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Plasmaarc452

Sun Oct 04 2009, 05:19AM

Registered Member #1394 Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111

Alright here is an update, the modeling is going sort of slow mainly because I have had 4 hours of sleep all week with school work so blame them (I got my nice 16 hour rem sleep so I am modeling up a storm now!).

Someone asked why I didn't use solenoids and here's the answer, the piston must push a projectile over 4 inches through the rotary magazine into the barrel and it must do so very fast. I have never seen a 4inch stroke solenoid (there may be one) and their power diminishes the farther they, push air pistons have full power during the whole stroke (assuming there is not an air pressure drop as the piston fills with air).

Ok so I added the two pistons (no piston rods yet), the stepper motor, and modified the unit to hold all of the parts (this took a while). This project is teaching me so much new stuff about inventor next i am going to add wires, air hoses, connectors, and maybe even a circuit board or two. Its helping me gear up for a 3d modeling competition which I hope to decimate

.

As for building this, its possible but I would have to find someone willing to make the giant plastic base piece.

klugesmith

Sun Oct 04 2009, 06:22AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Plasmaarc452 wrote ...
...Someone asked why I didn't use solenoids and here's the answer ... I have never seen a 4inch stroke solenoid (there may be one)

Uh, isn't that what a coilgun is?

and their power diminishes the farther they push. Air pistons have full power during the whole stroke.

Very good point. So if you have compressed air, you could save a lot of electrical hassle and make a cool auto-cycling air gun. 100 psi and 30 inch barrel would give you muzzle energy comparable to the 5% efficient coilgun. No caps to charge or coils to cool.

wylie

Sun Oct 04 2009, 07:45AM

Registered Member #882 Joined: Sat Jul 07 2007, 04:32AM
Location:
Posts: 103

Seriously, whats with the Anti-Modeling Trolling?

You got a sweet project in the works, keep at it.

Now, i don't know about the 1920x1080@60fps animations, that's a bit overboard. 640x480@30fps should be able to get the point across. And don't underestimate the power of still diagrams and photos.

For spreadsheet use (in excel at least), try this custom format i found on google: ###.000E+00

It might help with what Klugesmith said about keeping units straight. Dont be stingy with the cells, you got all the space you could need. Should we maybe do a HV-wiki article on spreadsheet-calculator tips? Or should it be left as an exercise to the dedicated experimenter?

rp181

Sun Oct 04 2009, 01:23PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529

May I suggest putting colors on the parts before putting them in an assembly? Also, you have multiple protrusions from the baseplate, how are those going to go on? The way you modeled it, It is all from one piece.

Plasmaarc452

Sun Oct 04 2009, 04:11PM

Registered Member #1394 Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111

The base plate is one piece but it is actually an assembly, it is composed of about 20 parts so far like nuts, bolts, motors ,pistons ect.... Some parts are put into the model but it reality it would be impossible to install the part. I could fix this by changing a few things and adding a clamping mechanism on the large ring parts that hold the mag and the pistons.

I thought it would be a bit overkill to do that so I didn't but I did realize it would be like that.

Plasmaarc452

Mon Oct 05 2009, 02:36AM

Registered Member #1394 Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111

Alright here's another update, I added hoses to the pistons this time and the air piping with threaded connectors on the other side. There are still no piston rods, I will work on those in a second but in the mean time check out these pics! BTW there are no hose connectors on the piston itself the hose just sits flush against the air hole (I might add those tomorrow if I can stay awake) the hose is also transparent blue so if I make it 100% opaque it will look like solid blue (I will see which looks better later on).

Its actually starting to bog my computer down now, my 4gb of ram in my laptop is about %75 full right now with only inventor running. I will have to turn on the paging file again in windows (I have an SSD in my computer so I turned it off to prolong its life). Its funny to watch the GPU temperature in this widget I have on vista the temperature is about 140 degrees when you are doing basic stuff and when inventor runs it jumps to around 165 to 175 degrees.

EDIT - On my above post where I said I was using 6 x 450v 2000 uf caps I just went and checked and found that they are actually 450v 3900uf capacitors which will put me closer to 2.1 to 2.2kj.

Plasmaarc452

Thu Oct 08 2009, 01:49AM

Registered Member #1394 Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111

Ok so here is another update with many BIG additions to the model, I spent the better part of 6 hours adding the barrel assembly, coils, water hoses, water cooling shrouds, break beam eyes, and the other little things that were all added (like the piston rods (finally)~:-().

The way the water cooling works is by pumping ice cold water through that large blue hose going between the coils. The hose feeds water into a large waterproof shroud/chamber that is around the coil. It is woven between the coils so water gets pumped in at the first coil on the bottom and then goes out the top of the first coil shroud to the top of the 2nd shroud which then feeds that water out the bottom to the 3rd. This way the water has the best chance of fully circulating throughout the coils which means nice icy cold coils.

The magazine and the water shrouds were faded out by like %50 so you could see stuff behind them. The animation is going to take a REALLY long time to render even at 640 x 480 it will probably take a week unless I can arm myself with some beefy computers. I encountered many obstacles but none were as stupid as the projectiles and the rotary mag. I could not get the projectile to spin in the mag correctly and spent hours yesterday trying to get it to work unsuccessfully until I asked on a cad forum. Then the next day I got a fantastic answer all you have to do is turn on "contact solver in inventor" and it will allow parts to interact so once the projectile is in the mag and the mag rotates the projectile will move with the mag. (I have been looking for some feature like this for months lol).

There is still MUCH more to go, all of the wiring needs to be put on it as well as connectors. Then I have to model the cap bank, scr's, charging unit everything............

1254966597 1394 FT76764 Projectile View 1

Mechanicus

Sat Oct 17 2009, 06:00AM

Registered Member #2439 Joined: Sat Oct 17 2009, 05:11AM
Location:
Posts: 1

This project looks very nice. I honestly only have three ideas to pose for your consideration. If you don't like them, it's cool.

1: consider notching your barrel if you're using a metal material. This will help to dissipate/disrupt eddy currents and increase your efficiency a little more. If you can, notch it all the way down. That'd eliminate teh eddy current factor for the barrel entirely. If it's not practical to use a "c" shaped semi-tube, I understand.

2: If you are using a metal material for the barrel, also consider using Bronze. It has the lowest coefficient of friction as far as metals go. While a perfectly tuned magnetic array may allow your projectile to float on magnetic waves and surf on inertia alone, there's always the chance of your projectile touching the barrel walls, especially if you intend to rifle it and use a coated (plastic? formed teflon?) projectile to engage the rifling. I doubt however that a gyroscopically stabilized projectile is on the list of concerns right yet when everyting is still in preplanning/prototyping stage.

3: If you don't like metal barrels, I'd recommend Kevlar fibre composite tubing. It's unaffected by magnetic fields so it won't crush when the coils are energized, it's tough, so a rogue bounce in your projectile's internal ballistics won't demolish it, and it's really easy to handle/machine compared to most metals.

Also, as a fourth point,
For anyone who thinks modelling, preplanning, etc. is uncool, do yourselves a favor and quit watching Dexter's Laboratory on Cartoon Network. We really don't want you to hurt yourself by willy-nilly tossing junk together and pretending it'll work like some amazing thing you saw on McGuyver. I am concerned for the welfare of science hobbyists, amateur scientists and other academic individuals. I'm not worried about them hurting themselves, I'm worried about the less-savvy hurting themselves and causing bans and laws shutting down private research and experimentation.

Please people, if you don't want to do the whole 3D animated gig, at least grab a nice fat pad of paper and a pencil. A little forethought saves a ton of health insurance premium. I, for one, am hugely interested in seeing the fully rendered and animated piece. Like the movie theatre, you're not obligated to see it if you don't wanna.

Turkey9

Sat Oct 17 2009, 09:47PM

Registered Member #1451 Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661

I think that bronze or brass barrels are the way to go. They NEED to be notched to prevent eddy currents, and they have a very thin wall compared to plastics. The gap between the inner coil wall and projectile should be as small as possible for good efficiency.

Also, it doesn't matter whether or not the barrel is affected by a magnetic field, its the actual coil that will shatter a barrel. The magnetic field will make the coil squeeze the barrel when using pretty high energy. So in other words, brittle matterials like glass are not a good idea.

Plasmaarc452

Sun Oct 18 2009, 03:54PM

Registered Member #1394 Joined: Sun Mar 16 2008, 06:18PM
Location:
Posts: 111

Thanks for the reply's.

I had always been under the impression that a metal barrel would cause problems with the magnetic field but I guess that's not the case anymore. I might change it in the model but the way I modeled the barrel will cause a few problems in doing that! Actually I takes that back I can cut a cylinder from the front to the back of the barrel to make the walls thinner and then the material can be changed to bronze.

Soon I am going to be getting a set of books on inventor simulation, modeling techniques, and advanced 3d modeling. The stress analysis feature (simulation) will be cool because I could actually make the coils contract and have the barrel change colors as to where to the most stress/force is being exerted on the barrel

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