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open track guns

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

andrsn

Just visiting...
Aug 26, 2001
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i'm trying to figure this out. how much effective guidance do you think the open tracks have on the spearshafts? do you think water acts as the significant medium for stableization? i was contemplating the remarks from steve alexander and truly wonder if the tracks aid in anything besides keeping your shaft in line for swinging the muzzle after your target.

then i got to thinking that most bands on open track guns are actually pulling the rear of the shaft downwards a bit because of their angle and insertion below the track line. i know riffe sells stableizers that bring up the bands to the same plane as the track. but, does this make a difference? will it cause less friction? is there any?

how about euro guns? i know my spear on my omer comp doesn't really rely on anything to guide it when being fired. i guess whatever direction it's pointed in, it'll go.

anyways, i'm contemplating making my own stock w/ a euro handle and want to figure this enigma out.

thoughts? :confused:

andrsn
 

Griff

Certified SCUBA Rider
May 7, 2002
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my (long) answer

Im not at all familiar with the Steve alexander guns, or the omer for that matter, but i own a rob allen. i assume that the rail and open track are one and the same idea.

your question about whether or not the track made a difference to the speargun accuracy got me thinking about what happens when the spear is fired. here are my thoughts

Looking at the Steve A guns and the riffe, the rubbers are below the spearshaft. the rubbers will pull the spear down onto the track, if there is one. if there isnt one, then the force is at the supports (the handle and the muzzle). before the gun is fired, then this doesnt realy make a difference because the distance from loading notch to the handle is small and the shaft will take the force easily.
When the gun is fired, then if there is a track, this support is provided for the entire lenght of the gun. if there is no track, the rubbers will pull the end of the spear down. this will be resisted by the inertia of the spear, and the water friction, so i dont know how much effect it will actually have.

What i found realy intersesting though, is the behaviour of the spear shaft the instant after the gun has been fired.
When the gun is loaded, the spear will be in tension, from notch to sear (sp? the bit that holds the spear), so the rest of the gun will only be subjected to the laws of gravity, and behave like a beam into cantilever, hence the need to have the correct lenght spear in a gun without a track so that the spear doesnt hog or sag.
When the trigger is pulled, and the spear is released, then the spear is subjected to a compression force. this force would be short lived though, because the only resistance that the spear can give to the rubbers is its own inertia, and water/track friction (friction is probably negligible because the spear had just started moving.
the problem with this is the eccentricities created by the position of the rubbers and the position of the notch relative to the spear.
in my RA railgun, the rubbers' centers are more or less in line with the center of the shaft (if i remeber correctly). but the notch is not cut to the centre of the spear. the reasons for this probably a strenght. this would make the spear bow downwards, and onto the rail, and hopefully the rail will eliminate this bow. Also the difference between wishbone centre and shaft centre is maybe 1mm so there probably wont be too much of an effect.
in the Steve A or riffe guns, it looks like they have loading tabs, so the effect would be greater because the tabs are on the side of the spear, and the eccentricities will be bigger. but then the spears are thicker and this would compensate to a certain degree. the guns also have tracks (dont they?) so this wouldnt be a problem. it may be an issue for someone who owns an euro gun without a track, and wants to use a 6.5mm spear with loading tabs instead of notches.

also, these effects may be very small because of the small amount of time that the spear spends under accelleration.
the euro spearguns that dont have a track seem to be very accuarate, so this probably makes almost zero difference.

As far as the friction between spear and track, this is from the rob allen website www.roballen.co.za

Does the spear resting on the rail not cause friction on the spear and slow it down?

When in the water the rail and spear are both wet. Once the spear gets going it will slide on a thin film of water, which eliminates the possibility of it touching the barrel. A well-used railgun shows no wear in the rail, which it would show if there was significant contact friction. This is similar to the way that a slipper bearing or a beach skimboard work.

i can vouch for the fact that there isnt any wear on the rail (so far).

I dont know if this is any help, or if it is entitely correct.

my ideas would be, if you fit the rubbers under the spear, then use a track and if you use a skinny spear, then use a track or dont use tabs.

Good Luck

Mark
 

andrsn

Just visiting...
Aug 26, 2001
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thanks mark,

i got to thinking about a bow and arrow. here, there's only one point of contact for the guide. and it's usually soft rubber, so i'd imagine it's only lining the arrow up instead of directing it as it fires. :confused:

but, the arrow is pretty stiff and light and has less fluid friction than a spearshaft(air v. h2o).

i guess this totally makes sense on how your shaft limits the amount of band power you can use before you lose accuracy. so, i'm wondering if the shaft whip on an open track gun whos spearshaft overhangs the barrel too much is going to bend down when it's fired due to the lateral restraint of the track? i guess this is why bill kitto suggests minimal overhang.

but, back to the bow and arrow, i'm imagining that, by preference, one would want to have their bands as much in line with the shaft as possible. again, hence the design of the RA muzzle. :hmm

i know from experience that my riffe loses accuracy(shoots down) when i put on the third band(w/ 5/16 tabbed shaft). i'm wondering if a shorter shaft would be more accurate? :confused:

this sucks, cause i just keep running into questions! :head

anyways, i think the stock i'd make would be of teak, open muzzle, with only a track on the last 1/4 of the barrel. it would also have teak band risers/stableizers, too.

alrighteee, back to work for me... :t

later
 

IBGuy

New Member
Apr 10, 2002
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My 2 cents worth

Anderson,

After reading your original post my thoughts headed in the same direction as yours with the archery analogy.

Archers, myself included spend a fair bit of effort in selecting their arrows with attention to spine (stiffness) and this in relation to length of shaft and weight of the point/broadhead. Spine weight is addressed in one of two ways. 1.) Shaft diameter 2.) Wall thickness. In spearfishing we're dealing with a solid shaft, the only variables that we have to play with are length, diameter and maybe stiffness of material (softer vs. harder metal). I'm going to ignore modern bows in which the force exerted by the string is in line with where the arrow rests on the bow. Consider a long bow, if you look at where the arrow rests vs. the vector of the string it's off to one side and yet the arrow goes straight. "archer's paradox". The arrow bends around the bow under the force of the string and that's why the spine of the arrow is so important especially with traditional bows.

I think that an open track speargun is not unlike a traditional bow in this regard and my guess is that if you lose accuracy with added power that if you A.) shorten the shaft B.) increase the diameter of the shaft or C.) use a stiffer material, or some combination of these that your accuracy will improve.:hmm

I'm not an engineer :head but that's my 2 cents

btw thanks for the advice on the OMER superstretch.

Cheers, Guy
 

icarus pacific

Human-in-training
Nov 7, 2001
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another opinion?

My experience of late with tracks has been on short guns that are ridiculously overloaded and I've found that in spite of having a very straight shaft (easy, lads :naughty ) and a straight barrel, with the loads from the bands tweaking the shaft, the shaft starts whipping almost as soon as it exits the trigger sear and away it goes, merrily banging on the barrel and expending most of it's oomph at the muzzle. That said, I think if you could do everything in your favor to get it all aligned and straight, then yeah, you'd only have to worry about your trigger pull being smooth.

But in reality, we're going to start adding 5/8 bands immediately and then off we go to head scratch land. I'm a firm, (easy folks! :naughty ) believer in a bang pad, if not an all out track, especially at the areas of the trigger sear and the muzzle. But if you're going to put two pieces on the barrel, make it all one piece, all the way down. The water will lube and help center the shaft, especially if you use a collar on the shaft, ala JBL or really get the fit sweet at the muzzle, but as soon as you use it, the straightness is going to take a hike, so be prepared to spend some time with a 2x4.

I'm trying to remember who it was that had a gun where the rubbers and the wishbones ran under the shaft... that would seem to be a nice solution to the shaft rubbing and band alignment.

One thing I've gone to on my longer stuff, (OK! That's enough!:rcard ) is making the bands in different lengths so the relative stretch they have is equal. I can't say it works, but it gave me something to do... The other thing that is interesting is the length of the tip out from the muzzle. Steve Alexander had a writeup in the last Hawaii Skin Diver and he said that he couldn't tell much of a difference, and indeed, in clear water where the fish is going to make out the mass of the gun before the proximity of the tip, longer is better, she said. Which is why she's not w/me... Why the shaft is heading South is an interesting dilemma, unless your 20 feet away, in which case, hey, gravity's a bitch. Might be that the shaft is ticking the muzzle and getting some help there, though if it's got a line muzzle, the line should be well out of the way by then... Sounds like alignment of the bands, shaft whip and too far fish, though IB has a definite take on the shaft going roundy-round. I prefer to have my tips a little close than factory, so they don't get all buggered in the kelp.

PS...Jay copped to the Teaks being better than the Metal Techs? :confused:

sven
 

thin_air

Alphabet
Sep 15, 2001
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although i have only limited knowledge of spearguns and any physics...


what about attaching to rubber to a "cart" this cart would then be pulled in a straight line, there would be a slight loss of force due to the friction of the cart against whatever it would ride on, but this could be overcome because the bands would all be attached to the same place

however, for this system to work:
1. the cart must be low profile
2. there must be a way to minimize the friction between the cart and whatever it "rides" on
3. the bands would be pulled over the cart
4. to mount the spear a cone shaped hole would be made in the cart, as to allow all diameters of spears to fit in
 
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icarus pacific

Human-in-training
Nov 7, 2001
2,880
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this kid's 15??!!

Nice stuff Vincent.

While I agree with your hypothisis on the use of a traveler to hold the shaft along it's trip down the barrel, now we've introduced another moving part to the mechanical equation and with every mechanical movement, there is a time penalty, thus even if we could negate or equal the friction of the cart to that of a shaft riding along a track of polymer/water, by the time the cart reached the apex of it's travel and then released it's momentum to the shaft, I fear that the dinner would be long gone.

Very nice idea though... keep it up. :cool:

sven
 

thin_air

Alphabet
Sep 15, 2001
404
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ok, one more idea, this one came to me during history, while i was suppose to be working on a year end project (we were actually discussing the way automatics transmitions are shifting faster, and then i just thought about spearguns, oh well)

what about, instead of having the hole for the rubber on the horizontal plane, putting the holes for the rubber vertically, one hole on each side of the barrel, the band is threaded up through them and ends up on the same plane as the spear with the spear passing right between the 2 holes, if more then one band is needed the hole can simply be made bigger and more bands passed through,
i can understand that this would put considerably more stress on the barrel, but im sure you can find a way of making it strong enough

just a thought, keep the ideas flowing
 

Iyadiver

Mr. Long Post
Apr 22, 2002
998
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SPEAROS,

OK, this is the Einstein in me thinking of the dynamics of a speargun ................. No throwing rotten eggs please. he he he.


I will not call a track on the Riffe Standard Series and Mid-Handle Series as a pure open track, I forgot how deep the groove of a Competitor series is. I think the mentioned series track is a 40% track. An open track in my opinion is like the JBL shaft slider and Riffe Metal Tech shaft slider. An enclosed track speargun only enclosed 70% of the shaft diameter. A fully enclosed track should be then a barrel.

Pneumatic speargun actually uses a 100% enclosed track ( barrel ) but the shaft doesn't ride on the barrel because the barrel conform to the piston diameter not shaft diameter. The shaft is being guided by a slide ring at the muzzle front but the power is purely driven from the rear of the shaft. I ruined more than 5 pneumatics and I can not find any speargun more accurate than this compressed air baby. Size for size, they are quite powerful and very-very accurate. I used 2 Mares Stern and 3 Scubapro. I can shoot a 3" long squid with these guns from 6 feet away. During my "indiscipline" days I shot a sleeping fish at night right into the eye ( I aimed the eye from 6 feet away ) because this 45 pounder species has such thick scales I was never able penetrate the flesh thru the scales ( with this short 90cm pneumatic ). I always get only the 3" round scale and if I do get the shaft to penetrate, it is always only 2" into it and the 8mm shaft will always break at the threaded end when the fish start going mad around the rocks. I do believe that by being pushed completely from behind the shaft and having a guiding slide ring on the muzzle, a spear shaft will shoot accurately.

Now back to the open track. I tested my Riffe Standard #2 with a 5/16" ( 8mm ) shaft and 3/8" (9.5mm ) shaft, this two sizes fits well on the track/groove. I tried shaking left and right and it has very little play. I am sure the track offers some sort of shaft guidance for accuracy, it must be. As why a 9/32" and 5/16" shaft whip when over powered, I am asumming that this is what happened :

We know that thin shaft actually has to some degree a bend occuring at the over hang length where the shaft is no more supported by the track. My #2 Riffe has about 10.5" ( 26cm ), this is a 24 threaded 5/16 ( 8mm ) shaft. If you add a regular spearhead add another 3-4" of extra length. An Ice Pick spearhead will add another like 6" extra length. All these weight will bow the shaft down, especialy a 9/32" shaft. Gravity made this happen. Kurt Bickel ( www.2xtreme.net ) mentioned this when he was fixing the accuracy problem of a friend's Riffe Island.
I agree with him to this point. Now I am adding my assumption again , if a shaft is already bowing an arc heading to 6 o'clock before being fired ...... the moment the gun fired, the water resistance will caused more bending. Terry Maas book mentioned that Steve Alexander and Harry Davis clocked shaft speed in their special testing tank. They also use slow motion video to learn of muzzle recoil. It was stated that the average speargun has a shaft launching speed of about 60 miles per hour right after leaving the muzzle. This is 96 KM/H or 26 meters per second or 86 feet per second.


Take a look at the data from MARES on shaft speed :


  Pneumatic System
Sample of Products Cyrano 970 (MARES)
Power unit 28 bar compressed air
Lo (Total length of Gun) 1,220 mm
Lt (Loading effort length) 780 mm
Max. Loading Effort 298 Newtons
Stored Energy 218 J
Shaft speed at 2.5 m 28.5 m/s
Shaft speed at 4.0 m 24.0 m/s

数字は Mares社が イタリアの Institute of Technogy & Mechanical System of Genoa University と共同で実験した結果だそうです。



This is not an awesome awesome shaft speed but what we must study is the acceleration involved. Let's visualize the gun being my Riffe Standard #2 powered by 4 x 9/16 bands using 5/16 shaft (8mm ) , it should qualify the shaft speed. The butt of the spear shaft to the most forward part of my gun's muzzle ( also the track/groove ) is 38" ( 96cm ). This means that the shaft achieved a speed of 26 meters per second only after travelling for 96 cm. Engineers figure it out what kind of super acceleration is involved. Actually in a gun using a rubber, the acceleration to this 26 meters/second occured not at the muzzle but rather behind it or should I say well before it reaches the muzzle because a rubber at a non-loaded state is already has it wishbone position 30% behind the muzzle. This means the achieved speed & acceleration is even faster than 26 meters per second.

This shaft which is supposedly already having its tip pointed rather downwards is being accelerated to such warp speed, what happened ? Water being like 2000 times denser than air is one horrible drag-rich atmosphere, I think the shaft will bend more in that fraction of a second. Thus a low shot occured because of the rudder effect of the shaft physical dimension. This is why Steve Alexander and Jay Riffe mentioned that 3/8" is quite resistant to shaft whip because it is stiff enough.

I also believe that a shock wave is created within the shaft physical properties/dimension caused by the sudden G force of this crazy acceleration, this is what Terry Maas explained as the rear of the shaft trying to catch up with the front. It explained that the shaft actually turned into a spaghetti the moment it is fired. If the shot were fired in air I am sure this would not happen because the drag of air is 2000 times less. Simple example is the cross bow gun, I know some models shoot light weight arrow up to +-200 feet/second or 60 meters per second.
This carbon or aluminum shaft is not that stiff but air resistance is unlike water resistance. Falling from a given height and at a speed of 60 miles per hours into water will give you almost an equivalent of hitting a concrete wall, depending on the angle of impact and total surface area involved. I think a stand still shaft un-fired and suddenly moving so fast when fired, actually undergone the same effect as hitting a "brick" of water, thus this is how I assume a shock wave was created to distort the shape of the shaft it is not stiff enough.

So to summarize my assumption on shaft whip is as follows :
If the power applied to a given shaft is within the shaft stifness treshold limit, accuracy should do well given that the hydrodynamic of the spearhead is not the ruining factor.

If the power applied to a given shaft exceed a shaft stifness treshold by a minor margin and the shaft overhang + its spearhead weight created a pre-fired bending, I think a very low shooting will occur.

If the power applied to a given shaft exceed its stifness threshold by a wide margin, erratic point of impact will occur because of the unpredictable nature of how the shaft will re-act to the shock wave.


Now allow me to assume again how enclosed track works on thin shafts : Enclosed track work not only because it guides a shaft almost 70% of its entire diameter and the entire length of the track, but what also happened is that extra stiffness is introduced to the shaft. How so ? The clearance of the enclosed track internal diameter is of a very reasonable tolerance compared to the shaft diameter. The process of having an outer wall made by the enclosed track for the shaft is equivalent of making the shaft "thicker" and thus it becomes stiffer. If I am not wrong, double thickness = quadraple stiffness. An enclosed track is longer than the shaft accelerating space/length, what do I mean by this ? As we know rubber/band when attach to a speargun in a non-loaded position is already about 30% behind the muzzle. So when a shaft is fired from an enclosed track speargun, 2/3 of the enclosed track length is the "shock-wave absorber" area, after this length there is no more increase in shaft acceleration but there is still 1/3 of the enclosed track length to guide the shaft nicely out of the gun.

Remember Steve mentioned that an enclosed track does not help if the shaft is not being over-powered, this must be because that mentioned shaft did not exceed its stiffness treshold limit. This also tells us that an open track is almost just as good, as long as my theory of "shockwave" did not occur on that shaft.

As for the Eurogun being accurate without track, if I am not wrong there is a little hole at the muzzle where you place the shaft in, this gives the "barrel " guiding effect. Also most European gun comes only with a single 16mm or 20mm ( new models ), this means only a maximum of 135 pounds of rubber pressure involved, I think still within limits for a 6.5mm shaft.

Also it is only fair to test or verify a gun accuracy based on the same shooting distance. For every feet extra shooting distance the accuracy grouping will have to expand/widen, depending on the amount of inherent accuracy built into the gun.

Wheeewww, I am spent. I will post again on my muzzle theory later.

Thank you for your time gentlemen. I hope you enjoy my imagination. :duh :duh

Now you may throw the rotten eggs at me.;)

IYA
 

Dogmatrix

Deeper Blues pet
Jun 4, 2002
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:) wow that was some post! You have brought up a few interesting points... I had a quick think about what you said and made a little list of factors to concider or overcome!

Factors affecting spear gun dynamics
1. Support for the spear
2. Positioning of “rubbers” or propulsion system
3. Material shaft is made out of
4. Length or shaft
5. Weight of spearhead or the resistance between spearhead and water

I figure first up we look at the support for the spear... the greatest acceleration or force exerted on the spear (no this isn't when a 100 pound sailfish decides to go mach 2 on you :naughty ) would be imposed on the spear after we pull the trigger and those 5 rubbers (got to be safe :)) force it out of the barrel. the spear is going to be oscillating like a tuning fork at this point so guidance like that offered by a "enclosed track" or a rail would be very helpful (I think single "support guides" are of little help at all) in minimising these oscillations snaking of the spear.
2, IVA i figure one of the reasons your pneumatic shoots so straight is that the propulsion comes from directly behind the shaft, i think the closer you get your rubbers on a conventional gun to the horizontal the more accurately it will shoot :p
3, the material the shaft is made from is important as it helps to control how the shaft will flex, the stiffer the shaft the less oscillation, thats why the bigger shafts shoot streighter i think :t. this "whip" in the shaft could also be lessened by stiffening the metal of the shaft... but this could make it brittle... remember what happened to the titanic :naughty !
4. the longer the shaft the more length and less resistance against whip there will be!
5. if you have a spear head that looks like a middle size nuclear missile it will create a lot of resistance in the water causing your spear shaft to whip or buckle like mad!

I hope that this has been useful; I guess it is more a collection of ideas then any solid facts, there are a few other forces involved but perhaps they are for some other time!

I guess the perfect spear gun would be a rail gun (sorry Rob a real rail gun :( ) as then the shaft would be fully supported without actually touching anything… but those have a way to go before the likes of us will ever see one! so for now Rob allen's version will do the Job:D !

Happy hunting! don't be the hunted! :duh
 

icarus pacific

Human-in-training
Nov 7, 2001
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Jeez... a little bored in Indo, eh?

I f we take the notion of the spearshaft bending around ala the arrow/bow example, it makes sense that the spear would tend to shoot low, as it's already being bent that way under the tension of the rubbers, and so will follow that direction almost as soon as the tail leaves the trigger sear. It goes to reason then that a lengthy shaft/tip hanging out from the muzzle's end will only exacerbate the problem.

It's a tradeoff between the lightness of a thinner diameter and thus faster shaft and one where the increased diameter will help hold the shaft to a straighter line, allow more punch, but be significantly slower and heavier, where gravity will drag it down, not flexion. I think this is where the euro :girlie guns get high marks- their thinner shafts combined with having the rubbers more in the same plane let their overall construction be lighter and thus faster to manuever. And if you can get a quick sliver into a fish and let the float do the work, hey, it's dinner. Trouble is, I've never been able to get the gap close enough that I felt comfortable with letting one fly at a maybe; not be sure I was going to be able to really stick it and keep it, so I've tended to go for more mass and punch and getting closer. If and when I can get to some clearer water where the viz is a factor, yeah I can see needing to look at thinner stuff that flies faster.

But what I really think is that we're too concerned with saving a few crowns with regard to the breakage of the equipment. Like I said before, it's the price you pay to do this kind of stuff. Golfers lose balls, car racers get flats, I tweak a shaft. It's still a lot more fun than picking dinner through the fish window at the market.

Anybody ever thought about an extruded shaft?

sven
 

Jay Styron

New Member
Aug 31, 2001
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GOOD POINT

I must say this has been some very enlightening conversation but I've noticed in a few of the latest post everyone wants more bang for their buck(don't even go there Sven:naughty ) but are worried about bending shafts or over powering them.ect. Match the shaft to the bands then match the gun to the fish. If you bend a shaft-oh well, thats the cost of doing business. It seems that if you're having to use a "closed track" barrel to control shaft whip, then aren't you losing the power to friction in the track that you thought you would gain by overloading the shaft.
Maybe--just maybe, we should should concentrate on the skills that will allow us to stay under an extra 10sec than a gun that can shoot an extra 10'? There by allowing the fish to come in a little closer. I'm not an apnea master by anymeans but isn't getting as close to the game what is all about?
As for shaft length, I generally go w/ a shaft for the next length gun i.e.-a shaft for a 116cm gun for my 110cm gun. I really haven't found a problem w/ accuracy, in fact the longer shaft in my new 90cm gun shoots high if anything. As usual just my HO.
Jay
 

Griff

Certified SCUBA Rider
May 7, 2002
557
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Recoil

Something i was wondering. does a riffe recoil with slight upward component? i dont know if it would, but the rubbers are been pulled down by the muzzle, which is where they are racing towards. the opposite reaction would be for the rubbers to pull the muzzle upwards. does this have any credability off of paper?

if it is the case then the most accurate you could hope for is a rubber that is in line with the spearshaft, so recoil is purely in the line of travel of the spear.
The RA double rubber muzzle, and a lot of the other :king euro guns has one rubber in line, with the second below the spear. so it might be worth it trying to bust one 20mil before going to 2 16's

Just a thought

Mark
 

Iyadiver

Mr. Long Post
Apr 22, 2002
998
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Hi Mark,

Since Steve Alexander and Larry H had the muzzle kicking up captured on video, it must be true. Why they need to make it up ? Every high power guns builders are using muzzle stab for paralleling the rubber position, they too have done actual test so I am sure it is a "certified" information. At first I think like you too, why not kick down instead ? I think its the rubber rebound...possible ??

I aim high on my #2 Riffe if I use 4 bands, I suppose the upward kick must be true. I think it applies to all high power guns. I think there is no safer and easier way to place so many rubbers/pressure other than exactly in front of the wood stock cause it is at the strongest compression resisting point. If you place so much rubber power on an elevated level like the Euro gun or JBL type "shaft level" wing muzzle , it is the same like trying to twist away (crow bar effect ) the muzzle from the teak stock or pipe barrel of the gun.

Anyway I do love day dreaming of what next on a speargun....as much as I like to think of babes.

Tell me does this make sense or not :
What if somehow someone design a speargun that has the actual rubber pulling on the opposite direction of the shaft exit direction. Say place the rubbers on the rear of the gun, perhaps near the butt and uses super long line/dacron wishbone all the way to the muzzle. So the muzzle act as a 180 degrees U turn point with mini rollers for the wishbone. So you load the gun just like how you load a regular rubber model but you are pulling by the wishbone only, so the rubber stretch is from rear to front, not from front to rear. The rubber positioning can be made very parallel but on a different height level in respect to the shaft position. So when u fire, the recoil of the shaft leaving the gun, which will produce a rearward recoil get somehow partially canceled by the rebound of the rubbers going the opposite direction. Almost like the Prodonovich roller gun but on a rather different rubber placement. Possible ?

What da ya say Sultan Sven ? Comments/flame please.
It is not boring here in Indo ( fish wise , yes, 100 miles of my city my radius ), I just love speargun talk ......he he he.

IYA
:p
 
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Griff

Certified SCUBA Rider
May 7, 2002
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thats a very interesting idea

one problem i can think of is the wishbone snagging the spear as it attempts to go back around the muzzle, but you can get around that by hooking the wishbone from underneath the spear.
taking that a bit further, why not have a long rubber that wraps around the muzzle. that way the rubbers drive for the entire lenght of the barrel because the neutral position of the rubbers would be 1 barrel length plus x from the notch, instead of 1 barrel lenght minus rubbers. i'd hate to think what the rubbers whipping around the corner would do to the muzzle in terms of recoil, but you never know...this could be the future for speargun design, (unless someone has already tried it, and in that case i retract my last comment.)

Speargun chat definately beats the report i'm trying to finish

Mark
 

Iyadiver

Mr. Long Post
Apr 22, 2002
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Mark,

This is the problem with a hobby, no time is more fun than talking & dreaming about it. Design comes from imagination first anyway.

See my ugly drawing. The line wishbone won't snag the spear because the Riffe/Alexander tab/shark fin is half rounded at the front to avoid snagging during launch. Shooting line is what get can snagged on line wishbone, thus I think we put it in front like a JBL slide ring but in a welded form like the Riffe/Alexander tab with hole. Since if the gun uses enclosed track, a shooting line pressing/circling a shaft like open muzzle type of guns is not required.

Well who knows some people out there with machining facility will try my crazy idea. With the rubber position as it is on the drawing, we already avoid loosing the 1/3 "uneffective" rubber length when neutral. The shaft will be propelled I think at least 90% of its track/barrel length. But I think the rubber stretch will need to go 350% or above. It will be not easy to load rubber only by the wishbone cause it is going to be painful, so I think small 14mm rubber is more suitable and put at least 4 of them. They can always make a 3 finger loop on the line wishbone for fingers to grip.........my own terms for something not yet exist.

Also the shaft must have a rest tab somewhere forward if this gun were to be made long like 155 cm and above. I seen short 170 cm guys load 170cm Riffe Blue Water or the way Terry Maas load his long gun, unique and not too easily done. I been thinking of this crazy idea for a month now and wondering when I will start making it for fun sake.

Anyway I am just dreaming of this idea...........Thanks 4 the interest you have, sure exiciting to share with someone. At least I get the forum computers busy.

Set the burner on high power and FLAME ME :duh :duh


Have Fun,
Iya
 
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Griff

Certified SCUBA Rider
May 7, 2002
557
60
0
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you should have got the patent first

The sketches show it all. one idea, maybe you should have a wing, like the pic of the MT5 you posted, to protect your hand from the rubbers. i dont like the idea of all those rubbers going off so close to my wrist. Also, its going to be a real hard one to load, unless you find a low friction combination between the line and the roller. like teflon or something. or els you can use a two hand loading technique. 1 hand to pull the rubbers forward, one hand to take up the slack on the wishbone and to pull it back.
or how about this, have the wishbone interlock with the roller and have a ratchet on the roller, so you can pull the wishbone forward, rest and carry on without loosing any headway. when the wishbones are in place, the ratchet can be released and the gun is ready to fire. sort of like a second safety pin.

ideas ideas,
just have to wade through all of them to find the winning combo

Mark
 

icarus pacific

Human-in-training
Nov 7, 2001
2,880
212
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Re: GOOD POINT

Originally posted by Jay Styron

Maybe--just maybe, we should should concentrate on the skills that will allow us to stay under an extra 10sec than a gun that can shoot an extra 10'? There by allowing the fish to come in a little closer. I'm not an apnea master by anymeans but isn't getting as close to the game what is all about?

Jay


BINGO!!

That's why you've got a lifetime exemption for hanging freebie at Club Sven!! Give yourself a little tongue, Jay and congratulations for getting it. I was thinking Bill and I were the only ones that weren't impressed with going into the water with bazookas, just with enough to get the jobs done. Youdaman!

sven
 

icarus pacific

Human-in-training
Nov 7, 2001
2,880
212
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Originally posted by Iyadiver

Set the burner on high power and FLAME ME.
Iya


Not my style.

I'll hand it to you, you've been thinking. As I mentioned earlier, there was an outfit that did have the rubbers below the shaft, traveling between the barrel and the shaft. I want to say that it was Cressi or somebody euro, but it may have been Voit/Swimaster, the originator of what is now owned by JBL.

In terms of being able to load your gun, you could probably incorporate something along the lines of a crank to wind the wishbones closer and over the tabs, much like loading a crossbow.

Not to throw cold water on your hot idea, but being a Product Design kinda guy, I can see that this thing is going to start getting complicated, like yesterday, and that's not what you want to have in a speargun or anything else for that matter.

While it's true that I'll take ten minutes (if I've had breakfast) to load my Islands up, especially when I'm using 5- 5/8" bands, floater/bungie to floater to float, I'm fine with never having to launch the thing. As Jay identified, bless him, I'm in it not so much to slay the fish as to just go down 10-15m and hang out and see what comes along, maybe do some thinking, listen to my heart rate, wish everything worked out in this life, yadda yadda.... I find that if I'm all aggro about my gear and the damage I want to do with it to some unsuspecting piece of protein, the dive doesn't suck but it's not as much fun. And that's what it's all about.

Discussing and postulating about gear like this is indeed great fun, but remember also to get wet.

Remind me to tell you about the hybrid I'm building... ;)

sven
 

Iyadiver

Mr. Long Post
Apr 22, 2002
998
72
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Hi Sven,

It is sure fun dreaming on speargun design. I do get wet almost every weekend but there is nothing much new. It is always the same thing, bad visibility & under 10 kg fishes and I don't see that size fish more than 15% of the dive.

In fact I been practicing my freediving this past few trips and hence Rainbow Runners been the target, the only available target anyway. If I live in Bali, then it is a decent fish heaven, getting a 40 lbs doog tooth tuna is no news. I know someone got a 205 lbs doog tooth, this is why plenty of Tuna fleet hang around Bali waters.

I am planning a far away trip to visit a sea mount, this is why I got the #4 Baja for but weather and water is no good now on this Indian Ocean's 50 meter deep plateau arising from 2,000 meters sea bed.

Jakarta sucks in terms of fish availability, the worst in the entire country. I recalled I saw a 3' tarpoons swimming under the fuel dock in Florida area when I was testing a yacht 4 a client, we don't get that kind of sighting here.... no way. Anyway we don't have tarpoon here. I mean the US has developed a good control of their water based resources, no matter how lousy u think it is now, to me it is still way above heaven. From the sporfishing magazine available in the US, it is simple to see what kind of industry and fish stock vailability you guys are enjoying.

So therefore I really enjoy communicating with fellow spearos who has the opportunity living in fish-rich area. Actual frequent use of the guns allow better minds to wonder on "crazy" ideas and good techniques.

Since 30-60 foot visibility doesn't occur more than 5% a year in Jakarta coastal water, and I go to sea mostly on weekend only, my most frequent routine while diving is not shooting but dodging jelly fish and floating garbage......indeed sad. If visibility gets 40+, feet I really enjoy just looking at things around me.....we call it just happy to get wet......:naughty. The biggest Giant Trevally I ever got was like only 50lbs, they are already a rare sight, not worth writing in this kind of high-caliber forum.

So how's the Hybrid doing....photo please. :p and tell me what is the "technical" advantage u planned into the gun ?
 
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