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roller gun

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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Fondueset

Fondueset

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Jul 27, 2004
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HUGE diff in trajectory between a compound and conventional because of the way they accelerate. The arrow gets going faster - it is still accelerating when it leaves the bow. With a conventional bow peak acceleration is at the moment of release - creating more stress on the arrow and dropping off immediately. At least that's what I recall from way back when I was into archery. Also the draw weight is limited by where the peak is relative to the arms best position for exertion and, of course - endurance - the first would be helpful in a speargun - the second; irrelevant. so in a compound you get greater effective weight than is even possible with a conventional bow and a smoother, flatter trajectory with greater velocity for that weight - these last obviously of most interest in a speargun.

Big diff is with a band-gun the bands = both the limbs of the bow and the string.

Compound/conventional bow explaination
 
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persiko

persiko

persiko
Jan 20, 2005
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unirdna said:
...................
Back to the subject... Very nice-looking craftmanship, persiko. Do you all suppose rollerguns are the wave of the future, or just a luxury for a select group of super-charged spearos. Has Daryl Wong or Jay Riffe ever made any, or posted any thoughts online re: such designs?

Ted

I task am one good road for having good power in a short arm.

I have tried it in water and have had one optimal impression, but I am making some small modifications for the gummies ones and a shifter of power
 
OregonSpearo

OregonSpearo

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Compound speargun

Limbs are definitely not the way to go underwater!
The main hurdle is fluid friction, proportional to speed, so the cam-effect must happen with little to no geometry change perpendicular to motion during release. Check out this compound speargun design:
http://rocknfish.com/SeaArcher.html
The drums have a large diameter so they don't need to spin that fast (unlike your typical rollergun). Geometry change of the cam effect is in-line with the direction of release. I think that's a pretty sleek design, which adapted to a speargun would allow for a more sensitive trigger.
 
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Fondueset

Fondueset

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Jul 27, 2004
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That's pretty close to what I was picturing - with the rollers mounted for minimum drag/water resistance. Wonder if it makes any diff for power in relation to length.

You might want two sets of rollers - one conventional set mounted near the muzzle - as in a regular roller gun - then the cam-rollers mounted under - or in the gun body to minimize their profile. Interesting idea - wish I had a way to test it.
 
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D

defofthecrown

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Oregon spearo I was just getting around to adding that link. Pretty neat little sling huh?
 
OregonSpearo

OregonSpearo

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defofthecrown said:
Oregon spearo I was just getting around to adding that link. Pretty neat little sling huh?
Too bad the design is patented.
 
rigdvr

rigdvr

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unirdna said:
Do you all suppose rollerguns are the wave of the future, or just a luxury for a select group of super-charged spearos.
Ted
Ted, the rollergun is far from a new concept. It hasnt really ever caught on for one reason or another and I'll leave it at that :D
 
OregonSpearo

OregonSpearo

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rigdvr said:
Ted, the rollergun is far from a new concept. It hasnt really ever caught on for one reason or another and I'll leave it at that :D

Spearguns designed in the 70's were far more technically advanced than today's. Take a look at some of those 70's designs, some real ingenuity went into them:http://rocknfish.com/Vintage.html
However, spearguns that won the market since are simple, cheap band-operated guns. Low-end simplicity always wins. As Paul Graham puts it :

"In technology, the low end always eats the high end. It's easier to make an inexpensive product more powerful than to make a powerful product cheaper. So the products that start as cheap, simple options tend to gradually grow more powerful till, like water rising in a room, they squash the "high-end" products against the ceiling."
 
rigdvr

rigdvr

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Oregon, I agree. Making my living on the sea though...usually simpler is better. On the other hand, if the advantages were that great, you would at least more high end custom makers with rollerguns.
 
miles

miles

BORN WILD!!!
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Jun 13, 2003
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Hiya

No offence to anybody, but please explain what makes a roller gun better than a normal gun??

I understand that you can make your gun more powerful, but adding another band will do exactly the same. Similarly, with a mid-handled gun, you have a VERY manouverable gun, with plenty of power (i'm thinking here of the idea of a small roller gun which is easy to manouver, yet has the power of a larger gun)

Persiko, the gun is BEAUTIFUL!!!!!

Regards
miles
 
persiko

persiko

persiko
Jan 20, 2005
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Tanks Miles
I can say that my 70 roller is power like an 100 gun (one band) but is 30 cm short, ideal for the ambush in italian coast why he is much maneuverable one.
construction is one a complicated more. but nothing is perfect!! :)
Now I think to a similar roller 70 but of 30 milimeter of thickness and a carbon wood construction.
ciao



miles said:
Hiya

No offence to anybody, but please explain what makes a roller gun better than a normal gun??

I understand that you can make your gun more powerful, but adding another band will do exactly the same. Similarly, with a mid-handled gun, you have a VERY manouverable gun, with plenty of power (i'm thinking here of the idea of a small roller gun which is easy to manouver, yet has the power of a larger gun)

Persiko, the gun is BEAUTIFUL!!!!!

Regards
miles
 
OregonSpearo

OregonSpearo

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miles said:
Hiya

No offence to anybody, but please explain what makes a roller gun better than a normal gun??
On a regular gun the bands pull the shaft with great first at the beginning, then less and less and almost no force near the end when the bands are relaxed, so the shaft accelerates strongly at the beginning and very little past halfway.

On a rollergun, the pull is strong all the way until the end. It's kind of like a pneumatic, where you have 250 psi when you shoot and still 200psi pushing when the shaft leaves the gun. Hence with the same barrel length a pneumatic will shoot further than a regular band gun. The roller system makes a band gun's dynamics be more like that of a pneumatic gun, so compared to a regular band gun, a roller gun of the same length will shoot further.
 
miles

miles

BORN WILD!!!
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Jun 13, 2003
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Hiya

Ok, understood!!!:D:D

But wouldn't adding a second rubber to your gun have the same effect?

Regards
miles
 
F

fuzz

Hawaiian transplant...
Sep 9, 2002
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miles said:
Hiya

Ok, understood!!!:D:D

But wouldn't adding a second rubber to your gun have the same effect?

Regards
miles


Yes it would. But then it wouldn't look so cool! :)


I've only been able to use a rollergun once.. & I ended up breaking it :( Not really my fault, the roller came whipping back at me when a screw stripped. But that's a whole other story.

The rollergun I used had a relatively soft band & while the increased power was noticeable, the real advantage I noticed was that the shot was smooth since the band stretch wasn't as short(makes some guns punchy). The power was extended longer & the shaft flew out of there with very little recoil. If I used a bigger band or a punchier one(like a white or blue band), I'm sure the recoil would have been horrible. But for the setup, as with most guns, the right band size/strength made a world of difference.
 
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