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Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Ragnarok » Wed Jul 29, 2009 5:20 am

inonickname wrote:Has anyone noticed how one sided and perfect he is?

On this note...

Boyntonstu, I almost get the impression that you're not here to discuss and get feedback on the idea, but that you're here to to brag that you've had said idea.

The thing is, you seem to be discarding any criticisms of the idea as unimportant, or you're avoiding answering them by spouting other scarcely related boasts as a distraction.

This forum is about discussing ideas. If you're not going to take on board and consider what we have to say, what exactly is the point of this topic, or even your membership of the site?
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Unread postAuthor: inonickname » Wed Jul 29, 2009 5:29 am

Yep, I noticed that extensively in his "HHO" topic..

Any time that somebody suggested it didn't increase mileage, it wasn't the worlds savior and it wasn't perfect they were immediately an idiot.

Boyn, I've seen replies on other forums towards you after similar things. You really should take other people's criticism and thoughts on board.

I'll say it now. Elastic bands will not become the next generation of mega powerful guns.
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Unread postAuthor: Technician1002 » Wed Jul 29, 2009 5:36 am

I hate to say it.. but could members discussions be taken to PM's.. It's looking like the start of a fame war here, which is against the rules.

Opps, I just read the rules..

Keep the flaming to a minimum.


Carry on, but keep it down.. :D
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Unread postAuthor: Ragnarok » Wed Jul 29, 2009 6:26 am

@ inonickname: On the note of other forums, to quote the man himself:

BoyntonStu wrote:What is it with newbies who think that by signing up for a forum they can shoot their newbie mouths off?

Words like pot, kettle and black come to mind.

I have no desire to create rocky relations with you, boyntonstu, but in this case it's you that's the newcomer to the forum, and you're shooting your mouth off at anyone who disagrees with your ideas or point of view - or simply treating them as though they're idiots.

<understatement>This is not going to make you popular.</understatement>

We've seen most ideas before. We've tried many of them (or something similar) ourselves. Some of us have the scars - or worse - from when these ideas backfired (sometimes literally).

When we say an idea has problems, we're doing it in your interests, and yours alone.
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Re: Check this out!

Unread postAuthor: boyntonstu » Wed Jul 29, 2009 6:35 am

Ragnarok wrote:
boyntonstu wrote:This is a homemade pneumatic forum, what does a store bought springer have to do with anything here?

You should always ask: Is the way I'm doing this an effective option?

What you're looking at is more complication, more risk and likely more cost than a conventional springer.

When I say more risk, let me explain. I crushed off part of the side of one of my fingers trying to do this kind of thing. It was pure blind luck that stopped me doing any worse.
This was in spite of precautions I was taking to avoid such things. In the end, even for an almost abnormally quick healer like me, it took months to recover and leaked all kinds of fluids I didn't even know the human body could produce for most of that time.
And I did that with a whole lot less power than you're trying to use.

Ask yourself if those are risks you're prepared to take.
Based on what I've seen of your posts on the forum, I'm really not sure you're fully aware of all the hazards that can exist with a project like this, nor how to spot and avoid them.

I'd advise starting with a less ambitious project, then come back to this when you're ready for it. I know, you wander in, see all these shiny projects and want to follow suit, but I started spudding years ago, and I've still got to double back to my ambitious early projects.

"A 300 pound slingshot isn't going to record 6 times the energy of a 50 pound slingshot."
On what evidence/theory do you base this statement?

A greater proportion of the total energy is absorbed as heat and kinetic energy in the elastic as draw strength and velocity increase.

It's just like if I pressurize my cannons to twice the pressure, I don't get back twice the kinetic energy.

Why is 1,200 fps so important?

The specific number isn't important. But I'm illustrating there are areas in which either form of power can best the other.

While slingshots might have a slight edge on energy, springers can wipe the floor with them on velocity and accuracy.

What I'm trying to say is that it's fairly pointless throwing up "Can ANY X do Y?" challenges, because it's easily parried and countered.


First, let me say that I take suggestions very seriously, especially safety warnings.

My ideas develop in reaction to suggestions.

I love criticism, it saves me time and trouble.

I am intrigued with the idea of obtaining kinetic energy with high speed without igniting fuel and without pre-compressing air.

I am not here to argue or to brag, just to share ideas and to listen.

Let me digress:

7 years ago, I shared my concept of building an elevator for under $100 on Google.

There were many naysayers, and after taking in their comments, my concept evolved. 7 years later, and after hundreds of hours of use, I believe that I have proven that a safe elevator could be built for $100.

http://www.youtube.com/watch?v=_hom61NxuaE

Back to the danger of the rubber snapping.

A little history: I was in the Navy when Nylon lines were substituted for manila. The 3" diameter Nylon stretched to about 70% in length with tremendous stored energy, and when it failed, the snap killed several sailors. Needless to say, the Nylon was discarded.

What I see as a possible solution in my gun design, is some sort of safety wall/deflector between the rubber an me. Should the rubber disconnect from its forward mount, it will snap towards the trigger and its inertia will take it further. I don't want to be in its way when it happens.

If there was a wooden or Plexiglas fence several inches high, I believe that it would protect me.

Would this idea have prevented your injury?

What caused your accident?

BoyntonStu
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Unread postAuthor: inonickname » Wed Jul 29, 2009 7:35 am

Alright, no problems then.

For a shield, I wouldn't recommend plexiglass. Lexan is a far better option. (polycarbonate)

Linky

(mods, it is slightly against forum rules, but only in the tiniest way and it's posting is valid I believe..)
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Re: Check this out!

Unread postAuthor: Ragnarok » Wed Jul 29, 2009 4:40 pm

boyntonstu wrote:First, let me say that I take suggestions very seriously, especially safety warnings.

Good choice. I see all too many people who don't take safety warnings.

You would have thought that looking down the barrel of a gun was a bad idea, but people can still be stupid enough to do it.

I am intrigued with the idea of obtaining kinetic energy with high speed without igniting fuel and without pre-compressing air.

Well, that's not exactly specific to a design like this. There are a great many ways to get kinetic energy without igniting fuel, or compressed air.

I have a design that fits the description in the pipeline, which uses magnetic fields to do the job.
I'll admit it's not the easiest solution to the job, but it's something of a challenge, and I like challenges. Also, it's cool (in a geeky way) to have a rifle pretty much lifted directly from science fiction.

7 years later, and after hundreds of hours of use, I believe that I have proven that a safe elevator could be built for $100.

Thus illustrating the importance of taking in feedback.
While I don't doubt the idea may have merits, you still need to ask yourself if this is the right way to go, considering not just cost and performance, but difficulty of construction and associated risks.

What I see as a possible solution in my gun design, is some sort of safety wall/deflector between the rubber and me.

Well, the only option to make something like this safe is isolating all dangerous parts from the user - or alternately, isolating the user from dangerous parts.

My accident made the choice of air rifle I later bought an easier one. If looking for a top of the line underlever spring rifle, the choices are really the Air Arms TX200 or the Weihrauch HW97K.

The one I eventually went for (the Air Arms) was the one that with the design that would stop me having a repeat accident. The design makes it damn near impossible to catch your fingers in it - you'd have to be TRYING to get yourself an injury.

Would this idea have prevented your injury?

The only thing that would have really worked is sealing away any moving parts. If you're doing this kind of thing, a shield here and there is a waste - seal it in properly, and have shields that can be moved for the parts you HAVE to get to, then put them back in place when you're done.

You'll also need to make sure the construction doesn't fail under load, for which you need to have a solid grip on the obscene forces generated in this kind of thing.

What caused your accident?

Complacency. I put a hand a hair too close to where shouldn't've been, and then a failsafe that I thought was solid failed on me - wham.

If I were doing it again, I'dn't've been daft enough to get myself in that position. Unlike some people, I learnt from it (without being scared off) and it was fortunately something that was capable of growing back - although I am still left with a less than pleasant scar as a reminder.
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Re: Check this out!

Unread postAuthor: boyntonstu » Wed Jul 29, 2009 4:51 pm

Ragnarok wrote:
boyntonstu wrote:First, let me say that I take suggestions very seriously, especially safety warnings.

Good choice. I see all too many people who don't take safety warnings.

You would have thought that looking down the barrel of a gun was a bad idea, but people can still be stupid enough to do it.

I am intrigued with the idea of obtaining kinetic energy with high speed without igniting fuel and without pre-compressing air.

Well, that's not exactly specific to a design like this. There are a great many ways to get kinetic energy without igniting fuel, or compressed air.

I have a design that fits the description in the pipeline, which uses magnetic fields to do the job.
I'll admit it's not the easiest solution to the job, but it's something of a challenge, and I like challenges. Also, it's cool (in a geeky way) to have a rifle pretty much lifted directly from science fiction.

7 years later, and after hundreds of hours of use, I believe that I have proven that a safe elevator could be built for $100.

Thus illustrating the importance of taking in feedback.
While I don't doubt the idea may have merits, you still need to ask yourself if this is the right way to go, considering not just cost and performance, but difficulty of construction and associated risks.

What I see as a possible solution in my gun design, is some sort of safety wall/deflector between the rubber and me.

Well, the only option to make something like this safe is isolating all dangerous parts from the user - or alternately, isolating the user from dangerous parts.

My accident made the choice of air rifle I later bought an easier one. If looking for a top of the line underlever spring rifle, the choices are really the Air Arms TX200 or the Weihrauch HW97K.

The one I eventually went for (the Air Arms) was the one that with the design that would stop me having a repeat accident. The design makes it damn near impossible to catch your fingers in it - you'd have to be TRYING to get yourself an injury.

Would this idea have prevented your injury?

The only thing that would have really worked is sealing away any moving parts. If you're doing this kind of thing, a shield here and there is a waste - seal it in properly, and have shields that can be moved for the parts you HAVE to get to, then put them back in place when you're done.

You'll also need to make sure the construction doesn't fail under load, for which you need to have a solid grip on the obscene forces generated in this kind of thing.

What caused your accident?

Complacency. I put a hand a hair too close to where shouldn't've been, and then a failsafe that I thought was solid failed on me - wham.

If I were doing it again, I'dn't've been daft enough to get myself in that position. Unlike some people, I learnt from it (without being scared off) and it was fortunately something that was capable of growing back - although I am still left with a less than pleasant scar as a reminder.


Here is another example of feedback from people like you helping me:

Craftsman 10” upside down Radial Arm Saw.

http://www.youtube.com/watch?v=sVpGi85HfnY

After the feedback, I improved the hold down and I never cut with the blade in front of me.

I stand aside the saw in line with the axis of rotation and simple slide the table from left to right.

I never pull the blade to me, or push the table from me to the blade.


I have never get any kickback and the sawdust blows away to my left.

I know of no safer way of cutting wood with a rotating blade.

Just my opinion. YMMV.


With respect to breaking rubber, we know the direction of travel and we need a defensive lineman to stop the motion.



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Unread postAuthor: Brian the brain » Wed Jul 29, 2009 5:02 pm

a late reply..but;
BTB,

A slingshot will launch as fast as the rubber travels.


Those were my thought exactly...
That's why I used a pully to double the travel ( via a rope) yet halve the power.
In order to make up for the powerloss, I added more bands.

Now it would travel twice as fast...

as posted by me in another mans thread about a century ago:

http://www.spudfiles.com/forums/crossbo ... t2172.html
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: boyntonstu » Wed Jul 29, 2009 6:58 pm

Brian the brain wrote:a late reply..but;
BTB,

A slingshot will launch as fast as the rubber travels.


Those were my thought exactly...
That's why I used a pully to double the travel ( via a rope) yet halve the power.
In order to make up for the powerloss, I added more bands.

Now it would travel twice as fast...

as posted by me in another mans thread about a century ago:

http://www.spudfiles.com/forums/crossbo ... t2172.html


Correct me if I am wrong but when a pulley is involved the speed goes in half not double.

For example:

http://www.harborfreight.com/cpi/ctaf/d ... mber=40765

I have this hoist. The cable speed is 33 ft/min.

Add the pulley and the lifting capacity doubles and the speed halves.

You do excellent work!

Keep it up.

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Unread postAuthor: Ragnarok » Wed Jul 29, 2009 7:05 pm

boyntonstu wrote:Correct me if I am wrong but when a pulley is involved the speed goes in half not double.

It entirely depends on which way it's connected. Just like a 2:1 gearset can be run one way for half speed/double torque (obviously ignoring losses) and the other for double speed/half torque, pulleys can do the same.

The trick is applying the force to the pulley, and the load to the free end of the wire/cable/whatever, as opposed to the inverse (which of course, would be the normal way of doing it).

The diagram in the thread he linked would work as he suggests to double speed rather than halve it.
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Unread postAuthor: boyntonstu » Thu Jul 30, 2009 7:22 am

Ragnarok wrote:
boyntonstu wrote:Correct me if I am wrong but when a pulley is involved the speed goes in half not double.

It entirely depends on which way it's connected. Just like a 2:1 gearset can be run one way for half speed/double torque (obviously ignoring losses) and the other for double speed/half torque, pulleys can do the same.

The trick is applying the force to the pulley, and the load to the free end of the wire/cable/whatever, as opposed to the inverse (which of course, would be the normal way of doing it).

The diagram in the thread he linked would work as he suggests to double speed rather than halve it.


My bad, I never even considered reversing a pulley hoist.

Thanks for the insight.

I would rather unlearn something that I had wrong than learn something new.

The question remains: For a single rubber band, would a marble go faster with compressed air or with a 1:2 pulley?

Another basic question is: What are the parameters that control the speed of the airowgun? Chamber/barrel ratio, etc?

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Unread postAuthor: Technician1002 » Thu Jul 30, 2009 2:33 pm

boyntonstu wrote:
Ragnarok wrote:
boyntonstu wrote:Correct me if I am wrong but when a pulley is involved the speed goes in half not double.

It entirely depends on which way it's connected. Just like a 2:1 gearset can be run one way for half speed/double torque (obviously ignoring losses) and the other for double speed/half torque, pulleys can do the same.

The trick is applying the force to the pulley, and the load to the free end of the wire/cable/whatever, as opposed to the inverse (which of course, would be the normal way of doing it).

The diagram in the thread he linked would work as he suggests to double speed rather than halve it.


My bad, I never even considered reversing a pulley hoist.

Thanks for the insight.

I would rather unlearn something that I had wrong than learn something new.

The question remains: For a single rubber band, would a marble go faster with compressed air or with a 1:2 pulley?

Another basic question is: What are the parameters that control the speed of the airowgun? Chamber/barrel ratio, etc?

BoyntonStu


The only thing often overlooked is the mass of the high speed moving part and the force needed to accelerate it. I've been a fan of accelerating stuff with mechanical advantage, but I prefer solutions that leave the kinetic energy in the projectile, not the launcher parts.


This why I like the air as a spring.. Less kinetic energy lost to the spring, bow, string, arm, etc, and more transferred to the projectile.
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Unread postAuthor: Ragnarok » Fri Jul 31, 2009 9:26 am

Technician1002 wrote:This why I like the air as a spring.. Less kinetic energy lost to the spring, bow, string, arm, etc, and more transferred to the projectile.

Unfortunately, the numbers disagree with you.

Springers are about 30% efficient in converting spring energy to kinetic energy. Crossbows - over 90% efficient.
This energy is all wasted in the compression of the air.

So, with a straight mechanical energy transfer like a crossbow or similar, you can stand to lose quite a lot of that efficiency into the mechanism (provided of course you don't damage it in the process) and you'll still be winning out.

...Actually, I've just been helpfully reminded of a design I did last year for a high velocity crossbow that used mechanical advantages to propel projectiles to much higher speeds than normal (at surprisingly little efficiency loss) but the problem is although I can remember the basic principles of the design, I can't immediately remember the finer points of its operation.
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Unread postAuthor: boyntonstu » Fri Jul 31, 2009 9:42 am

Ragnarok wrote:
Technician1002 wrote:This why I like the air as a spring.. Less kinetic energy lost to the spring, bow, string, arm, etc, and more transferred to the projectile.

Unfortunately, the numbers disagree with you.

Springers are about 30% efficient in converting spring energy to kinetic energy. Crossbows - over 90% efficient.
This energy is all wasted in the compression of the air.

So, with a straight mechanical energy transfer like a crossbow or similar, you can stand to lose quite a lot of that efficiency into the mechanism (provided of course you don't damage it in the process) and you'll still be winning out.

...Actually, I've just been helpfully reminded of a design I did last year for a high velocity crossbow that used mechanical advantages to propel projectiles to much higher speeds than normal (at surprisingly little efficiency loss) but the problem is although I can remember the basic principles of the design, I can't immediately remember the finer points of its operation.


I am interested in learning more about your high velocity crossbow design.

Do you understand why the Airowgun shoots .22 pellets at 600 fps instead of 300 fps string velocity?

Joerg's slingshots are directly producing 50 fpe.

I am close to completing my prototype 'airslingun'.

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