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Spear tails and line slides: the Engineering that Time Forgot

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popgun pete

popgun pete

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Jul 30, 2008
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Pneumatic spearguns from the beginning used a coil spring as a shock absorber in the line slide assembly on their spear shafts once they quit using front tied spears. That was almost universal until Mares introduced their first Cyrano which was a gun dedicated to shooting 7 mm shafts. Mares introduced a new hydrodynamic plastic line slide backed by the usual metal stop ring or thick washer, but the intervening coil spring was gone. Instead they tied a rubber ring like a big "O" ring into a line loop in the line end connected to the muzzle which acted as a shock absorber to protect the shooting line from strong jerks, plus it also had the advantage of tensioning the shooting line when the line wraps were wound on the gun’s line hooks.

What they had forgotten was the shock absorbing coil spring also protected the line slide from shocks, particularly shocks that had the potential to crack the plastic versions. The purpose of the metal stop ring is to spread the impact over as wide an area as possible on the back of the line slide and this was also achieved with the coil spring by pinching the last coil at each end and grinding the spring ends flat so that the line slide sat on an almost complete metal ring. The omission of this coil spring meant that plastic line slides were then being hammered as the spear collected them on the way out the muzzle. This effect was exacerbated when plastic line slides appeared with crosscut slotted backs to weaken them further in the interests of running mono shooting line close to the shaft as the shaft flies through the water. Metal line slides have been used instead, but to keep their weight down they are rarely symmetrical and drag the shaft from one side. Ideally the shooting line should be pulled in the shaft's wake running coaxial to the shaft and this was usually accomplished by line running from either side of the line slide in a short loop that connected to the shooting line, the loop being just long enough to extend past the shaft’s tail end.

The old-style plastic line slides were more robust than the current crop which in seeking streamlining have become too weak, plus depressingly many seemed designed only for mono. You can still buy the older designs from suppliers like Salvimar who also make parts for many other brands.
Cyrano slider
Mares original line slide

Salvimar line slide

MARES STEN LINE SLIDE
 
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tromic

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Aug 13, 2007
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In may opinion it is much better to use titanium or even stainless steel line slide having hydro damper possibility.
For example like this Tomba700XS line slide "www.youtube.com/watch?v=iRg3rxIwDH8&t=913s"
1647172876316

or Pelengas titanium hydro damping line slide
1647173821404
 
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popgun pete

popgun pete

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Most manufactures want to keep their costs low so still use plastic line slides, the only exception being the Omer “Airbalete” which had a strange tubular metal line slide. This is in keeping with integral tip spears which are cheaper to make than threaded spears with the additional screw on spear tip. Omitting tail springs also saved money. At one time Mares tried offering shafts that had lugs punched on the sides to catch the stop ring rather than a screw on tail of 1 mm larger diameter. These were a failure, in fact they came out when the Mirage was released and if you look closely you can see them on the Mirage exploded parts diagram. The stop ring soon chewed the leading edge of the bumps creating sharp edges which needed to be kept off the inner barrel wall so you definitely did not want the shaft to come loose in a cocked gun.
 
marco15499

marco15499

Laguneros Spearfishing
Apr 4, 2011
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I've been trying the "Tumolo" slide system and so far I love it. Sometimes, simplest things do the job better than sophisticated solutions. This is genius.

 
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popgun pete

popgun pete

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I watched the video, a running line loop on the shaft, a method that Tromic has mentioned here in the past, would not be of much use to me as a shaft that breaks off is a lost shaft disappearing into an often uneven weedy bottom. Only shafts I have found by chance once belonged to others.
 
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tromic

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Aug 13, 2007
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I found some old ideas presented a years ago on this forum. Most of the images are invisible now (they were hosted by Image Shark).

1647330119801

Here is climax tied to the small stainless steel ring. It is better than to make a loop on the shaft directly. Friction is much lower.
This was for use with Tomba kit so there are some additional parts on the shaft which are not necessary in different setup.


This was an another idea, very similar to "free shaft" concept, much better in performance, but less safe regarding possibility to lose the shaft...
 
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7BDiver

7BDiver

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Sep 5, 2019
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Can you explain how the hydro damping works, it is a little difficult to tell from the picture. I could see that a line slide with an integrated barrel sliding over the seal with small holes for water to be forced out might work in a similar fashion to the shock spring but more like a hydraulic shock. Have you seen any slides built that way?
 
popgun pete

popgun pete

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Jul 30, 2008
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Hydro damping works by using a polyurethane bush acting as the front end of the shaft tail stop which pushes into a slightly larger diameter recess in the back end of a metal line slide. Water which is incompressible is then squeezed out of the gaps at either end of the line slide thereby slowing the impact down just enough to remove the strong jerk. The downside is these impacting components can stick together and then require a sharp pull to separate the line slide from the shaft tail so that it is ready for the next shot, but it is not that hard to do if you grab the shooting line and jerk it free. These polyurethane bushes eventually wear out, although later versions are able to be replaced by the user. Found in spearguns from Russia and Ukraine where this design has been in use for many years.
Taimen spear tail replaceable polyurethane bush
 
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tromic

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Aug 13, 2007
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Can you explain how the hydro damping works, it is a little difficult to tell from the picture. I could see that a line slide with an integrated barrel sliding over the seal with small holes for water to be forced out might work in a similar fashion to the shock spring but more like a hydraulic shock. Have you seen any slides built that way?
Here is the physics behind hydro damper presented in the video "www.youtube.com/watch?v=iRg3rxIwDH8&t=913s"
What Pete explained is an different type of "hydro damper" having additional polyurethane bush.
There is combined action of both water and polyurethane bush.
My design uses only water for damper to work.
 
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popgun pete

popgun pete

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Jul 30, 2008
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The polyurethane bush helps with the spear’s tail stop passing through the vacuum cuff in guns with sealed muzzles, but it also helps the line slide or slider in not being jammed up by grit that gets caught in the tiny annular gap between the components. Spears if they miss can end up on the bottom and may pick up grit and it would not take much to jam a tight gap. Because the polyurethane is yielding it allows the slider to be pulled free even though slight damage may occur to the polyurethane with grit tearing it. That is why the polyurethane bushes eventually wear out, but as you can see above they can be replaced, although in the past you needed a new spear as the polyurethane was moulded into position.
 
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