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Mortimerex
10-03-2006, 05:58 AM
http://img.photobucket.com/albums/v159/DirtyHairy/carbine_stuff.jpg

Here are some pictures of my current project of making a fully mechanical (no batteries required) auto fire bb gun. This may be of interest because all parts are machined (using my mini mill or mini lathe) to some extent.

The picture was rotated sideways, the Algor (finite element analysis software) and Autodesk Inventor boxes were simply used because I keep them at the front of the bookshelf and they were the right size to prop things up. Actually, it seems appropriate as in a sense the project rests on those 2 bits of software. The 3d models and 2d CAD detail drawings were generated using Inventor while the frame that holds both my mini mill and lathe were structurally verified before being built by doing a finite element analysis to determine approximate maximum stress and deflections. I actually had subscriptions for both so I basically kept the box from the first versions and threw the rest (of the boxes) away after detaching the barcode & serial numbers. So all my software CD and updates are in one box each instead of about 50.


There is a 4000 count bb container and a 12g co2 cartridge for scale. The 12g cartridge was intended for the uzi/mac10 (box magazine attached thru the handgrip) submachine pistol but then I ran across a much larger 255g Brass Eagle refillable bottle. Since I had originally wanted a carbine size I decided to shelve the pistol design since the carbine has almost identical mechanism with main exception being it can have a larger, rugged box magazine without having a “fat” feeling pistol grip. Of course the carbine shoots a lot longer (approximately 20x) before needing to recharge/replace the c02 power source. The larger 255g Brass Eagle refillable co2 bottle is obviously a lot bigger and you can see its simple and robust end fitting seal/connection which finalized my decision to go with it.

Since I don’t have cnc (yet) the shells/ outer housings were made of wood, “chicken fence”, plastic screen, cardboard and ‘bondo’ automotive body putty. Hand shaped and mostly cosmetic these will be patterns for making the injection molded parts -at least for prototypes and early low volume production until I can get a cnc mill and make a more commercial quality (prettier and less variation from the 3d model) set of patterns. They are outer patterns, inner cores will of course be machined precisely and located with dowels in the molds. Again, the inner cores will be rather basic while once I get cnc capability I can make cores that reduce the amount of excess polymer material to make the part by making it more of a true shell rather than a block with a few bores and hollow boxes in it. I just painted them with dark green lacquer except for the stock cover which I broke while sanding. I neglected using screening just cardboard and bondo (over wood formers later removed) which doesn’t tolerate too rough handling when its that thin. I was holding it near the middle and sanding away on the other end like it was 1/4” thick reinforced plastic instead of 1/16” bondo sandwiching 1/16” thick cardboard. The picture of the shells make them look worse than they are as they hadn’t been finish sanded and polished yet and there was orange peel, bad lighting, and somewhat out of focus picture.

The 12” length sch40 pipe for the outer barrel is turned down to .75” od. Beautiful but it needs something to blue or otherwise surface treat so it doesn’t rust. I really don’t want to paint as that would remove the fine lathe tool marks which some might consider a blemish but which I prefer (on a gun barrel’s outer surface) to a finely ground “perfect” barrel finish. Next to the 12” outer barrel is an 8” inner barrel which is an alloy of aluminum/magnesium I think but it was scrounged from my model rc airplane supplies so not sure precisely what alloy. So it looks like my initial prototype will have only an 8” barrel tho I’m still thinking of 12” for the final product. Brass or bronze would be better inner barrel but none I’ve found have precisely the same id as this -which is ideal for bb. For production I intend to locate a supply for brass or bronze inner barrels but there may be some aluminum alloys that have good wear resistance and low coefficient of friction with steel.

The magazines are 30-40 round depending on spring used and one prototype is aluminum and a larger is acetal. The larger is simpler to make using only 2 half pieces (instead of 3 stacked) and has room for larger diameter spring. The left shows a close up of the acetal mag since the main picture is sadly lacking. The corners were nicely rounded using approx 1/16” - 1/8” r corner rounding/radiusing endmill. The magazine outer surface is very non slippery and secure grip since it was milled using a rough end mill. It would be nice if I could pattern and injection mold this as it takes hours to machine (without cnc) but I fear the surface texture would not transfer even to silicon or plaster-of-paris mold. Well, its already made and I intend the production version to use a 3.5” od approximately 300 round drum w/ helix feed magazine. The drum mag will definitely be molded so the box mag is likely only to see use initially and only in prototype testing (since its already built).

The intended design parameters are for a muzzle velocity of about 400 fps (at about 3-6 rounds/second) which with bbs should provide at least several 300 round magazines before changing/recharging the power source ( have to wait for tests and tuning before I can give any definite figures on muzzle velocity and endurance). This design is NOT intended for hunting or to kill anything, definitely not anything larger than sparrows or rabid chipmunks (although misuse could seriously or fatally injure people or pets –but then so could stumbling on the sidewalk). 400 fps gives a lot of paper target shredding power and should easily penetrate empty aluminum soda cans (a bb gun favorite target of mine). Yes, there are 22 caliber hunting pellet guns using a comparable air source shooting around 1000 fps to kill game up to raccoon size- BUT they can only shoot a dozen or so shots per canister. And even though 1000fps is about the same as a .22 caliber firearm, the pellet (which masses a lot more than a bb) is still a lot less massive than a .22 caliber bullet meaning its “stopping power” is a lot less. My interest here is in high rate of fire and have little current interest in designing anything that might be confused with a firearm (ballistically speaking) or that would require large 20 pound scuba tanks on the back. Mass production model cost estimated at approximately $50-$100 depending on features, manufacture methods and materials, and inclusion of brass eagle or equivalent refillable power cartridges ( those cost almost as much as the carbine itself).

This design would only require slight modifications to produce a paintball or softair versions although if I did that I might rearrange the magazine to point up (at an angle to clear the sights) and just use gravity feed although drum/helix mag may appeal more by not requiring it to be held upright to feed and fire rounds. Of course the bores would need to be changed as well as the tuning of the various springs. But still, no batteries required unless you want a laser sight of course.

Designed by degreed mechanical engineer, BSME

I don’t give out my name because I once almost got fired for calling an idiot an idiot in an e-mail. Plus I’m a healthy 40 yrs old and certainly don’t need to be put on a spam list for cheap Canadian viagra meds.

Millman
10-03-2006, 06:13 AM
SWEET, how much will they cost? I would forego some much needed tooling to buy one of those. Lookout neighborhood pests....and people.

Mortimerex
10-03-2006, 08:53 AM
Sorry, I don't think peddling stuff is allowed here. I did mention a target cost of $50-$100 mass produced not to try and drum up customers but simply that any design you may consider even potential for future sale you need to set a target price which will eliminate alot of manufacturing methods and keep you from specifying in the prints to mill it from a block of titanium or something similar that would utterly bankrupt a commercial attempt.

Of course custom crafted, entirely cnc machined "works" products can be made (for astronomical price) and in effect my prototype is in that nature except I'm being cheap and trying to skip closer to the mass produced item using (home made)plastic injection molding with patterns easily made from wood, bondo, acetal, and/or machinable wax.

For pests I don't intend it to have alot more than 400fps but maybe tunable via spring & bolt change between 400-600 but that still is only good, like I said for sparrows and rabid chipmunks. Don't shoot a person with it, not even in self defense. I suspect it would make them much MORE likely to kill you than less.

I hope to have several limited edition hand crafted versions ready before Christmas to try to sell for enough to buy a cnc mill and quit my day job too. Ha, ha. Not likely, true. But its part of the American (and probably Canadian, British, Chinese, etc, etc) dream.

By the way, for the turned steel outer barrel does anyone have any suggestions for a good blueing compound or some similar surface treatment that really inhibits rust without changing the surface detail? I was originally thinking some kind of crude electroplating to give it a sort of stainless steel finish but may just use simple blueing.

Rex
10-03-2006, 10:04 AM
Nickel plating is relatively easy to do in a small shop.

Mortimerex
10-03-2006, 01:35 PM
Nickel plating is relatively easy to do in a small shop.

Thanks!

That sounds like what I'm after. Of course for production an ugly plastic barrel will be likely be necessary to keep costs down but for my own I want it pretty even if only half of it is visible.

lazlo
10-03-2006, 02:37 PM
Nickel plating is relatively easy to do in a small shop.

I'd like to try this too -- is it easier to start with a Caswell kit? I already have a power supply that would work, but can you buy the chemicals seperately somewhere?

Rex
10-03-2006, 06:02 PM
It's been many years since I've done it, but as I recall you needed Nickle suphate in a water solution, a nickle bar for the source, DC power.

Caswell might be the best place to get the chemical and the nickle anode.

Here's an alternate: http://www.bullnet.co.uk/shops/test/nickel.htm

Here's the long version how-to:

http://www.pfonline.com/articles/pfd0015.html

Mortimerex
10-06-2006, 08:17 AM
I just read up on it too (the Caswell kit) but I imagine they are all similar. A few points I believe are very important:

1. Nickel plating is very enviroment friendly- no toxic waste sludge produced like in the chrome plating tetravalent method. IE no hazardous waste dump in your backyard.

2. Nickel plating provides the same functionality as chrome plating, looks almost as pretty, and also very cheap even disregarding hazardous waste disposal of chrome plating.

dsergison
10-06-2006, 11:11 AM
have you seen the Drozd select fire "uzi" by IZH Baikal?

http://www.airgunwarehouseinc.com/bbguneuamard.html

I have an IZH 46m. nice work.
http://us.st11.yimg.com/us.st.yimg.com/I/yhst-41902112641410_1914_7870770

Tell us more about the mechanical operation. Is the operation by blowback from popet valve like a stacked tube paintball gun?


I work on paintball stuff, and air gun stuff too.
http://www.sergisonmachine.net/gallery_paintball.html

Mortimerex
10-06-2006, 08:40 PM
Mechanical operation ok. I did mention that it was entirely mechanical which means no little electric motor or batteries necessary. I never actually used or disassembled a paintball gun so am not real familiar with the benefits of poppet. Um, any fully mechanical full auto or even semi auto single action would require "blowback" which is rather vague and self explanatory while not really explaining how my mechanism works. To clarify, my inspiration was the Crosman Walther ppk/s bb gun that works by what I term blowback (not a stupid revolver like most of em) and while not really a great deal similar in detail the concept is very similar. The Crosman ppk is a very fun bb pistol that I highly recommend despite its ballistic shortcommings compared to other c02 bb pistols due to the blowback having to move the realistic steel slide weighing nearly the same as a real 9mm firearm and that it has such a very short barrel. It does have a "kick" like a real .22-.32 caliber firearm auto pistol which is expending some of the power that could be propelling the bb.

Lets just say that my mechanism has more similarities with real firearms than with paintball or most bb guns. And I admit that I was thinking of and eventually used a mechanism similar in many respects to a real military rifle (but older than the m-16 and ak47). The Russian Drozd uses the tiny 12g c02 (plus it requires batteries) where my carbine uses 255g refillable c02 so no comparison there at all tho the Drozd probably looks prettier. Aside from having a Bachelor of Science degree in Mechanical Engineering (BSME) I was also in the Army for 4 years active duty the last 2 years or so as the arms room nco (sergeant e-5).

Its possible my mechanism is very similar to some pnuematic air hammers (although I have never disassembled one so maybe not).

I'm checking out your other links right now, I love seeing stuff like that. Frankly, I wouldn't consider buying the Drozd even if they were only $50 but if you got something better... I can never have too many bb guns, especially since the big companys like Daisy and Crosman mostly just built the same crap bb guns that were around when I was a kid (probably when my grandpa was a kid too).

Hmm, your pistol looks like a pump to me. Also like a precision target type. I think the world has more than enough single shot bb guns, I want to shred paper. Maybe its just me, being in the Army all that time and I only once got to shoot an m16 on full auto. Yeah, shot the m-60 but its a "crew served" weapon so not the same. When in the weapons platoon I was always assigned as the 60 or m203 gunner when what I wanted was the SAW.

Mortimerex
10-07-2006, 08:39 AM
Ok, I've decided to show the carbine "blowback" mechanism here just for the record since I do not plan to patent it, because it is rather prosaic and besides very similar at least in concept to the WW2 m1 carbine "short-stroke piston" mechanism. "in the Williams system the gas port leads to a small hollow block beneath the barrel, inside which is a flat headed piston with a stem barely half an inch long protruding through the back of the block...When the gas behind the bullet goes through the port in this design it drives the tiny piston back very forcefully, since the piston weighs no more than couple of ounces. The system is light, simple, and easy to manufacture, which makes it all the more surprising that few other designs have ever adopted it." (Handguns and Rifles: The Finest Weapons from around the World", Ian Hogg. Similar in concept, but not ever having an m1 carbine to disassemble I cannot say how similar in detail. Heres a picture with some other parts not shown. This is "for the record" in case someone tries to patent my design which I likely won't ever patent. The tiny stem is what transfers the mechanical impulse to throw the bolt back. The radial holes simply vent the back side of the short stroke piston and can tune down (ie, increase resistance, air spring type damping in the event the transferred force is far larger than desired causing excess wear and fatigue) the fairly great deal of force from a given pressure charge (due to its surface area being alot larger than the projectile bore).
http://img.photobucket.com/albums/v159/DirtyHairy/bbmechanism.jpg

Mortimerex
10-07-2006, 09:38 AM
Ah, the light came on about the poppet valve question. The answer is that I will use as efficient a valve I can make or buy. For example a "poppet" valve is usually more efficient than a ball check valve although generally more difficult to make but the difference in effeciency can vary and overlap. So, yes if I can buy poppet valves cheap instead of the ones I am currently making (non cnc, not really high precision) and hand lapping. Of course a butterfly or gate valve may provide less resistance but then are generally more problematic getting a true consistent seal. I don't want the majority of the c02 leaking out when it hasn't even been used after all.

dsergison
10-07-2006, 10:02 AM
Your a bit heavy on the big words and cad plans.

- and disturbingly light on the knowledge of:

what is out there,
their function,
strengths,
weaknesses,

and woefully short on hands on experience with any of it.

and arrogant too.

best of luck, I'll show myself out.

Mortimerex
10-07-2006, 11:08 AM
Your a bit heavy on the big words and cad plans.

- and disturbingly light on the knowledge of:

what is out there,
their function,
strengths,
weaknesses,

and woefully short on hands on experience with any of it.

and arrogant too.

best of luck, I'll show myself out.

Um, can you provide a specific example of any of your complaints listed above? For example, just because most existing bb and paint ball guns are practically clonal copies of each other doesn't mean that they are well designed. I am arrogant, in that I do not take well to vague philosophical suggestions. But mostly I was just speaking of personal preference when saying things like, "I think the world has more than enough single shot bb guns.."

Your point about heavy on CAD plans is good tho, but I always prefer too much detail to insufficient. It does tend to make me get sidetracked on almost purely cosmetic items (like the shell which is only to enclose and protect the innards and could easily look more like near scale outlines of the mp-44 or ak-47, and plating the steel barrel which could be turned out of pvc or other plastic ). Just because you may know the name of more obscure widgets than I do does not mean you comprehend their operating principles. I may be wrong here but for example a "poppet" valve I seem to recall the air pressure is always seeking to pop the valve open which requires spring to keep closed, and though an automotive type valve also has a spring the air tends to close the valve or at least not force it open. Which is better and for what application? Well, poppet valves are no longer used in internal combustion engines while they seem to have found favor in bb and paintball guns likely due to simple ignorance.

By the way, I think you should stick to poetry and not argue engineering principles with degreed engineers.

BillH
10-07-2006, 11:23 AM
Simplification is the highest level of reform.
I dont like Co2 anything, gets old having to refill it up. A semi auto pump bb gun would be nice. 10 Pumps gets you 5 shots.

Mortimerex
10-07-2006, 11:57 AM
Now that is a good suggestion. Whether I like it or not is beside the point, the concept surely has merit. The reason I might not like it is because it may distract me from finishing the basic mechanism. (Getting the cart ahead of the pony). Plus my time is limited by a day job and another more secret project that is alot more economically viable. The carbine design is such that it uses a refillable 255g can that could as easily be "pumped up" with air since the original mechanism was designed for a pistol, in the carbine I have lots of room. And eventually I may modify the mechanism to be select fire or semi auto only as well as a manual air pump type.

A question, how many pumps are you willing to make for 30 shots? Is 60 reasonable? It sounds like alot of work to me and what about the 300 round drum mag? I am not making fun of you but of my own laziness.

Actually, I saw manual pumps designed for the brass eagle can on the net somewhere so no need to design anything. All you have to do is open the hatch, unscrew the can, screw the can to the pump, and pump away. Having a pump built in to the gun itself increases stress on the parts, increases the cost and difficulty of manufacture, and increases the weight of the gun. Doesn't seem much point to me.

BobWarfield
10-07-2006, 02:02 PM
Just because you may know the name of more obscure widgets than I do does not mean you comprehend their operating principles. I may be wrong here but for example a "poppet" valve I seem to recall the air pressure is always seeking to pop the valve open which requires spring to keep closed, and though an automotive type valve also has a spring the air tends to close the valve or at least not force it open. Which is better and for what application? Well, poppet valves are no longer used in internal combustion engines while they seem to have found favor in bb and paintball guns likely due to simple ignorance.

Mortimer, you say you have an undergrad degree in Mech Engineering. In fact, it's hard to get you not to say it in every post unless you are on about your Chemical Engineering background with Evan.

I find it interesting that a MechE (with Chemical Engineering too) didn't know what a poppet valve was and goes on to erroneously state they're no longer used in internal combustion engines. There's nothing obscure about a poppet valve, they're in common use for a variety of applications including internal combustion engines.

Try Google the next time you wonder what someone is talking about. Any one of the first page's links would've helped you avoid that "simple ignorance" of poppet valves.

You would do well to review the literature on firearms more fully as well. The M1 Carbine has a locking action, specifically a rotating bolt. As such, it is not classified as a blowback operated action. Try Googling "M1 Carbine Blowback" versus "M1 Carbine Locking". See how easy that was?

If you'd like to understand how different actions compare, try Wikipedia:

http://en.wikipedia.org/wiki/Firearm_action

Something a MechE would have thought of is the relative forces acting on your short piston based on the pressures and the BB's inertial mass holding onto that pressure long enough to work the action before leaving the barrel altogether, relative to the forces needed to actuate your mechanism and chamber another round. If there isn't enough back pressure to operate the mechanism, not much happens. Blowback mechanisms are very finely balanced around these parameters, and if you get them wrong, the gun either doesn't cycle properly, or may have a cyclic rate that is ridiculously high. For example, try Googling to understand what the cyclic rate is of the 1911 Colt were it to go off full auto.

Perhaps you'd care to share with us the calculations you worked through on that so we can better see the genius of your idea? I assume you wouldn't build your design without having done the calculations, lest you waste your time on an idea that wouldn't work.

Most paintball designs can use more sophisticated mechanisms than blowback per se because there is a supply of gas that persists for much longer and is much cooler and easier to manage than combustion gas from smokeless powder. They typically use a set of valves to route that gas around to do what it needs to do by way of propelling the paintball and operating the bolt. BB guns are the same story.

I do happen to own an older paintball SMG modeled on the British Sten gun that has a blowback mechanism that is an almost literal copy of the Sten. Having handled the Sten components as well as this guns, I can assure you the masses and spring pressures are quite different to make the paintball gun work. It looks to me like the tiny mass of a BB would make it really hard to implement a true blowback design there. The bolt would have to be tiny and the spring pressure light.

Best of luck,

BW

Mortimerex
10-07-2006, 04:34 PM
Your points are well taken and I must point out my descriptions were very simplified. I have mentioned several times tuning the cyclic rate and muzzle velocity although I am now thinking that at least once I get fairly close to the desired area, the actual product may be tuned from 400 to 600 fps just by changing the "firing pin" assembly. Also, a very high cyclic rate is actually desired as stated before (3-6 rounds per second)

"Something a MechE would have thought of is the relative forces.."

Actually, that is why I went with a short piston in the first place. To blast the bolt back about the same time the bb leaves the barrel. Yes, alot of fine tuning with mass of bolt, spring rates, etc. As mentioned the short piston I have designed can be dampened by rotating a matching disk over the "vent" holes. That should give very precise adjustment, granting I can machine the parts precisely enough (although lapping helps there). The point with the short piston design is to at least get the impulse necessary to cycle the action BEFORE the bb leaves the barrel.

As for calculations, those I have mentioned before are quite basic and I was too lazy to calculate losses due to friction and drag but the numbers come out about 30-40% better than actual (due my lack of calculating friction forces). This is not rocket science nor did I attempt to make it so, just basic physics. Whether the propellent is fart fumes or co2 is not a question I am really concerned with. I'm only interested in the forces and accelerations.

Here I was just lambasted for being too technical and now for not doing what your hypothetical MechE would.

The poppet valve is not used in the combustion chamber valving of any modern production engine I ever heard of. I did not say they did not have application is less demanding situations like say pressure relief valves, etc, where a stupid wood cork could do almost as well.

All your points seem relevant but are utterly false. What the heck is your problem?

Evan
10-07-2006, 05:35 PM
The poppet valve is not used in the combustion chamber valving of any modern production engine I ever heard of. I did not say they did not have application is less demanding situations like say pressure relief valves, etc, where a stupid wood cork could do almost as well.

http://vts.bc.ca/pics/valve.jpg



A poppet valve is the type of valve (http://experts.about.com/e/v/va/valve.htm) system used in most piston engine (http://experts.about.com/e/p/pi/piston_engine.htm)s, used to seal the intake and exhaust ports. The valve is usually a flat disk of metal with a long rod known as the valve stem out one end. The stem is used to push down on the valve and open it, with a spring generally used to close it when the stem is not being pushed on. Desmodromic valves (http://experts.about.com/e/d/de/Desmodromic_valve.htm) are closed by positive mechanical action instead of by a spring, and are used in some high speed motorcycle (http://experts.about.com/e/m/mo/motorcycle.htm) and auto racing (http://experts.about.com/e/a/au/auto_racing.htm) engines, eliminating 'valve float (http://experts.about.com/e/v/va/valve_float.htm)' at high RPM (http://experts.about.com/e/r/rp/RPM.htm).
http://experts.about.com/e/p/po/Poppet_valve.htm



Valve performance plays a significant role in the overall power production of an engine. If the valves are too small, the air flow will be restricted, and the engine torque will decrease. The airflow through the inlet and the exhaust ports of an engine is unsteady, due to the periodic opening and closing of the inlet and the exhaust valves.
There are several types of valves that are used: a poppet, rotary, disc and a sleeve. The most common valve is the poppet valve. The poppet valve is inexpensive and has good sealing properties, making it such a popular choice. The following evaluation will assume poppet valves are used for both the inlet and exhaust ports.

http://www.engr.colostate.edu/~allan/fluids/page2/page2.html (http://www.engr.colostate.edu/%7Eallan/fluids/page2/page2.html)




Abstract

The topic of this paper is the computational modeling of gas injection through various poppet valve geometries in a large bore engine. The objective of the paper is to contribute to a better understanding of the significance of the poppet valve and the piston top in controlling the mixing of the injected fuel with the air in the cylinder. In this paper, the flow past the poppet valve into the engine cylinder is computed for both a low (4 bar) and a high pressure (35 bar) injection process using unshrouded and shrouded valves.
http://cat.inist.fr/?aModele=afficheN&cpsidt=16028106




SAE Standards

Document Number: J775 Date Published: November 2004
Title: Engine Poppet Valve Information Report
Issuing Committee:
Elev Temp Prop Of Ferrous Metals Committee
Scope:
This specification supplies engineers and designers with: 1) poppet valve nomenclature; 2) poppet valve alloy designations; 3) chemical compositions of poppet valve alloys; 4) a guide to alloy metallurgy and heat treatments; 5) general information on properties of valve alloys; 6) a guide to the applications of alloys; 7) a description of valve design and construction, and their relation to valve alloy selection; and 8) valve gear design considerations that affect valves.
Product Status: In Stock
File Size: 166K
Purchase more ground vehicle standards and save! J-Paks (http://store.sae.org/jpaks/) offers a customized subscription plan that lets you pay for just the documents that you need, when you need them. Learn more > (http://store.sae.org/jpaks/)

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Noun

S: (http://wordnet.princeton.edu/perl/webwn?o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&s=poser&i=0&h=000#c) (n) (http://www.homeshopmachinist.net/bbs/)poseur (http://wordnet.princeton.edu/perl/webwn?o2=&o0=1&o7=&o5=&o1=1&o6=&o4=&o3=&s=poseur), poser (a person who habitually pretends to be something he is not)

Mortimerex
10-07-2006, 06:05 PM
Calculations given: barrel length = 8", 4000bb wt = 2.9375#, 1bb wt = (approx) 7.34x10-4, m=wg, g= 32.174ft/s2

What is the acceleration?
a=fm (assume we want 100psi constant pressure)
F=pa=100psi[pie(.177"/2)2]=2.46#
a=f/m=2.46#(32.174ft/s2)/7.34x10-4# = 107,856 ft/s2

What is the time to reach end of (8") barrel?
d=v1t+.5at2, v1=0, d=.5at2
t=square root(d/.5a)= .00351second

What is the velocity at the end of barrel?
v=at=107,856ft/s2(.00351s)=
v= 379 ft/second

Short cylinder dia = .375"

f=pA=100psi (.11in)2= 11.0#

Given same time as bb reaches end of barrel what is the distance given weight of 1 oz?
Thinking Aluminum maybe even plastic with a small steel stem 3/16" diameter by about 1/2" long
and I probably should have done some calculations there.
d=v1t+.5at2, v1=0
a=f/m=11.0#/(1/16#)(1/32.174ft/s2)=5662.6 ft/s2
d= .5(5662.6ft/s2)(.00351s)2= .42"

Kinetic energy = ke = .5v2(m) =.5(19.87ft/s)2(1/16#)(1/32.174ft/s2) = .383ft#

Yeah, alot of assumptions and I didnt double check. It was more in the nature of feasibility.
Besides, this project is a "hobby" type relying on what I can scrounge and the accumulated change
left from my lunch money. Certainly, even if entirely correct not grounds to claim I'm a genious but and
if this was on a real job you can believe I would be doing quite alot of dynamic event simulation and probably calculating drag and friction losses.

I did these calculations in my project notebook more as entertainment than as solid basis so some numbers and all exponents are not exponented since I'm too lazy to reformat the text. If you can verify an error in the solutions, feel free to do so.

Its ironic that high school dropouts call degreed engineers posers nowdays.

Evan
10-07-2006, 06:14 PM
http://vts.bc.ca/pics/pcard.jpg

Mortimerex
10-07-2006, 06:57 PM
What were you doing in the Berkeley, California computer center? My university had a few machinists for the mfg lab. They didn't have engineering degrees nor were engineers. Show me your degrees and I will show you mine.

Har, har!

Now whos the poser?

Evan
10-07-2006, 07:15 PM
I don't have a degree nor have I claimed to have one. I did study computer science and psychology at the University of California at Berkeley. I do have enough credit from various places to get a couple of degrees but never got around to it as people were waving too much money in my face to work for them.

That is a top card from a program deck for the CDC 6400. The only people that were able to get time on that machine (supercomputer) aside from faculty and grads were those majoring in computer science as I was.

As for being a poser, would you care to explain how a ME doesn't know what a poppet valve is?

BTW, it was at that time possible for a high school dropout to enroll at Cal. All you had to do was score in the top 2% on the entrance exams. It was called the "2 percent rule". You could also skip grade 12 by the same method. I did.

pntrbl
10-07-2006, 10:54 PM
Hmm. I always thought the term "poppet valve" referred to early IC engines where the valve was opened by the vacuum of the piston instead of the mechanical action of a cam. I guess the term is more generic than I thought.

But apparently desmodromic valves are not poppet? Why not? They have the same shape and seat just like conventional valves.

What do you suppose the pnuematic valves used in F1 are called?

As long as we know how they work ... do we really care?

Bill W.

sidegrinder
10-07-2006, 11:47 PM
Desmo valves are closed by different means than normal poppet valves. I don't have the proper terminology on the tip of my tongue, but for lack of something better, they have rockers to both open and close. They actually do have springs too, but they are a much lighter duty than standard valve springs. They only need to hold the valve shut against a few thous of valve lash. Hope I've explained something here that makes sense--I'm tired! Sidegrinder

BobWarfield
10-08-2006, 03:18 PM
The desmodromic valves are still poppet valves. There is a good illustration of them here:

http://en.wikipedia.org/wiki/Desmodromic_valve

The term "poppet" only refers to a valve that consists of a mushroom-shaped plug that moves axially in a bore. The means of actuation, whether Formulat 1 pneumatic, cam and valvespring, desmodromic, hydraulic, electrical solenoid, or even pressure differential is independent of the valve being a poppet valve.

Best,

BW

mochinist
10-08-2006, 08:34 PM
What were you doing in the Berkeley, California computer center? My university had a few machinists for the mfg lab. They didn't have engineering degrees nor were engineers. Show me your degrees and I will show you mine.

Har, har!

Now whos the poser?You wasted $150,000 on an education you could have got for a buck fifty in late charges at the public library. :D

rfrey
10-08-2006, 09:00 PM
What were you doing in the Berkeley, California computer center? My university had a few machinists for the mfg lab. They didn't have engineering degrees nor were engineers. Show me your degrees and I will show you mine.



I'm sure the thrill will wear off after you've had it a month or two.

Rod Frey
DEGREED ENGINEER
BA, MA, BSc, BEng, MEng, BLAH, BLAH, BLAH