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

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Old 07-01-2020, 10:21 PM   #1
hydroid
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Salvimar Tomahawk

Saw an interesting gun that came on my FB feed, Salvimar Tomahawk. Not that I'm in the market, just need to use the ones I got hahaha.
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Old 07-01-2020, 10:37 PM   #2
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Re: Salvimar Tomahawk


https://www.apneapassion.com/equipme...-unique-power/
Rollergun with stretch limited black bands and red doubled up rear sets of bands.

Last edited by popgun pete; 07-01-2020 at 10:52 PM.
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Old 07-02-2020, 02:09 AM   #3
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Re: Salvimar Tomahawk

That's the one, thanks popgun pete.
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Old 07-06-2020, 10:31 PM   #4
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Re: Salvimar Tomahawk

Does the braintrust have any opinions on this gun?
The band system is interesting.
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Old 07-07-2020, 01:27 AM   #5
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Re: Salvimar Tomahawk

Mass market version of what has been available from the specialists, but alloy barrel and plastic parts to contain costs.
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Old 07-15-2023, 09:23 PM   #6
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Re: Salvimar Tomahawk

If we look at the Salvimar Tomahawk which is a production rollergun using stretch limited front bands we can estimate the elongations used by laying out the static band length against what it is stretched. Note that a band with 100 percent elongation is stretched by a factor of two, a band with 200 percent elongation is stretched by a factor of three and so on. We can see from the photo that Salvimar keep the band stretch factors from being too large, remaining below 300 percent elongation or a stretch factor of four. Bear in mind that when stretched the front band wraps the muzzle rollers.

Note that a second rear band, not shown here, has to stretch further onto the rearmost anchor point.
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Old 07-15-2023, 09:29 PM   #7
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Re: Salvimar Tomahawk

You can see claims of rubber being taken to 600 or even 800 percent elongation as a material, but that is not realistic for speargun power bands. At higher elongations rubber begins to yield and will not return fully to its original length or strength. Spearguns use around 300 percent elongation, if you use much more then the bands get tired and don't perform like they used to. What you need in a speargun are reproducible shots. Using rubber bands at around 300 percent elongation the results are consistent. The stretch limited bands are to preserve the elasticity of the rubber from being overstrained in the hybrid rollerguns. Truly elastic materials don't lose their shape and return energy from being deformed, in that sense rubber is not truly elastic, but we use the term in that sense.

An example of elastic collisions is those metal balls on strings in a suspension frame swinging back and forth clicking into each other in groups. They continue swinging due to the high elasticity of steel balls. Also think of those very hard "superballs" that you could drop from a high vantage point and bounce right back up to you, which is elastic behaviour.

In order to have our power bands perform elastically in the technical sense we use low stretch factors so that they operate for a long period as reliable energy storage mediums. For a time I worked in the rubber industry and know that there were many laboratory tests used to routinely assess the characteristics of different blends or compounds of rubber, one of them being their elongation under load and repeated cycling.
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Old 07-16-2023, 02:06 AM   #8
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Re: Salvimar Tomahawk

Looking from underneath the Salvimar Tomahawk with all bands cocked.
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Old 07-17-2023, 11:08 PM   #9
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Re: Salvimar Tomahawk

Deconstructing the Salvimar gun, although here I am showing a layout using a three band battery rather than two. The benefit of the muzzle roller is it acts as a damper by folding rubber that passes over it, whereas the standard gun receives all the band energy directly onto the spear. I am pretty sure that this damping effect is what takes most of the jerk out of rollergun recoil, but not all of it. Bending rubber requires some energy, if you pulled a band back and forth over a roller then you would find the band heats up.
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Old 07-19-2023, 09:14 PM   #10
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Re: Salvimar Tomahawk

Quote:
Originally Posted by popgun pete View Post
Deconstructing the Salvimar gun, although here I am showing a layout using a three band battery rather than two. The benefit of the muzzle roller is it acts as a damper by folding rubber that passes over it, whereas the standard gun receives all the band energy directly onto the spear. I am pretty sure that this damping effect is what takes most of the jerk out of rollergun recoil, but not all of it. Bending rubber requires some energy, if you pulled a band back and forth over a roller then you would find the band heats up.
They are losing about 2-3in per side of band stretch with those long "wishbones" & and junctions. If they could tighten up their bands they prob could squeeze a bit more out of her.
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Old 07-20-2023, 10:53 PM   #11
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Re: Salvimar Tomahawk

Does not look to be a very heavy gun, they probably decided on what was needed without overdoing it. Most guns using this format of band drive are timber guns or carbon fiber and would be heavier than this gun from Salvimar which borrows from their other models. They are expensive for what they are, but a recent sale with the price reduced by about 50 percent saw all the guns sold.
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Old 07-29-2023, 10:54 AM   #12
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Re: Salvimar Tomahawk

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Originally Posted by popgun pete View Post
Does not look to be a very heavy gun, they probably decided on what was needed without overdoing it. Most guns using this format of band drive are timber guns or carbon fiber and would be heavier than this gun from Salvimar which borrows from their other models. They are expensive for what they are, but a recent sale with the price reduced by about 50 percent saw all the guns sold.
The review given on youtube claimed that the gun was very muzzle light and the shooter would have to correct the shot a lot due to the muzzle wanting to lift at depth.
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Old 07-29-2023, 07:42 PM   #13
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Re: Salvimar Tomahawk

Review here https://apnealogy.com/salvimar-tomahawk-speargun/
Reviews are often thinly disguised adverts, so they need to be taken for what they are, and that is to provide incentive to buy one.

If there is a muzzle buoyancy problem then weight could be added to it such as inside what looks like a tubular roller axle. Gun buoyancy after the spear departs should not be mistaken for muzzle lift.

Band sets seem expensive!
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Old 07-30-2023, 07:37 AM   #14
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Re: Salvimar Tomahawk

Primeline says the maximum stretch of their tubing is 400%. However, they recommend that you keep max stretch right around 380% to maximize performance and tubing longevity. Also, to maximize longevity, they recommend storing your tubing at 70 degrees and 50% humidity and store in a dark place. Hot and humid air will rapidly break down latex tubing. I know some folks like to keep their tubing in the refrigerator or freezer but that is also not recommended. Air in the refrigerator is dry and the air in the freezer is even dryer and this is not good for the tubing as it will dry the moisture from the tubing. So if you live in a hot/humid area, to maximize band life place the bands/tubing in a plastic bag and place them in a dark closet or dresser drawer inside your home.
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