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#68490 90 Celica Questions

Posted by merlinski on 27 November 2005 - 07:44 PM in Off Topic

Toyota engine's are overengineered like no other, which is why they last forever. So if you really wanted to, you could put a forced induction system in there, provided you blueprinted and rebuilt your cylinder heads. The better option is probably an engine swap, depending on how serious you are. The Celicas came with 3 differnet stock engines, with the 1.6L as the smallest. As a result, if you take a bigger engine from 1990's celica, it'll probably bolt right into your car since it was meant to fit in the same engine bay. I'd suggest the 3SGTE engine. You'd probaby need a new transmission though, which is what kills a lot of engine swaps. Keep in mind that's a very labor and knowledge intense process, and not something to undertake unless your very serious.

If you want to do anything to your car, I'd suggest getting the block and cylinder heads blueprinted and rebuilt by someone who knows what their doing. Otherwise you run the risk of blowing a cylinder head or, at in the best case, losing a lot of power.



#66112 Cars

Posted by merlinski on 19 October 2005 - 02:00 PM in Off Topic

Umm, no.

The purpose of a blow-off valve is to allow pressure built up in the intake manifold to escape when the engine is no longer under load. If it didn't do this, the pressure would back up into the turbocharger and cause it to stop, damaging it. This is because when the engine isn't under load, the exhaust pressure is significantly less. That's why a blow-off valve releases pressure when you shift - if you take your foot off the gas, the exhaust pressure drops rapidly while there is still intake pressure. This isn't a problem in naturally aspirated engines, because you don't have pressure building up in your intake manifold. That only happens in forced induction engines, i.e. one with a turbocharger or supercharger.



#64498 Cars

Posted by merlinski on 28 September 2005 - 12:23 PM in Off Topic

Dream car for me right now would be a 1995 Mazda RX-7 with a 7.0L Lingenfelter Spec LS1, Twin Garrett Turbos, and all the necessary engine mods.

Best production car? Hands down the 2005 Bugatti EB16/4 Veyron. Fastest Production car in History, 1001 HP from a 8L Quad Turbo W16 Engine. Not only is it quite possibly the sweetest car ever made, it's hands down my favorite engine configuration.



#63260 An Actual Semi-auto Design

Posted by merlinski on 07 September 2005 - 04:12 PM in Homemades

This design has been discussed many times over and I don't even think that this version is feasible. You're "regulator" is a piece of brass nested between two o-rings? And you expect this to be able to maintain a constant pressure difference between the tanks? Not only that, but you really need to draw a much better diagram if you want people to fully understand what you're talking about. I suggest you look at the homemade section of this site to see what a well-done regulator assembly looks like.



#62017 Homemade Projector

Posted by merlinski on 15 August 2005 - 07:04 PM in Off Topic

Regarding the need for a dark room:

Most high end rear-projection home theater setups are set up by home theater buffs who want a huge diagonal screen and powerful surround sound with it. For that reason, many of the people who do projectors put them in rooms with no windows or very small windows - I've seen tons of setups where the room was designed originally to be a projector screening room, with no windows and sensitive to acoustics. There really isn't a way around this, and its the biggest reason projectors haven't replaced big screen tv's.

The best chance to get around this is a technology recently developed by Sony (though not on the market yet) for projector screens. It's a black screen that only reflects pure red, green, and blue light, and absorbs white or wide-spectrum light coming from flourescent or ambient lighting. This means that projectors can have pure blacks and sharp contrast even in bright environments. However, I'm pretty sure this only works for DLP projectors because they use only those three pure colors - I doubt this would be successful with an LCD projector.



#61478 The Better Nerf Grenade

Posted by merlinski on 08 August 2005 - 11:45 PM in Homemades

Have you actually tried this out?

I have a hard time believing that the baking soda/vinegar reaction is sudden enough to provide any kind of explosive force.



#61393 Future Of Warfare

Posted by merlinski on 07 August 2005 - 08:02 PM in Off Topic

Merlinsky, if you had ever held an M-16 and fired one, youd know 2 things:

A. The recoil on this gun is lower, and reduced more by shock absorbers in the butt.

B. this gun is about 3 pounds lighter, which sounds small, but when youre holding it for 14 straight hours, getting shot at, and firing back, your arms will get tired. They wont so much with this gun.

The other new feature is the fact that it can be completely refitted from one setup to another in 10 minutes flat. thats no exaggeration either. The gun is desighned to be able to be put together by a soldier fresh out of bootcamp in about 15. Plus, instead of macking x ammount of machine gun models, x ammount of loser rifles, and x ammount of carbines, you can make Y ammount of the XM8 and have all of them.
Another thing that makes this MUCH better than the M16 is the overall desighn of the firing mech. the M8 is very reliable and does not jam nearly as much as the M16 does.

Hope i cleared that up Merlinsky.

PS: the reason for the subtitle is so that we dont get a bunch of anti military, anti gun people in here destroying the topic.

How would firing an M-16 tell me that this gun has less recoil? If anything it'd probably have more, considering that the gas can't exhaust back into the chamber.

Boltsniper replied to your topic on NHQ and seemed to confirm my thoughts, I'd like to see what he thinks of this, considering that he probably has the most experience out of any of us with the M-16/AR-15 design.



#61367 Future Of Warfare

Posted by merlinski on 07 August 2005 - 03:46 PM in Off Topic

While the picture is nice, it doesn't seem like there's anything new about this gun. The Heckler and Koch G3 rifle (the company that's also developing this) also has carbine, machine gun, and sharpshooter variants. The only big difference the article details is the use of a gas-action piston instead of a direct gas blowback setup used in the M16. I'm pretty sure that's been used in other guns before.

I'm just interested as to what makes it so much better than the M16, other than looking futuristic. Oh yeah, and your topic subtitle is stupid.



#61198 America's Army

Posted by merlinski on 05 August 2005 - 04:02 PM in Off Topic

I played it on and off from when it first came out (Version 1.0 "Recon") to version 2.2 or so. I was pretty damn good, I had a global kill to death ratio of about 3 to 1 with well over a few thousand kills. I'm playing mostly Battlefield 2 now, although the past week has been taken over by a nerf-related project.



#60170 Far Revisited

Posted by merlinski on 25 July 2005 - 01:53 PM in Homemades

We use PTC ProDesktop at my school and the biggest problem I've had has been lining components up. It uses a pretty complex "workplane" system, and it's hard to assemble components in three dimensions to the specifications that I'm looking for.



#60164 Far Revisited

Posted by merlinski on 25 July 2005 - 11:33 AM in Homemades

Rapid Prototyping is the shiznit. We have a lab for it in the engineering building at Brown as well, tho I haven't gotten a chance to use it yet. However, I'm pretty sure that the prototypes aren't going to stand up to the kind of impact forces you're talking about.

Very nice CAD work. I'm seriously impressed. What program did you use and what if any training in CAD did you receive? I'm still relatively new at it, and it's frustrating as hell to get used to the interface.

Instead of looking to Rapid Prototyping, I'd suggest trying to machine a bolt out of aluminum or steel. Once you have the CAD files for the bolt, it should be relatively easy to machine it from a blank, assuming you have access to the right machines.



#59843 Air Travel And Nerf

Posted by merlinski on 21 July 2005 - 09:21 PM in General Nerf

My dad is an airline pilot for United, so I shall tell you people some stuff.

-The pressure difference is far more than 10 pounds p.s.i.. The first jet airliner, the BOAC Comet, initially had problems due to structural failure from pressure.

-The cargo hold is pressurized. If you look at the floor of an airliner, especially near the walls, you can tell that the floor isn't solid. The seats are all screwed to pallets, so you can change the class configuration, or, in some cases, revenue type (passenger or cargo). What it boils down to is that instead of being separate "rooms", a more appropriate analogy is that of a single "room" with a partition.

-The cargo hold is also heated for the same reason. The landing gear wells, however, are not, as a Pakistani man learned when he tried to flee the country by stowing away in an airliner. He froze to death.

The overall lesson here is that your Nerf guns are safe in checked baggage.

~TAD, your favorite little screaming man. :w00t:

Thanks for the clarification, tho you're wrong about the pressure difference. I was also off in my earlier guess. At 35,000 feet, atmospheric pressure is about 3.5 psi. At sea level, it's 14.7. So the pressure difference is actually 11.2 psi.



#59769 New Member-saying Hello

Posted by merlinski on 20 July 2005 - 06:21 PM in General Nerf

More than anything else, it's the fact that he's so defensive that's encouraging this. I'm sorry about the misunderstanding, I consider Long Island to be part of the city. If you just let this go, the thread will die and you'll have plenty of time to prove yourself.

Just because people have nothing to gain from lying doesn't mean that they don't still do it. Look at the fake firefly claims, etc.



#59754 Air Travel And Nerf

Posted by merlinski on 20 July 2005 - 01:48 PM in General Nerf

Good call. They're not as likely to freak out if you put your guns in checked baggage, but I'm pretty sure the cargo hold or parts of the cargo hold can get really really cold or they can depressurize, because they tell you not to put any aresol cans in your checked baggage. You wouldn't want to get there and find out all your o-rings are cracked or all your air tanks are ruptured....

::goes and contemplates the practicality of a barometrically powered nerf gun::

Even if the hold is depressurized, the difference in pressure between atmospheric pressure and the cargo hold isn't going to be more than 10 psi, which is something even the weakest nerf air tanks are capable of storing. Your guns would be fine.

I'd definitely say check the bags. Security personnel love to look like they're doing their job, which means questioning you extensively at the least and possibly confiscating the guns.



#59753 New Member-saying Hello

Posted by merlinski on 20 July 2005 - 01:44 PM in General Nerf

Yeah, sorry but that's bullshit.

http://www.nysdmv.com/broch/c41.htm

Limited Junior License (limited class DJ) is only to school or work.
Junior License (class DJ) is anywhere without supervision between 5 a.m. and 9 p.m.



#59713 New Member-saying Hello

Posted by merlinski on 20 July 2005 - 12:43 AM in General Nerf

Alright time do defend myself, first things first. I am in high school but I am only sixteen and in the loveley state of New York you need to be seventeen to have your license.

Um as me being some one living in NY state, I would like to say thats not how I know it. I am 16 and have my permit and at 16 and a half I will have my junior liscense, then at 18 full liscense unless you take drivers ed. Maybe its different in the seperate counties, oh and which one do you live in any way? I live in westchester.

It's not done by county, the law applies for all of New York. At 16 you can get your permit, at 16.5 you can get your junior license, which lets you drive except between 9 p.m. and 5 a.m. You get your full license at 18 automatically, or at 17 automatically if you have taken drivers ed.



#59589 New Member-saying Hello

Posted by merlinski on 18 July 2005 - 02:35 PM in General Nerf

CX just said everything I was thinking while reading this thread. It'd be great to be proved wrong, but it just seems that there's a lot of very, well, unbelievable statements. Especially the part about the FAR's.

As for milsim, I love it. However, it's always seemed that nerf is not really capable of it - the properties of the guns lend themselves to a more run-and-gun style of play. I'd love to work in a squad, yet I have the feeling that Bounding Overwatch wouldn't be nearly as effective with slow moving ammo that travels 100 feet at most.



#59360 Mazda Rx-7 1987-90

Posted by merlinski on 14 July 2005 - 10:55 PM in Off Topic

oxide, you're a little off with your description of transmissions.

There's a difference between "tiptronic" or "manumatic" transmissions found in your average middle-of-the-line car and the gearbox that you're referring to. The tiptronic transmissions are fundamentally automatic transmissions, meaning that they use a viscous clutch and a planetary gearbox. It's just that pressing the button overrides the computer and shifts the automatic gearbox.

The transmissions in race cars which use a lever are insanely different from tiptronic transmissions. They're called "Sequential Manual Gearboxes" or "Direct Shift Gearboxes", depending on the company. It usually uses a complex controller to convert linear motion of the lever into the switching of gears, which are normal gears (not planetary) in the form that would be found in a manual gearbox. The direct shift gearbox by Audi uses a double-clutch system where a second clutch is always engaged, so the shift requires no clutching. Some of these sequential manual gearboxes only have one clutch, which is the lever/clutch system you've found in race cars. For a comparison, google image search "planetary gearbox", then google image search "direct shift gearbox".



#59295 Mazda Rx-7 1987-90

Posted by merlinski on 14 July 2005 - 12:02 PM in Off Topic

Xedice - the 3 tips he's referring to are called the apex seals, which is what I referred to in my post.

While the tiptronic is cool, it's really not a manual at all. First of all, it's mechanically an automatic transmission (automatic and manuals are very different) that just allows you to control the shifts manually. There's a delay between pushing the lever for the shift and the shift actually taking effect, so you actually have to shift a second or two before you want a gear change. And most importantly, there's no clutch, so it really doesn't feel like a manual at all - there's no control over starts or shifting, and you lose the feel of connection with the car.



#59263 Mazda Rx-7 1987-90

Posted by merlinski on 13 July 2005 - 09:09 PM in Off Topic

First of all, a manual is the only true way to drive. Automatics are boring as hell. I've driven a manual for the past 2 years and I love driving it - as soon as I get behind the wheel of an automatic I lose all my love for driving.

The second-gen mazda RX-7 is a pretty decent car. The reliability issues stem from it being a rotary engine - which are notoriously bad for blowing apex seals. This shouldn't be too much of a problem unless you're running a lot of boost, and I'm assuming you aren't going to be installing a turbo. It's also pretty cheap for the kind of performance you'll be getting. I'm not sure about the second-gen, but the third gen (93-95) was one of the best handling cars in history. Not only that, but if you're feeling ambitious you can swap a GM LT1 or LS1 engine (V-8) into the Mazda using only a relatively cheap swap-kit, and you can get major power in a light body. If you want I'll get you the link to some sites about that.

As long as you're not an idiot and the car's not a lemon, it shouldn't break down too much. I'm willing to bet that the reason ItallionStallion's friend's BMW M3 breaks down so much is because his friend just beats the hell out of his car. Just because a car's fast doesn't mean you can drive it at its limits constantly. It's fine to push it once in a while, but if you're constantly dropping the clutch and peeling out or revving the engine high, any car will break down.

The fact that it's a stick-shift shouldn't matter as long as you know how to drive an automatic. I agree learning to drive for the first time on a manual can be difficult, but once you've got the basics of driving an automatic down it's a piece of cake to learn a manual. It'd take a few days at most to get the mechanics of it down.

In a few years (once I've saved up the cash) I'm probably going to buy a 93-95 Mazda RX-7. I'd get one from an earlier year except that I don't like the wedge design and the 93-95 just looks stunning. Of course, I'm looking to do an engine swap that's been done only a few times before (Toyota 2JZ-GTE if anyone's interested), so that's a major project car for me. Good luck with your car.



#59029 Powerclip Homemade Clip

Posted by merlinski on 10 July 2005 - 03:42 PM in Homemades

I'm assuming so, since pretty much every part of every nerf gun (except the springs) is made of PVC. PVC doesn't just mean pipe - it's an incredibly common plastic.



#59022 Powerclip Homemade Clip

Posted by merlinski on 10 July 2005 - 01:27 PM in Homemades

this thread is kinda old but it's still on page one and I have an important contribution
http://nobel.scas.bc...tic/plastic.htm
that page includes instructions on how to make plastic from milk

To make that into an actual clip you'd need an exteremly large amount of milk and vinegar, as well as a very powerful stove and a large pot. It seems more applicale to patching holes in air tanks, depending on how well it bonds to polyvinyl chloride.



#58956 All Purpose Movie Topic

Posted by merlinski on 09 July 2005 - 04:15 PM in Off Topic

Regarding the EMP - a lot of devices are magnetically shielded. Most home stereo speakers are because of the large magnets they contain - an unshielded speaker could cause interference in a Stereo receiver, DVD player, or TV. I don't believe that car electronics are shielded. So theoretically the camera could have been shielded to prevent normal magnetic fields from interfering or damaging it.

And although the aliens were a far superior race, that doesn't mean that they would have fully considered the ramifications of bacteria. Even though they did visit the planet, we're led to believe that they did so a long period of time ago, and bacteria evolve at a fast pace. Additionally, they might have overestimated their potential to resist the bacteria or could have assumed that it would be the same as it was millions of years ago (or whenever they visited). Just because they're more intelligent doesn't necessarily mean that they're omniscient.

For me the most unrealistic aspect was the aliens being buried. With the amount of construction we do on a regular basis, it'd be almost impossible for us to never discover one of those things, considering their massive size and placement in cities. That's a plot device that worked in 1920 but not now.



#58711 Live 8

Posted by merlinski on 05 July 2005 - 12:02 AM in Off Topic

I'm about 3/4 with Talio on this thing, which is a first.

Chopin and Vivaldi definitely kick collective ass. Hell, Chopin has a vodka named after him, biatch.

I gotta disagree with you about the traffic thing. Yeah, they fucked up daily life in Philly for a concert that accomplished very little. But you know what else fucks up traffic? Other concerts. And baseball games. And basketball games. And retarded fucking drivers who can't stay in their own lane and kill 3 people on the thruway. A lot of your criticism of this concert is spot-on, but there are lots of things that screw up daily life and cause traffic in Philadelphia or any other major city, and many of them are things like other concerts with a pure profit motive. Even if this concert failed miserably to raise awareness, it's still a better reason to fuck up traffic than a $80 ticket Lindsey Lohan concert.

You pretty much summed up the problem with this shit when you mentioned the awareness bracelets. It's not about helping people, and it's sure as hell not about raising awareness - it's about showing people that you care about people less fortunate and are therefore worthy of their respect. How many people actually saw a livestrong bracelet and said "Holy fuckin shit man, there are people with cancer out there? Goddamn I gotta go buy them a baseball hat" It's the same thing with Live 8 - it's an opportunity for people to use the pretense of raising awareness as a way of showing the world that they're aware, even if they're not doing a goddamn thing. And if you think about the collective cost of this, how many vaccines would this thing fund? It's not as glamorous to inject a 4-year old, but it's a helluva lot more effective use of a dollar.

Also, does anyone realize that Africa is a continent that really doesn't want our help?  You've got civil wars all over the place.  You think we're just going to step in and end that shit because you sang a pretty song?  Hell no.  We've sent help to them and they shot at us.  We try to get a vigilanty dictator out of the Sudan and get one of the biggest failed missions this country has ever seen.  People, there's not a whole lot you're going to do about it.


Eh, that's not a clear issue. The presidents of Sudan and Kenya recently released statements essentially saying that they need the help of the G8 if they're to escape complete poverty. Then the president of Libya, Gaddafi, said that they should stop begging and work together. Seeing as it's a continent, not a country, there's lots of different views regarding the west.

The mission that you're referring to is probably the operation in Somalia, not Sudan. Yeah, we were shot at, but that was partially by the soldiers of the guy we were trying to remove (those were the guys that downed the helicopters), and partially by civilians who saw the Rangers and Delta Force as distinct units from the Red Cross who were feeding them - they only saw the Rangers when they were shooting people in their neighborhood. They don't exactly have a free and expansive news service there, so they had no way of knowing that the Task Force was there to enable distribution of food. My point is that we can't use the confusion and anger of 10,000 Somalians as a reason for not trying to help Africa. Even though that mission ended in disaster, for a period of a few months we were very effectively fighting the famine that had killed 300,000.

I gotta agree with your assessment of people actually doing something. What happens when you have everyone raising awareness? Nothing gets done. Millions of people watched these concerts and nothing happened. But if millions of people donated $20, you'd have millions of pounds of food. Or if millions of people joined Doctors Without Borders, or the International Red Cross, or Oxfam, and volunteered to work in less-than-desirable areas, you'd have the beginnings of a solution.

Yazz, you're an idiot who happened to stumble upon the right side of politics, and in doing so have embarassed every liberal on these boards, including me. You deserve a punishment that fits your age. Go to your room.



#58650 All Purpose Movie Topic

Posted by merlinski on 03 July 2005 - 10:27 PM in Off Topic

Wow dude, you're way off.

First of all, it's not "our spirit and our air". It's our bacteria, which if you study history, is probably the most realistic reason for the failure of invasions of any kind. The line about how man earned his right to live here with a billion deaths refer to how many people have died in the course of our exposure to diseases that we eventually have become immune to. Just look at the common cold - that killed an uncounted number of Native Americans and barely affected Europeans, because they had become relatively resistant to it. There are millions of types of bacteria that could cause diseases if we were exposed to them for the first time.

Not only that, but the ending isn't hollywood at all. It's literature circa 1920, which makes it even more insane that H.G. Wells could come up with as realistic a cause for failure before we had even a fraction of the knowledge about bacteria that we do today.

Of all the alien movies I've seen, that's by far the most realistic ending.



#58612 New Way To Test Strength Of Blasters.

Posted by merlinski on 03 July 2005 - 12:51 AM in General Nerf

What are you talking about? Initial velocity is pretty much the only important factor. Dart drag can be easily factored in as if it's frictional force without loosing much accuracy.

If you want to experimentally determine the effect of air resistance on range, then you could calculate it with some accuracy. But it's definitely not something the software would be able to do, and it's definitely beyond any of our resources to calculate the actual coefficient of drag.



#58600 New Way To Test Strength Of Blasters.

Posted by merlinski on 02 July 2005 - 08:06 PM in General Nerf

Does the software calculate the ranges of the gun?

The software isn't designed for nerf, and it'd be impossible to do that. Range depends on a lot of properties, only one of which is initial velocity. It is also affected by the coefficient of drag for the dart, the mass, and the air pressure (although this has a smaller effect).



#58510 Is It Feasible?

Posted by merlinski on 30 June 2005 - 08:29 PM in General Nerf

Yeah I looked at Boltsniper's FAR and I think I discovered a way to theoretically modify it so the plunger could be fully automatic, but would it actually work? I have no idea. I'd have to try it out and it probably would end up not working anyway. The problem is with the bolt and how I could make that automatic. Yes I could buy an electric motor, but as you said it would cost a ton of money. Did Hasbro discontinue the Powerclip, because I can't find it anywhere except for ebay.

Would it just be easier to try and replicate the Powerclip instead of trying to make another type of automatic?

What is your theoretical plan? Because the basic problem is that you need a source of energy - whether it is from electricity or air. You could also theoretically make one plunger pull fire multiple shots, but if it's any more than 3 or 4 shots you wouldn't have much range.



#58474 I Hate Topics Like This

Posted by merlinski on 30 June 2005 - 12:53 PM in Off Topic

Holy Shit! I know the guy that made that film. I'd seen it before but this time I recognized the name of the director. He's a sophmore at Brown (my school) and I've been part of an on-campus debate he organized about the ROTC. That's fucking awesome, I'll have to ask him about it next time I see him.



#58473 Is It Feasible?

Posted by merlinski on 30 June 2005 - 12:48 PM in General Nerf

While boltsniper's FAR is an absolutely awesome homemade, it's still quite a bit behind the kind of technology and complexity you would need to build something fully automatic - which says a lot about how insanely difficult it would be to build this. That said, I looked into it a bit so I'll give you my ideas.

The powerclip is based on a repeating mechanism that utilizes a spring and air pressure. Air is allowed to seep from the tank into this mechanism, and as the pressure rises, the mechanism expands (with the movement of the reservoir being opposed by a spring). As soon as it reaches a certain point, the air is released, and the spring closes the valve again and the process starts over. There are several different designs that could accomplish this, but they're all pretty difficult.

The other option is to follow the Airsoft route and make it electric powered. You could theoretically modify boltsniper's FAR to complete an electrical circuit at the point where the gun must be cocked, and use an electric motor or linear actuator to retract the spring. However, the force of the spring in his gun makes it nearly impossible to do this with any kind of speed without using a huge and expensive electrical motor.



#58435 My Needs And Wants

Posted by merlinski on 29 June 2005 - 01:55 PM in Homemades

While your intentions are good, there are flaws with your plan for presenting them.

First, there's no such thing as a free flash program. By flash you mean .swf files, and there are only two programs (Flash and Swish) that can make those files. Neither are free. So unless you meant you need to pirate Macromedia Flash, you're out of luck.

Second, Flash isn't 3D. If you want to make 3D models you'll need a different program like 3D max or Swift (Not Swish). Swift makes 3D models for flash animations, and is your only shot at animated 3D models. However, it's not free and believe me, it's insanely hard to make animations that look decent in three dimensions.

My advice is to keep working with paint. It's a lot easier to use than flash, and since 3D is impossible without shelling out some cash, it's got everything you need to make drawings. Just look at boltsniper's FAR diagrams - you can get a lot of detail using just colored lines.



#58114 New Way To Test Strength Of Blasters.

Posted by merlinski on 24 June 2005 - 01:47 PM in General Nerf

That's a very cool way of measuring velocity. There would still be variance - not everyone would accurately record the mass of projectile and mass of pendulum, but you're right that its much more standardized than "mine shot 100 feet flat".



#58061 Absolute Ideal Barrel Length

Posted by merlinski on 23 June 2005 - 08:59 PM in Homemades

You're not going to find a barrel length that is optimal for both range and accuracy, so lets start with range. As you said, a barrel which results in 14.7 psi (or 1 bar) of pressure as the dart leaves will not yield optimal range because of friction. What you should look for is a barrel where, at the point at which the dart leaves the barrel, the acceleration has reached 0. This ensures that all possible acceleration has taken place and the dart is at its maximum attainable velocity. Acceleration will reach 0 when the force of friction working against the dart is exactly equal to the force due to air pressure behind the dart. This will yield a net force of 0, which according to F=m*a yields a net acceleration of 0. In order to calculate the barrel length, you would have to calculate the pressure required, which requires knowledge of the coefficient of kinetic friction. Unless you want to look up the coefficient of friction between foam backer rod and brass, this will have to be experimentally determined.

Before delving into that, I want to look at the most accurate barrel length, since this is easier. Any difference in pressure between the barrel and the atmosphere at the point when the dart leaves the barrel results in turbulence, which throws off the accuracy of the dart. So in order to maximize accuracy, you are looking at a situation where the pressure inside the barrel should be 1 bar at the point that the dart leaves. This is a significantly easier calculation, since it only requires knowledge of the internal volume of the barrel and the air tank (as well as the pressure after a certain number of pumps). However, a barrel of this length would mean that the dart underwent negative acceleration as the pressure dropped towards 14.7 psi, so you would certainly lose range.

Back to the range-optimizing barrel. I didn't quite understand ompa's idea for determining the coefficient of friction, and I think he's mixing up energy and force. So I'll offer my own method. We can find the energy transferred to the dart by following the formula Kd=.5*m*v^2, where K is kinetic energy of the dart, m is mass, and v is velocity. Take the starting point of the experiment to be the dart sitting in the barrel before the trigger is pulled - the initial Kd is zero. The end point of the experiment will be just as the dart exits the barrel - the maximum kinetic energy. If you know the mass of the dart and the speed as it exits the barrel, you can calculate the final Kd and hence the change in energy over the course of the experiment.

Assuming we can calculate Kd, we now need to break it down into it's parts. Kd is determined by the following equation:
Kd=Ep-Ef
Where Ep is the energy transferred from the pressurized air to the dart and Ef is the energy robbed by friction (or, more accurately, converted to heat). The goal will be to find Ep and hence solve for Ef - if we can find Ef, we can calculate the coefficient of friction.

The energy transferred by the pressure can be calculated using a few basic equations. The first is:
Energy = the integral of Force with respect to distance

You may have seen this in it's non-calculus form, E=F*x. The calculus is necessary because the force of air pressure will change as the dart moves down the barrel (and is hence a function of the distance moved by the dart). The boundaries of the integral will be 0 and y, where y is the distance from the initial position of the dart to the end of the barrel. The next step is to formulate an equation that calculates force as a function of the dart's position in the barrel. The force due to pressure is represented by:
F=P*A, where P is the pressure and A is the area of the surface it is acting upon (in this case the area of the back of the dart). So we now need to find a formula which expresses the Pressure of the air as a function of the dart's position in the barrel. This will be determined by the gas law, which states that as long as the amount of air and the temperature stays the same, the quantity P*V, where P is pressure and V is volume, will be constant. This is expressed as:
(P1)*(V1)=(P2)*(V2)
where P1 and V1 are the initial pressure and volume and P2 and V2 are the final pressure and volume. Rearranging this formula to solve for P2 gives:
(P2)=(P1)*(V1)/(V2)
P1 and V1 will be fixed - the initial pressure and volume of the air tank. V2 will be the volume of the air tank plus the volume of the space in the barrel behind the dart - this will vary as the dart leaves.

So what does this all give us? The integral of (P2)*A with respect to x from 0 to y. If you can follow that you get a cookie.

This will all result in the value for Ep. Now we have Ep and Kd, so we can calculate Ef. The energy sapped by friction is expressed by the formula:
Ef=f*y
Where f is the force due to friction and x is the distance traveled by the dart. Since the force due to kinetic friction is not affected by velocity, you don't need a integral to calculate this. Just divide Ef by y to calculate the force of friction. Now that you have this, you can calculate the pressure necessary to perfectly counter the force of friction - the pressure will allow you to calculate the volume of the barrel, which allows you to set the length to the optimal value.

So it's actually not that hard, assuming you know the internal dimensions of your air tank and barrel, you have a way of testing the pressure of your air tank, you can measure the speed of the dart exiting the barrel, and can perform several tests to verify your results.

Of course, you could use the empirical method that Doom suggested and probably save some time, but this was mainly a thought exercise anyway.



#58024 Punch Into A Shot?

Posted by merlinski on 23 June 2005 - 04:32 PM in General Nerf

Merlinski: Imagine you throw a rubber ball at ten miles an hour. Now imagine throwing the ball at ten miles an hour while riding a bike at fifteen. You get a twenty five mile per hour toss instead with the same effort. This is how this works. However, there is a limit to it set by the terminal velocity of the dart. The darts being such a lightweight foam, air resistance hinders it alot, which is why despite the best mods and even using c02 people can't seem to get much more than 150' out of anything dart sized. This just helps to get it to that maximum velocity, so guns that are already close to that (such as a modded SM1500) won't benifit as much as, say, a scout pistol.

I understand why it works, but you missed my point. I was saying that this is more like being able to throw a rubber ball 75 miles an hour, and then riding a bike 5 miles an hour while doing it. Yeah, you get the whole 80 mile per hour throw, but the increase is range is relatively small compared to the stability you lose. I was thinking along the lines of modified guns, so I guess that if you have a pistol with 20 feet of stock range then it could be useful.



#57989 Punch Into A Shot?

Posted by merlinski on 23 June 2005 - 01:20 PM in General Nerf

I have a hard time believing that this makes any noticable difference in a gun with decent range. All you're doing is increasing the initial velocity of the dart, but the speed at which you can punch with a gun in your hand is significantly less than the velocity of a dart exiting a barrel.



#57564 Rev-8 Firefly - It's Summer! Where Is It?

Posted by merlinski on 15 June 2005 - 01:01 PM in General Nerf

I recall the conversation was that the timeframe was "summer".

You recall wrong:
http://nerfhaven.com...indpost&p=52361

You quoted his post which revealed that the timeframe was fall, and voiced your own assumption that he must have meant "summer" because its a big toy season.

Oh, and after a quick look over that topic I gotta correct you. The darts aren't fluorescent, they're phosphorescent. Phosphorescent material continues to glow after exposure to certain frequencies of electromagnetic radiation, whereas fluorescent material stops glowing as soon as exposure ceases.



#57438 Your Favorite Nic Contribution

Posted by merlinski on 13 June 2005 - 04:05 PM in General Nerf

I would have to agree with Halfing. My favorite contribution in the NIC was by a guy named Cxwq, with this little gem.

Holy crap, did you even read cx's post?

It's about what YOUR favorite contribution MADE BY YOU is. I thought it was clear enough already. Oh, and if you really want to be mature, you'd stop ripping on NHQ - RAMBO your statement is not even close to the truth and only constitutes a baseless insult at the expense of other people who are part of this community. Way to be "mature".

Now, to answer the poor man's question, my favorite contribution would probably be my site (Nerf Net) which I stopped updating a few years ago. At its busiest it was getting around 200 hits a week, and ended up having over 10,000.



#57166 Firefly Speculation

Posted by merlinski on 10 June 2005 - 02:34 PM in General Nerf

merlinski, I understand that the formula doesn't factor in the material or tip design, and that's precisely my problem. Suppose you have a micro size dart 3x longer than usual, and the front 1" has a special material or design so that it absorbs the impact of the dart very effeciently. Given that type of dart, you should safefly be able to shoot it much faster, and yet KED equation doesn't take that into acount.

You misunderstood what I said about material not making a difference. Even if you had this special dart, think about how ridiculously soft the front foam would be to extend the impact to even half a second long. There's just no practical way to make a dart fired from a nerf gun absorb much more of the impact than foam darts already do.



#57055 Firefly Speculation

Posted by merlinski on 09 June 2005 - 02:45 PM in General Nerf

Frank - the formula limits Kinetic Energy Density, which is not in any way affected by the material - kinetic energy depends only on mass and speed. As for the absorption, how much of a difference does different foam really make? In order to significantly decrease the force, it would have to spread it out over a longer time, which would mean serious compression. And in order to have a nerf dart's foam actually compress on impact, it would have to be extremely fast or extremely soft.

It makes sense that nerf would turn to smaller darts (micros instead of megas) - the decrease in mass is proportionally greater than the decrease in area, so initial speed can be greater.

This also explains why the Vortex guns were able to go so much farther than nerf guns - the initial velocity was significantly less.

So given the drag coefficient, mass, and area, the maximum out of box range for a given dart could be calculated.

chiefthe, are you allowed to tell us what the maximum KED allowed is? Has Hasbro reached the limits or do you go under the max with most guns? Thanks again for all your help, it's been really interesting.



#56977 Virtual Stock Exchange

Posted by merlinski on 08 June 2005 - 03:24 PM in Off Topic

I bought 3000 stocks in companies that all went up the day before last, and yesterday, they all went down. :P

That's why you don't buy stocks based on how they did yesterday.