Rope Arrow

[god_is_my_goldfish]

Ok, before i tackle this beast i'de like to first know what would work best for it. I drew up a simple sketch here-

 

http://208.49.149.118/TheDarkMod/Art-Conce...s/ropearrow.jpg

 

but it has a problem in that the rope would knock into the bow as it's being fired. It was suggested that the rope is loosly attached on a ring, and is pulled from a coil as it's fired (i'm doing something similar in the movie) but this would not work very well for gameplay.

 

One aspect i would like to keep for the final version above all else is the nooks in the head, these would help embed it into the wood better. It would also help for an easy subtle recognition of what arrow is 'loaded'.

 

Thoughts, ideas, comments?

[Springheel]

I was actually thinking of something with much stronger barbs. And you're right, at the moment the rope would get in the way of a shot. Perhaps putting it in some kind of tube? Ultimately, don't get too wrapped up in the details...something like a rope arrow demands some suspension of disbelief.

 

These are some rough ideas I was starting to play with...just in case they're helpful.

 

[New Horizon]

Yeah, it's the kind of thing where the whole "magic" deal might come in handy....but I liked the idea of it coming through a ring..but that might be harder to implement than it's worth. Really, it should just be simple...even if that means working the way it did in T1 and 2.

[Darkness_Falls]

I like GIMG's barbed head idea. The pitchfork one is a nice idea, but just doesn't do it for me from a visual standpoint. As for the unraveling of the rope, I'm with NH in that it'd probably be better to leave this one to magic.

 

And something has come to light in this thread that I hadn't thought about. Remember my noisemaker concept? It had a barrell. With it being at the front of the arrow, would it still be launchable or would it get in the way? I can see if it was at the back of the arrow it would immediately be a problem. But with it at the front, I think there's a chance we'd be okay.

[god_is_my_goldfish]

Yeah, might want to make it a head, with a tip, to avoid this problem.

Edited January 21, 2005 by god_is_my_goldfish

[Ishtvan]

I'm voting for magic also. That explains how the rope always falls just the right amount, and how the arrow launches it. I suppos it _COULD_ be a very thin thread with a high tensile strength, but then it would probably cut thru your hands when you tried to climb it. Also, this would have to be something naturally occuring (like spidersilk) or made by magic. I don't think we want to give our world the technology to create carbon nanotube fibers... WE can't even do that yet.

[god_is_my_goldfish]

I'll do a few variations tomorrow and we'll see which one would work best.

[sparhawk]

Of course a rope arrow doesn't have a real world back up. Though I seem to recall movies where a grappling hooks has been fired with bows. I think this would be possible, but certainly not with such a wrapped up arrow. And since I Thief wouldn't carry a big rope with him, has the time to put it on the floor in nice coils, so that he can properly shoot them, this will have to suspend believe anyway. But still the rope arrow should at least LOOK as if it could working. This means that a rope wrapped around the shaft wouldn't really work for the simple reason that it would jerk the arrow off it's path.

[oDDity]

NO, we're not taking the easy way out. GIMGs original idea is sound. THe rope should be wrapped more neatly arouind the length of the rope though, not 'tied' there.

This would not get in the way of the shot, you look down on the arrow and your eyes are to the left of it, you are not looking down its length. All you basically have is a fatter arrow.

[oDDity]

Another idea whioch would require no visual indecators would be to hollow out the arrow and have the rope squashed upo inside it like a spring. When the arrow it's the spring-like rope shoots out.

Don't ask me what material this springy rope is made of though. All ideas require some suspension of disbelief, but that's no reason to go the whole way and say it's a magic rope.

[sparhawk]

This would not get in the way of the shot, you look down on the arrow and your eyes are to the left of it, you are not looking down its length. All you basically have is a fatter arrow.

 

Any rope that would be tied to the shaft would cause an arrow to not fly well. In Scientific America was an article some years ago about arrow physics. And contrary to what you may think, an arrow does NOT fly straight. The impulse it recieves from the string in such a short times causes the arrow to twist and bend while in flight. A rope that would would be ied to the shaft would cause the arrow to get severly distracted from it's course, because not only would the bedingin of the arrow cause the rope to start moving accordingly, the rope untying itself would have the effect that the arrow would get a pull sideways because of the weight of the rope. Just tie a rop around a stick and pull the rope, You will see that it will NOT unroll nicely, instead it will cause the stick to move randomly. Additionaly the increasing weight and movement of the uncoiled rope would also cause problems for the arrow.

[sparhawk]

Another idea whioch would require no visual indecators would be to hollow out the arrow and have the rope squashed upo inside it like a spring. When the arrow it's the spring-like rope shoots out.

That could work. Because it wouldn't distract the path of the arrow while in flight. Of course, as I said. Any rope arrow has big problems if you try to make it believable.

[oDDity]

The hollowed out shaft with the rope crammed inside it would only require a longer and fatter arrow shaft.

THe arrow shaft should also be made of metal, not wood, and the head and shaft should be one piece. Since it's a hollow tube the weight wouldn't be an issue, and the rope arrow isnt required to travel long distances anyway.

I don't see how the trident arrow head shape would help it to take more weight, those prongs wouldn't be very strong.

I'd say a barbed crossheaded tip would be better.

[Springheel]

I just came up with a sketch that I think might work. It is basically an arrow-shaft with a hollow tube attached to one side, On impact, the tube comes loose from one end and hangs down, allowing a coiled rope to come out. I'll have to wait until I get home to scan and post it.

[oDDity]

May as well just have the hollowed out metal arrow shaft as the tube though, what's the point adding an extra one on the side?

[god_is_my_goldfish]

So is this what we're doing for the arrow then? Should i bother doing concept art for it then, as spring says he already has one done?

[Springheel]

May as well just have the hollowed out metal arrow shaft as the tube though, what's the point adding an extra one on the side?

 

Well, the tube swivels down after impact to release the rope. It's hard to describe without the picture. I'll be able to post it in a few hours.

 

Should i bother doing concept art for it then, as spring says he already has one done?

 

There's no guarruntee people will like mine.

[Darkness_Falls]

I liked that rope arrows were re-usable in T2. I'll admit it was kind've cool to see the magical *poof* when you took your arrow back. (Maybe that was just on vine arrows? Not sure.) At any rate, if we make rope arrows some sort of mechanically believable contraption rather than magic, it will be a chore to figure out how to make them reusable. Then we start having to think about 'how do we recoil the rope back up into the arrow?' etc. Figuring out how to reuse mechanical noisemakers was easy. Having to do this for rope arrows will kind've dilute the DarkMod's Thief experience, imo, and will keep sendinig it down the road of just some James Bond 007, real world, thief game. Having to re-load both noisemakers and rope arrows just wouldn't be my preference.

[god_is_my_goldfish]

Well there really isn't a problem with them just dissapearing into your inventory when you frob them, in fact, i'de prefer that over anything else. Though we could possibly have some wood splinters fly out as it's "pulled" from the wood.

 

Do you really think we're going to have the player re-wind the noisemaker when they frob it?

Edited January 21, 2005 by god_is_my_goldfish

[Springheel]

Ok, here's the concept I came up with today. Basically, there is a hollow tube attached to the arrow (on the left side so it can be fired without problem). The tube is attached to the arrow at the front, and by a weak clasp at the back. On impact, the clasp at the back comes off and the tube falls down, releasing the coiled rope inside. The spines on the head keep the arrow from going so deep that the tube is knocked off, and can give a little extra gripping strength if the head goes deep enough.

 

(Obviously this wouldn't be able to work in real life, but no rope arrow can. At some point either magic or unexplainable technology (same thing as far as I'm concerned) have to come into play. No one will spend as much time dissecting rope arrows as we will.)

 

[oDDity]

No, my design is simpler and more elegant. You don't add extranious bits to a design unless necessary.

Adding the tube to the design has two drawbacks and no advantages - the tube would interfere with the flight of the arrow, and the entire weight of your body climbing up the rope has to be taken by the tiny clasp where the tube is attached to the arrow, it also add extra weight.

Having a one piece metal arrow and head with a hollow shaft holding he coiled rope makes more sense. There is a button or lever on the arrow head which is activated when the arrow hits its target and that releases the rope.

[Ishtvan]

** Here comes the Science!! **

The problem I have with realistic rope arrow is the added mass of all that rope to the arrow. A heavier arrow, when shot from the same bow, will not fly nearly as far as your basic broadhead. If you don't believe me, here's the physics explanation below:

 

[Physics Explanation - Skip this if you already understand why this is]

The bow can only impart so much kinetic energy to the arrow. In the most simple model, think of the bow a system of several springs. The most kinetic energy it can impart to the arrow is equal to the potential energy of the springs when the bow is fully drawn (in reality it will impart a little less, due to friction losses, etc). Okay, so we've got some number in mind for the most kinetic energy the bow can impart to the arrow.

 

Now as some of you may remember from high school physics, the kinetic energy of the arrow is 1/2*mass*veloctiy^2. Set this equal to the max potential energy of the bow when fully drawn. max potential (bow) = 1/2*mass*velocity^2 (arrow).

 

Solve for v:

 

initial velocity = sqrt (2 * max potential / mass ). [1]

 

Since the max potential is always the same for a given bow, you can see that increasing the mass of the arrow decreases the arrow's initial velocity when fired from the bow.

[End explanation]

 

Now, think about how long a rope you need to climb up 5 stories (~50 ft / 15 m). How much do you think that rope weighs per unit length?

 

With MODERN polymer materials, I got some numbers from this climbing rope company site: http://www.yatesgear.com/climbing/wallropes/ . It weighs 55-77 g / meter. So for a 5 story rope,

total modern rope weight = 15 m * {55-77 g/m} = 0.825 - 1.16 kg

 

Now for MODERN broadheads, "Minimum arrow weight was determined to be 25 grams." [ref: http://www.bagjakt.org/study_eng.htm ] So now we have enough information to calculate the fractional decrease in speed when going from a broadhead to "broadhead + rope"

 

Plug everything into [eq 1] :

 

velocity_ropeArrow / velocity_broadhead = sqrt( 0.025 [kg] / (0.025 + rope_mass [kg] )

 

velocity_ropeArrow / velocity_broad = 0.17 (based on lightest modern rope)

 

velocity_ropeArrow / velocity_broad = 0.14 (based on heaviest modern rope)

 

Conclusion

With MODERN materials, adding 5 stories of rope to an arrow will decrease the initial arrow velocity (and therefore how far it can travel) to 14%-17% of a broadhead's initial velocity! This means shooting a rope arrow from a shortbow would be like shooting one of those NERF bow and arrows, compared to the broadhead. There's no chance in hell that you'd be able to shoot that 5 stories up (maybe with the Bow Upgrade )

 

This analysis didn't even consider the heavier tip you would need to anchor on to things. Also, all the numbers used were for MODERN materials. Polymer ropes, aluminum/graphite epoxy composite arrows, etc. Rope arrows would fly even worse using the technology they had in medieval or even Victorian times. I guess you could make up something about using "spidersilk" rope or some crap like that... but at that point, might as well use magic.

 

Supplemental Info

 

I found this, which might settle some debate: Arrow Flight Simulator program

 

More detailed article on bow physics, including the effects of heavier/lighter arrows (w/ typos because it was translated from Italian?)

[Springheel]

I'm just going to quote myself here....

 

Obviously this wouldn't be able to work in real life, but no rope arrow can.

[Ishtvan]

Haha, I started writing that before you posted Springheel, but if that's the case... why not just use magic? IMO it's MORE believable to use magic (in a world that has it), than to try to shove an unrealistic 'scientific' explanation down someone's throat.

Edited January 21, 2005 by Ishtvan

[Springheel]

Well, you don't have to convince me. I'm very pro-magic.

 

I actually prefer it when we don't explain things too much, especially when it comes to the 'gadgets' so that the people who are ok with magic can assume it's magic, and those who are anti-magic can assume it's tech.