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08-22-2017, 02:04 PM | #46 | |
Blue Water Killer
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Re: More about the inverted polispast rollers
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the guns already exist and are from Itio , are the best made i ever saw on such wood guns , the little thing are the costs that could temperate some peoples ! i myself play making some inverted carbon guns and they shot the point from shaft at 9 meters from hand on a 122 or a 130 cms tubes . i do not release those for sell as i do not appreciate the amount of time spend on building those , and i am still awaiting to received some special shafts ordered in April that are not coming fast from Hunt ! About G spearguns , the videos with some shot on wahoos or dogtooth are in FB on his private page or in some FB groups . Yes Poema is / or ? was w G and i am sponsoring her . Same some her videos from her killing 30/35 kgs wahoos w my own made 2 rubbers carbon guns are in my FB pages .. i ll PM you the links rgds |
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08-22-2017, 02:23 PM | #47 | |
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Join Date: Jan 2014
Posts: 397
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Re: More about the inverted polispast rollers
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I always accept to have witnesses in my pool tests,like this one https://www.youtube.com/watch?v=B8ORqQWHUa0&t=10s The guy is one of biggest local importers of spearfishing gear.I dont have business with him.He is diving in the Med only with one of my guns.He wanted to be a witness himself and I didnt bribe or violate him I have always tried to be objective as possible!I dont oblige anybody to believe to my work.My work is much more than tieing bands and playing in the pool.In fact,i start to like pool shooting.I even start to think about mooving targets))) Soon I will film a detailed test with the gun the whole story is about! |
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08-22-2017, 03:14 PM | #48 |
Blue Water Killer
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Re: More about the inverted polispast rollers
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08-22-2017, 03:15 PM | #49 |
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Join Date: Aug 2016
Posts: 45
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Re: More about the inverted polispast rollers
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08-22-2017, 03:47 PM | #50 | |
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Join Date: Jan 2017
Location: Stockholm, Sweden
Posts: 286
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Re: More about the inverted polispast rollers
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The most pathetic about that is that the forum admin is well aware of how bad it is and he has not even the sense to comment on a thing that is upsetting to so many forum members. If it is cowardness, ignorance or just plain ol' disregard... who knows? |
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08-22-2017, 03:56 PM | #51 |
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Re: More about the inverted polispast rollers
Clicks make money
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08-22-2017, 04:03 PM | #52 |
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Join Date: Jan 2017
Location: Stockholm, Sweden
Posts: 286
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Re: More about the inverted polispast rollers
Wonder if the advertisers know or care about that the mass click generators are threads consisting of rasist and conspiratory bs?
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08-22-2017, 04:26 PM | #53 | |
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Join Date: Sep 2013
Posts: 318
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Re: More about the inverted polispast rollers
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Power: Bestiarius invert model with bottomside Archimedes pulley (sorry Seal but polispast is no allround accepted ) with setup 2 bottom pairs 18 mm and one 14 mm booster band and shaft 7.5 mm thick can be compared with classical 15-20 cm longer three band speargun. On thicker shaft like 8-9 mm I put additional bottom pair of bands. Range: in function of power so obviously .... Here in Croatia tuna spearfishing is not allowed but in Montenegro which is also on Adriatic sea is allowed and this and last year some guys had close meetings with 50-90 kg tuna. Leaved on line with 120 rollergun with 150/8,5 shaft on 5-7 m from the tip. Accuracy: much less recoil in combination with soft trigger and ergonomic high placed handle result in better accuracy especialy outside of pool in real spearfishing conditions when shots are taken in various body positions Complexity: are we talking of complexity of manufacturing or using? If I do not need any extra loadding hook, no extra rope for catching I think it's not any mode complicated than classic speargun. Ok, three loadings are needed... Field use: Answer is already given, maybe just can add that bands are on normal stretching factors 330-350%, so you don't need go to gym practice few months for loading bands on 400% Mainterance: some sweet water from time to time, silicone spray or some grease on trigger mech, changing main transmission dyneema rope every 4-5 years , changing bands no often than on classical speargun... |
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08-22-2017, 04:50 PM | #54 | |
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Join Date: Aug 2016
Posts: 45
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Re: More about the inverted polispast rollers
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I saw your gun in person at Andre's shop in Bali last year and was really impressed by the workmanship! I have a question: what stretch percentage do you put on the bottom 18mm rubbers? The first pair is easy to load because of the pulley advantage, but to stretch the second pair of 18mm without the pulley is difficult unless the stretch percentage is not high. Thanks! |
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08-22-2017, 05:35 PM | #55 |
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Location: Big Island
Posts: 5,098
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Re: More about the inverted polispast rollers
Lagfish, are you Geoff?
Thanks for the references Marc and Nevin. Nevin, Seal, do you or any in your area have experience with this concept? Does it work or is it just for stories?
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08-22-2017, 06:12 PM | #56 | |
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Location: Los Angeles
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Re: More about the inverted polispast rollers
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For that reason, I'm not sure how well the "gearshift roller" idea in those pictures you posted would work. While being able to play with torque certainly adds a fun new dimension, the line that is exerting force on the "gearshift roller" would probably have to have some means of ensuring contact (i.e. when a bike chain meshes with the spikes on the gears to ensure it doesn't slip). Otherwise, with the amount of forces involved, I would have to assume a fair amount of energy would be lost due to slippage. Apologies if I'm missing something fundamental or if this is way off base, just a ramble based on guesswork. |
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08-22-2017, 06:47 PM | #57 | |
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Re: More about the inverted polispast rollers
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I am not Geoff - just a newcomer to the sport who's really interested in guns . I spent 2 months in Bali earlier this year and I've been to Andre's shop a few times. I can offer some unsolicited advice regarding the pulley system as a mechanical engineer. I think it offers the following advantages over the pulley block: -You can get an extra 5cm or so of band stretch for a given size gun because you don't need pulley blocks to go between the rubber and pulley -There is a bit less mass (15g per pulley, which is very small compared to the mass of the rubbers) -There is a bit less water resistance from the movement of the pulleys through water -You can specify an exact gear ratio between the shaft and rubber instead of being stuck to multiples of 2:1 with the pulley block. You could even use a conical pulley to have a variable ratio to provide more force at the start of spear travel and more speed at the end of spear travel: The DreamAir gun uses something like this but with an air powered powerplant instead of pneumatic: It's more compelling to use a conical pulley for a rubber powered gun because the force vs. contraction speed of a pneumatic powerplant is probably much flatter than a rubber gun (think electric vs. gasoline motor). You can approximate the functionality of the conical pulley by using a large diameter rope and a small enough channel width so the rope spools in a single layer. As the rubbers contract, it will pull more rope from the pulley which will cause its effective diameter to be smaller and gear ratio to be greater, providing more speed for the spear. -Less moving parts Potential downsides: -Probably less efficient because now you have 4 ropes that are spooling over themselves rather than just the plastic pulley which creates more friction -Maybe you can get some side forces on the spear if the rope lengths are not matched or they spool on the pulleys differently on the left and right side of the gun which can potentially make the gun less accurate -Untested concept that needs more R&D Last edited by lagfish; 08-22-2017 at 07:16 PM. |
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08-22-2017, 07:51 PM | #58 |
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Location: Big Island
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Re: More about the inverted polispast rollers
Dang, we're always happy to have Mechanical Engineers in Speargun Performance conversations. Especially ones who know how good that little lunch place is accross the street from Dre's. I lived in Bali for 23 years.
I guess we are always looking for Force Multipliers.. Essentially we are on the quest to mimic the Cam's and increases in Retraction speeds you find in Archery.
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08-23-2017, 01:07 AM | #59 |
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Re: More about the inverted polispast rollers
Neven:Bestiarius invert model with bottomside Archimedes pulley (sorry Seal but polispast is no allround accepted )
I hope its a joke and you mean just the word is not accepted?Its true I used for first time the word "polispast",taking it from the compound bows.Thats how we call them here. But for spearguns " Arhimede" and "Polispast" is the same thing. |
08-23-2017, 02:06 AM | #60 | |
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Posts: 318
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Re: More about the inverted polispast rollers
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Last edited by gspearguns; 08-23-2017 at 02:15 AM. |
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