the camera rolling ... no cherry picking. |
12-04-2016, 05:02 PM | #60 |
Registered User
Join Date: Mar 2006
Posts: 4,245
|
Re: Alemanni Demultiplied Rollerguns
A comparison of energy stored in cable gun and conventional multi-band gun.
Note that if you directly compare the lower left hand triangle with a small rectangular base (due to the pre-load on band group 2) with the lower right hand triangle you will see that the four band gun is much more powerful in terms of its energy storage. That is energy stored, it says nothing about energy going out. The losses in the four band gun have to be lower as there is no other hardware being propelled, hence the four band gun should out-shoot the rollergun, but will give a strong jerk unless the gun is ballasted with sufficient bulk to still make it a floater. Modelling assumes both guns use the same band material with band stretch based on the various triangles shown on the second "band lengths" diagram. Last edited by popgun pete; 12-05-2016 at 01:36 PM. Reason: explanation |
Bookmarks |
Thread Tools | |
Display Modes | Rate This Thread |
|
|