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titanium tubing

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

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Jan 3, 2004
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Only the members of DB would consider 65" to be a short span:)
 
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peskydor

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Jul 19, 2004
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Waverider, if you can find some 0.035 titanium alloy it will be strong enough for guns up to 60" rubber pull. Fill it with 3# foam for buoyancy.

I saw a big aluminum gun buckle. It was a heavily loaded Sea Hunter Custom with 60" pull. The gun with muzzle and aluminum grooved barrel was 1 1/4 X0.035 X 69 . So, titanium of the same dimensions should be plenty strong.

I'd better add the fact that I saw these guns in use in all kinds of situations for many years, saw 250lb black sea bass taken with them, and only after years of fatigue and corrosion, did I see one fail. We went to stainless steel with our replacements, but titanium alloy should be fine for your purposes, just a tad thicker.

Pure titanium has crap for tensile strength. This stuff is rare in the retail market but sometimes tubing which is intended for corrosives is made of commercially pure metal. Almost any alloy one can name has huge strength.
 
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ajwaverider

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Jan 3, 2004
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What I have is an alloy . I was waiting for you to post .You get
very technical with some of your post so I knew after you post I would have all bases covered. The length of the pipe for the gun will be 50" with 9"or so of that for the buttrest and trigger mech/housing.The length from the muzzle to where the trigger mech will be is around 43" so that is really where the flex if any will occure . I'm not sure but I think that anything behind the trigger mech will not count as barrel length . Any ideas on it from you are welcome . I spent most of last night and this mourning on generator duty so i.m not all here at the moment.
 
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peskydor

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Jul 19, 2004
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Hey wave, I could quote some stats if I knew the alloy but for a gun with 43 inch pull the 0.030 barrel thickness should be fine. The foam will add quite a bit of stiffness. Irrespective, the 0.030 barrel will probably show zero flex up to 300 pounds load. If you go heavier, just take a sight along the barrel to check for flex. Duralumin, the material used for most barrels, has 45,000 psi tensile strength. Any titanium alloy should be at least twice that.
 
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peskydor

New Member
Jul 19, 2004
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Have you thought about a plastic rail? Somebody mentioned delrin(TM). That stuff should make for a good rail.
 
icarus pacific

icarus pacific

Human-in-training
Nov 7, 2001
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Originally posted by ajwaverider
Only the members of DB would consider 65" to be a short span:)

Actually, I'm just getting done pulling the clamps on what will be a 63" gunstockwith a net 61" pull. It's purple . Stay tuned.
 
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ajwaverider

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Jan 3, 2004
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Pesky! I wish I knew what alloy but i'm not sure.I'm going to use a jbl rail because it will save time and the LDS has some instock.
I read a post of someone saying something about seeing a euro with an enclosed track and I plan on building one .I want to shoot 9/32 shafts 45 inches long or just 4" or 5" hanging off the muzzle so maybe an enclosed track will not help me,only if I overpower it .

Sven! Just goes to show . When you think your gun is big somebody always has one bigger.Now i'm feeling inadequate:(
 
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peskydor

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Jul 19, 2004
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Wave, I calculated the deflection of a 43 inch titanium alloy tube with 400 pounds axial load. I used 0.030 wall and 1.25 inch dia. The deflection is 0.009 inches. If the load is slightly off center, as with a typical speargun, the deflection will be a few percent greater than 9 thousandths, maybe about 10-11 thousandths. Doesn't look bad. I used a typical alloy, Titanium 6-4 in making this estimate.
 
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peskydor

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Jul 19, 2004
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If you are still considering the Sea Hornet trigger I would urge that you buy a new Biller trigger instead. The sear is hardened steel. Biller has changed the pivot position of the trigger and also shortened the stroke. The Biller trigger can handle fairly heavy loads in a 43 inch pull which is comparable to the Biller 54 with three 9/16 bands of 24 inch low modulus or 26 inch high modulus rubber.
 
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peskydor

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Jul 19, 2004
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I don't understand the 45" shaft thing. As you can see, the Biller Tahitian shaft, at 54 inches, just barely fits the gun, a gun with 43 inch pull. I suggest a 55" shaft.
 
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ajwaverider

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Jan 3, 2004
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The trigger mech will be either a riffe or a yokooji.For bands 2 5/8
I will use riffes band pull measurment to size band length.If 45" is to short I will have to get the next size up wich is proball 55".Is the biller you are refering to in the modifying the biller 54 thread?I
just don't want the spear sticking out to far past the muzzle.I got a question for you .Have you seen the muzzle on the picasso century pacific? The muzzle fits over the barrel instead of inside it like most tube guns. Do you think there is any advantages or
disadvantages having it this way. I don't have access to a lathe but I can drill a hole for the barrel with my drill press.I'll look at that thread and see what you got going on .
 
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peskydor

New Member
Jul 19, 2004
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I looked at a 67" tube with 430 lb load. Deflection should be only .015. I don't know what's up with that. If it's actually deflecting .125 or better, modulus would be about the same as dead soft aluminum. I donno.....
 
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peskydor

New Member
Jul 19, 2004
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I don't know why Picasso would use an exterior muzzle. That method is done with wood for obvious reasons. There isn't enough side torque on the aluminum barrel to drive that decision. It could have to do with the stand off of the arrow from the barrel or the method of attaching rubber bands. Dunno. I'll take a look sometime.
 
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GilbertG.

New Member
Jul 28, 2004
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IP - 63" ?? Dang that's a beast! What you got brewing a tuna gun? Post some pics dude. WOOD like to see...

AJ - I think your test on the 67" inch piece should cover you plenty on your 43" barrel. Have fun building.

P'dor - Your deflection calcs seem pretty low. 0.009 inch is barely visible to the human eye. Maybe your mixing up axial deflection (shortening) versus lateral deflection (bowing outward). Try this equation for lateral deflection: d = PeL^2/(8EI). d = lateral deflection, P = compressive load, e = eccentricity or load offset from centerline, E = young's modulus, I = moment of inertia. Take my word on this one, its a fairly common equation found in many engineering handbooks. Hope this helps.

Gil :)
 
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peskydor

New Member
Jul 19, 2004
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Thanks, Gilbert, I believe you are correct.
 
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