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#11 GKU

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Posted 04 February 2014 - 08:11 PM

IMO,
One will need to give up one of two things, distance and or the spin rate of. The limited power of the human lung puts out a fixed X amount of energy and it will be used (shared) in propelling the dart forwards and some of that X amount of energy will be used (shared) to spin the dart. I would think one needs to figure out the maximum distance he or she will be using. From there they will need to figure out the spin rate at witch when reaching that distance it will be still spinning at lease a little before impact. At muzzle, spin rate will be higher than lets say down range at 50 feet. It will slow down fast then the dart drops off it's curve or even come to a complete stop altogether.

It's hard for me to give up distance to add spin to my darts. Even if it will add a little more accuracy at what less of a distance and how much added accuracy ? Lost of 30 feet to gain 1/4 inch more accuracy ?

If you may already notice that traditional cone darts already spin a little by them selves. Mark all the cones on a set of darts with a dot and load with the dot on top when loading. On impacting the target the dot on the cone will be at a different location. Have you ever wonder about flyers (the one that goes off the mark with no apparent reason) ? Well, there are other reason for them also but, I have notice that the ones that spin the most are often a flier ! My theory it that the spinning adds a slight spiraling and this increases the distance traveled and POI will be change as well.

FOOD FOR THOUGHT: More importantly find a way to STOP the traditional cone from spinning and we will have Great Distances with the added benefit of accuracy also !

In smooth bore riffle in guns were limited to the amount of gun powder one used. In blowguns the human lung. So adding rifling to guns was the easy direction (solution) at there time, if it's distance suffered use more gun powder. We can't add more lung power, so I believe more time is needed to find another path in the other direction, hence the above.

Don't mean to be the killer of JOY ! ...... in any and all case(s), good luck !!!

#12 Teach

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Posted 05 February 2014 - 12:52 PM

GKU makes very valid points here. 

 

Something to keep in mind when thinking about rifling as it applies to firearms is this. For this discussion you have basically two components that concern us of rifling......those are "lands and grooves". The tops of the lands are the actual bore diameter. The grooves are cut further into the barrel to provide something for the barrel to "bite" the bullet with to impart spin to the bullet. Ideally you would want the bullet sized so as to just touch the bottom of the grooves or be a thousandth or two bigger so as to create a seal of the burning gasses so they stay behind the bullet and keep pushing it until the bullet leaves the barrel. The force of the lands cutting into the bullet as it moves into the barrel to impart spin to the bullet is tremendous and the pressure of the burning gun powder is needed to overcome that resistance. If you were to try that with a blow gun under the power of the human lung one of two things will happen. Either the force required to propel that dart into the rifling would be too great or the loss of air moving past the dart cone as a result of poor seal would negate any advantage of spinning the projectile. Yes there are variables here one way or the other but that is why I still feel that the best results of imparting spin to a dart will happen by incorporating spin with the dart itself and not with the blowgun barrel the same way vanes or feathers on an arrow can impart spin to that arrow when used in a helical fashion. 

 

Something like this - www.youtube.com/watch?v=7w2WM-gVHCg 

 

Now maybe this guys methods are not the best or maybe they are? He is the only person I have seen who has tried to incorporate this idea using similar materials to that of other commercially made cones. But I really feel that this idea of using the cone to impart spin to the dart is the BETTER way to go. 

 

You have no losses of precious propulsion air pushing past the cone like in a rifled barrel.

Rifling would create air leaks that could not be overcome sufficiently with just lung power.

Darts are meant to be shot over and over and over. In a smooth bore thats possible with no relative harm to the cone.

Proper rifling would eventually erode the outer sealing edge of the cone creating even greater losses of propulsion air over time.

 

As I see it this one is a no brainer. But once I get my head around an idea I have also been known to be a little stubborn too! LOL



#13 GKU

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Posted 05 February 2014 - 09:11 PM

To rifle a bore is very difficult to do once correctly let alone repeatedly. Buy two exactly the same gun and they more than likely will shoot differently. One will be more accurate than the other at different velocities with the same pellet.

With that said, I would think adding this to a cone will be very difficult to replicate it's accuracy with all 5 match set of darts. I've notice that couple of minds had accuracy on their own but not together as a set with the others. They all look and had the same physical properties and etc as far as I could do. They all had their own separate flight characteristics. Shooting once and going back and forth to recover one dart would be a chore or remembering each of the 5 different compensations and shoot them.

Too or adding rifling to a blowgun I would think will be a lot different than in gun barrels. It would have large grooves and very shallow round landings. The spin rate will also be less, maybe just half of a turn for a 5 feet BG.


I would like to try it one day, but refuse to give up the distance for the added spin. For now I do prefer my long range shooting !

#14 Teach

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Posted 06 February 2014 - 12:16 AM

Well my friend, just hearing that you had success with individual darts is very encouraging, but that the problem was that each dart flew differently clearly suggests to me that fault lie in the manufacturing process. Having seen other types of darts that you make GKU I believe fully that you took great pains to reproduce each dart identically so as to obtain consistency. 

 

In that video I posted the link for GKU the guy in the video re used/re cycled old plastic materials that had already gone through the stretch and blow process in making that container to start with which may not be the best way to go. I could see problems with cone weights being inconsistent even though the cone might look identical to the one next to it simply because of a difference in plastic thickness relating to where/what part of the container the plastic was taken from.......ie the sides might be thinner than say the bottom of a container etc.. I'd be willing to bet that if a person could obtain say PE plastic that was new and of uniform thickness  the result would be quite different. And as it would be about to be put into it's first use you could eliminate any side affects or adverse affects from a materials first use when using recycled material. 

 

So material is a biggy, next comes making a suitable form and to do that in a perfect world we would use a CNC machine which most of us don't have access to but if we did..............

 

It is very easy to impart spin onto a dart. Even a simple narrow strip of tape placed on the cone at an angle from the plane of the shaft will impart spin to the dart. What we must overcome is finding a way to do said methods exactly the same each and every time. And doing it by hand the way we do paper or tape cones just adds more inconsistencies to the process. I suspect this is why speculum cones are proving to be the most accurate cones available. One fella even mentioned imparting spin to a bamboo dart but using a square dart shaft and heating the shaft - twisting the shaft while hot - holding the dart shaft in that position until it cooled. So it can easily be done. We need uniform materials and method repeatability. Thats all really.

 

My training coach at our local archery club proved to the club members that it took very little to stabilize an arrow and as long as the method was done exactly the same each time that match accuracy could be obtained. He then went on to kick everyones butt's that night with plastic drinking straws glued onto his arrow shafts as vanes using his fletching jig at home. If you can do that with arrows, surely it can be done with a dart. But, smaller is generally harder cuz our fingers sometimes being fat and stubby get in the way.

 

It will be a fun road to travel with many problems to discuss with friends and many successes to also celebrate. Together we will find a way.



#15 GKU

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Posted 06 February 2014 - 08:27 AM

I was into Archery many years ago.

The propulsion theory is not the same, a lot more like a sling shot.
BG and Air gun are closely related.

I used scapula, heated and remolded them with a jug I made. I remember it was an event that was very fun to try and shoot !

#16 squirrelslinger

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Posted 06 February 2014 - 05:35 PM

I have some twisted square shafts. It is actually quite difficult to twist a bamboo shaft of decent stiffness without cracking it. Incredibly so. 

1/8th inch square shafts, carefully split, cut, and gently planed from large diameter bamboo, with the edges just barely rounded...

can be twisted 360 degrees on an 8 inch shaft with an 80% survival rate.

The main problem is that with a manufactured skewer that is square, it is rarely perfectly straight and of perfectly consistent size down its length, which makes one part twist more than another, which leads to cracking. It is possible to improve the rate to 85-90% pass by using wet heat(steam@300 F) and GREEN(aka not cured) bamboo. Also, the shafts need to be heated to almost 300 degrees without burning them, also quite difficult to do. It is also critical that they be heated near-perfectly consistantly. My favorite method is to use a metal tube, with a little bit of water in it, to hold the shafts. They are ready to twist when the water has been gone for 5 mins. NEVER CAP THE TUBE. 

If you don't add the water, the shafts tend to crack. 

They do spin very well though.


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#17 GKU

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Posted 07 February 2014 - 09:04 AM

Yes, They were made that way by :

The Houma, Choctaw, and Creek people of the Southern US.

squirrelslinger , What kind of accuracy and distances are you achieving with these darts compared to traditional ones may I ask ?

I might be interested in making some.

#18 squirrelslinger

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Posted 07 February 2014 - 02:46 PM

They don't fly quite as far as the plain square shaft ones, but they are also signifigantly lighter, losing velocity quicker.

I use a .62 PVC blowgun 5 feet long.

They are more accurate(well, about half will land in a small group,  with the others scattered around... Its always the same ones in that group too) out to about 20 yards. I never shoot past 20 for accuracy.


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#19 squirrelslinger

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Posted 07 February 2014 - 02:49 PM

my accuracy does suck, so it isn't a good comparison to you guys.

make sure you have GREEN bamboo if you are going to just bake them. Or cure it yourself.

Else it either cracks or doesn't work too well. Tempered flooring is horrible for this.

if you buy some canes from someone, and they are whole, they will work fine. I grow my own bamboo(well, it is River Cane, which is an american species of bamboo) and split it.

if you cannot get any, I can send you some pieces, as much of it was killed by the -15 degree temps.


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#20 GKU

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Posted 07 February 2014 - 08:40 PM

squirrelslinger,

I appreciate the info in your post replies and a honest ones at that !

My neighbor up the street has bamboo growing in his yard, I'll be asking him for some.

60 feet is far man, that past the peck of the curve about 30-35 feet (trajectory fall off, witch I have been calling, "Over the other side of the Rainbow") any shooting past that is not easy ! This is where very unusually thing(s) can occur and IMO is the MOST interesting ranges to shoot in any closer is kind of boring for me. To get a dart to shoot at those ranges constantly accurately wail applying good shooting technic, is a on going challenge for me for the past 9 months. It's where I'm putting most of my shooting and dart making designing into at the moment.

So with all that said, that's good shooting squirrelslinger !!!




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